Prevalence of Staphylococcus aureus and of methicillin-resistant S. aureus (MRSA) along the production chain of dairy products in north-western Greece

•Of 367 samples tested, 212 (57.8%) were S. aureus-positive & 11 (3%) MRSA-positive.•4 spa types (t127, t3586, t1773, t4038) identified; t127 was most prevalent (7/11).•spa types t3586 and t1773 were isolated for the first time in Greece.•PFGE analysis indicated clonal circulation through the dairy production chain.•Humans, animals & environment can be involved in dairy products contamination.

The objective of this study was to estimate the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in the production chain of dairy products. Of 367 tested samples (36 bulk tank milk (BTM), 19 dairy products, 72 human, 185 animal, 55 equipment), 212 (57.8%) were found positive for S. aureus. Almost all isolates (99.6%) were resistant to at least one antimicrobial and 13.3% were multi-drug resistant (MDR), exhibiting resistance to three or more antibiotic classes. Eleven samples (3%) were found contaminated by MRSA carrying the mecA gene. None of the MRSA isolates carried the mecC or the Pandon-Valentine leucocidin (PVL) genes. Four spa types were identified among the MRSA isolates: t127, t3586, t1773, t4038, with t127 being the most prevalent (7 out of 11). Two of them, t3586 and t1773, were isolated for the first time in Greece. Furthermore, Pulse-Field Gel Electrophoresis (PFGE) analysis indicated clonal circulation through the dairy production chain. The presence of MDR S. aureus, and especially MRSA, in animals and dairy products represents a potential threat for the spread of this pathogen in the community. The results indicated that human, animal and environmental sources could be involved in the contamination of dairy products along their production chain and therefore further investigation of contamination sources is needed to control the dispersion of MRSA in the community.