Studies of community-associated meticillin resistant Staphylococcus aureus (caMRSA) carriage in people and animals

Abstract

Meticillin resistant Staphylococcus aureus (MRSA) is a leading cause of bloodstream infections in Australia and is one of the top ten pathogens with an adverse impact on human health worldwide. Infections caused by this organism were originally associated with the healthcare setting, termed healthcare-associated MRSA (haMRSA). New strains of MRSA termed community-associated caMRSA (caMRSA), with different genetic characteristics to haMRSA strains, were first identified in patients residing in remote communities in Western Australia during the early 1990’s. Colonisation with caMRSA precedes and increases the risk of subsequent infection with this organism. Research on caMRSA carriage in community settings has mainly come from Europe and the US. Community specific data for caMRSA carriage in Australia is sparse. This study aimed to detail the prevalence of MRSA in community members (n=283), as well as in groups at risk for the acquisition of MRSA, comprising contact sports participants (n=199), dogs (n=108), dog handlers (n=94), horses (n=310), horse handlers (n=38), veterinary nurses (n=48) and veterinarians (n=60). The role of household contacts and the environment as sources of caMRSA was investigated in the veterinary cohort. Genotypic analyses were used to differentiate strains of caMRSA from haMRSA, and unique strain characteristics were detailed. Genotypic tests included multiplex real-time PCR (RT-PCR), macro-restriction pulsed field gel electrophoresis (PFGE), SCCmec typing, multilocus sequence typing (MLST) and DNA microarrays. The findings of the present study revealed caMRSA poses a greater risk to veterinarians (20%), veterinary nurses (6.25%) and horse handlers (5.26%) than to all other cohorts investigated in which prevalence of caMRSA was found to be low (<2%) or absent.