title: Epidemiology and molecular characterization of methicillin-resistant Staphylococcus aureus nasal carriage isolates from bovines.
abstract: BACKGROUND
  Staphylococcus aureus is a common bacterium usually found on skin and mucous membranes of warm blooded animals. Resistance in S. aureus has been increasingly reported though depending on the clonal lineage. Indeed, while hospital acquired (HA)-methicillin resistant S. aureus (MRSA) are typically multi-resistant, community associated (CA)-MRSA are by large more susceptible to many antibiotics. Although S. aureus isolated from animals are often susceptible to most antibiotics, multi-resistant livestock associated (LA)-MRSA have been recovered from bovine mastitis.In this study, we investigated the prevalence and types of MRSA present in the nose of healthy bovines of different age groups and rearing practices. Since no validated methods for MRSA isolation from nasal swabs were available, we compared two isolation methods. Molecular characterization was performed by means of spa-typing, MLST, SCCmec typing and microarray analysis for the detection of antimicrobial resistance and virulence genes.
  
  
  RESULTS
  MRSA between herd prevalence in bovines was estimated at 19.8%. There was a marked difference between rearing practices with 9.9%, 10.2% and 46.1% of the dairy, beef and veal calve farms respectively being MRSA positive. No significant difference was observed between both isolation methods tested. Most isolates were ST398 spa type t011 or closely related spa types. Few ST239 spa type t037 and t388 and ST8 spa type t121 were also found. SCCmec types carried by these strains were mainly type IV(2B), IV(2B&5) and type V. Type III and non-typeable SCCmec were recovered to a lesser extent. All isolates were multi-resistant to at least two antimicrobials in addition to the expected cefoxitin and penicillin resistance, with an average of resistance to 9.5 different antimicrobials. Isolates selected for microarray analysis carried a broad range of antimicrobial resistance and virulence genes.
  
  
  CONCLUSIONS
  MRSA were mainly present in veal farms, compared to the lower prevalence in dairy or beef farms. Multi-resistance in these strains was high. Though mainly CC398 spa t011 was found, the genetic diversity was higher than what was found for pigs in Belgium. CC8 strains, a typically human lineage but also recently found also in association with bovines, has been retrieved here also.
authors.affiliation: Department of General Bacteriology, Veterinary and Agrochemical Research centre, Groeselenbergstraat 99, B-1180 Ukkel, Belgium. Stephanie.Nemeghaire@coda-cerva.be.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Nemeghaire
authors.forename: M Angeles
authors.initials: MA
authors.lastname: Argudín
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.forename: Patrick
authors.initials: P
authors.lastname: Butaye
mesh_terms: D000375:Aging; D000818:Animals; D002353:Carrier State; D002417:Cattle / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification*; D009666:Nose / Q000382:microbiology*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods / Q000662:veterinary; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods / Q000662:veterinary; D012680:Sensitivity and Specificity