Transmission of methicillin-resistant Staphylococcus aureus from food production animals to humans: a review

International surveillance of antimicrobial use in food animal production shows that methicillinresistant Staphylococcus aureus (MRSA), traditionally a human pathogen associated with hospitals, has emerged in the community and animals. Since 1961, MRSA has been causing human infections in hospitals worldwide and a vast majority of them were caused by five major epidemic clones. After 1990, other clones have emerged in the community, leading to infections in relatively young and healthy individuals. The origin of these clones is largely unknown, and extensive diversity among isolates exists. Companion animals have been indicated as a reservoir. However, most studies suggest that they are initially infected by humans and subsequently animals re-colonize humans. More recently, a new zoonotic reservoir in food production animals was found. This involves a specific clone, MRSA ST398, which spreads extensively in animals and is also found in retail meat. It poses a potential threat to public health, as people in contact with food production animals are at much higher risk of colonization. The most probable transmission route seems to be by (in)direct contact, as dust in stables was found positive for MRSA ST398. The role of MRSA ST398 as a food pathogen needs more research. To prevent colonization in humans, it is important to investigate transmission routes and transmission dynamics between animals, between animals and humans and between humans. Collaboration of human and veterinary epidemiologists and microbiologists is needed to identify the implications of this strain for public health and to develop cost-effective control strategies.