Methicillin-resistant Staphylococcus aureus (MRSA) in sheep and goat bulk tank milk from Southern Italy

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA), an important widespread cause of severe infection in both humans and animals, is a pathogen of significant public health concern. In this paper the prevalence of MRSA in sheep and goat bulk tank milk from southern Italy was assessed and nasal swabs from people working on the positive farms were collected. MRSA isolates from milk and nasal swabs were characterized by spa typing, MLST and SCCmec typing and tested for antimicrobial resistance. MRSA was detected in 2 of the 162 (1.23%) bulk tank samples analysed: the first from a sheep farm (Farm 1) and the second from a goat farm (Farm 2). As for farm personnel, no MRSA was detected in the unique nasal swab from Farm 1; while MRSA was detected in all the 3 nasal swabs from Farm 2. The MRSA isolate from Farm 1 was spa type t127, ST1, SCCmec IVa. The MRSA isolates from bulk tank milk and humans in Farm 2 showed an identical genetic profile: spa type t1255, ST398, SCCmec V. In Farm 2 all the isolates had the characteristics of general multidrug resistance and the milk and human MRSA had the same antimicrobial resistance pattern. Although the results showed low prevalence of MRSA in sheep and goat milk from southern Italy, the detection of recognized zoonotic genotypes in milk of both farms and the isolation in people working in one of the positive farm of MRSA strains with a genetic profile identical to that of MRSA from milk, emphasize the public health concern and highlight the need for additional surveillance including the detection of MRSA.