A study published by a consortium of US army medical centres observed that USA300 starin of methicillin-resistant Staphylococcus aureus (MRSA) has emerged as an important cause of healthcare-associated bloodstream infection (BSI) in metropolitan centres. USA300 was associated with a significantly increasing proportion of MRSA BSI when examined over sequential time periods: 4% of 51 isolates during 2001–2003, 19% of 47 isolates during 2004–2006, and 36% of 53 isolates during 2007–2009.
Surprisingly, this trend did not appear to be attributable to skin and soft-tissue infection or wounded service members. This suggests that USA300 MRSA continues to encroach into the healthcare setting and that it possesses a complex and dynamic epidemiology that may vary between patient populations and healthcare systems. Time and again, S. aureus demonstrates its seemingly limitless pathogenicity and ability to widely disseminate throughout community and hospital settings alike. Vigilant and dynamic infection control measures are needed to effectively combat the relentless migration of USA300 MRSA.