Prevalence and molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) among subjects working on bovine dairy farms.

Meticillin-resistant Staphylococcus aureus (MRSA) is a major cause of healthcareassociated infections worldwide [1]. In addition, MRSA has recently been identified as an emerging pathogen in livestock and companion animals [2-5]. It is a common cause of mastitis in dairy cows and it has been isolated from bulk tank milk [6-8]. Livestock associated MRSA (LA-MRSA), belonging to the clonal complex 398 (CC398), have been found in farmers and food producing animals, especially pigs and calves [9-17]. Several reports have shown parallel occurrence of MRSA CC398 in both animals and humans [3, 12, 14-17], but evidence for animal-to-human transmission of MRSA is often indirect and based on parallel observations in genetic or resistance patterns [18, 19]. Since MRSA CC398 may cause severe infections in humans, contact with people working on livestock might represent a risk factor for the development of MRSA-associated illness [20, 21]. The aim of our study was to evaluate the prevalence of MRSA among dairy farmers of the province of Ragusa (South-Eastern Sicily), their animals and bulk tank milk samples. We characterized MRSA isolates with respect to antimicrobial resistance, virulence-associated genes and ability to form biofilm