a prospective molecular epidemiologic study of s. aureus was performed in a 12-bed icu at the university hospital in montpellier , france , during 5 months in 2011 .
s. aureus nasal carriage was investigated at admission and weekly in 89 patients and monthly in 63 volunteer health care workers ( hcws ) .
simultaneously , all s. aureus isolates from clinical samples were obtained from the hospital laboratory of bacteriology and clinical data were recorded .
pneumonia was diagnosed on the basis of clinical , biologic , and radiologic criteria , and a colony count 10 cfu / ml in bronchoalveolar fluid culture or 10 cfu / ml in sputum cultures .
bronchial colonization was defined as a colony count < 10 cfu / ml in sputum cultures in asymptomatic patients .
random sampling of surfaces was performed monthly in all rooms of the icu ( 864 environmental sites ) .
isolates were characterized by using multilocus sequence typing , double - locus sequence typing ( dlst ) , and accessory gene regulation ( agr ) typing .
virulence genes and erma , ermc , ermt , and msra genes were screened for by using pcrs . during the survey period , the number of samples obtained ranged from 1 to 32 per patient and from 1 to 3 per hcw .
of these samples , 125 s. aureus isolates ( 110 mssa and 15 mrsa ) were obtained from 33 patients , 26 hcws , and 36 environmental sites ; these isolates belonged to 28 sts and 12 ccs . among these 125 isolates ,
12 isolates from 5 patients , 2 isolates from 2 hcws , and 15 isolates from 15 environmental sites belonged to cc398 ( figure 1 ; technical appendix ) .
the 29 strains were mssa and belonged to st398 ( n = 25 ) or to a new st submitted to the mlst database ( http://www.mlst.net/ ) as st2658 ( n = 4 ) .
st398 and cc398 were the most prevalent genotype and clonal complex identified : 25/125 ( 20% ) and 29/125 ( 23.2% ) isolates , respectively ( figure 2 ) .
flowchart of selection for methicillin - sensitive staphylococcus aureus clonal complex ( cc ) 398 from intensive care unit , france , 2011 .
principal clonal complexes ( ccs ) among 125 isolates of staphylococcus aureus from intensive care unit , france , 2011 .
the prevalence of mssa cc398 carriage was 3.2% ( 2/63 ) in hcws and 5.6% ( 5/89 ) in patients .
the prevalence of mssa cc398 infection was 2.25% ( 2/89 patients ) ( figure 1 ) .
these patients were hospitalized during the same period ; nosocomial pneumonia developed after nasal colonization , and was associated with bacteremia in 1 case .
demographic and clinical characteristics were similar in patients colonized or infected with mssa cc398 or with other genotypes ( table 1 ) .
genotype cc398 was found more frequently in the icu environment ( 15/36 , 41.7% ) than in patients ( 5/33 , 15.2% ;   4.7 , p = 0.03 ) and hcws ( 2/26 , 7.7% ;   7.1 , p = 0.007 ) ( technical appendix ) .
* copd , chronic obstructive pulmonary disease ; crf , chronic respiratory failure ; is , immunosuppressive therapy ; icu , intensive care unit ; saps ii , simplified acute physiology score ii .
four strains belonged to the new st2658 , which differed from st398 by a synonymous mutation ( ag ) at position 198 of the pta gene .
these 4 strains were isolated from nasal carriage samples ( n = 2 ) , bronchial colonization samples ( n = 1 ) , and pneumonia testing samples ( n = 1 ) from 2 patients hospitalized at the same time .
all mssa cc398 strains were agr type 1 , spa type t571 ( determined by using dnagear software ; http://w3.ualg.pt/hshah/dnagear/ ) , and dlst type 144186 ( dlst spa 186 corresponding to spa type t571 ) .
genes encoding panton - valentine leukocidin , toxic shock syndrome toxin 1 , and staphylococcal enterotoxin a were not detected . sensitivity testing of mssa cc398 isolates showed that all isolates were resistant to erythromycin and had an inducible macrolide  lincosamide  streptogramin b phenotype .
in addition , resistance to penicillin and amoxicillin caused by -lactamase production was observed in 41.4% ( 12/29 ) of the strains .
resistance to kanamycin , tobramycin , and gentamicin was observed in 24.1% ( 7/29 ) of the strains ; all 7 strains were isolated from environmental samples .
analysis of genes encoding antimicrobial drug resistance identified the ermt gene in all the cc398 strains and a variable distribution of erma and ermc genes .
* p , patient ; hcw , health care worker , e , environment . 
s , sputum ; n , nose ; bal , bronchoalveolar lavage fluid ; b , bloodstream . 
bl , -lactamase ( resistance to penicillin and amoxicillin ) ; imls , inducible macrolide  lincosamide  streptomycin b ; ktg , kanamycin , tobramycin , gentamicin . 
identification of mssa cc398 in hcws , patients without exposure to livestock , and the environment in an icu indicates emergence of this clone in a hospital in france .
the prevalence of nasal carriage in hcws and patients was high ( 5.6% ) in the context of the icu , where these persons have frequent contact with each other .
the small number of patients colonized or infected with s. aureus cc398 limits statistical comparison of the 2 groups and identification of risk factors for infection . despite the monocentric nature and the short period of the study , which limit extrapolation of our results to other settings ,
our study underlines the capacity of mssa cc398 to circulate among and between patients , hcws , and the icu environment .
reported prolonged survival of bovine mssa st398 strain in the human nose after artificial inoculation , which suggested that competition with human strains might facilitate its spread ( 12 ) .
identification of st2658 in 2 patients hospitalized at the same time reinforces the hypothesis of an increased capacity of transmission of this clonal complex between patients .
person - to - person spread of mssa st398 has been reported within community households ( 8,10 ) and more recently in a hospital ( 11 ) and an urban jail ( 9 ) , in which a high proportion of detainees sharing a holding tank were colonized with mssa st398 ( 9 ) .
these findings contrast with limited transmissibility of livestock - associated mrsa st398 , which is partially explained by molecular signatures of bacterial host adaptation identified only in the mssa st398 genome , such as different composition of adhesion genes that result in enhanced adhesion to human skin ( 10 ) .
all strains were spa type t571 , which is the major spa type associated with mssa st398 ( 2,3,57 ) .
there are other similarities between our strains and strains from china , spain , belgium , and the united states .
( 2,6,7,11 ) , such as agr type 1 , the presence of the ermt gene , tetracycline susceptibility , and macrolide  lincosamide  streptogramin b phenotype . in icus ,
the association of mssa cc398 with the icu environment suggests that this environment could play a role as a bacterial reservoir as described ( 14 ) .
one hypothesis for such an association is the capacity to form a biofilm , which could be correlated with the s. aureus genetic background ( 15 ) .
our findings emphasize potential hospital - adapted characteristics of s. aureus cc398 , which is supported by others studies ( 6,11 ) , and indicate that surveillance programs are needed to determine the role of this clonal complex , particularly in the hospital setting .
distribution of staphylococcus aureus cc398 isolates from patients in intensive care unit , health care workers , and environmental sites , france , 2011 .
 during testing for staphylococcus aureus in an intensive care unit in france in 2011 , we found that methicillin - sensitive s. aureus clonal complex 398 was the most frequent clone ( 29/125 , 23.2% ) . 
 it was isolated from patients ( 5/89 , 5.6% ) , health care workers ( 2/63 , 3.2% ) , and environmental sites ( 15/864,1.7% ) . 
 results indicate emergence of this clone in a hospital setting . 
The Study
Conclusions
None