Methicillin-Resistant Staphylococcus aureus in Food Animals

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic human pathogen primarily associated with skin and soft tissue infections (SSTIs), but it is also an important cause of invasive and life-threatening infections. The emergence of livestock-associated MRSA (LA-MRSA) clones over the last two decades is worrisome, as they pose an additional threat to human health. LA-MRSA is most prevalent in industrial pig production systems in Europe and Asia but has also been increasingly recognized in other food animals and geographical regions. S. aureus has a remarkable ability to adapt to different host species, which is mediated by fixation of beneficial mutations and acquisition of mobile genetic elements encoding antimicrobial resistance determinants as well as colonization and virulence factors. LA-MRSA is a major cause of SSTIs among livestock workers, who are thought to serve as a source of transmission to their household members and into the local rural community, from where the bacterium can spread into healthcare settings. Importantly, these populations include a higher proportion of elderly and immunocompromised people with an elevated risk of developing invasive staphylococcal illnesses. In contrast, the risk of foodborne transmission appears to be low, even though LA-MRSA is a frequent contaminant of retail foods. Thus, there is an urgent need to identify and implement effective control measures to prevent spillover of LA-MRSA from livestock workers into the general population.