Genetic and Phenotypic Identification of Vancomycin-Resistant Staphylococcus aureus Isolates from Retail Poultry Carcasses in Omu-Aran, North-Central Nigeria

Staphylococcus aureus is a well-known agent of zoonotic infections. Livestock-associated methicillin-resistant S. aureus (LA-MRSA) had been receiving public health attention for over a decade. Recently, the genomes of some MRSA strains evolved further by enabling acquisition of vanA gene from enterococcus which drives the emergence of vancomycin-resistant S. aureus (VRSA), thus signaling a higher threat to antimicrobial chemotherapy and diagnostic microbiology. This study was designed to examine slaughtered chicken carcasses in Omu-Aran, North-Central Nigeria for the presence of VRSA using vancomycin agar screen (VAS) as recommended by the Clinical and Laboratories Standards Institute (CLSI). To provide independent witness to further support the evidences from VAS, a 235 bp marker for vanA gene was simultaneously detected by PCR. From April 2013 through May 2014, chicken carcasses (n=784) were collected and studied. Among 155 (19.8%) samples which yielded S. aureus, VAS and vanA PCR methods unequivocally identified VRSA in 22 (14.2%). Compared with 46.2% VRSA report from Zaria, North-Western Nigeria, the incidence of VRSA is much less in Omu-Aran chicken carcasses than those of Zaria. Further investigation in other parts of Nigeria is recommended in order to generate nation-wide data on VRSA in this country.