Profiles of Non-aureus Staphylococci in Retail Pork and Slaughterhouse Carcasses: Prevalence;Antimicrobial Resistance;and Genetic Determinant of Fusidic Acid Resistance

As commensal colonizers in livestock;there has been little attention on staphylococci;especially non-aureus staphylococci (NAS);contaminating meat production chain. To assess prevalence of staphylococci in retail pork and slaughterhouse carcass samples in Korea;we collected 578 samples from Korean slaughterhouses (n=311) and retail markets (n=267) for isolation of staphylococci and determined antimicrobial resistance phenotypes in all the isolates. The presence of and prevalence of fusB-family genes (fusB;fusC;fusD;and fusF) and mutations in fusA genes were examined in fusidic acid resistant isolates. A total of 47 staphylococcal isolates of 4 different species (Staphylococcus aureus;n=4; S. hyicus;n=1; S. epidermidis;n=10; Mammaliicoccus sciuri;n=32) were isolated. Fusidic acid resistance were confirmed in 9/10 S. epidermidis and all of the 32 M. sciuri (previously S. sciuri) isolates. Acquired fusidic acid resistance genes were detected in all the resistant strains; fusB and fusC in S. epidermidis and fusB/C in M. sciuri. Multi-locus sequence type analysis revealed that ST63 (n=10;31%) and ST30 (n=8;25%) genotypes were most prevalent among fusidic acid resistant M. sciuri isolates. In conclusion;the high prevalence of fusB-family genes in S. epidermidis and M. sciuri strains isolated from pork indicated that NAS might act as a reservoir for fusidic acid resistance gene transmissions in pork production chains.