Patent Publication Number: US-2019167734-A1

Title: Pharmaceutical composition and methods for the prevention and/or treatment of Staphylococcus aureus using artificial bacterial colonization

Description:
The present invention relates to the prevention and/or treatment of bacterial colonization by  Staphylococcus aureus.    
     The present invention also relates to compositions (e.g. pharmaceutical compositions) comprising at least one  Corynebacterium  sp. and  Staphylococcus  sp. and related methods, said compositions and methods being particularly associated with the prevention and/or treatment of bacterial colonization by  Staphylococcus aureus.    
       Staphylococcus aureus  is a major cause of infection in humans. It is responsible for a wide range of pathologies including skin and soft tissue infections, bone and joint infections, endocarditis, and sepsis. While  S. aureus  can asymptomatically colonize the anterior nares, skin, mucus membranes and gastrointestinal tract, asymptomatic carriage is associated with an increased risk of endogenous  S. aureus  infection, particularly in surgical and dialysis patients. Asymptomatic carriers also act a reservoir for the transmission of  S. aureus , increasing the risk of infection in both the community and in hospital settings. Indeed, at any given time, an estimated 30% of the population carries  S. aureus  in the anterior nares, the principal site of  S. aureus  colonization. 
     In order to decrease the risk of transmission and infection by  S. aureus , in particular in hospital settings where patients are particularly susceptible, many healthcare centers recommend routine patient screening prior to admission, coupled with the elimination of  S. aureus  nasal carriage, otherwise known as “nasal decolonization.” Indeed, it has been shown that the risk of infection by  S. aureus  is increased when the level of  S. aureus  present in the nares is high (White, 1963, van Belkum, 2009). Adequate nasal decolonization methods are therefore critical to limiting  S. aureus  transmission and infection. 
     To date, a variety of methods have been used for nasal decolonization, including the application of local antibiotics and/or antiseptics, the use of systemic antibiotics, and artificial bacterial colonization of the nares. However, local antibiotic and antiseptic treatment methods have low efficacy and have led to the rapid emergence of antiseptic and antibiotic resistance in  S. aureus  strains. The use of systemic antibiotics has similarly led to the rapid emergence of antibiotic resistant strains, coupled with the presence of undesirable side effects. Artificial bacterial colonization consists in the administration of bacterial species and/or strains that compete with  S. aureus . Notably, artificial colonization of the nares with  S. aureus  strain 502A was used to prevent colonization by more virulent  S. aureus  strains in neonates during outbreaks, and in patients with recurrent infection, in the 1960s. However, this method was abandoned after strain 502A itself was found to be the cause of several  S. aureus  infections and was even linked to a death. More recently, several studies have evaluated the effects of other bacterial species on  S. aureus  colonization in the nares, with varying and often contradictory results. For example, Uehara et al., 2000, has shown that  S. epidermidis  is unable to eliminate  S. aureus  from the nares. In contrast, Iwase et al., 2010, has reported that  S. epidermidis  can in fact eliminate  S. aureus  carriage. Similarly, while Uehara et al., 2000, has shown that artificial colonization with  Corynebacterium  can eliminate  S. aureus  carriage, Yan et al., 2013 has more recently shown that the presence of  Corynebacterium accolens  in the nares is associated with carriage of  S. aureus . Yan et al., 2013 has further shown that  C. accolens  can facilitate growth of  S. aureus.    
     Despite the known disadvantages of local antibiotic administration, nasal decolonization currently relies essentially on the use of a locally applied antibiotic, mupirocin. In efforts to slow the development of  S. aureus  resistance to mupirocin, treatment is limited to patients at risk of severe infection, with antibiotic administration for very short periods of time (e.g. a five-day treatment course in patients undergoing resuscitation or surgery). Attaining patient compliance can be difficult, however, as mupirocin must be applied repeatedly. Furthermore,  S. aureus  recolonization is frequent after treatment, indicating that mupirocin has little long-term treatment effect. Indeed, while mupirocin efficacy is significant, as many as half of the patients remain colonized with the same  S. aureus  strain five weeks after the start of treatment. It has furthermore been reported that mupirocin treatment of individuals exempt from  S. aureus  colonization can be deleterious and cause them to become carriers, making it necessary to screen for carriage prior to treatment (Wertheim et al., 2005). 
     Despite these efforts,  S. aureus  antibiotic-resistant strains are now detected in up to 50% of patients in rehabilitation and long-term care facilities. Of the antibiotic-resistant strains, methicillin-resistant  S. aureus  (MRSA) is the most prevalent, though cases of mupirocin-resistant MRSA have been reported. Infections due to antibiotic-resistant  S. aureus  (e.g. MRSA) are associated with increased mortality, morbidity, length of hospitalization and cost, when compared to infections due to methicillin-sensitive  S. aureus  (MSSA). 
     As a result, there exists a need for new products and methods for the prevention and/or treatment of  S. aureus  colonization on the skin and mucus membranes. In particular, there is a need for new products and methods preventing and/or treating  S. aureus  colonization of the nares. There is a further need for new products and methods that can be administered over a long period of time (e.g. weeks or months), in particular for the duration of the healing of an accidental or surgical wound. This need is particularly important in the context of orthopedic and cardiac surgery, in patients bearing implanted devices, and in patients residing in rehabilitation or long-term care facilities, where  S. aureus  colonization and/or infection are frequent. Given the propensity of  S. aureus  to develop antibiotic and antiseptic resistance, these new products and methods should not be based on the use of either antibiotics or antiseptics, and should function in particular in the prevention and/or treatment of MRSA. They should also have few side effects and be available at a reasonable cost. 
     The present invention is directed to a composition comprising at least one  Corynebacterium  sp. and at least one  Staphylococcus  sp., preferably comprising at least one  Corynebacterium  sp. and at least  S. pasteuri . The composition according to the invention may comprise any of the preferred characteristics described below relative to the pharmaceutical composition, which is itself a preferred embodiment of the composition. In particular, the composition comprises at least one  Corynebacterium  sp. and  Staphylococcus  pasteuri, wherein said at least one  Corynebacterium  sp. is selected from  C. accolens, C. propinquum, C. pseudodiphtheriticum, C. amycolatum, C. glutamicum, C. aurimucosum, C. tuberculostearicum , and  C. afermentans , preferably  C. accolens  and/or  C. propinquum . Preferably, the composition further comprises  Staphylococcus epidermidis. Preferably, the composition comprises at least  10 3  CFUs of  Corynebacterium  sp., at least 10 3  CFUs of  Staphyloccocus pasteuri , and, optionally, at least 10 3  CFUs of  Staphylococcus epidermidis  per dose. Preferably, the composition comprises a total of at least 10 3  bacterial CFUs per dose, preferably at least 1.2×10 3 , more preferably at least 1.4×10 3 , even more preferably at least 3×10 3  bacterial CFUs per dose. Preferably, the ratio of  Corynebacterium  sp. to  Staphylococcus  pasteuri to  Staphyloccocus epidermidis  is comprised in the range of 1:0.01:0.01 to 1:1:1. Preferably, the composition further comprises at least one excipient, preferably a pharmaceutically acceptable excipient. Preferably said at least one excipient comprises at least one lyoprotectant, preferably selected from peptone, glycerol, lactose, gelatin, glucose, sucrose, trehalose, dextran, maltodextrin, adonitol, and sodium glutamate. Preferably, the composition is lyophilized or freeze-dried. Preferably, the composition further comprises at least one gelling agent, preferably a pharmaceutically acceptable gelling agent. 
     Preferably, the present invention is directed to a pharmaceutical composition comprising at least one  Corynebacterium  sp. and at least one  Staphylococcus  sp., preferably comprising at least one  Corynebacterium  sp. and at least  S. pasteuri . Said at least one  Corynebacterium  sp. is preferably selected from  C. accolens  and  C. propinquum , or comprises both  C. accolens  and  C. propinquum . The present invention is further directed to a pharmaceutical composition comprising at least one  Corynebacterium  sp.,  S. pasteuri , and at least one additional  Staphylococcus  sp., preferably  S. epidermidis . Thus, according to a particularly preferred embodiment, the present invention is further directed to a pharmaceutical composition comprising  C. accolens  and/or  C. propinquum, S. pasteuri  and  S. epidermidis . The invention is further directed to said composition for use as a medicament, in particular in the prevention and/or treatment of  S. aureus  colonization. Indeed, the inventors have surprisingly found that a composition comprising a combination of at least one  Corynebacterium  sp. and  S. pasteuri  or a combination of at least one  Corynebacterium  sp.,  S. pasteuri  and  S. epidermidis  can prevent and/or treat  S. aureus  colonization. 
     The combination of these bacterial species is particularly advantageous as the inventors have surprisingly shown that the three bacterial species  C. accolens, S. pasteuri  and  S. epidermidis , individually inhibit  S. aureus  colonization, with  C. accolens  and  S. pasteuri  having a strong synergistic effect, inhibiting  S. aureus  growth by more than 95%. The inventors have also surprisingly shown that other  Corynebacterium  sp., such as  C. propinquum  similarly inhibit  S. aureus  colonization, with  C. propinquum  and  S. pasteuri  having a particularly strong synergistic effect, inhibiting  S. aureus  growth by more than 98%. Moreover, growth of  C. accolens  is potentiated by  S. pasteuri , as  C. accolens  does not grow in the absence of  S. pasteuri  in certain conditions. The presence of  S. pasteuri , or of both  S. pasteuri  and  S. epidermidis , improves persistence of  Corynebacterium  sp., such as  C. accolens  or  C. propinquum  by enabling the establishment of a biofilm. Furthermore, although a combination of  C. accolens  and  S. epidermidis  has an antagonistic tendency, reducing the inhibitory effect on  S. aureus  growth seen with  S. epidermidis  alone, the combination of all three bacterial species also has surprisingly high anti- S. aureus  activity, inhibiting  S. aureus  growth by more than 95%. As  S. epidermidis  is an essential colonizer of the nasal flora, it is preferably included in the pharmaceutical combination.  S. epidermidis  may notably provide a protective bacterial layer in vivo, contributing to the prevention of  S. aureus  re-establishment. Thus, a pharmaceutical composition comprising at least one  Corynebacterium  sp.,  S. pasteuri  and  S. epidermidis  prevents  S. aureus  colonization, and is particularly advantageous. 
     The pharmaceutical composition of the present invention is advantageous as the composition is not based on the administration of antibiotics or antiseptics, but rather on the administration of at least two, preferably three bacterial species, thereby minimizing the risk of the emergence of further  S. aureus  resistance. Advantageously, said composition can be administered for longer periods of time than current methods. Advantageously, the present composition can prevent colonization by antibiotic resistant  S. aureus , such as MRSA, in a patient. Advantageously, the present composition can treat colonization by antibiotic resistant  S. aureus , such as MRSA, in a patient. The composition of the invention is also advantageous as none of the selected bacterial species possess virulence traits. Even more advantageously, all selected bacterial species are commonly detected in the nasal microflora and/or on the skin of healthy subjects. 
     Prevention and/or treatment of colonization via the pharmaceutical composition of the present invention is particularly advantageous as colonization is associated with both an increased risk of endogenous infection and transmission. Thus, preventing and/or treating  S. aureus  colonization represents the most effective way of reducing the total number of  S. aureus  infections. Furthermore, current methods for treating  S. aureus  are not recommended for prophylactic use due to the possibility of increasing antibiotic resistance. In contrast, the pharmaceutical composition according to the invention can be administered prophylactically to subjects. The pharmaceutical composition according to the invention can also be administered to subjects colonized by  S. aureus.    
     The term “patient” or “subject” is defined herein as any human individual, regardless of their age. In a preferred embodiment, the subject is hospitalized for any reason. In a more preferred embodiment, the subject is hospitalized for cardiac or orthopedic surgery, bears an implanted device, or resides in a rehabilitation or long-term care facility. In cases where the subject is not colonized by  S. aureus  at the time of hospital admission, the pharmaceutical composition of the invention may be used prophylactically, to prevent later colonization by  S. aureus . Alternatively, in cases where the subject is already colonized by  S. aureus  at the time of hospital admission, the pharmaceutical composition of the invention may be used to treat colonization by  S. aureus.    
     The subject may be an adult or child. The term “adult” refers herein to an individual of at least 16 years of age. The term “child” comprises infants from 0-1 years of age and children from 1-8 years of age, 8-12 years of age, and 12-16 years of age. The term “child” further comprises neonatal infants from birth to 28 days of age and post-neonatal infants from 28 to 364 days of age. The composition may be administered to an adult or a child, including neonatal infants. The pharmaceutical composition of the invention is particularly advantageous as existing treatment methods using antibiotics are limited in children due to unwanted side effects. 
     The pharmaceutically acceptable composition comprises a sufficient quantity of each of the bacterial strains to be therapeutically effective. As a non-limiting example, the pharmaceutical composition may comprise at least 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , 10 10 , 10 11 , or 10 12  colony forming units (CFUs) of each of the bacterial strains, or a total of at least 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 , 10 9 , 10 10 , 10 11 , or 10 12  CFUs of all bacterial strains taken together. The quantities of each bacterial strain need not be identical. The ratio of the amount of each of the bacterial strains to the other one or more strains is also such that the pharmaceutically acceptable composition is therapeutically effective. As a non-limiting example, when two strains are comprised in the pharmaceutical composition, the ratio of one strain to the other may range from 1:0.01 to 1:2, including for example, ratios of 1:0.02, 1:0.04, 1:0.2, 1:0.4, or 1:1. As a non-limiting example, when three strains are comprised in the pharmaceutical composition, the ratio of one strain to each of the others may range from 1:0.01:0.01 to 1:1:1, including for example, ratios of 1:0.02:0.02, 1:0.1:0.1, or 1:0.2:0.2. 
     In a preferred embodiment, the pharmaceutical composition of the present invention comprises from 10 3  to 10 12  CFUs of the at least one  Corynebacterium  sp., from 10 3  to 10 12  CFUs of  S. pasteuri , and, optionally, from 10 3  to 10 12  CFUs of  S. epidermidis  per dose. More preferably, the composition comprises from 10 4  to 10 10  CFUs of the at least one  Corynebacterium  sp., from 10 4  to 10 10  CFUs  S. pasteuri  and, optionally, from 10 4  to 10 10  CFUs of  S. epidermidis  per dose. Even more preferably, the composition comprises 10 5  to 10′ CFUs of the at least one  Corynebacterium  sp., 10 5  to 10 9  CFUs  S. pasteuri  and, optionally, from 10 5  to 10 9  CFUs of  S. epidermidis  per dose. 
     Preferably, the composition of the present invention comprises a total bacterial concentration of at least 10 3 , 10 4 , 10 5 , 10 6 ,  10   7 , 10 8 , 10 9 ,  10   10 , 10 11 , or 10 12  CFUs, preferably at least 1.2, 1.4, 2 or 3×10 3  CFUs, at least 5, 5.02, 5.04, 5.2, or 5.4×10 3  CFUs, at least 1.02, 1.04, 1.2, 1.4, 1.5, 2 or 3×10 4  CFUs, at least 5, 5.02, 5.04, 5.2, or 5.4×10 4  CFUs, at least 1.02, 1.04, 1.2, 1.4, 1.5, 2, or 3×10 5  CFUs, at least 1.02, 1.04, 1.2, 1.4, 2, or 3×10 6  CFUs, at least 1.02, 1.04, 1.2, 1.4, 2, or 3×10 7  CFUs, at least 1.02, 1.04, 1.2, 1.4, 2, or 3×10 8  CFUs, at least 1.02, 1.04, 1.2, 1.4, 2 or 3×10 9  CFUs, at least 10 10  CFUs, at least 1.02, 1.04, 1.2, 1.4, 2 or 3×10 10  CFUs, at least 1.02, 1.04, 1.2, 1.4, 2 or 3×10 11  CFUs, or at least 1.02, 1.04, 1.2, 1.4, 2 or 3×10 12  CFUs per dose. 
     The term “dose” is defined herein as amount of the pharmaceutical composition that is administered at a given time. Preferably, the dose administered is therapeutically effective. 
     The dose may be expressed herein in terms of weight, volume, or CFUs of the pharmaceutical composition. 
     The term “colony forming unit” or “CFU” is defined herein as a unit used to indicate the number of viable bacteria in a sample, wherein one colony forming unit corresponds to one viable bacterial cell. 
     In the pharmaceutical composition of the present invention, the ratio in CFUs of the at least one  Corynebacterium  sp. to the at least one  Staphyloccocus  sp. (e.g. the ratio of the at least one  Corynebacterium  sp., preferably  C. accolens:S. pasteuri ) is preferably comprised in the range from 1:0.01 to 1:2, more preferably 1:0.01 to 1:1. In the pharmaceutical composition of the present invention, the ratio in CFUs of the at least one  Corynebacterium  sp. to  S. pasteuri  to  S. epidermidis  is preferably comprised in the range from 1:0.01:0.01 to 1:1:1. Advantageously, the ratio of the at least one  Corynebacterium  sp., preferably  C. accolens , to  S. pasteuri  to  S. epidermidis  is comprised in the range from 1:0.02:0.02 to 1:1:1, preferably from 1:0.1:0.1 to 1:1:1, even more preferably from 1:0.2:0.2 to 1:1:1. 
     As a non-limiting example, the at least one  Corynebacterium  sp. may be selected from  C. accolens, C. propinquum, C. pseudodiphtheriticum, C. amycolatum, C. glutamicum, C. aurimucosum, C. tuberculostearicum , or  C. afermentans  in the pharmaceutical composition. The above-mentioned species have notably all been isolated from the nares and/or the skin. The similar effects of different  Corynebacterium  spp. are notably illustrated in the examples. In some cases, two or more  Corynebacterium  spp. may be present in the pharmaceutical composition. For example,  C. accolens  may be combined with at least one other  Corynebacterium  sp., for example selected from one or more of those listed above, such as  C. propinquum.    
     According to a preferred embodiment, the at least one  Corynebacterium  sp. is selected from  C. accolens, C. propinquum, C. pseudodiphtheriticum, C. amycolatum, C. glutamicum, C. aurimucosum, C. tuberculostearicum , and  C. afermentans . According to a more preferred embodiment, the at least one  Corynebacterium  sp. comprises  C. accolens  or  C. propinquum , or a combination of both  C. accolens  and  C. propinquum , according to any of the embodiments described herein. The similar effects of different  C. accolens  strains are notably illustrated in the examples. 
     In the context of the pharmaceutical composition, any strain of  S. epidermidis  may be used. As a non-limiting example, a strain of  S. epidermidis  may be selected from the strains isolated from the nares. 
     In the context of the pharmaceutical composition, any strain of the  S. pasteuri  species may be used. The similar effects of different  S. pasteuri  strains are notably illustrated in the examples. 
     The pharmaceutical composition may be administered prophylactically, in the absence of detection of  S. aureus , preferably to the skin and/or nares, more preferably to the anterior nares. Alternatively, the pharmaceutical composition may be administered following detection and elimination of  S. aureus  on the skin or in the nares. Alternatively, the pharmaceutical composition may be administered in the absence of testing. 
     The composition may be administered to a subject one or more times daily (e.g. one, two, three, or four times) and can be administered for several consecutive days (e.g. for one, two, three, four, five, six, seven, eight, nine, ten days or more), weeks (e.g. for one, two, three, four, five, six, seven, eight, nine, ten weeks or more), or months (e.g. for one, two, three, four, five, six months or more). In a preferred embodiment, the composition is administered 1 to 3 times per day for 8 to 12 days, preferably in subjects hospitalized for cardiac or orthopedic surgery. In an alternative preferred embodiment, the composition is administered for weeks or months in subjects bearing an implanted device or residing in a rehabilitation or long-term care facility, or for the duration of the healing of an accidental or surgical wound. In a particularly preferred embodiment, the composition is administered 1 to 3 times per day for one to four weeks, or for one to six months, in subjects bearing an implanted device, residing in a rehabilitation or long-term care facility, or healing from an accidental or surgical wound. In an even more preferred embodiment, the composition is administered for the duration of a hospital stay, the duration of the presence of an implanted device, the duration of residence in a rehabilitation or long-term care facility, or for the duration of the healing of an accidental or surgical wound, preferably 1 to 3 times per day. 
     Alternatively, the composition may be administered to a subject intermittently (e.g. every other day, every two days, or as necessary) or cyclically (e.g. administration for several days in a row, followed by an absence of administration, or “withdrawal,” for several days, at the end of which the cycle is repeated). Preferably, the composition is administered for at least 1 day followed by a period of withdrawal for at least 1 day, followed by the administration for at least 1 day (for example 1 day, 2 days, 3 days, etc.). preferably, this cycle is reproduced several times. Preferably, the composition is administered 1 to 3 times per day. More preferably, the composition is administered for 1 to 12 days followed by a period of withdrawal for 1 to 12 days, followed by the administration for 1 to 12 days. In a preferred embodiment, the composition is administered for 8-12 days followed by a period of withdrawal. 
     Alternatively, the composition may be administered on demand. 
     If a protective effect is observed following administration, administration may be repeated as appropriate to maintain said protective effect. If  S. aureus  colonization is detected following administration of the composition, the administration regimen should be repeated. 
     The duration and frequency of administration of the composition can be adapted by the skilled person, based on their general knowledge. In particular, the adaptation of these parameters can depend on the length of time during which it is desired that  S. aureus  colonization is reduced or is absent in the nares and/or on the skin of a subject. For example, it may be desired that  S. aureus  colonization is absent for the duration of a hospitalization. 
     In a preferred embodiment of the invention, the pharmaceutical composition further comprises at least one pharmaceutically acceptable excipient. 
     The term “pharmaceutically acceptable excipient” is defined herein as a component, or combination of components, that is compatible with the pharmaceutical composition, does not generate unwanted side-effects in the patient, and that is generally considered to be non-toxic. A pharmaceutically acceptable excipient is most commonly implicated in facilitating administration of the composition, increasing product shelf-life or efficacy, or improving the solubility or stability of the composition. The pharmaceutically acceptable excipient is generally considered to be pharmacologically inactive. However, in some cases, the excipient itself may also have a therapeutic effect, for example, by making it more difficult for  S. aureus  to colonize the treated site (i.e. site of administration). 
     Pharmaceutically acceptable excipients or carriers are well-known in the prior art and can easily be adapted by the skilled person based on the desired galenic formulation of the composition. The galenic formulation, method of administration, and dosage can further be determined based on widely-accepted criteria for adapting patient treatments, including their general health, age, weight, tolerance to treatment, etc., as necessary. 
     The pharmaceutical composition of the present invention may be administered topically to the epithelium (e.g. the skin) and/or mucus membranes. Preferably, the pharmaceutical composition of the present invention may be administered to the nares, sinuses, or on the axilla, groin, inguinal and perirectal regions, or elsewhere on the skin or mucus membranes. According to a preferred embodiment, the composition is administered to the nares. 
     The term “nares” as defined herein comprises both the anterior nares or nostrils and the nasal cavity. Preferably, the pharmaceutical composition of the invention is administered to the anterior nares, or nostrils. 
     While  S. aureus  may colonize various sites on the human body, it is recognized that its primary ecological niche is the anterior nares, from which it can spread to other tissues or organs (Kluytmans et al., 1997). Much like the skin (e.g. forearm skin), the anterior nares are lined by skin-like, fully keratinized, squamous epithelium with hairs, sebaceous glands and sweat glands. Genetic studies have moreover demonstrated that microbial communities from these two physically distinct niches share identical compositional patterns (Yan et al., 2013). Thus,  S. aureus  colonization is similar in the skin and anterior nares, with the skin furthermore representing an excellent and easily accessible model for both of these sites. 
     Advantageously, the composition of the present invention comprises any suitable pharmaceutical preparation for administration to the skin and/or mucus membranes, such as a patch, gel, cream, lotion, ointment, film, emulsion, or salve. Advantageously, the viscosity or texture of the composition is modulated to improve application or efficacy (e.g. contact time). Advantageously, the composition is such that it does not cause adverse effects to the nasal epithelium. Even more advantageously, the pH and/or the osmolarity of the composition is similar to that of the nares. 
     As the pH of the nasal epithelium is generally within the range of 5.5 to 7.5, the pharmaceutical composition of the present invention advantageously has a pH in said range. 
     The one or more pharmaceutically acceptable excipients included in the composition of the present invention may further comprise one or more antioxidants, buffers, bulking substances, suspending agents, solubilizing agents, lyoprotectants, matrix forming additives, film formers, humectants, diluents, solvents, plasticizers, oily/emulsifying/aqueous bases, gelling agents, preservatives, tonicity adjusting agents, vehicles, and stabilizers. 
     As a non-limiting example, the composition of the present invention may comprise at least one pharmaceutically acceptable excipient or carrier well known to the skilled person. Said at least one excipient may be selected from water, glycerin, mineral oils (e.g. vaseline, paraffin), animal oils or fats (e.g. beeswax or wool fat), semi-solid hydrocarbons (oleaginous), or vegetable oils (e.g. coconut oil, mango butter, palm oil, soybean oil, olive oil, shea butter and cacao butter, essential oil), glyceride, xanthan gum, lactose, dextran, mannitol, methylcellulose, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, sodium carboxy methylcellulose, carboxypropyl methylcellulose, polyethelyne glycol, polypropylene glycol, hyaluronic acid, starch-based biodegradeable polymers, tragacanth, pectin, chitin and chitosan derivatives, carrageenan, guar gum, agar, alginate, gelatin, fibrin, albumin, phosphate buffered saline, Polycarbophil, hydrogenated palm oil, glyceride, Carbomer 934P, macrogol, methyl paraben, glyceryl polymethacrylate, cyanoacrylate, triethanolamine, sorbic acid, NaOH, Carbopols (e.g. Carbopol 974P), diazolidinyl urea, Poloxamer 184, dimethicone, cellulose gum, lactic acid, methyl paraben, propylparaben, polyvinyl pyrrolidone, polyvinyl pyrrolidone-vinyl acetate, polyvinyl alcohol, polyacrylic acid, polyacrylamide, homo- and copolymers of acrylic acid crosslinked with a polyalkenyl polyether, sodium hydroxide, sodium chloride, and potassium chloride, and the like. 
     In a preferred embodiment, the pharmaceutically acceptable composition is a gel, preferably a bioadhesive or mucoadhesive gel. The term “gel” is defined herein as a dispersion of particles interpenetrated with a liquid to generate a semisolid material. The term “bioadhesive gel” is defined herein as a gel which adheres to a biological surface (e.g. stratified squamous epithelium such as the skin or anterior nares). The term “mucoadhesive gel” is defined herein as a gel which adheres to a mucus coat (e.g. mucus membrane). 
     In a preferred embodiment, the at least one pharmaceutically acceptable excipient is a gelling agent selected from hydroxypropyl methylcellulose, hydroxyethyl cellulose, chitosan and derivatives thereof, for example chitin, carrageenan and derivatives thereof, alginate and derivatives thereof, pectin and derivatives thereof, homo- and copolymers of acrylic acid crosslinked with a polyalkenyl polyether, or mixtures thereof. 
     If a tonicity adjusting agent is present, said tonicity adjusting agent is preferably selected from potassium chloride, mannitol, dextrose, glycerin, or sodium chloride. 
     In a preferred embodiment, the pharmaceutical composition comprises at least one gelling agent and at least one tonicity adjusting agent. In a preferred embodiment, sodium chloride is present in the pharmaceutical composition at an isotonic concentration. 
     If a vehicle is present, said vehicle is preferably selected from water, a water miscible solvent (e.g. glycerin) or a water immiscible solvent (e.g. vegetable oil). 
     If a preservative is present, said preservative is preferably selected from benzyl alcohol, cresols, benzoic acid, phenol, parabens and sorbic acid. 
     If a stabilizer is present, said stabilizer is preferably selected from surfactants, polymers, polyols, a poloxamer, albumin, gelatin, trehalose, proteins, sugars, polyvinylpyrrolidone, N-acetyl-tryptophan (“NAT”)), caprylate (i.e. sodium caprylate), a polysorbate (i.e. P80), amino acids, and divalent metal cations such as zinc. 
     According to a further aspect of the invention, bacteria are lyophilized or freeze-dried. “Lyophilization” is a process well known to the skilled person for the removal of water from frozen bacterial cultures by sublimation under reduced pressure. General methods are described in “Lyophilization: Introduction and Basic Principles” (Jennings, 1999). Said process includes the following steps: providing an aqueous formulation comprising viable bacteria, freezing, primary drying (sublimation), and secondary drying (desorption). Lyophilized bacteria are obtained from said process. 
     According to a preferred mode, bacteria are lyophilized in the presence of a lyoprotectant. The lyoprotectant may be intracellular or extracellular or a combination of both. Preferably, said lyoprotectant is selected from peptone, glycerol, lactose, gelatin, glucose, sucrose, trehalose, dextran, maltodextrin, adonitol, and sodium glutamate. 
     According to a preferred mode, bacteria are lyophilized in presence of a matrix forming additive. Preferably, said matrix forming additive is mannitol or skim milk. 
     Preferably, lyophilized bacteria are stored at refrigeration temperatures (e.g. +3 to +6° C.) or at room temperature (e.g. between 20 and 25° C.). 
     Preferably, each bacterial species is lyophilized separately. According to a first preferred embodiment, each lyophilized bacterial species is reconstituted separately with at least one pharmaceutically acceptable excipient just before use. Reconstituted bacteria may then be administered individually or admixed prior to administration. According to a second preferred embodiment, all bacterial species are admixed together following lyophilization. In this preferred embodiment, lyophilized bacteria are reconstituted together with at least one pharmaceutically acceptable excipient just before use. According to a third preferred embodiment, all bacterial species are admixed together prior to lyophilization. In this preferred embodiment, the mixture is reconstituted with at least one pharmaceutically acceptable excipient just before use. 
     The “reconstitution” of the lyophilized bacterial composition is defined herein as placing the composition in contact with a specific amount of at least one pharmaceutically acceptable excipient (e.g. a liquid or gel), said excipient hydrating the lyophilizate. Preferably, the mixture is agitated or stirred to ensure complete hydration. Preferably, reconstitution is performed within the range of 17° C. to 37° C., more preferably at or above room temperature (20° C. to 25° C.), even more preferably at room temperature. 
     Preferably, the composition is reconstituted immediately before use. If the reconstituted composition is not administered immediately, the reconstituted composition is preferably refrigerated until administration. If the reconstituted composition is not administered immediately and is not refrigerated, the reconstituted composition is preferably administered the same day as reconstitution. The skilled person can easily select appropriate reconstitution and storage conditions according to his general knowledge. 
     According to a first preferred embodiment, separately reconstituted bacteria are administered separately, one after the other. According to a second preferred embodiment, separately reconstituted bacteria are admixed prior to administration for simultaneous application. According to a third preferred embodiment, bacteria that are reconstituted together are administered simultaneously. 
     Alternatively, viable bacteria may be stored at temperatures comprised between about +4° C. and +8° C. (e.g. for several days), at temperatures comprised between about −25° C. and −40° C. (e.g. for several weeks), or at temperatures comprised between about −72° C. and −85° C. (e.g. for several years). Lyophilized bacteria may also be stored at temperatures comprised between +4° C. and +8° C. for several days following reconstitution. Appropriate storage conditions at each of these temperature ranges are well-known to the person skilled in the art. 
     The present invention further comprises the pharmaceutical composition for use in the prevention and/or treatment of  S. aureus  colonization. Said pharmaceutical composition for use in the prevention and/or treatment of  S. aureus  colonization comprises all aspects of the pharmaceutical composition of the invention as described herein. Preferably, the invention comprises the pharmaceutical composition for use in the prevention and/or treatment of nasal colonization by  S. aureus , more preferably, comprising the administration of the composition to the anterior nares, and/or for use in the prevention and/or treatment of skin colonization by  S. aureus . Skin colonization by  S. aureus  is advantageously prevented and/or treated in a subject having increased susceptibility to said colonization, for example in a subject having an eczema, such as atopic dermatitis, or having diabetes mellitus. 
     In a preferred embodiment, the invention comprises the pharmaceutical composition for use in the prevention and/or treatment of colonization by antibiotic-resistant  S. aureus , preferably for use in the prevention and/or treatment of colonization by methicillin-resistant  S. aureus . More preferably, the pharmaceutical composition is used in the prevention and/or treatment of nasal colonization by methicillin-resistant  S. aureus . The term “methicillin-resistant” indicates the lack of susceptibility of a bacterial strain to the bactericidal effects of methicillin. MRSA strains may comprise resistance to additional antibiotics (e.g. penicillin, vancomycin, mupirocin, quinolones, etc.). Alternatively, the pharmaceutical composition of the invention may be used in the prevention and/or treatment of nasal colonization by methicillin-sensitive  S. aureus . Methicillin-sensitive strains are susceptible to the bactericidal effects of methicillin but may comprise resistance to other antibiotics. 
     The term “colonization by  S. aureus ” is defined herein as the presence of at least one strain of  S. aureus  on a body surface, but that does not induce a detectable immune response and/or that does not invade tissue or otherwise cause tissue damage. Alternatively, colonization may be considered to be the presence of  S. aureus  in the absence of infection. Colonization may be temporary, intermittent, long-term or even permanent in some cases. In particular, colonization by  S. aureus  may occur in the nares, sinuses, throat, gastrointestinal tract, or on the axilla, groin, inguinal and perirectal regions, on wounds, or elsewhere on the skin or mucus membranes.  S. aureus  colonization is a risk factor for later  S. aureus  infection. 
     The term “infection by  S. aureus ” is defined herein as the presence of at least one strain of  S. aureus  on a body surface inducing a detectable immune response and/or undergoing uncontrolled bacterial growth. The immune response may be specific or non-specific (e.g. fever).  S. aureus  infection can cause skin and soft tissue infections (SSTIs), such as abscesses, furuncles, carbuncles, boils, impetigo, bacterial focculitis or cellulitis, stys, rash, staphylococcal scalded skin syndrome, necrotizing fasciitis, pneumonia, wound infection, endocarditis, gangrene, osteomyelitis, septic arthritis, septicemia, etc. 
     The term “nasal colonization by  S. aureus ” is more specifically defined herein as the presence of  S. aureus  bacteria in the nares. 
     The term “nasal decolonization” is defined herein as a method for reducing or eradicating  S. aureus  from the nares. Complete decolonization is defined herein as the absence of detection of  S. aureus  in the nares for at least two consecutive weeks. Partial decolonization is defined herein by the reduction of  S. aureus  in the nares by at least 50% for at least two consecutive weeks as compared to the level of  S. aureus  in the nares prior, preferably by at least 80%, more preferably by at least 90%, more preferably by at least 95%, and even more preferably by at least 99%. 
     The presence of  S. aureus  bacteria in the nares can be detected by methods well-known in the art, comprising obtaining a sample from the anterior nares, for example via a nasal swab, and detecting  S. aureus. S. aureus  can be detected at the species and/or strain level. Detection methods include, for example, culture-based methods (e.g. sample plating on selective media, such as chromogenic and/or blood agar) and molecular diagnostic methods (e.g. PCR, real-time PCR, ribotyping, pulsed-field gel electrophoresis, random amplified polymorphic DNA sequencing, BOX-A1R-based repetitive extragenic palindromic-PCR (BOX-PCR), multilocus sequence typing, whole genome sequencing, etc.). 
     According to another aspect, the present invention comprises a method of preventing and/or treating  S. aureus  colonization in a human subject in need thereof, comprising administering a therapeutically effective dose of the pharmaceutical composition according to the invention. All aspects of the pharmaceutical composition as described herein are comprised in the method of preventing and/or treating  S. aureus  colonization. 
     The term “preventing” as used herein are not meant be an exclusively absolute term. Indeed, the term “prevention” as used herein may be a delay in colonization by  S. aureus , a reduction in the level of colonizing  S. aureus , or a reduction in the frequency of  S. aureus  colonization. 
     The terms “treating” or “treatment” and the like as used herein refer more particularly to a reduction in the level of  S. aureus  colonization at the treated site. Said reduction in the level of colonizing  S. aureus  may be partial or complete. 
     The term “therapeutically effective dose” as used herein refers to an amount of the pharmaceutical composition that is sufficient for preventing and/or treating  S. aureus  colonization at least partially, preferably completely, at the treated site. In the context of prevention and/or treatment of  S. aureus  colonization, this term notably refers to an amount sufficient to delay  S. aureus  colonization or to reduce the level or frequency of  S. aureus  colonization. The therapeutically effective dose may be administered in one or more administrations. In some cases, the pharmaceutical composition may be used to prevent and/or treat  S. aureus  colonization at multiple sites within a single subject (e.g. to both the skin and the anterior nares). In this case, a therapeutically effective dose is administered to each site, and according to the appropriate schema of administration. 
     Accordingly, the present invention encompasses the use of the pharmaceutical composition for preventing and/or treating colonization by  S. aureus  based on the modalities described herein. 
     According to a first aspect, the method of preventing and/or treating  S. aureus  colonization comprises the administration of the pharmaceutical composition in which the ratio of  Corynebacterium  sp. to  S. pasteuri  is comprised in the range of 1:0.1 to 1:2, or in which the ratio of  Corynebacterium  sp. to  S. pasteuri  to  S. epidermidis  is comprised in the range of 1:0.01:0.01 to 1:1:1. According to a second aspect, the method of preventing and/or treating  S. aureus  colonization comprises the administration of the pharmaceutical composition having at least 10 3  CFUs of  Corynebacterium  sp., at least 10 3  CFUs of  S. pasteuri , and, optionally, at least 10 3  CFUs of  S. epidermidis  per dose. Preferably, the method of preventing and/or treating  S. aureus  colonization comprises the administration of the pharmaceutical composition having from 10 3  to 10 12  CFUs of  Corynebacterium  sp., from 10 3  to 10 12  CFUs of  S. pasteuri , and, optionally, from 10 3  to 10 12  CFUs of  S. epidermidis  per dose. According to a preferred aspect, the method of preventing and/or treating  S. aureus  colonization comprises the administration of the pharmaceutical composition comprises a total of at least 10 3 , preferably at least 1.2, 1.4, 2 or 3×10 3  CFUs per dose. Preferably, said pharmaceutical composition is lyophilized or freeze-dried. 
     Preferably, the method of preventing and/or treating  S. aureus  colonization comprises the administration of the pharmaceutical composition further comprising at least one pharmaceutically acceptable excipient. According to a first aspect, said at least one pharmaceutically acceptable excipient is a lyoprotectant, preferably selected from peptone, glycerol, lactose, gelatin, glucose, sucrose, trehalose, dextran, maltodextrin, adonitol, and sodium glutamate. According to a second aspect, said at least one pharmaceutically acceptable excipient is a gelling agent. Said at least one pharmaceutically acceptable excipient may be selected from those listed above, or from excipients that are well known in the art. 
     Preferably, the method of preventing and/or treating  S. aureus  colonization comprises the administration of the pharmaceutical composition to the anterior nares and/or the skin. 
     Preferably, the method of preventing and/or treating  S. aureus  colonization of the present invention prevents or reduces  S. aureus  nasal colonization. Preferably, the method of preventing and/or treating  S. aureus  colonization of the present invention prevents or reduces MRSA or MSSA nasal or skin colonization. 
     A further object of the present invention is a method for preventing nasal or skin colonization by  S. aureus  in a subject comprising:
         a) determining if  S. aureus  is present in the nares or on the skin; and   b) administering the pharmaceutical composition of the invention to said subject if  S. aureus  is not detected.       

     A further object of the present invention is a method for treating nasal or skin colonization by  S. aureus  in a subject comprising:
         a) determining if  S. aureus  is present in the nares or on the skin; and   b) administering the pharmaceutical composition of the invention to said subject if  S. aureus  is detected.       

     A further object of the present invention is the pharmaceutical composition for use in the prevention and/or treatment of  S. aureus , comprising
         a) determining if  S. aureus  is present in the nares or on the skin and   b) administering said pharmaceutical composition.       

     Preferably, said  S. aureus  present in the nares or on the skin according to any of the above aspects is MRSA or MSSA, preferably MRSA. 
     The present invention also comprises the use of the composition according to the invention for the manufacture of a medicament for the prevention and/or treatment of colonization by  S. aureus.    
     The present invention also comprises the use of the composition according to any of the embodiments described herein in the prevention and/or treatment of colonization by  S. aureus , preferably in the nares and/or on the skin. 
     The present invention also comprises a method for preventing and/or treating colonization by  S. aureus  in a subject in need thereof, preferably in the nares and/or skin, comprising administering the composition described herein. 
     The subject of any of the methods provided herein may be any subject previously identified in the context of the use of said composition. In particular, said subject may be a subject hospitalized for cardiac or orthopedic surgery, a subject bearing an implanted device, a subject residing in a rehabilitation or long-term care facility, a subject having an accidental or surgical wound, a subject having an eczema, such as atopic dermatitis, or a subject having diabetes mellitus. 
     The present invention has for further object a kit comprising the composition, preferably the pharmaceutical composition, described herein, a gel suitable for nasal and/or skin use and, in case of nasal administration, a means for nasal administration. The present invention has for further object a kit comprising the pharmaceutical composition described herein and:
         a gel, a cream, a lotion, an ointment, an emulsion, or a salve, suitable for nasal use and a means for nasal administration, or   a gel, a cream, a lotion, an ointment, an emulsion, or a salve, suitable for skin use.       

     Preferably, the kit comprises:
         a) the pharmaceutical composition comprising  C. accolens, S. pasteuri , and, optionally,  S. epidermidis , and at least one pharmaceutically acceptable excipient, said composition having a lyophilizate formulation,   b) at least one pharmaceutically acceptable component,   c) a means for nasal administration of said composition, and   d) optionally, a notice of use.       

     Preferably, the at least one pharmaceutically acceptable component of b) is an aqueous solution for the reconstitution of said lyophilizate or a gelling agent. More preferably, the component of b) comprises both an aqueous solution for the reconstitution and a pharmaceutically acceptable gelling agent. 
       Corynebacterium  sp., may preferably be selected from  C. accolens, C. pseudodiphtheriticum, C. amycolatum, C. glutamicum, C. aurimucosum, C. tuberculostearicum, C. afermentans , and/or  C. propinquum  in the kit.  C. accolens  may notably be combined with at least one other  Corynebacterium  spp., such as  C. propinquum  in the kit. According to a preferred embodiment,  C. accolens  is replaced by  C. propinquum  in the kit. 
     A means is also provided herein for dispensing the pharmaceutical composition such that it is applied to the epithelium or mucous membranes, preferably to the nares. The term “means” is defined herein as any device for local, topical application. Preferably, the means for dispensing the pharmaceutical composition also mixes the lyophilized bacteria with the at least one pharmaceutically acceptable excipient, when lyophilized bacteria are used. 
     In cases where the pharmaceutical composition is present as multiple doses in a single means, a specific means for measuring a single dose may be further comprised. As an example, a single dose may be the equivalent of one or two depressions of a dispenser. 
    
    
     
       FIGURE LEGENDS 
         FIG. 1 : Growth of  C. accolens  in co-culture with  S. pasteuri  or  S. epidermidis    
       Bacterial growth of  C. accolens  AF2345 was determined in co-culture with either (A)  S. pasteuri  AF2653 or (B)  S. epidermidis  AF2302, according to the methods described in Example 2.  C. accolens  colonies were observed after 72 hours (A) or 7 days (B), at the same magnification.  S. pasteuri  and  S. epidermidis  spots are indicated by an arrow.  C. accolens  colonies are visible in co-culture with  S. pasteuri  with the naked eye, but are smaller with increasing distance from the  S. pasteuri  spot. In contrast,  C. accolens  colonies grown in co-culture with  S. epidermidis  are much smaller than those observed even at a distance from the  S. pasteuri  spot in  FIG. 1A , and are not visible with the naked eye. 
         FIG. 2 : Mixed biofilms with  C. accolens    
       Bacterial growth of  C. accolens  AF2345 alone or as part of a single or mixed biofilm in the presence of  S. pasteuri, S. epidermidis , or both  S. pasteuri  and  S. epidermidis  was evaluated according to the methods described in Example 8. Growth was observed in the presence of either  S. pasteuri  alone or both  S. pasteuri  and  S. epidermidis . No significant difference in growth occurred between these two conditions (p=0.0651) 
         FIG. 3 : Mixed biofilms with  C. propinquum    
       Bacterial growth of  C. propinquum  AF1882 alone or as part of a single or mixed biofilm in the presence of  S. pasteuri, S. epidermidis , or both  S. pasteuri  and  S. epidermidis  was evaluated according to the methods described in Examples 8 and 9. Growth was observed in all conditions. No significant difference in growth of  C. propinquum  occurred when in the presence of either  S. pasteuri  alone or both  S. pasteuri  and  S. epidermidis  (p=0.0748). 
         FIG. 4 : Production of extracellular matrix when  C. accolens  is co-cultured with  S. pasteuri, S. epidermidis  or both  S. pasteuri  and  S. epidermidis  Bacteria were grown alone or in various combinations in wells of a 96-well plate filled with TSB. Biofilm formation was estimated after 48 hours of incubation at 37° C. by measuring the optical density of solubilized crystal violet-stained extracellular matrix at 595 nm. Production of extracellular matrix was significantly increased when  C. accolens  was co-cultured with  S. pasteuri, S. epidermidis , or both  S. pasteuri  and  S. epidermidis . The greatest effect was obtained with the combination  C. accolens/S. pasteuri/S. epidermidis  (˜7.6-fold increase vs  C. accolens  alone, 12-fold increase vs  S. pasteuri  alone and 3.1-fold increase vs  S. epidermidis  alone). 
         FIG. 5 : Bacteriotherapeutic effect of  C. accolens/S. pasteuri on  adherent  S. aureus  cells 
         S. aureus  bacteria were inoculated in a 96-well plate and were allowed to adhere for 6 h. Bacteria were then treated with  C. accolens  and/or  S. pasteuri  (≈5×10 7  CFU/well for each species). After 24 h of incubation, wells were washed, immersed in an ultrasound bath to disrupt the biofilm, and  S. aureus  CFUs enumerated. (A)  S. aureus  log 10  CFU. (B) Delta  S. aureus  log 10  CFU (each condition versus control). Although a significant bacteriotherapeutic effect was observed with  S. pasteuri  alone, the combination  C. accolens/S. pasteuri  surprisingly showed a further improved synergistic effect. Control: untreated  S. aureus  cells. **p&lt;0.001 versus control. 
         FIG. 6 : Prevention of  S. aureus  colonization in an in vivo model of stratified squamous epithelium 
       (A) Picture of the hydrocolloid patch  on  a healthy volunteer&#39;s forearm skin. Punched holes (corresponding to skin wells) received the bacterial suspensions to be tested covered by the polyurethane sterile incision film. (B) Inhibition of  S. aureus  29213 (5×10 3  CFU per skin well) when inoculated with  C. accolens, S. pasteuri  and  S. epidermidis  alone or combined, each at a dose of 2×10 6  CFU per well.  S. aureus  alone was inoculated as positive control. The [(Threshold−CT)/Threshold] ratios are plotted for each condition tested. 
         FIG. 7 :  S. aureus  decolonization by bacteriotherapy in an in vivo murine model of stratified squamous epithelium. 
       Murine stratified squamous epithelium skin wells previously colonized with  S. aureus  were treated with  C. accolens, S. pasteuri  and, optionally,  S. epidermidis  in various combinations, at a dose of ≈10 6  CFU per species. Twenty-four hours later, mice were euthanized, and the area of each skin well was swabbed to quantify  S. aureus  CFUs. A.  S. aureus  log 10  CFU. B. Delta  S. aureus  log 10  CFU (each condition versus control). A significantly lower level of  S. aureus  was observed when wells colonized with  S. aureus  were subjected to bacteriotherapy with the combination  C. accolens/S. pasteuri  or  C. accolens/S. pasteuri/S. epidermidis . The  S. aureus  burden was 5.50 log 10  CFU per well with the control. Control: untreated  S. aureus  cells. *p&lt;0.05 versus control. **p&lt;0.005 versus control. 
     
    
    
     EXAMPLES 
     The following examples are included to demonstrate preferred embodiments of the invention. All subject-matter set forth or shown in the following examples and accompanying drawings is to be interpreted as illustrative and not in a limiting sense. The following examples include any alternatives, equivalents, and modifications that may be determined by a person skilled in the art. 
     The representative bacterial strains used in these examples are detailed in Table I, below. The strains selected for use in the examples (listed in Table 1) include reference strains, which possess the characteristics representative of all strains of a given species. 
     
       
         
           
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 Strains used. 
               
            
           
           
               
               
            
               
                 Strain 
                 Source/origin/collection number 
               
               
                   
               
               
                   Staphylococcus aureus  USA300 ATCC 
                 MRSA, Wrist abscess 
               
               
                 BAA-1556 
               
               
                   Staphylococcus aureus  AF3147 
                 MSSA, nasal swab, our collection 
               
               
                   Staphylococcus aureus  AF2419 
                 MSSA, nasal swab, our collection 
               
               
                   Staphylococcus aureus  ATCC 29213 
                 MSSA,  S. aureus  subsp.  aureus  Rosenbach 
               
               
                   
                 (strain Wichita) 
               
               
                   Corynebacterium accolens  AF2345 
                 Nasal swab, our collection, CNCM I-5395 
               
               
                   Corynebacterium accolens  AF3612 
                 Nasal swab, our collection 
               
               
                   Corynebacterium accolens  CIP 104783T 
                 Collection of the Pasteur Institute, Paris, 
               
               
                   
                 France 
               
               
                   Corynebacterium propinquum  AF1882 
                 Nasal swab, our collection, CNCM I-5393 
               
               
                   Staphylococcus epidermidis  AF2302 
                 Nasal swab, our collection, CNCM I-5394 
               
               
                   Staphylococcus pasteuri  AF2653 
                 Nasal swab, our collection, CNCM I-5396 
               
               
                   Staphylococcus pasteuri  AF2062 
                 Nasal swab, our collection 
               
               
                   Staphylococcus pasteuri  CIP 103540T 
                 Collection of the Pasteur Institute, Paris, 
               
               
                   
                 France 
               
               
                   Staphylococcus pasteuri  CIP 103830 
                 Collection of the Pasteur Institute, Paris, 
               
               
                   
                 France 
               
               
                   
               
            
           
         
       
     
     Abbreviations: MRSA, methicillin-resistant  Staphylococcus aureus ; MSSA, methicillin-susceptible  Staphylococcus aureus . Strains with a collection number were deposited with the Collection Nationale de Cultures de Microorganismes (CNCM), Institut Pasteur, 25 rue du Docteur Roux, F75724 Paris CEDEX 15, France  on  Jan. 25, 2019 by the UFR des sciences de la santé Simone Veil, 2 avenue de la source de la Bievre, 78180 Montigny le Bretonneaux, France, represented by Prof. Jean-Louis Gaillard. 
     Example 1: In Vitro Inhibition of the Growth of  S. aureus  by  C. accolens    
     In view of the prior art describing contradictory effects of  C. accolens on S. aureus  colonization in vivo, the effect of  C. accolens on S. aureus  growth was first evaluated here in vitro. 
     Materials and Methods 
     250 μl of a 1.0 McFarland (McF) suspension of  C. accolens , prepared from a 48 h-culture on Columbia 5% sheep blood agar at 35+/−2° C., was inoculated by swabbing  on  a 90-mm diameter blood agar plate in order to obtain ≈5×10 4  CFU/cm 2 . 250 μl of saline was inoculated as negative control. One 50 mm 0.2 μm track-etched filter was placed  on  top of the  C. accolens  suspension.  S. aureus  suspensions prepared from a 24 h-culture  on  Columbia −5% sheep blood agar at 35+/−2° C. and containing a target number of 100 CFUs, 10 CFUs, or 1 CFU in 10 μl were spotted on the 50-mm diameter filter. 
     After incubation for 48 h at 35° C.,  S. aureus  colonies on filter were harvested and bacteria resuspended in saline (2.5 to 10 mL). The number of  S. aureus  CFUs present in each colony was then determined by measuring optical density (OD) at 600 nm. To quantify the growth inhibition of  S. aureus  in the presence of  C. accolens , the OD/colony with or without  C. accolens  was determined. Each set of experiments was repeated at least twice. 
     Results 
       C. accolens  was surprisingly responsible for a reduction of 27.78% to 51.93% of  S. aureus  growth depending on the  C. accolens  and  S. aureus  strain tested (cf. Table II). Also, surprisingly, the growth of both MRSA ( S. aureus  USA300) and MSSA ( S. aureus  AF3147 and AF2419) strains was significantly inhibited. The percent growth inhibition appears to depend on the  C. accolens  strain used, as no significant differences in growth inhibition were observed between different  S. aureus  strains grown in the presence of a same  C. accolens  strain. 
     
       
         
           
               
               
             
               
                   
                 TABLE II 
               
             
            
               
                   
                   
               
               
                   
                   S. aureus  growth inhibition (mean (SD), %) 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                 P-value a   
                 P-value a   
                 P-value a   
               
               
                 
                   C. accolens 
                 
                   S. aureus  strain 
                 USA300 vs 
                 USA300 vs 
                 AF3147 vs 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 strain 
                 USA300 
                 AF3147 
                 AF2419 
                 AF3147 
                 AF2419 
                 AF2419 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 AF2345 
                 51.75 
                 51.86 
                 51.93 
                 0.969 
                 0.946 
                 0.980 
               
               
                   
                 (2.93) 
                 (3.71) 
                 (3.33) 
               
               
                 CIP104783T 
                 30.01 
                 27.78 
                 32.70 
                 0.437 
                 0.361 
                 0.115 
               
               
                   
                 (3.33) 
                 (3.21) 
                 (3.33) 
               
               
                 AF3612 
                 41.67 
                 38.90 
                 42.32 
                 0.308 
                 0.823 
                 0.281 
               
               
                   
                 (2.89) 
                 (3.21) 
                 (3.85) 
               
               
                   
               
               
                   a Student&#39;s t-test (p values &lt;0.01 were considered as significant), 
               
               
                 SD: standard deviation. 
               
            
           
         
       
     
     Example 2: Growth Promotion of  C. accolens  in Co-Culture with  S. pasteuri    
     We next studied the interaction of  C. accolens  and  S. pasteuri  in vitro. The effect of  S. pasteuri on  growth by  C. accolens  was studied using plate count agar (PCA), which allows the growth of  S. pasteuri , but not that of  C. accolens. S. epidermidis  was used as a control species. 
     Materials and Methods 
     500 μl of a 10 −2  dilution of a 0.5 McFarland suspension of  C. accolens  (strain AF2345), prepared as described in Example 1, was inoculated onto PCA medium. After complete drying, 10 μl of a 1.0 McFarland suspension of  S. pasteuri  (strain AF2653) or  S. epidermidis  (strain AF2302), prepared from a 24 h-culture on Columbia −5% sheep blood agar at 35+/−2° C., was spotted at the center of the plate. Ten μl of sterile saline was spotted as a negative control. Growth of  C. accolens  was determined after 72 hours of incubation at 35° C. Growth was determined by the presence of colonies visible with the naked eye. 
     Results 
     Growth of  C. accolens  was detected on the periphery of the  S. pasteuri  spot after 72 hours of incubation ( FIG. 1A ) while abortive colonies were detected around the  S. epidermis  spot ( FIG. 1B ) or the control spot (not shown). The  C. accolens  colonies detected on the periphery of the  S. pasteuri  spot could be detected with the naked eye, while the abortive colonies around the  S. epidermis  spot could not be detected without magnification. Incubation of  C. accolens  in co-culture with  S. epidermis  for longer periods of time did not further improve  C. accolens  growth, even when the plates were incubated for up to a total of 7 days. Thus, in contrast to  S. epidermidis, S. pasteuri  promotes growth of  C. accolens.    
     Example 3: Synergistic Inhibition of the Growth of  S. aureus  by  C. accolens  in Combination with  S. pasteuri  In Vitro 
     As  S. pasteuri  promoted  C. accolens  growth, we studied the anti- S. aureus  activity of  S. pasteuri  and  C. accolens , alone or in combination. Anti- S. aureus  activity of  S. epidermidis , was also tested alone or in combination with  C. accolens.    
     Materials and Methods 
     For each strain alone or in combination, 250 μl of a 1.0 McFarland suspension prepared from cultures on Columbia −5% sheep blood agar at 35+/−2° C. ( C. accolens:  48 h of incubation;  S. pasteuri, S. epidermidis:  24 h of incubation) was inoculated by swabbing on a 90 mm diameter blood agar plate (≈5×10 4  CFU/cm 2 ). 250 μl of saline was inoculated as negative control. One 50 mm 0.2 μm track-etched filter was placed on top of the spot.  S. aureus  USA300 suspensions containing a target number of 100 CFUs, 10 CFUs, and 1 CFU in 10 μl were spotted on the 50 mm diameter filter. Materials and methods were otherwise as described in Example 1. 
     Results 
     Table III presents the results obtained with  C. accolens  AF2345 , S. pasteuri  AF2543 and  S. epidermidis  AF2302. As shown, the combination of  C. accolens  and  S. pasteuri  was significantly more inhibitory than each species alone and inhibited  S. aureus  growth by more than 95%. In contrast, the combination of  C. accolens  and  S. epidermidis  was not synergistic and even tended to be antagonistic (mean  S. aureus  growth inhibition of 68.92% versus 79.28% with  S. epidermidis  AF2302 alone, p=0.0133). 
     
       
         
           
               
               
               
             
               
                 TABLE III 
               
               
                   
               
               
                   
                   S. aureus  growth 
                   
               
               
                 Strain/combination 
                 inhibition (mean (SD), %) 
                 P-value a   
               
               
                   
               
             
            
               
                   C. accolens  AF2345 
                 55.96 (2.59) 
                 — 
               
               
                   S. pasteuri  AF2653 
                 81.87 (2.59) 
                 — 
               
               
                   S. epidermidis  AF2302 
                 79.28 (3.66) 
                 — 
               
               
                   C. accolens  AF2345 + 
                 96.12 (1.30) 
                 vs AF2653 alone: 
               
               
                   S. pasteuri  AF2653 
                   
                 3.4216 × 10 −7   
               
               
                   C. accolens  AF2345 + 
                 68.92 (3.66) 
                 vs AF2302 alone: 
               
               
                   S. epidermidis  AF2302 
                   
                 0.0133 
               
               
                   
               
               
                   a Student&#39;s t-test (p values &lt; 0.01 were considered as significant). 
               
            
           
         
       
     
     We tested other combinations of  C. accolens  and  S. pasteuri  strains in the same conditions. As shown in Table IV, all combinations tested inhibited  S. aureus  inhibition by more than 95%. 
     
       
         
           
               
               
             
               
                 TABLE IV 
               
               
                   
               
               
                   
                 
                   S. aureus 
                 
               
               
                 Combination 
                 growth inhibition (%) a   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                   C. accolens  AF2345 +  S. pasteuri  AF2062 
                 99.43 
               
               
                   C. accolens  AF2345 +  S. pasteuri   
                 95.38 
               
               
                 CIP103540T 
               
               
                   C. accolens  AF2345 +  S. pasteuri  CIP103830 
                 99.61 
               
               
                   C. accolens  CIP104783T +  S. pasteuri   
                 95.38 
               
               
                 AF2653 
               
               
                   C. accolens  CA3612 +  S. pasteuri  AF2653 
                 95.38 
               
               
                   
               
               
                   a OD was measured from a pool of ten colonies suspended in saline. 
               
            
           
         
       
     
     Example 4: Dose-Effect Relationship of the Combination of  C. accolens  and  S. pasteuri    
     Materials and Methods 
     Serial 1/5 dilutions were prepared from a 1.0 McFarland suspension of each strain and 250 μl of each bacterial suspension was inoculated by swabbing on a 90 mm diameter blood agar plate, to obtain each strain alone or in combination at a plated density of ≈5×10 4 , ≈10 4 , ≈2×10 3 , ≈4×10 2 , and ≈0.8×10 2  CFU/cm 2 . Materials and methods were otherwise as described in Example 3. 
     Results 
     As shown in Table V, the combination of  C. accolens  and  S. pasteuri  was surprisingly significantly synergistic at all bacterial densities tested, with the strongest synergistic effect obtained at ≈0.8×10 2  CFU/cm 2 . However, only the densities superior or equal to ≈2×10 3  CFU/cm 2  (e.g. ≈5×10 4  CFU/cm 2 , ≈10 4  CFU/cm 2 , and ≈2×10 3  CFU/cm 2 ) showed anti- S. aureus  activity that inhibited bacterial growth by more than 95%. 
     
       
         
           
               
               
               
             
               
                 TABLE V 
               
               
                   
               
               
                   
                 
                   S. aureus 
                 
                   
               
               
                   
                 growth 
               
               
                   
                 inhibition 
                 P-value a   
               
               
                   
                 (mean 
                 AF2653 + AF2345 vs 
               
               
                 Strain/combination 
                 (SD), %) 
                 AF2653 alone 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 ≈5 × 10 4  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   C. accolens  AF2345 
                 50.00 (5.89) 
                   
               
               
                   S. pasteuri  AF2653 
                 86.46 (1.80) 
               
               
                   C. accolens  AF2345 +  S. pasteuri   
                 97.71 (0.36) 
                 4.1433 × 10 −5   
               
               
                 AF2653 
               
            
           
           
               
            
               
                 ≈10 4  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   C. accolens  AF2345 
                 41.69 (5.87) 
                   
               
               
                   S. pasteuri  AF2653 
                 80.21 (3.46) 
               
               
                   C. accolens  AF2345 +  S. pasteuri   
                 96.64 (0.47) 
                 0.0001828 
               
               
                 AF2653 
               
            
           
           
               
            
               
                 ≈2 × 10 3  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   C. accolens  AF2345 
                 25.02 (5.91) 
                   
               
               
                   S. pasteuri  AF2653 
                 71.88 (3.45) 
               
               
                   C. accolens  AF2345 +  S. pasteuri   
                 95.06 (0.45) 
                 2.5551 × 10 −5   
               
               
                 AF2653 
               
            
           
           
               
            
               
                 ≈4 × 10 2  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   C. accolens  AF2345 
                 14.59 (9.08) 
                   
               
               
                   S. pasteuri  AF2653 
                 54.17 (4.17) 
               
               
                   C. accolens  AF2345 +  S. pasteuri   
                 80.21 (1.81) 
                 6.0412 × 10 −5   
               
               
                 AF2653 
               
            
           
           
               
            
               
                 ≈0.8 × 10 2  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   C. accolens  AF2345 
                  0.00 (0.00) 
                   
               
               
                   S. pasteuri  AF2653 
                 16.66 (5.90) 
               
               
                   C. accolens  AF2345 +  S. pasteuri   
                 73.96 (1.80) 
                 3.6798 × 10 −6   
               
               
                 AF2653 
               
               
                   
               
               
                   a Student&#39;s t-test p values &lt; 0.01 were considered as significant). 
               
            
           
         
       
     
     Example 5: Anti- S. aureus  Activity of the Combination of  C. accolens, S. Pasteuri  and  S. epidermidis    
     In view of our previous results presented in Example 3, we evaluated whether or not the addition of  S. epidermidis  had a negative impact on the inhibitory activity of the combination of  C. accolens  with  S. pasteuri  against  S. aureus.    
     Materials and Methods 
     For each strain in combination, 250 μl of a 1.0 McFarland suspension prepared from cultures on Columbia −5% sheep blood agar at 35+/−2° C. ( C. accolens:  48 h of incubation;  S. pasteuri, S. epidermidis:  24 h of incubation) was inoculated by swabbing on a 90 mm diameter blood agar plate (≈5×10 4  CFU/cm 2 ); 250 μl of saline was inoculated as negative control. One 50 mm 0.2 μm track-etched filter was placed on top of the spot. A  S. aureus  USA300 suspension containing a target number of 100 CFUs, 10 CFUs, and 1 CFU in 10 μl were spotted on the 50 mm diameter filter. Materials and methods were otherwise as described in Example 1. 
     Results 
     As shown on table VI, the same level of  S. aureus  growth inhibition was obtained with the combination  C. accolens  AF2345 /S. pasteuri  AF2653 versus the combination  C. accolens  AF2345 /S. pasteuri  AF2653 /S. epidermidis  AF2302. 
     
       
         
           
               
               
               
             
               
                 TABLE VI 
               
               
                   
               
               
                   
                   S. aureus  growth 
                 P-value a  AF2345 + AF2653 
               
               
                   
                 inhibition (mean 
                 vs 
               
               
                 Combination 
                 (SD), %) 
                 AF2345 + AF2653 + AF2302 
               
               
                   
               
             
            
               
                   C. accolens  AF2345 + 
                 98.91 (0.16) 
                 1.00 
               
               
                   S. pasteuri  AF2653 
               
               
                   C. accolens  AF2345 + 
                 98.91 (0.16) 
               
               
                   S. pasteuri  AF2653 + 
               
               
                 
                   S. epidermidis 
                 
               
               
                 AF2302 
               
               
                   
               
               
                   a Student&#39;s t-test (p values &lt; 0.01 were considered as significant). 
               
            
           
         
       
     
     Example 6:  C. propinquum  May Replace  C. accolens  in the Combinations  C. accolens/S. pasteuri  and  C. accolens/S. pasteuri/S. epidermidis    
     We then studied whether or not other species of  Corynebacterium , such as  C. propinquum , may also have anti- S. aureus  activity alone and/or in combination with  S. pasteuri  or with  S. pasteuri  and  S. epidermidis.    
     Materials and Methods 
     Materials and methods were as described in Example 3 except that  C. propinquum  AF1882 replaced  C. accolens  AF2345. 
     Results 
     As shown in Table VII, the combinations  C. propinquum/S. pasteuri  and  C. propinquum/S. pasteuri/S. epidermidis  were both synergistic and had significant anti- S. aureus  activity, inhibiting  S. aureus  growth by more than 95%. 
     
       
         
           
               
               
               
             
               
                 TABLE VII 
               
               
                   
               
               
                   
                   S. aureus  growth 
                 P-value a  vs 
               
               
                   
                 inhibition (mean % 
                 AF1882 
               
               
                 Strain/combination 
                 (SD)) 
                 alone 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   C. propinquum  AF1882 
                 81.25 (4.42) 
                   
               
               
                   C. propinquum  AF1882 +  S. pasteuri   
                 98.33 (0.30) 
                 0.002415 b   
               
               
                 AF2653 
               
               
                   C. propinquum  AF1882 +  S. pasteuri   
                 98.59 (0.27) 
                 0.0005017 b   
               
               
                 AF2653 +  S. epidermidis  AF2302 
               
               
                   
               
               
                   a Student&#39;s t-test (p values &lt; 0.01 were considered as significant). 
               
               
                   b AF1882 + AF2653 versus AF1882 + AF2653 + AF2302, P-value = 0.3524. 
               
            
           
         
       
     
     Example 7: Anti- S. aureus  Activity of Bacterial Combinations at Various  Corynebacterium sp.:Staphylococcus  sp. ratios 
     The anti- S. aureus  activity of various ratios of  Corynebacterium  sp.: Staphylococcus  sp. was also evaluated. In particular, we evaluated various ratios of the combination  C. accolens:S. pasteuri:S. epidermidis  or the combination of  C. propinquum:S. pasteuri:S. epidermidis.    
     Materials and Methods 
     Appropriate dilutions of  C. accolens  AF2345,  C. propinquum  AF1882 , S. pasteuri  AF2653 and  S. epidermidis  AF2302 were prepared from a 2.0 McFarland suspension of each strain and 25 to 250 μl of each bacterial suspension were co-inoculated by swabbing on a 90 mm diameter blood agar plate, thereby obtaining ≈10, ≈5×10 4 , ≈10 4 , ≈5×10, and ≈10 3  CFU/cm 2  of  C. accolens  AF2345 or  C. propinquum  AF1882 combined with  S. pasteuri  AF2653 and  S. epidermidis  AF2302 at the following ratios ( Corynebacterium:S. pasteuri/S. epidermidis ): 1:1:1, 1:0.2:0.2, 1:0.1:0.1, 1:0.02:0.02, 1:0.01:0.01. Materials and methods were otherwise as described in Example 3. 
     Results 
     Tables VIII and IX show the results obtained with  C. accolens - and  C. propinquum -based combinations, respectively. 
     As shown in Table VIII, the combination  C. accolens:S. pasteuri:S. epidermidis  surprisingly has an anti- S. aureus  activity exceeding 95% at all densities and ratios tested, except for ratios 1:0.01:0.01 at densities ≤10 4  CFU/cm 2 , for ratios 1:0.02:0.02 at densities ≈5×10 3  CFU/cm 2 , and for ratio 1:0.1:0.1 at a density of 10 3  CFU/cm 2 . However, anti- S. aureus  activities remained significant at all concentrations and densities tested. Indeed, even at the lowest tested concentration and density (e.g. a ratio of 1:0.01:0.01 at a density of 10 3  CFU/cm 2 )  S. aureus  growth remained inhibited by at least 74%. Increasing either the ratio (e.g. to 1:0.02:0.02) or the density (e.g. to 5×10 3 ) increased anti- S. aureus  activity, inhibiting  S. aureus  growth by approximately 83% and 85%, respectively. 
     
       
         
           
               
             
               
                 TABLE VIII 
               
             
            
               
                   
               
               
                   C. accolens / S. pasteuri / S. epidermidis  combination at various 
               
               
                 ratios and densities 
               
            
           
           
               
               
               
            
               
                   
                 Density/ratio 
                   S. aureus  growth inhibition (mean % (SD)) 
               
               
                   
                   
               
            
           
           
               
            
               
                   C. accolens  at ≈10 5  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio a  1:1:1 
                 99.70 (0.10) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 99.07 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 99.27 (0.41) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 97.87 (0.19) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 97.33 (0.19) 
               
            
           
           
               
            
               
                   C. accolens  at ≈5 × 10 4  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 99.80 (0.00) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 99.33 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 98.67 (019)  
               
               
                   
                 Ratio 1:0.02:0.02 
                 97.87 (0.19) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 97.33 (0.38) 
               
            
           
           
               
            
               
                   C. accolens  at ≈10 4  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 99.60 (0.00) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 98.53 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 96.40 (1.18) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 96.53 (0.38) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 93.87 (0.38) 
               
            
           
           
               
            
               
                   C. accolens  at ≈5 × 10 3  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 99.50 (0.10) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 98.53 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 96.53 (0.38  
               
               
                   
                 Ratio 1:0.02:0.02 
                 93.07 (0.38) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 85.07 (0.75) 
               
            
           
           
               
            
               
                   C. accolens  at ≈10 3  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 98.13 (0.19) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 97.73 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 92.27 (0.38) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 83.47 (0.75) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 74.93 (0.75) 
               
               
                   
                   
               
               
                   
                   a Ratio is expressed as the quantity of  C. accolens : S. pasteuri : S. epidermidis   
               
            
           
         
       
     
     As shown in Table IX, the results obtained with  C. propinquum  were similar to those obtained with  C. accolens . Indeed, anti- S. aureus  activities for bacterial combinations including  C. propinquum  also surprisingly exceeded 95% at all densities and ratios tested, except for ratios 1:0.01:0.01 at densities ≤5×10 3  CFU/cm 2 , and for ratios 1:0.1:0.1 and 1:0.2:0.2 at a density of 10 3  CFU/cm 2 . As seen for combinations with  C. accolens , anti- S. aureus  activities of combinations with  C. propinquum  remained significant at all concentrations and densities tested, and were in fact generally higher than those seen for  C. accolens . Indeed,  S. aureus  growth was inhibited by at least 81% at the lowest tested concentration and density (e.g. a ratio of 1:0.01:0.01 at a density of 10 3  CFU/cm 2 ). Increasing either the ratio (e.g. to 1:0.02:0.02) or the density (e.g. to 5×10 3 ) increased anti- S. aureus  activity, inhibiting  S. aureus  growth by approximately 89% and 93%, respectively. 
     
       
         
           
               
             
               
                 TABLE IX 
               
             
            
               
                   
               
               
                   C. propinquum / S. pasteuri / S. epidermidis  combination at various 
               
               
                 ratios and densities 
               
            
           
           
               
               
               
            
               
                   
                 Density/ratio 
                   S. aureus  growth inhibition (mean (SD), %) 
               
               
                   
                   
               
            
           
           
               
            
               
                   C. propinquum  at ≈10 5  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio a  1:1:1 
                 99.80 (0.00) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 99.60 (0.00) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 99.33 (0.19) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 98.13 (0.19) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 97.47 (0.19) 
               
            
           
           
               
            
               
                   C. propinquum  at ≈5 × 10 4  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 99.50 (0.10) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 99.50 (0.10) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 99.07 (0.19) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 98.67 (0.19) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 97.73 (0.19) 
               
            
           
           
               
            
               
                   C. propinquum  at ≈10 4  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 99.70 (0.10) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 99.50 (0.10) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 98.53 (0.19) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 97.33 (0.19) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 95.87 (0.19) 
               
            
           
           
               
            
               
                   C. propinquum  at ≈5 × 10 3  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 99.60 (0.00) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 98.93 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 97.33 (0.19) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 95.87 (0.19) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 93.73 (0.19) 
               
            
           
           
               
            
               
                   C. propinquum  at ≈10 3  CFU/cm 2   
               
            
           
           
               
               
               
            
               
                   
                 Ratio 1:1:1 
                 98.53 (0.19) 
               
               
                   
                 Ratio 1:0.2:0.2 
                 97.07 (0.19) 
               
               
                   
                 Ratio 1:0.1:0.1 
                 91.73 (0.38) 
               
               
                   
                 Ratio 1:0.02:0.02 
                 89.87 (0.75) 
               
               
                   
                 Ratio 1:0.01:0.01 
                 81.33 (0.75) 
               
               
                   
                   
               
               
                   
                   a Ratio is expressed as the quantity of  C. accolens : S. pasteuri : S. epidermidis   
               
            
           
         
       
     
     Example 8:  C. accolens  Forms a Biofilm in the Presence of  S. pasteuri    
       C. accolens  requires a complex medium and tryptic soy broth (TSB) does not support its growth. Here we show that  C. accolens  and  S. pasteuri  can form a mixed biofilm supporting the growth of  C. accolens  in conditions where it is normally unable to grow. 
     Materials and Methods 
     Bacterial suspensions of a turbidity of McFarland 0.5 were prepared from cultures on Columbia −5% sheep blood agar plates as described in Example 3. 50 μl of the suspension (approx. 2×10 CFU) of  C. accolens  AF2345 was distributed in 12 wells (row A); 50 μl of a 1:100 dilution (approx. 2×10 4  CFU) was distributed in 12 wells (row B); 50 μl of the suspension of  S. epidermidis  AF2302 (approx. 2×10 6  CFU) was distributed in columns 1, 2, 3, 7, 8, and 9; 50 μl of the suspension of  S. pasteuri  AF2653 (approx. 2×10 6  CFU) was distributed in columns 4, 5, 6, 7, 8, and 9. Columns 10, 11, and 12 contain  C. accolens  AF2345 suspended in 100 μl of culture medium. 
     The plates were centrifuged, the suspension saline was removed and 100 μl of TSB were added to each well. After 24 hours of incubation, 50 μl of the medium was removed and replaced with fresh TSB. The plates were examined for growth. After 48 hours the plates were observed, the medium removed and the wells gently washed twice with saline. 200 μl of saline was added to each well and the plate immersed in an ultrasound bath to disperse and resuspend the biofilm. For each well, 5 μl ( 1/40th) was transferred to 95 μl of saline ( 1/800 th ). 5 μl of this suspension was then transferred to a fresh plate containing 95 μl of saline ( 1/16000 th ). 10 μl of each suspension was then applied to a Mueller Hinton 2 agar plate and to a Mueller Hinton 5% blood NAD enriched defibrinated agar plate containing mupirocin (128 μg/ml). 
     The bacteria grown after 24 h were suspended in 2.2 ml ampules and the turbidity measured using a McFarland reader. 
     Results 
     The results obtained with the high and the low inocula of  C. accolens  (row A and row B) are qualitatively similar. However, the bacterial density obtained after 24 hours of incubation with the lower inoculum was too low to allow quantification using the McFarland turbidimeter. Data reported hereunder are obtained from the higher inoculum tested (row A). 
     As expected,  C. accolens  does not grow in TSB and does not form a biofilm. In contrast, both  S. epidermidis  and  S. pasteuri  form a biofilm in TSB (data not shown). Surprisingly,  C. accolens  is capable of growing within a  S. pasteuri  biofilm or a mixed  S. pasteuri  and  S. epidermidis  biofilm, although it does not grow within a biofilm of  S. epidermidis  alone (cf.  FIG. 2 ). As expected, no growth is observed in the control wells containing  C. accolens  in TSB, since it is known that TSB does not support the growth of  C. accolens . The difference between the growth of  C. accolens  in a  S. pasteuri  biofilm and a  S. epidermidis  biofilm is significant (p=0.0065). The difference between the growth of  C. accolens  in a  S. pasteuri  biofilm and a mixed  S. pasteuri  and  S. epidermidis  biofilm does not reach statistical significance (p=0.0651). 
     Example 9: Growth of  C. propinquum  in Mixed Biofilms 
     The same experiment presented in Example 8 was performed by replacing  C. accolens  with  C. propinquum.    
     Materials and Methods 
     Experiments were performed as described in Example 8 except that  C. propinquum  AF1882 were tested instead of  C. accolens  AF2345. 
     Results 
     As shown in  FIG. 3 ,  C. propinquum  is capable of forming a robust biofilm in TSB. It can also form mixed biofilms in combination with  S. epidermidis  and  S. pasteuri . The growth within  S. epidermidis  is significantly lower than growth in biofilms containing  S. pasteuri  (p=0.019). However, as was the case with  C. accolens , the presence of  S. epidermidis  does not adversely affect the growth within  C. accolens  containing biofilms ( C. propinquum  with  S. pasteuri  versus  C. propinquum  with  S. pasteuri  and  S. epidermidis , p=0.0748). 
     Example 10: Synergistic Effect of Combining  C. accolens  with  S. pasteuri  and/or  S. Epidermidis  on Biofilm Formation 
     In addition to the quantification of bacterial growth (as illustrated above in Examples 8 and 9), biofilm formation of  C. accolens  grown alone or in combination with  S. pasteuri, S. epidermidis , or both  S. pasteuri  and  S. epidermidis  was evaluated here by staining the extra-cellular matrix with crystal violet, which allows the relative quantification of biofilm formation in vitro. 
     Materials and Methods 
     1.0 McFarland suspensions of  C. accolens  AF2345 , S. pasteuri  AF2653 and  S. epidermidis  AF2302 were prepared in tryptic soy broth (TSB) as described in Example 1. Fifty μL of the undiluted  C. accolens  suspension and 50 μL of a 10 −2  dilution of the  S. pasteuri  and  S. epidermidis  suspensions were seeded in the wells of a 96-well plate either alone or combined as follows:  C. accolens/S. pasteuri, C. accolens/S. epidermidis  and  C. accolens/S. pasteuri/S. epidermidis . The volume was completed to 200 μL per well with TSB and the plate was incubated at 37° C. After incubation for 48 hours, the wells were rinsed with distilled water, air-dried and the biofilm was stained with 200 μL of a 0.2% crystal violet solution prepared in distilled water. The wells were then rinsed with distilled water, air-dried and the fixed crystal violet solubilized in 200 μL of a 30% acetic acid solution prepared in distilled water. 100 μL of the solubilized crystal violet solution was transferred to a new 96-well plate and the biofilm extra-cellular matrix quantified by measuring the optical density of the suspension at 595 nm. 
     Results 
     As shown in  FIG. 4 , significantly more extracellular matrix was produced when  C. accolens  was grown in combination with  S. pasteuri, S. epidermidis  or both  S. pasteuri  and  S. epidermidis  than with each bacterial species alone. Enhancement of extracellular matrix production was the highest with the combination  C. accolens/S. pasteuri/S. epidermidis.    
     Furthermore, the quantity of extracellular matrix produced by the combined bacteria was greater than the expected additive effect expected in view of the quantity produced by each species alone. Thus, a synergistic effect is observed when  C. accolens  is co-cultured with  S. pasteuri  and/or  S. epidermidis . The effect is maximal when  C. accolens  is co-cultured with both  S. pasteuri  and  S. epidermidis.    
     Example 11: Treatment of Adherent  S. aureus  Cells with the Combination  C. accolens/S. pasteuri  Inhibits  S. aureus  Development and Biofilm Formation 
     We further studied whether treatment with  C. accolens  alone,  S. pasteuri  alone or the combination  C. accolens/S. pasteuri  had a bacteriotherapeutic effect on  S. aureus , in particular inhibiting the development and biofilm formation of already adherent  S. aureus.    
     Materials and Methods 
     A 1.0 McF suspension of  S. aureus  (strain USA300) was prepared from a 24 h-culture on Columbia 5% sheep blood agar at 35+/−2° C., in sterile water. 200 μl of this suspension diluted 1:100,000 in Trypto-Casein-Soy (TCS)+5% glucose was inoculated into wells (≈10 3  CFU/well) of a 96-well plate and incubated for 6 h at 35+/−2° C. 
     50 McF, 5 McF and 3 McF suspensions of  C. accolens  (strain AF2345) and  S. pasteuri  (strain AF2653), respectively, were prepared in TCS supplemented with 0.05% polysorbate 80 (also referred to as Tween 80 or T80) from a 48 h-culture ( C. accolens ) or a 24 h-culture ( S. pasteuri ) on Columbia 5% sheep blood agar at 35+/−2° C. These suspensions were further diluted in TCS+T80 0.05% in order to obtain a bacterial concentration of ≈10 8  CFU/mL 
     After 6 h of incubation at 35+/−2° C., 100 μl of the  S. aureus  suspension was eliminated per well in the 96-well plate, and replaced by 100 μl of bacterial suspension ( C. accolens  alone,  S. pasteuri  alone, or a combination of  C. accolens/S. pasteuri ), thus at a concentration of ≈10 7  CFU/well for each species. 100 μl of TCS+T80 0.05% also was added in place of the bacterial suspension in control wells (“untreated  S. aureus ”). 
     After further incubation for 24 h at 35+/−2° C., wells were washed three times, filled with 200 μl of sterile water, and immersed in an ultrasound bath to disperse and resuspend the biofilm.  S. aureus  CFUs were enumerated on MRSA agar plates (Biomérieux, Marcy-I&#39;Etoile, France). Results were measured in triplicate and expressed as the mean log 10  CFU and as the mean percent of CFU reduction versus control. 
     Results 
     As shown in  FIG. 5 , while both  C. accolens  and  S. pasteuri  alone had a bacteriotherapeutic effect, inhibiting  S. aureus  development and biofilm formation, the combination  C. accolens/S. pasteuri  showed an even stronger bacteriotherapeutic effect.  S. aureus  levels were notably reduced from 8.90 log 10  CFU/mL to 7.53 log 10  CFU/mL ( FIG. 5A ), corresponding to a mean CFU reduction of 95.0%. 
     Surprisingly, the bacteriotherapeutic effect observed with the combination of  C. accolens/S. pasteuri  was synergistic as it was greater than with  C. accolens  alone,  S. pasteuri  alone, or the expected effect of the combination of  C. accolens/S. pasteuri  ( FIG. 5B ). 
     Thus, the development of  S. aureus  cells adhering on a surface is the most efficiently combatted by the synergistic combination of at least  C. accolens  and  S. pasteuri.    
     Example 12: Treatment of Adherent  S. aureus  Cells with the Combination  C. propinquum/S. pasteuri  Inhibits  S. aureus  Development and Biofilm Formation 
     We further determined if other species of  Corynebacterium , such as  C. propinquum , may also inhibit  S. aureus  development and biofilm formation. 
     Materials and Methods 
     Materials and methods were as described in Example 11 except that  C. propinquum  AF1882 (bacterial suspension: 2 McF) replaced  C. accolens  AF2345 (bacterial suspension: 50 McF). Reference strain  S. pasteuri  CIP 103830 was used in a similar manner to  S. pasteuri  AF2653 as described in Example 11. 
     Results 
     The mean log 10  CFU of  S. aureus  was significantly lower when adherent  S. aureus  cells were treated with the combination  C. propinquum/S. pasteuri  (8.45±0.24 versus 9.61±0.12 for untreated  S. aureus  cells, p=0.0008), with a mean CFU reduction of 92.76%. Thus, the combination of  C. propinquum/S. pasteuri  may also inhibit  S. aureus  development and biofilm formation. 
     Example 13: Reconstituted Lyophilized Bacteria Prevent  S. aureus  Colonization 
     As the final formulation may include freeze-drying the bacteria, we verified that this process does not impair  C. accolens ′ ability, in combination with  S. pasteuri  and  S. epidermidis , to prevent growth of  S. aureus  in vitro. We therefore compared the anti- S. aureus  activity of “fresh” versus reconstituted freeze-dried bacteria. 
     Materials and Methods 
     Bacterial suspensions of  C. accolens  AF2345 , S. pasteuri  AF2652 and  S. epidermidis  AF2302 were combined at a 1:1:1 or a 1:0.1:0.1 ratio, respectively, in freeze-drying buffer. One part of these suspensions, hereafter named “fresh bacteria,” was used to inoculate 90 mm petri dishes at final densities of 10 3  CFU/cm 2 , 10 2  CFU/cm 2  or 10 1  CFU/cm 2  by swabbing 300 μL of the suspension on the surface of the agar plate. 300 μl of sterile water was inoculated as negative control. One 50 mm 0.2 μm track-etched filter was placed on top of the inoculated surface and  S. aureus  USA300 suspensions containing a target number of 10 and 100 CFU in 10 μl were spotted in triplicate on the filter surface. Materials and methods were otherwise as described in Example 3. The other part of the prepared suspensions was lyophilized in a shelf freeze dryer, using a two-stage process at negative pressure (primary drying: sub-zero temperatures; secondary drying: 15° C.). At the end of the process the vials were sealed under vacuum and stored at 4° C. in the dark until use. On the day of the assay, the lyophilized cake was resuspended in 400 μL of sterile water and the reconstituted suspensions were inoculated according to the same conditions and dilutions as were used for the fresh bacterial suspensions. 
     Results 
     As shown below in Table X, the inhibition of  S. aureus  growth is similar when using fresh or reconstituted lyophilized  C. accolens/S. pasteuri/S. epidermidis  combinations, regardless of the bacterial density or ratio tested in the assay (no significant differences are observed). 
     
       
         
           
               
             
               
                 TABLE X 
               
             
            
               
                   
               
               
                 Anti- S. aureus  activity of fresh or reconstituted 
               
               
                   C. accolens / S. pasteuri / S. epidermidis   
               
               
                 combinations at various densities. 
               
            
           
           
               
               
               
            
               
                   
                   
                 P-value a   
               
               
                   
                   S. aureus  growth inhibition, 
                 Fresh vs 
               
               
                   
                 mean % (SD) 
                 lyophilized 
               
            
           
           
               
               
               
               
            
               
                 Density 
                 Fresh bacteria 
                 Lyophilized bacteria 
                 bacteria 
               
               
                   
               
            
           
           
               
            
               
                 1:1:1  C. accolens / S. pasteuri / S. epidermidis  ratio 
               
            
           
           
               
               
               
               
            
               
                   C. accolens  at 
                 96.82 (0.70) 
                 96.54 (0.46) 
                 0.60 
               
               
                 ≈10 3  CFU/cm 2   
               
               
                   C. accolens  at 
                 90.35 (2.00) 
                 88.95 (0.56) 
                 0.31 
               
               
                 ≈10 2  CFU/cm 2   
               
               
                   C. accolens  at 
                 63.40 (3.08) 
                 66.12 (3.08) 
                 0.34 
               
               
                 ≈10 1  CFU/cm 2   
               
            
           
           
               
            
               
                 1:0.1:0.1  C. accolens / S. pasteuri / S. epidermidis  ratio 
               
            
           
           
               
               
               
               
            
               
                   C. accolens  at 
                 90.95 (0.65) 
                 91.11 (0.76) 
                 0.80 
               
               
                 ≈10 3  CFU/cm 2   
               
               
                   C. accolens  at 
                 66.77 (3.50) 
                 61.32 (6.60) 
                 0.27 
               
               
                 ≈10 2  CFU/cm 2   
               
               
                   C. accolens  at 
                  23.95 (10.85) 
                 20.65 (8.04) 
                 0.69 
               
               
                 ≈10 1  CFU/cm 2   
               
               
                   
               
               
                   a Student&#39;s t-test (p &lt; 0.05 for significance). 
               
            
           
         
       
     
     Thus, freeze-drying a combination of bacteria (in this case  C. accolens, S. pasteuri  and  S. epidermidis ) does not impair the anti- S. aureus  activity of the bacterial combination.  S. aureus  colonization may therefore still be successfully prevented. 
     Example 14: The Combination  C. accolens/S. Pasteuri , and, Optionally,  S. Epidermidis  Inhibits  S. aureus  Nasal Colonization in Mice 
     We studied here the capacity of the combination  C. accolens/S. pasteuri , and, optionally,  S. epidermidis  to reduce  S. aureus  nasal colonization in the mouse. 
     Materials and Methods 
     Six-week old BALB/c_JRj mice were obtained from Janvier Labs (Le Genest-Saint-Isle, France) and were used after one week of acclimatization (IERP, INRA, Jouy-en-Josas, France). A 10 McF suspension of  S. aureus  (strain USA300) in normal saline (≈10 9  CFU/mL) was prepared from a 24 h-culture on Columbia 5% sheep blood agar at 35+/−2° C. Lyophilized  C. accolens  (strain AF2345),  S. pasteuri  (strain AF2653) and  S. epidermidis  (strain AF2302) were reconstituted with sterile distilled water in order to obtain a suspension of ≈2.10 10  CFU/mL for each species. Mice were inoculated intranasally with  S. aureus  (≈10 7  CFU) and the combination  C. accolens/S. pasteuri/S. epidermidis  (0.10 8  CFU for each species, thus ≈3×10 8  CFU, ratio 1:1:1) at a final volume of 10 μl per nostril;  S. aureus  alone was inoculated as a control (“untreated  S. aureus ”). At 6 h post-inoculation, mice were euthanized and the two nostrils were sampled with a single 0.6 mm interdental brush (GUM; Levallois-Perret; France) to quantify  S. aureus  CFUs as described in example 11. Results were expressed as the mean+/−standard deviation (SD) per animal (five measurements) of the log 10  CFU of  S. aureus  and as the mean percentage of  S. aureus  CFU reduction versus control. 
     Results 
     The application of the combination  C. accolens/S. pasteuri/S. epidermidis  significantly reduced  S. aureus  nasal colonization (mean (SD): 3.91 (0.46) log 10  CFU vs 4.68 (0.64) log 10  CFU for control; p=0.030), with a mean CFU reduction of 86.4%. 
     Thus, the combination  C. accolens/S. pasteuri/S. epidermidis  also shows anti- S. aureus  activity by the intranasal route. 
     Example 15: Synergistic Effect of Combining  C. accolens  with  S. pasteuri  and/or  S. epidermidis  in Preventing of  S. aureus  Colonization In Vivo in a Human Skin Model 
     We studied the capacity of freeze-dried strains of  C. accolens, S. pasteuri  and  S. epidermidis  formulated alone or in various combinations to inhibit  S. aureus  growth on the forearm skin of a healthy individual using punched hydrocolloid sterile patches as templates to outline the experimental area (as illustrated in  FIG. 6A ). Indeed, as indicated previously, the forearm skin is an excellent model of both the skin and anterior nares, in view of the similarities in structure and microbial community composition between these sites. 
     Materials and Methods 
     Vials of lyophilized  C. accolens  strain AF2345 , S. pasteuri  strain AF2652 and  S. epidermidis  strain AF2302 were prepared as described in Example 13. Nine evenly spaced 4.5 mm diameter holes were punched in hydrocolloid sterile patches, each hole constituting a 30 μl skin-bottom well. On the day of the assay, two patches were applied to the skin of the internal aspect of the forearm of an informed consenting healthy human volunteer. The lyophilized bacterial cakes were resuspended in sterile water and diluted to a concentration of 3×10 8  CFU/mL.  S. aureus  ATCC 29213 was subcultured on blood agar and a saline suspension having a turbidity of 1 McFarland was prepared and diluted to obtain a suspension of ˜10 8  CFU/mL. 
       C. accolens, S. pasteuri  and  S. epidermidis  alone or in various combinations were added to the skin wells at a dose of 2×10 6  CFU per species per well and  S. aureus  at a dose of 5×10 3  CFU per well. The hydrocolloid patches and the surrounding skin was then covered by sterile polyurethane adhesive surgical incision film ( FIG. 6A ). The patches were left in place for 30 hours, after which they were peeled off and the skin area corresponding to each well sampled with a humidified swab to quantify  S. aureus . The head of the swabs were cut using sterile surgical clippers and collected in sterile containers. DNA was extracted using Dneasy Blood and Tissue Kit (Qiagen), according the manufacturer&#39;s protocol. DNA extracts were amplified by quantitative real time PCR (qPCR) on the CFX96 C1000 Touch real time system (Biorad) using primers targeting the Spa gene. The reaction mixture was prepared with 1× Itaq Universal Probes supermix (Biorad), 500 nM for each primer, 250 nM probe and DNA template in a final volume of 20 μl. For qPCR, an initial denaturation step (95° C., 5 min) was followed by 40 cycles of 95° C. 15 s and 60° C. for 1 min. Forty amplification cycles were performed and the CT determined. Results were expressed as the [(Threshold−CT)/Threshold] ratio. This ratio reaches one when Spa DNA is detectable without amplification, and reaches zero when there is no detection of Spa DNA at the end of the 40-cycle amplification. 
     Results 
       FIG. 6B  shows the [(Threshold−CT)/Threshold] ratios obtained with  S. aureus  qPCR after co-incubation of  C. accolens, S. pasteuri  and  S. epidermidis  alone and in various combinations. When taken alone, none of the species inhibited  S. aureus  growth. In contrast, a synergistic inhibition of  S. aureus  growth was observed for the bacterial combinations  C. accolens/S. pasteuri  (2.9-fold reduction  S. aureus  in growth when compared to growth of  S. aureus  alone) or the combination  C. accolens/S. pasteuri/S. epidermidis  (12.6-fold reduction), in accordance with the present invention. 
     No irritation, erythema or alteration of the skin of the volunteer was observed. 
     Example 16: The Combination  C. accolens/S. Pasteuri  Shows a Synergistic  S. aureus  Decolonization Effect in a Murine Model of Stratified Squamous Epithelium 
     Our previous results obtained in vitro showed a synergistic bacteriotherapeutic activity of the combination  C. accolens/S. pasteuri  against  S. aureus  cells in vitro (see Example 11). We studied here the capacity of this combination to reduce  S. aureus  colonization ( S. aureus  decolonization) in an in vivo model of stratified squamous epithelium relevant for both the skin and anterior nares, using Nude mice. We further evaluated whether  S. epidermidis  had an antagonistic effect towards the combination  C. accolens/S. pasteuri.    
     Materials and Methods 
     Six-week old BALB/cAnNRj-Fox1 nu/nu mice were obtained from Janvier Labs (Le Genest-Saint-Isle, France) and were used after one week of acclimatization (IERP, INRA, Jouy-en-Josas, France). A 10 McF suspension of  S. aureus  (strain USA300) in physiological water (PSA) was prepared from a 24 h-culture on Columbia 5% sheep blood agar at 35+/−2° C. After homogenization, ≈250 μl was vaporized (Amber boston glass bottle, One Trillion, China) on the back of each mouse. Twenty-four hours later, a hydrocolloid sterile patch (Compeed, Paris, France) having five evenly spaced punched holes (diameter: 4.5 mm) was applied to the back of each mouse, with each hole constituting a 30 μl skin-bottom well. Lyophilized suspension of  C. accolens  (strain AF2345),  S. pasteuri  (strain AF2653) and optionally  S. epidermidis  (strain AF2302) were reconstituted with distilled sterile water to obtain a suspension of ≈10 10  CFU/mL for each species. Bacteria were inoculated in the skin well at a volume of 10 μl (≈10 8  CFU per skin well). The hydrocolloid patch and the surrounding skin were then covered by sterile polyurethane adhesive surgical incision film. Four conditions were tested:  C. accolens  alone;  S. pasteuri  alone;  C. accolens  combined with  S. pasteuri; C. accolens  combined  S. pasteuri  and  S. epidermidis ); 10 μl of physiological water was inoculated as control (“untreated  S. aureus ”). 
     Twenty-four hours later, mice were euthanized, the adhesive surgical incision film was peeled, and the skin area of each well was sampled with a humidified swab (ESwab®, COPAN, Brescia, Italy), and  S. aureus  CFUs enumerated by counting CFUs on MRSA agar (Biomérieux, Marcy-I&#39;Etoile, France). Results were measured in duplicate and expressed as the mean+/−SD log 10  CFU and as the mean percentage of CFU reduction versus control. 
     Results 
     Firstly, it should be noted that the mean number of  S. aureus  CFUs found with the control was 5.51 per well area (15.9 mm 2 ). Thus,  S. aureus  skin colonization reached a density of ≈2×10 4  CFU/mm 2  48 h post-inoculation, confirming the relevance of our model compared to available models of  S. aureus  nasal colonization in rodents. Indeed, in comparison, in an “optimized” model of nasal colonization using mice treated with oral streptomycin to reduce the natural nasal flora, ≈5×10 3  CFUs of  S. aureus /nose was found 8 hours after the intranasal instillation of 5×10 8  CFUs of  S. aureus  (Park et al., 2011). Similarly, in the cotton rat model, a well-established model for  S. aureus  nasal colonization which also requires the oral treatment of animals with streptomycin,  S. aureus  colonization was ≈5×10 4  CFU/nose 8 hours after inoculation (Baur et al., 2014). As  S. aureus  colonization occurs in the murine model used herein at levels similar to those described existing murine models, this model represents a clinically relevant model that should be considered as an appropriate equivalent to existing models. 
     The combination  C. accolens/S. pasteuri  showed a significant decolonization effect compared to the control (untreated  S. aureus ), with a mean CFU reduction of 72.6% (p&lt;0.005 versus control); this effect was synergistic as it was greater than with  C. accolens  alone,  S. pasteuri  alone, or the expected effect of the combination of  C. accolens/S. pasteuri  ( FIG. 7B ). 
     The combination  C. accolens/S. pasteuri/S. epidermidis  also showed a significant effect, with a comparable CFU reduction (66.5%, p&lt;0.005 versus control).  S. epidermidis  thus had no impact on the decolonization effect of the combination of  C. accolens/S. pasteuri.    
     CONCLUSION 
     Taken together, these Examples illustrate the surprising synergistic anti- S. aureus  activity that occurs when combining at least one  Corynebacterium  sp., such as  C. accolens  or  C. propinquum , with  S. pasteuri , and, optionally,  S. epidermidis . Furthermore, these results indicate that  S. pasteuri  particularly promotes growth of  Corynebacterium  spp. such as  C. accolens , and furthermore promotes biofilm formation of  C. accolens  in a synergistic manner when in co-culture as illustrated by quantification of the extracellular matrix. Biofilm formation was similarly improved in a synergistic manner when a  Corynebacterium  sp. was cultured with both  S. pasteuri  and  S. epidermidis . Advantageously, a composition comprising said bacterial species can furthermore be successfully lyophilized and reconstituted with no loss of effect, as the reconstituted composition prevents  S. aureus  colonization at the same level as fresh bacteria. Bacteriotherapeutic effects were clearly illustrated in murine models of both  S. aureus  nasal colonization and more generally in decolonization of stratified squamous epithelium, which functions as model of both the skin and the anterior nares. 
     Furthermore, administration of the composition to human forearm skin, which represents the most common ecological niches of  S. aureus  (i.e. the skin and the anterior nares), yielded similar results, greatly reducing colonization by  S. aureus  in vivo. 
     These Examples provide the first evidence that a composition comprising at least one  Corynebacterium  sp., preferably at least  C. accolens  or  C. propinquum , and  S. pasteuri , and, preferably also  S. epidermidis , represents a novel, unexpected and highly advantageous composition for use in the prevention and/or treatment of both MSSA and MRSA  S. aureus  colonization. 
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