Risk of MRSA High Among People Living With HIV

HIV-positive patients are 6 to 18 times more likely to contract a methicillin-resistant Staphylococcus aureus (MRSA) infection than their HIV-negative counterparts. A meta-analysis of 32 studies between 1990 and 2013 examined data on 6558 HIV-positive individuals to determine how common being a carrier of MRSA was in this population. It found that globally 6.9% of HIV-positive people are MRSA carriers; in North America that figure is 8.8%.

Researchers also determined that the risk of carrying MRSA increases more than threefold (risk ratio [RR], 3.11 [95% CI, 1.62-5.98]), if the person was hospitalized during the previous 12 months, and increases by 77% (RR, 1.77 [95% CI, 1.26-2.48]), if the person is currently or was previously incarcerated. Taking trimethoprim-sulfamethoxazole (TMP-SMX) or antiretrovirals did not change the risk of carrying the MRSA bacterium. However, study authors note, "Individuals who receive antiretroviral therapy and TMP-SMX prophylaxis might have a lower CD4 count than those who do not receive therapy, and this may increase their risk of MRSA colonization."

Of the 11 studies that reported on MRSA colonization among the HIV-positive by CD4 count, slightly more studies (6) found that lower CD4 counts increased the risk of being a MRSA carrier, while the remainder found no such correlation. Only one of the studies reported on drug resistance among patients who are taking TMP-SMX; all MRSA strains isolated from patients taking TMP-SMX in that study were resistant to that antibiotic.

Interestingly, the seven studies conducted in Europe reported low or no MRSA colonization among their study population. The authors of this meta-analysis, however, call for further studies to confirm this low estimated prevalence.

Screenings for MRSA are commonly conducted by nasal swab. This analysis also studied the reliability of such screenings and found that in almost one-third (31.6% [95% CI, 15.8-50.0]) of patients only samples from other areas of the body -- most notably the groin and perirectal regions -- yielded a diagnosis as MRSA carriers. This also means that the nasal mupirocin ointment widely used to decolonize MRSA is likely insufficient, researchers said.

The study authors concluded that, "Given that HIV-positive individuals are at increased risk for MRSA infection and that colonization has been associated with infection, these findings emphasize the need for evaluation and implementation of MRSA prevention strategies that focus on this highly vulnerable population. In this effort, specific attention should be drawn to the important burden of colonization in extranasal sites."