Prevalence, multidrug resistance and molecular typing of methicillin-resistant Staphylococcus aureus (MRSA) in retail meat from Punjab, India

Abstract

This study reports the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in retail meat from Punjab, India. Classical microbiological methods were applied to isolate and identify S. aureus isolates. Isolates also underwent Etest. PCR and sequencing were used to identify and characterise antimicrobial resistance genes. MLST, SCCmec and spa typing were performed. A total of 408 meat and 101 swab samples were processed for S. aureus isolation. Phenotypic resistance was highest to penicillin (90.97%), followed by ciprofloxacin (61.80%), tetracycline (45.14%) and erythromycin (11.11%). Isolates from chicken samples showed significantly higher MICs for tetracycline than chevon and pork samples and significantly higher MICs for trimethoprim/sulfamethoxazole and gentamicin than chevon and swab samples (P<0.05). No isolates were phenotypically resistant to vancomycin (MICs of 0.5-2μg/mL). Most isolates (52.78%, 95% CI 44.63-60.93%) were multidrug-resistant and carried resistance genes to penicillin (blaZ), oxacillin (mecA), gentamicin (aacA-aphD), erythromycin (ermB, ermC) and tetracycline (tetK, tetL, tetM). MRSA was only found in chicken samples (2.72%; 4/147). Seven S. aureus (5.07%) were borderline oxacillin-resistant (MIC range 4-8μg/mL). All MRSA were SCCmecV-pvl+-t442, among which three isolates were ST5. Their genotype was mecA+, blaZ+, aacA-aphD+, tetK+, ermC+/-. Among the erythromycin-resistant isolates, 25% were MRSA, of which 12.5% isolates expressed an inducible macrolide-lincosamide-streptogramin B (iMLSB) phenotype. These data confirm the presence of ST5-t442-MRSA-SCCmecV-pvl+ and iMLSB MRSA in meat samples, indicating a potential role of meat in the dissemination of multidrug-resistant S. aureus strains and successful MRSA lineages in Punjab.