Global phylogenomics of multidrug-resistant Staphylococcus aureus sequence type 772: the Bengal Bay clone

The global spread of antimicrobial resistance (AMR) has been well documented in Gram-negative bacteria and healthcare-associated epidemic pathogens, with emergence often from regions with high levels of antimicrobial use and lack of effective stewardship. However, the degree to which similar processes occur with Gram-positive bacteria in the community setting, such as with community-associated (CA-) MRSA, is less well understood. Given the heavy burden and costs associated with MRSA infections, there is an urgent need to elucidate the patterns and drivers of the spread of novel virulent and multidrug-resistant MRSA clones. Here, we present whole-genome sequence data of 340 sequence type (ST) 772 S. aureus isolates, also known as the Bengal Bay clone. The collection encompasses the global distribution of a recently emerged, multidrug-resistant CA-MRSA lineage first reported from India and Bangladesh in 2004. Genomic and epidemiological data support an origin and spread of ST772 from the Indian subcontinent, often associated with travel and family contacts. We show that there is potential for short-term outbreaks to occur following intercontinental transmission, although ongoing endemic transmission is uncommon. Acquisition of a multidrug resistance integrated plasmid was instrumental in the emergence of a dominant clade (ST772-A) in the early 1990s. Phenotypic data suggest that the integrated plasmid did not incur a fitness cost. The Bengal Bay clone therefore combines the multidrug resistance of traditional healthcare-associated clones with the epidemiological and virulence potential of CA-MRSA.