BACKGROUND
it is assumed that methicillin-resistance genes had evolved in coagulase-negative staphylococci  and were then horizontally transferred among staphylococci  <cit> .
particularly s. sciuri  <cit>  and s. fleurettii  <cit>  are discussed as natural reservoir of the methicillin-resistance gene meca.
the meca gene is located on a mobile genetic element called staphylococcal cassette chromosome  and confers resistance to methicillin by encoding an altered penicillin-binding protein , which shows limited affinity to beta-lactam antibiotics.
the meca gene is now distributed among both coagulase-positive and -negative staphylococcal species.
in recent years, the isolation of methicillin-resistant cns  from diverse sources was reported.
dakic et al.
<cit>  detected mr-cns on medical devices, silva et al.
<cit>  in healthy humans, de mattos et al.
<cit>  and ruppe et al.
<cit>  in ambulatory patients, and diekema et al.
<cit>  in human bloodstream infections.
according to kloos and bannerman  <cit> , s. epidermidis and s. haemolyticus are the principal pathogens involved in foreign body infections.
miragaia et al.
<cit>  discussed s. epidermidis as one of the most important causes for hospital-acquired bacteremia and found many isolates from hospitalized patients to be methicillin-resistant.
recently, several authors reported mr-cns also in healthy animals.
the existence of mr-cns in animals was first described by kawano et al.
<cit> , who detected mr-cns in chicken.
worldwide, mr-cns were isolated from horses  <cit> , dogs  <cit> , cattle  <cit> , as well as from sheep, goats, and pigs  <cit> .
however, mr-cns were also found in animals with clinical infections.
van duijkeren et al.
<cit>  detected methicillin-resistant s. haemolyticus from cats with cystitis and rhinitis, from dogs with bronchitis and pyoderma, and from a horse with vaginitis.
moreover, fessler et al.
<cit>  reported different mr-cns species in association with bovine mastitis.
however, comprehensive data on mr-cns along the meat and milk production line were so far missing.
the present work is a subsequent study of a previously published study on the prevalence of mrsa in switzerland.
the aim of the present study was to evaluate the occurrence of mr-cns in livestock  and chicken carcasses, bulk tank milk  and minced meat, as well as people in contact with farm animals , to identify the occurring cns species, and to assess antibiotic resistance profiles of isolated strains.
RESULTS
mr-cns occurrence
using the described procedure, mr-cns were detected in 1' <dig>  of the 2' <dig> analyzed samples from livestock and chicken carcasses, btm and minced meat, and humans .
amongst the 1' <dig> samples from livestock and chicken carcasses, mr-cns were found in  <dig> % of samples.
thereby, the proportion of positive samples ranged from  <dig> % in pigs to  <dig> % in calves.
analysis of the  <dig> samples from btm and minced meat yielded an average mr-cns occurrence of  <dig> % .
of the  <dig> human samples,  <dig> % turned out to test positive for mr-cns .
1) nasal swabs.
2) herd-wise pooled neck skin samples.
3) at most three animals per farm were sampled.
4) at most two animals per farm were sampled.
species identification
a total of  <dig> strains were selected and subjected to species identification using maldi-tof ms. amongst samples, seven different cns species were detected .
sequencing of soda from a subset of  <dig> strains  confirmed the results obtained by maldi-tof ms. overall, s. sciuri  and s. fleurettii  were most frequently found, followed by s. haemolyticus , s. epidermidis , and s. lentus .
moreover, s. cohnii and s. warneri were only rarely identified .
btm: bulk tank milk; sh: slaughterhouse employees
within the  <dig> selected mr-cns strains of animal origin, the majority of strains was identified as s. sciuri , followed by s. fleurettii , s. lentus , s. haemolyticus , s. epidermidis , and s. warneri .
thirty of the  <dig> s. lentus strains isolated originated from chicken.
of the  <dig> strains isolated from calves,  <dig> were identified as s. sciuri.
the  <dig> strains from pigs were identified as s. sciuri  and s. fleurettii .
the  <dig> mr-cns strains isolated from cows also mainly consisted of s. sciuri  and s. fleurettii .
of the  <dig> mr-cns strains isolated from btm and minced meat samples,  <dig> % of strains were identified as s. fleurettii, followed by  <dig> % of strains identified as s. sciuri.
the remaining seven strains belonged to s. haemolyticus , s. epidermidis , s. cohnii , and s. warneri .
of the  <dig> mr-cns strains isolated from humans, s. haemolyticus  and s. epidermidis  accounted for the great majority.
s. lentus were only isolated from eight employees of a poultry slaughterhouse, whereas s. fleurettii was found in a veterinarian, two pig farmers, and three slaughterhouse employees.
the remaining three mr-cns strains isolated from two veterinarians and a slaughterhouse employee were identified as s. cohnii, s. warneri and s. sciuri.
antimicrobial susceptibility testing
the results of the phenotypic antibiotic resistance testing of the  <dig> mr-cns strains are shown in tables  <dig>   <dig> and  <dig>  although all characterized strains harbored the meca gene, phenotypic resistance to beta-lactam antibiotics  varied between  <dig> %  and  <dig> % .
resistance to ciprofloxacin, clindamycin, erythromycin, gentamicin, sulphamethoxazole/trimethoprim, and tetracycline varied between  <dig> % and  <dig> %.
on the other hand, resistance to rifampin and vancomycin was only detected in  <dig> % and  <dig> % of strains, respectively.
table  <dig> shows the species-specific situation of mr-cns strains to cefoxitin.
amp: ampicillin; cef: cefoxitin; cip: ciprofloxacin; cli: clindamycin; ery: erythromycin; gen: gentamicin; oxa: oxacillin; pen: penicillin; rif: rifampin; sxt: sulphamethoxazole/trimethoprim; tet: tetracycline;van: vancomycin.
amp: ampicillin; cef: cefoxitin; cip: ciprofloxacin; cli: clindamycin; ery: erythromycin; gen: gentamicin; oxa: oxacillin; pen: penicillin; rif: rifampin; sh: slaughterhouse; sxt: sulphamethoxazole/trimethoprim; tet: tetracycline; van: vancomycin.
with regard to resistance rates of individual mr-cns species , more than 87% of the s. sciuri and s. haemolyticus strains showed phenotypical resistance to beta-lactam antibiotics.
on the other hand, of the s. epidermidis, s. fleurettii, and s. lentus strains only 60% to 80% were resistant to beta-lactam antibiotics.
apart from one exception, more than 54% of strains from cows, calves, veterinarians and pig farmers were resistant to ciprofloxacin, clindamycin, erythromycin, and tetracycline .
in contrast, apart from two exceptions, less than 27% of strains isolated from btm, minced meat, pigs and slaughterhouse employees, were resistant to the four antibiotics mentioned above.
no strains from btm, minced meat, and chicken were resistant to sulphamethoxazole/trimethoprim , whereas  <dig> % of strains from pig farmers and  <dig> % of strains from veterinarians showed resistance to sxt.
none of the strains isolated from btm and minced meat samples were resistant to rifampin or vancomycin.
discussion
methicillin-resistant staphylococci are a major concern to public and animal health.
in veterinary medicine and along the meat and milk production line only very limited data were available on characteristics of mr-cns.
the present study provides an overview on the mr-cns situation in swiss livestock, chicken carcasses, btm, minced meat, and persons in contact with farm animals.
since data of studies with comparable procedures are lacking, direct comparison of results is not possible.
therefore, we discussed our results in comparison to data that we considered most appropriate and as close to our own results as possible.
in our study, mr-cns were detected at an average of  <dig> % in 2' <dig> samples.
the occurrence varied thereby from  <dig> % in slaughterhouse employees to  <dig> % in calves.
the mr-cns occurrence rates mentioned above are in contrast to the low mrsa prevalence in switzerland  <cit> .
in the present study,  <dig> % of all samples from livestock  and chicken carcasses tested positive for mr-cns.
mr-cns were also found in cows and pigs by zhang et al.
<cit> .
in contrast, bagcigil et al.
<cit>  did not detect any mr-cns in pigs and cattle.
the species most frequently detected in animal samples of the present study were s. sciuri , followed by s. fleurettii , and s. lentus .
in calves,  <dig> % of mr-cns strains were identified as s. sciuri, whereas in cows only  <dig> % belonged to this species.
the strains from pigs were divided about half-and-half in s. sciuri and s. fleurettii.
the high percentage of s. sciuri in pigs is especially relevant, since this cns species is also reported to cause fatal exudative epidermitis in piglets  <cit> , which is normally caused by exfoliative toxin producing s. hyicus.
interestingly, methicillin-resistant s. sciuri were also found to predominate in horses  <cit> .
furthermore, the mr-cns strains isolated from chicken in our study were mainly  of s. lentus, whereas kawano et al.
<cit>  did not detect methicillin-resistant s. lentus in their samples.
methicillin-resistant s. lentus have also been described in other animal species such as horses  <cit> , pigs, cattle, sheep, and goats  <cit> .
other data on species-specific identification of mr-cns from livestock are limited.
in the btm and minced meat samples of the present study, mr-cns were detected in  <dig> % of minced meat and in  <dig> % of btm samples.
respective data on mr-cns from these sample categories are hardly found.
the species predominantly found in btm and minced meat samples of the present study, were s. fleurettii accounting for  <dig> % of all analyzed strains, followed by s. sciuri comprising  <dig> % of strains.
in bovine quarter milk samples, gillespie et al.
<cit>  found mainly cns of s. chromogenes, s. hyicus, s. epidermidis, and s. simulans.
in a subsequent study, sawant et al.
<cit>  found  <dig> of  <dig> s. epidermidis strains to harbor the meca gene and show phenotypic resistance to ampicillin and oxacillin.
on the other hand, cns are also frequently isolated from clinical and in particular subclinical intramammary infections in cattle  <cit>  and small ruminants  <cit> .
cns found in this context generally showed a species distribution different from that present in our samples.
in the  <dig> nasal swabs from humans in contact with farm animals, mr-cns were detected in  <dig> % of samples.
in view of contact persons, two studies found the prevalence of mr-cns in horse personnel to be 37% and 63%  <cit> .
moreover, a study among healthy humans without association to hospital or animals found an mr-cns prevalence of 24%  <cit> .
in human samples of the present study, the most frequently isolated species were s. haemolyticus  and s. epidermidis .
mr-cns of species s. haemolyticus  <cit>  and s. epidermidis  <cit>  were also frequently isolated from horse personnel.
these two predominant species are also of importance for human infections.
as discussed above, s. epidermidis and s. haemolyticus are frequently isolated cns species involved in clinical cases of humans.
there are not much data available on the antimicrobial susceptibility of mr-cns isolated from colonized livestock and humans, or from btm and minced meat.
in the present study, mr-cns strains from btm, minced meat, and chicken were only in limited numbers resistant to antibiotics other than beta-lactams.
in view of mr-cns as food contaminants and potential vectors of antibiotic resistance, these results suggest a favorable situation.
in contrast, strains isolated from calves, cows, pig farmers, and veterinarians showed multi-resistance to a great extent.
this situation may also be caused by frequent direct contact of these individuals with antibiotics.
interestingly, resistance rates of strains from pigs and slaughterhouse employees were in-between the groups mentioned above.
furthermore, it is noteworthy that in our mr-cns strains, phenotypic resistance to oxacillin was by far a better indicator for the presence of the meca gene than resistance to cefoxitin.
interestingly, for indication of meca in mr-cns using mic, both cefoxitin and oxacillin are discussed as valuable approaches  <cit> .
CONCLUSIONS
in conclusion, the results obtained indicate a high mr-cns prevalence  in samples from livestock, chicken carcasses, btm and minced meat, as well as persons in contact with livestock.
the occurrence thereby ranged from  <dig> % in slaughterhouse employees to  <dig> % in calves.
this is the first study detecting mr-cns in a large collection of samples taken along the meat and milk production line.
for species identification of mr-cns isolated from different origins, maldi tof ms proved to be a fast and reliable tool and is therefore suitable for screening of large sample amounts.
furthermore, based on the present data, the occurrence of methicillin-resistant staphylococci should be continuously evaluated in surveillance programs within the scope of veterinary public health aspects.
otherwise, further studies are required to investigate the impact of the high mr-cns prevalence on human and animal health.

 it is assumed that methicillin-resistance genes had evolved in coagulase-negative staphylococci and were then horizontally transferred among staphylococci. particularly s. sciuri and s. fleurettii are discussed as natural reservoir of the methicillin-resistance gene meca. the meca gene is located on a mobile genetic element called staphylococcal cassette chromosome and confers resistance to methicillin by encoding an altered penicillin-binding protein, which shows limited affinity to beta-lactam antibiotics. the meca gene is now distributed among both coagulase-positive and -negative staphylococcal species. in recent years, the isolation of methicillin-resistant cns from diverse sources was reported. dakic et al. detected mr-cns on medical devices, silva et al. in healthy humans, de mattos et al. and ruppe et al. in ambulatory patients, and diekema et al. in human bloodstream infections. according to kloos and bannerman, s. epidermidis and s. haemolyticus are the principal pathogens involved in foreign body infections. miragaia et al. discussed s. epidermidis as one of the most important causes for hospital-acquired bacteremia and found many isolates from hospitalized patients to be methicillin-resistant. recently, several authors reported mr-cns also in healthy animals. the existence of mr-cns in animals was first described by kawano et al., who detected mr-cns in chicken. worldwide, mr-cns were isolated from horses, dogs, cattle, as well as from sheep, goats, and pigs. however, mr-cns were also found in animals with clinical infections. van duijkeren et al. detected methicillin-resistant s. haemolyticus from cats with cystitis and rhinitis, from dogs with bronchitis and pyoderma, and from a horse with vaginitis. moreover, fessler et al. reported different mr-cns species in association with bovine mastitis. however, comprehensive data on mr-cns along the meat and milk production line were so far missing. the present work is a subsequent study of a previously published study on the prevalence of mrsa in switzerland. the aim of the present study was to evaluate the occurrence of mr-cns in livestock and chicken carcasses, bulk tank milk and minced meat, as well as people in contact with farm animals, to identify the occurring cns species, and to assess antibiotic resistance profiles of isolated strains.  mr-cns occurrence using the described procedure, mr-cns were detected in 1' of the 2' analyzed samples from livestock and chicken carcasses, btm and minced meat, and humans. amongst the 1' samples from livestock and chicken carcasses, mr-cns were found in % of samples. thereby, the proportion of positive samples ranged from % in pigs to % in calves. analysis of the samples from btm and minced meat yielded an average mr-cns occurrence of %. of the human samples, % turned out to test positive for mr-cns. 1) nasal swabs. 2) herd-wise pooled neck skin samples. 3) at most three animals per farm were sampled. 4) at most two animals per farm were sampled. species identification a total of strains were selected and subjected to species identification using maldi-tof ms. amongst samples, seven different cns species were detected. sequencing of soda from a subset of strains confirmed the results obtained by maldi-tof ms. overall, s. sciuri and s. fleurettii were most frequently found, followed by s. haemolyticus, s. epidermidis, and s. lentus. moreover, s. cohnii and s. warneri were only rarely identified. btm: bulk tank milk; sh: slaughterhouse employees within the selected mr-cns strains of animal origin, the majority of strains was identified as s. sciuri, followed by s. fleurettii, s. lentus, s. haemolyticus, s. epidermidis, and s. warneri. thirty of the s. lentus strains isolated originated from chicken. of the strains isolated from calves, were identified as s. sciuri. the strains from pigs were identified as s. sciuri and s. fleurettii. the mr-cns strains isolated from cows also mainly consisted of s. sciuri and s. fleurettii. of the mr-cns strains isolated from btm and minced meat samples, % of strains were identified as s. fleurettii, followed by % of strains identified as s. sciuri. the remaining seven strains belonged to s. haemolyticus, s. epidermidis, s. cohnii, and s. warneri. of the mr-cns strains isolated from humans, s. haemolyticus and s. epidermidis accounted for the great majority. s. lentus were only isolated from eight employees of a poultry slaughterhouse, whereas s. fleurettii was found in a veterinarian, two pig farmers, and three slaughterhouse employees. the remaining three mr-cns strains isolated from two veterinarians and a slaughterhouse employee were identified as s. cohnii, s. warneri and s. sciuri. antimicrobial susceptibility testing the results of the phenotypic antibiotic resistance testing of the mr-cns strains are shown in tables and although all characterized strains harbored the meca gene, phenotypic resistance to beta-lactam antibiotics varied between % and %. resistance to ciprofloxacin, clindamycin, erythromycin, gentamicin, sulphamethoxazole/trimethoprim, and tetracycline varied between % and %. on the other hand, resistance to rifampin and vancomycin was only detected in % and % of strains, respectively. table shows the species-specific situation of mr-cns strains to cefoxitin. amp: ampicillin; cef: cefoxitin; cip: ciprofloxacin; cli: clindamycin; ery: erythromycin; gen: gentamicin; oxa: oxacillin; pen: penicillin; rif: rifampin; sxt: sulphamethoxazole/trimethoprim; tet: tetracycline;van: vancomycin. amp: ampicillin; cef: cefoxitin; cip: ciprofloxacin; cli: clindamycin; ery: erythromycin; gen: gentamicin; oxa: oxacillin; pen: penicillin; rif: rifampin; sh: slaughterhouse; sxt: sulphamethoxazole/trimethoprim; tet: tetracycline; van: vancomycin. with regard to resistance rates of individual mr-cns species, more than 87% of the s. sciuri and s. haemolyticus strains showed phenotypical resistance to beta-lactam antibiotics. on the other hand, of the s. epidermidis, s. fleurettii, and s. lentus strains only 60% to 80% were resistant to beta-lactam antibiotics. apart from one exception, more than 54% of strains from cows, calves, veterinarians and pig farmers were resistant to ciprofloxacin, clindamycin, erythromycin, and tetracycline. in contrast, apart from two exceptions, less than 27% of strains isolated from btm, minced meat, pigs and slaughterhouse employees, were resistant to the four antibiotics mentioned above. no strains from btm, minced meat, and chicken were resistant to sulphamethoxazole/trimethoprim, whereas % of strains from pig farmers and % of strains from veterinarians showed resistance to sxt. none of the strains isolated from btm and minced meat samples were resistant to rifampin or vancomycin. discussion methicillin-resistant staphylococci are a major concern to public and animal health. in veterinary medicine and along the meat and milk production line only very limited data were available on characteristics of mr-cns. the present study provides an overview on the mr-cns situation in swiss livestock, chicken carcasses, btm, minced meat, and persons in contact with farm animals. since data of studies with comparable procedures are lacking, direct comparison of results is not possible. therefore, we discussed our results in comparison to data that we considered most appropriate and as close to our own results as possible. in our study, mr-cns were detected at an average of % in 2' samples. the occurrence varied thereby from % in slaughterhouse employees to % in calves. the mr-cns occurrence rates mentioned above are in contrast to the low mrsa prevalence in switzerland. in the present study, % of all samples from livestock and chicken carcasses tested positive for mr-cns. mr-cns were also found in cows and pigs by zhang et al.. in contrast, bagcigil et al. did not detect any mr-cns in pigs and cattle. the species most frequently detected in animal samples of the present study were s. sciuri, followed by s. fleurettii, and s. lentus. in calves, % of mr-cns strains were identified as s. sciuri, whereas in cows only % belonged to this species. the strains from pigs were divided about half-and-half in s. sciuri and s. fleurettii. the high percentage of s. sciuri in pigs is especially relevant, since this cns species is also reported to cause fatal exudative epidermitis in piglets, which is normally caused by exfoliative toxin producing s. hyicus. interestingly, methicillin-resistant s. sciuri were also found to predominate in horses. furthermore, the mr-cns strains isolated from chicken in our study were mainly of s. lentus, whereas kawano et al. did not detect methicillin-resistant s. lentus in their samples. methicillin-resistant s. lentus have also been described in other animal species such as horses, pigs, cattle, sheep, and goats. other data on species-specific identification of mr-cns from livestock are limited. in the btm and minced meat samples of the present study, mr-cns were detected in % of minced meat and in % of btm samples. respective data on mr-cns from these sample categories are hardly found. the species predominantly found in btm and minced meat samples of the present study, were s. fleurettii accounting for % of all analyzed strains, followed by s. sciuri comprising % of strains. in bovine quarter milk samples, gillespie et al. found mainly cns of s. chromogenes, s. hyicus, s. epidermidis, and s. simulans. in a subsequent study, sawant et al. found of s. epidermidis strains to harbor the meca gene and show phenotypic resistance to ampicillin and oxacillin. on the other hand, cns are also frequently isolated from clinical and in particular subclinical intramammary infections in cattle and small ruminants. cns found in this context generally showed a species distribution different from that present in our samples. in the nasal swabs from humans in contact with farm animals, mr-cns were detected in % of samples. in view of contact persons, two studies found the prevalence of mr-cns in horse personnel to be 37% and 63%. moreover, a study among healthy humans without association to hospital or animals found an mr-cns prevalence of 24%. in human samples of the present study, the most frequently isolated species were s. haemolyticus and s. epidermidis. mr-cns of species s. haemolyticus and s. epidermidis were also frequently isolated from horse personnel. these two predominant species are also of importance for human infections. as discussed above, s. epidermidis and s. haemolyticus are frequently isolated cns species involved in clinical cases of humans. there are not much data available on the antimicrobial susceptibility of mr-cns isolated from colonized livestock and humans, or from btm and minced meat. in the present study, mr-cns strains from btm, minced meat, and chicken were only in limited numbers resistant to antibiotics other than beta-lactams. in view of mr-cns as food contaminants and potential vectors of antibiotic resistance, these results suggest a favorable situation. in contrast, strains isolated from calves, cows, pig farmers, and veterinarians showed multi-resistance to a great extent. this situation may also be caused by frequent direct contact of these individuals with antibiotics. interestingly, resistance rates of strains from pigs and slaughterhouse employees were in-between the groups mentioned above. furthermore, it is noteworthy that in our mr-cns strains, phenotypic resistance to oxacillin was by far a better indicator for the presence of the meca gene than resistance to cefoxitin. interestingly, for indication of meca in mr-cns using mic, both cefoxitin and oxacillin are discussed as valuable approaches.  in conclusion, the results obtained indicate a high mr-cns prevalence in samples from livestock, chicken carcasses, btm and minced meat, as well as persons in contact with livestock. the occurrence thereby ranged from % in slaughterhouse employees to % in calves. this is the first study detecting mr-cns in a large collection of samples taken along the meat and milk production line. for species identification of mr-cns isolated from different origins, maldi tof ms proved to be a fast and reliable tool and is therefore suitable for screening of large sample amounts. furthermore, based on the present data, the occurrence of methicillin-resistant staphylococci should be continuously evaluated in surveillance programs within the scope of veterinary public health aspects. otherwise, further studies are required to investigate the impact of the high mr-cns prevalence on human and animal health. 
in veterinary medicine and along the meat and milk production line, only limited data were so far available on mr-cns characteristics. multiresistant cns strains might become an emerging problem for veterinary medicine. s. sciuri and s. fleurettii thereby predominated in livestock, btm and minced meat samples, whereas s. epidermidis and s. haemolyticus predominated in human samples. for species identification of mr-cns isolated from different origins, maldi-tof ms proved to be a fast and reliable tool and is suitable for screening of large sample amounts. after two-step enrichment and growth on chromogenic agar, mr-cns were detected in % of samples from livestock and chicken carcasses, % of samples from bulk tank milk and minced meat, and % of human samples. the aim of the present study was to evaluate the prevalence of mr-cns, to identify the detected staphylococci to species level, and to assess the antibiotic resistance profiles of isolated mr-cns strains. using matrix-assisted laser desorption ionization-time of flight mass spectrometry, selected mr-cns strains belonged to seven different species.
 methicillin-resistant coagulase-negative staphylococci are of increasing importance to animal and public health. in veterinary medicine and along the meat and milk production line, only limited data were so far available on mr-cns characteristics. the aim of the present study was to evaluate the prevalence of mr-cns, to identify the detected staphylococci to species level, and to assess the antibiotic resistance profiles of isolated mr-cns strains.  after two-step enrichment and growth on chromogenic agar, mr-cns were detected in % of samples from livestock and chicken carcasses, % of samples from bulk tank milk and minced meat, and % of human samples. using matrix-assisted laser desorption ionization-time of flight mass spectrometry, selected mr-cns strains belonged to seven different species. s. sciuri and s. fleurettii thereby predominated in livestock, btm and minced meat samples, whereas s. epidermidis and s. haemolyticus predominated in human samples. in addition to beta-lactam resistance, 33-49% of all strains were resistant to certain non-beta-lactam antibiotics.  a high prevalence of mr-cns was found in livestock production. this is of concern in view of potential spread of meca to s. aureus. multiresistant cns strains might become an emerging problem for veterinary medicine. for species identification of mr-cns isolated from different origins, maldi-tof ms proved to be a fast and reliable tool and is suitable for screening of large sample amounts. 