Molecular epidemiology of methicillin-resistant Staphylococcus sciuri in healthy chickens.

Staphylococcus sciuri is commonly found on the skin of animals and humans as well as in the environment. However, little is known on its prevalence, resistance and epidemiology. Therefore, we investigated the prevalence of methicillin resistant S. sciuri (MRSS) strains in poultry, as they may represent a reservoir of resistance genes for other strains. In 2011, 281 poultry farms were sampled by taking nasal swabs of 20 animals. The swabs were pooled and MRSS were selectively isolated. Genus and methicillin resistance were determined by PCR and species identification was performed using transfer RNA-intergenic spacer analysis. MRSS were further characterised by SCCmec typing, PFGE, microarray and susceptibility testing. Eighty-seven MRSS were isolated resulting in an estimated prevalence of 31.0%. The prevalence in broilers did not significantly differ from that in layers. Most isolates harboured a non-typeable SCCmec and a little less than 40% carried SCCmec type III. Isolates from broiler farms carried mostly the SCCmec type III, while isolates from layer farms carried mostly the non-typeable SCCmec cassette. The 87 isolates generated 47 different SmaI-PFGE profiles that grouped in two main clusters corresponding to the two farm types. All isolates were resistant to fusidic acid, tiamulin and gentamicin and were sensitive to rifampicin and vancomycin. Isolates selected for microarray analysis carried a broad range of antimicrobial resistance and virulence genes. This study showed that MRSS is carried by healthy chickens at the same level in both broilers and layers. They represent a large reservoir for resistance and virulence genes. Strains from layers and broilers represent different clusters.