Methicillin-resistant Coagulase-negative Staphylococci (MRCoNS) in Retail Meat

Introduction: Coagulase-negative Staphylococci (CoNS) have been demonstrated as a larger reservoir of mecA than Staphylococcus aureus and speculated as the origin of mecA. Since methicillin-resistant S. aureus (MRSA) has been recovered from US retail meat, the extent of methicillin-resistant coagulase-negative staphylococci (MRCoNS) in retail meat needs to be studied.

Purpose: To understand the extent of MRCoNS serving as the mecA reservoir in retail meat.

Methods: MRCoNS were isolated from retail meat (beef, chicken, and turkey) in Detroit and characterized by sodA gene sequencing for species identification, staphylococcal cassette chromosome mec (SCCmec) typing, and pulsed-field gel electrophoresis (PFGE).

Results: Unique MRCoNS isolates recovered from 25 meat samples were comprised of S. sciuri (n = 13), S. fleuretti (n = 4), S. lentus (n = 3), S. epidermidis (n = 2), S. vitulinus (n = 1), S. saprophyticus (n = 1) and S. pasteuri (n = 1). Heterogeneous and composite SCCmec types, including I, III, IV, V, I+V and III+V were identified in 16 isolates. Same SCCmec types were recovered in different staphylococcal species and meat sources. Indistinguishable PFGE patterns were also observed in S. sciuri isolated from beef, chicken, and turkey, and with different SCCmec types.

Significance: Multiple CoNS species can serve as reservoirs for mecA. In addition to the clonal transmission of MRCoNS in meat, horizontal occurrence of SCCmec is observed in staphylococcal species.