MRSA: High Incidence Rates Linked to Gay Population Raise Concerns

In a study investigating the prevalence of the multidrug-resistant community-acquired MRSA strain USA300 in San Francisco, researchers have found the highest incidence in areas with a high proportion of same-sex couples. The high rate of USA300 infections linked to the gay community raises concerns about an increasing spread to heterosexuals and calls for vigilant surveillance.

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium that is resistant to a large number of broad spectrum antibiotics including methicillin, oxacillin, penicillin and amoxicillin. MRSA infections occur most frequently among hospitalized immunocompromised patients and in patients in healthcare facilities (such as nursing homes and dialysis centers). MRSA in healthcare settings has been shown to affect up to 4.6% of all inpatients and commonly causes serious and potentially life threatening infections, such as bloodstream infections, surgical site infections, or pneumonia.

However, more recently, MRSA has started to spread outside the hospital setting, causing so-called community-acquired (CA) infections. These predominantly include skin and soft tissue infections (SSTIs) and are less resistant than hospital MRSA strains. In the US, the particularly virulent CA-MRSA strain USA300 has emerged as the predominant cause of SSTIs. Recently, a multidrug-resistant form of this strain has emerged in the US.

A study by Diep et al. (2008) investigating the prevalence of infections with multidrug-resistant USA300 in the San Francisco area has now found that most cases occurred in areas of the city with a high proportion of same-sex couples. While the overall prevalence of multi-drug-resistant USA300 was 26 cases per 100,000 people annually, case numbers in districts with a high number of homosexual couples were nearly 15 times as high as in other areas of the city, indicating that USA300 is spread particularly rapidly in the gay community.

These findings are highly concerning. Not only may multidrug-resistant USA300 have turned into a sexually transmitted disease in the gay community, but its rapidly increasing incidence could also lead to a rise in infection numbers in the heterosexual community. With few treatment options available, strict surveillance is indicated and every effort should be made to avoid further spread of the pathogen.