Incidence of Methicillin-resistant Staphylococcus aureus in milk and dairy and assessment genotypic and phenotypic properties of antibiotic resistance

Abstract

Abstract Background Methicillin-resistant Staphylococcus aureus bacteria are considered an emerging food-borne pathogens. This study aimed to evaluate the MRSA incidence and its genotypic and phenotypic properties of antibiotic resistance in raw milk and dairy. Methods Three hundred and eighty raw milk and traditional dairy samples were collected. S. aureus was examined by culture method. MRSA was identified as simultaneous resistance against cefoxitin and oxacillin. MRSA genotypic and phenotypic antibiotic resistance was evaluated by PCR and disk diffusion, respectively. Results S. aureus contamination rate in milk and dairy samples was 15.78% (70 of 380 samples). Thirty-eight out of 60 (63.33%) S. aureus isolates were identified as MRSA. MRSA distribution among isolates with sources of raw milk and dairy was 55.55% and 66.66%, respectively. MRSA isolates revealed the maximum resistance rate toward cefotaxime (100%), ceftriaxone (100%), penicillin (100%), erythromycin (85.78%), tetracycline (84.21%) and gentamicin (73.68%). Resistance of raw milk and dairy MRSA isolates against more than 7 antibiotic agents was 20% and 32.14%, respectively. The blaZ (100%), blaCTX-M (100%), tetK (55.26%), msrA (50%), aacA-D (47.36%), ermA (44.73%), mefA (44.73%) and gyrA (42.10%) were the most predominant genes encode resistance. Conclusions Dairy and milk in traditional and raw formats may be MDR-MRSA sources with boosted hygienic threats to consumers.