Abstract
Staphylococcus aureus is a major cause of clinical infections in humans and its enterotoxins cause foodborne disease. In the present study, we tested a total of 51 isolates of S. aureus from small-ruminant dairy farms with artisan dairy facilities, all located in Latium, Italy. The farms have a known history of a high prevalence of methicillin-resistant S. aureus (MRSA). Most of the MRSA isolates (27 of 51) belonged to spa-type t127 (43.1%), followed by t2678 (3.9%), t044 (2%), t1166 (2%), and t1773 (2%). PFGE performed on mecA positive strains identified one cluster (≥ 80% of similarity), comprising 22 MRSA. Nine of twenty-two MRSA isolates were assigned human host origin, and 13 isolates did not belong to a specific host. During the characterization study, one strain isolated from bulk tank milk samples harbored the pvl gene; the strain was not enterotoxigenic with a non-specific host according to the biotyping scheme, highlighting the possible emerging risk of transmission of bacterial virulence factors by foods, the environment, and foodhandlers. These findings stress the importance of hygienic measures at all processing steps of the food production chain and underline that monitoring for the presence of MRSA throughout the food chain is essential for public health.
Highlights
S. aureus is one of the most important etiological agents of intramammary infections in small ruminants [1]
The aim of this study was to investigate the genetic diversity, as determined by pulsed-field gel electrophoresis (PFGE) and spa-types, of methicillin-resistant S. aureus (MRSA) and MSSA isolated from samples of udder milk, raw milk, cheeses, nasal swabs of workers, and skin swabs of ewes taken from dairy sheep farms with a history of MRSA in bulk tank milk, as documented in a previous survey
This study revealed the presence of multiple MRSA strains among animals at the farms with possible human contamination
Summary
S. aureus is one of the most important etiological agents of intramammary infections in small ruminants [1]. In sheep it is responsible for clinical mastitis in 5–11% of cases and for sub-clinical mastitis in 0.22–2.06% of cases [2,3]. Its presence is a major economic and public health concern in the milk and dairy product sector [4]. S. aureus contamination of dairy products can occur anywhere in the food chain, while intra-farm spread mainly occurs through milking procedures [5], where infected mammary glands are the main reservoir [6]. S. aureus can switch and adapt to different host species, leading to host restriction [8]
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