Evaluation of the Emission Distance of P. Aeruginosa From the Respiratory Tract of People With Cystic Fibrosis
Condition: Cystic Fibrosis
MeSH terms: Cystic Fibrosis; Fibrosis
Study type: Observational

Summary: 
      It is well known that an association exists between the acquisition of some respiratory
      pathogens and prognosis of CF people. About 57 % of patients has a lung infection due to
      P.aeruginosa (PA). Transmission of PA between CF patients is possible and several prevention
      measures are recommended. Among these measures, all international guidelines recommend that
      CF people maintain a minimum distance of 1 meter between them. However, this recommendation
      is not supported by specific studies and scientific evidence. In other words, the
      investigators don't know if this measure is sufficient or excessive, as it is based only on a
      theoretical rationale.

      This study aims at measuring experimentally the distance that can be reached by PA emitted
      from airways of colonized CF patients during cough and during conversation.

      To this purpose, the investigators will evacuate the presence of PA on surfaces placed at 4
      different distances from patients, through the collection of 8 swabs, 4 of which following
      cough and 4 following conversation. Swabs will be collected on sterile surfaces comprised
      between tra 0 - 0,5 mt; 0,5 -1,00 mt.; 1,00 - 1,5 mt and 1.5-2 mt.

      All the PA-positive CF patients of the CF Centre of Tuscany aged 14 or more will be
      recruited.
    

Detailed description: 
      Background

      Cystic Fibrosis (CF) represents the most frequent genetic disorder with autosomal recessive
      transmission having a negative prognosis in Caucasian populations, with an incidence of about
      1 in 3000. CF is a multisystemic disease involving the exocrine functions, in particular, of
      the respiratory tract and the gastroenteric system. The mutated gene causes an alteration in
      the transportation of chloride and sodium that leads to the production of denser bronchial
      secretion, favouring the onset of chronic respiratory infections, inflammations and
      respiratory insufficiency. Indeed, pulmonary infections are one of the primary
      characteristics, as well as the main cause of morbidity and mortality in CF.

      There is an association between the acquisition of some respiratory pathogens (mainly B.
      cepacia complex [BCC] and P. aeruginosa [PA]) and the worsening of the parameters of
      respiratory function and a lower survival rate.

      Recent epidemiological data show that 57.3% of CF patients have a pulmonary infection caused
      by PA.

      Therefore, to prevent the clinical consequences deriving from chronic colonization of PA,
      avoiding contact with the infected patient when possible can be of fundamental importance.

      The means by which the patient comes in contact with these pathogens is still not entirely
      clear; nevertheless, it is believed that transmission can occur through direct contact or
      droplets, or through indirect contact with inert surfaces used in common by colonized and
      non-colonized patients, or by reservoirs and surfaces in the care environment itself.
      Droplets are defined as large drops (>5 microns) produced by coughing, sneezing or speaking,
      or by the implementing of certain procedures such as aspiration or broncoscopy.

      As for indirect means of transmission, it has been demonstrated that these pathogens have
      high survival rates on inert surfaces: for example, PA suspended in physiological solution
      can survive on dry surfaces for 24 hours and in patient expectoration for 8 days.

      If expelled with coughing or sneezing from the CF patient's respiratory tract, therefore, PA
      and BCC [20] can linger on the surfaces of the health care centre for a long time, later to
      enter into contact with the respiratory mucosa of CF patients attending the same centre,
      through contact of the patients' hands on contaminated surfaces.

      Only a limited number of studies has evaluated the prevalence of pathogens on non-critical
      surfaces in a CF centre.

      In one recent study our research group evaluated over a 4-year period the prevalence of the
      pathogenic micro-organisms for CF in specimens taken from non-critical surfaces and sinks of
      an out-patient clinic dedicated exclusively to the care of CF patients, with the aim of
      improving the prevention of cross-infections in CF centres.

      As for direct transmission of PA, there are various international prevention guidelines. All
      the guidelines include the recommendation that CF patients maintain a minimum distance of 1
      meter between one another.

      A recent study has demonstrated the theoretical possibility of airborne PA transmission.

      Specific Aims and Rationale According to all international guidelines for controlling and
      preventing infections in CF patients, it is necessary to maintain a minimum distance of 1
      meter from other CF patients in order to avoid the transmission of PA and BCC and the
      clinical consequences of a chronic infection from this pathogen. This indication derives from
      a similar recommendation contained in the CDC Guidelines on hospital isolation precautions
      relative to all infectious diseases transmitted through droplets. It is based on the
      theoretical assumption that, besides transmission by direct contact, the transmission of PA
      takes place prevalently through droplets.

      There have been only two studies on the distance reached by PA emitted from the respiratory
      tract of CF patients. The first study [18] examined PA emission from CF patients' coughing,
      making them cough onto a dish held by the patients themselves, then onto a plate held at a
      distance of about a meter. In the second study six PA-colonized patients coughed in the
      direction of a soap bubble holder held at a distance of 10 cm, 20 cm, 30 cm, 40 cm and 50 cm
      from the mouth.

      The results obtained in these two studies have shown the possibility of transmitting PA
      through coughing at a distance of at least one meter, and the possibility of emitting PA at
      distances greater than 40 cm. However, these studies do not provide proof that one meter is
      an effective indicator of the distance necessary for preventing PA emitted by one patient
      from reaching another.

      It appears that no study has ever investigated if PA can be expelled from a carrier's
      respiratory tract by coughing at a distance greater than the recommended one meter "safety
      distance" between CF patients, and no study has been done on the maximum distance PA emitted
      during a normal conversation can reach.

      In any case, aside from the distance PA can actually reach; there are no studies on the
      effectiveness of a 1-meter distance between CF patients as a measure for preventing PA
      cross-infections.

      Since there are very few data available on how far PA emitted from the respiratory tract of a
      colonized CF patient through coughing can reach and no data relative to simple conversation,
      the recommendation of a one-meter distance does not seem to be backed up by sufficient
      evidence. In other words, one meter may not be a great enough distance for preventing the
      potential risk of transmission; therefore, the recommendation to maintain a minimum distance
      of one meter may be inadequate.

      Our study thus intends to contribute to filling the knowledge gap to this regard, and to
      clarifying the validity of the minimum distance of one meter as a prevention measure in the
      transmission of PA from one CF patient to another.

      The objectives in this study are:

        -  To evaluate what distance can be reached by PA expelled through the emission of droplets
           from the respiratory tract of a CF patient during a simple conversation and coughing.

        -  To verify if the 1-meter distance from patients colonized by PA is actually an effective
           prevention measure in regard to PA infection, as reported in the International
           Guidelines.

      Experimental study not checked with convenience sample. This study will evaluate the distance
      reached by Pseudomonas aeruginosa after a normal conversation and after coughing by CF
      patients.

      With this aim, we will evaluate the presence of PA on surfaces at 4 different distances from
      the patient, by culturing 8 swabs taken from the surfaces themselves, 4 of which after normal
      conversation and 4 others after coughing.

      Data collection At the time of inclusion in the study the following data will be collected:
      Patient name and surname, age in months, Rx score, FEV1, BMI, Micro-organisms present in the
      previous and current expectorate culture, PCR.

      After collecting the specimens and preparing the culture plates, PA growth in the mediums
      corresponding to the various collection distances will be observed.

      The results of the laboratory analysis will be reported in the patient's file, thus:

      Presence of Pseudomonas Aeruginosa

        -  after conversation: 0 - 0.5 m; 0.5 - 1.00 m; 1.00 - 1.5 m; 1.50 - 2.00 m.

        -  after coughing: 0 - 0.5 m; 0.5 - 1.00 m; 1.00 - 1.5 m; 1.50 - 2.00 m.

      Safety measures Personnel will wear single-use gloves and coats.

      Data management and statistical analysis The data will be entered into Microsoft Access 2000
      database. For each of the four distances and for each of the two modes (coughing and
      conversation) the percentage of PA presence will be determined and the confidence intervals
      will be defined to 95% of the percentages.

      Moreover, we will look for associations between the presence/absence of PA at each distance
      and for each of the modes, and the clinical variables in each patient.

      For qualitative variables statistical analysis will be made with Chi-square test. For
      quantitative variables statistical analysis will be done with Student's T-distribution.

      Expected Results:

      We expect to obtain estimates of the proportion of contaminated areas so as to estimate the
      CF patient risk of being reached by secretions expelled from the respiratory tract of other
      CF patients at different distances.

      Clinical protocols

      Recruitment:

      Upon a patient receiving a check-up at the CF Centre, the researcher will decide, on the
      basis of demographics and microbiology, if the patient can be included in the study group.

      If the patient has reached the age of 14 and the last microbiological culture of his
      expectorate is positive for PA, the patient will be asked (and his parents, if under age) to
      participate in the study and will be given background information. After all his questions
      are answered, if the patient decides to participate his written consent will be taken
      (co-signed by his parents, if under age). Subsequently, the patient's entry data will be
      taken by filling out a patient questionnaire, after which the specimens will be collected.

      The study does not call for the assignment of a therapeutic strategy; the clinical and
      laboratory data relative to the patients participating in the study will be obtained during
      routine follow-up, without modifying current clinical practice.

      Specimen collection methods To collect the specimens, a special ruled table (0.5 X 2.10) will
      be set up and covered with a single-use waterproof surgical cloth after the patient has been
      enlisted in the study.

      The patient will then be asked to place himself in front of the table at the 0 m point.

      The table will be regulated according to the patient's height, at the level of his navel.

      Then the patient will be asked to read a text placed in front of him out loud, in order to
      recreate a normal conversation.

      We will then proceed to take the specimens with 4 sterile swabs, each one of which will be
      used for collecting specimens on the table surface subdivided into the following distances: 0
      - 0.5 m; 0.5 - 1.00 m; 1.00 - 1.5 m; 1.50 - 2.00 m.

      Specimen collection with a sterile swab from the surface of the sterile cloth will be done by
      rubbing entirely each of the four surfaces into which the sterile cloth is subdivided
      entirely, using a boustrophedonic movement.

      After the first set is collected, the single-use cloth will be substituted in order to
      restore sterile conditions.

      Next, the patient will be asked to perform two FET sequences which consist in giving one or
      two forced expirations with the glottis open, starting with medium-low lung volume, followed
      by a rest period in which diaphragm breathing is maintained. At this point the collection of
      the next 4 specimens will be taken in the method described above.
    

Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        People with CF attending the CF Center of Tuscany, aged 14 or older, with documented
        pulmonary Pseudomnas aeruginosa infection.
      
Keywords: pulmonary infection; transmission; P.Aeruginosa; surfaces