HIV Positive Individuals are at Greater Risk for Resistant Staph Infection

Community-acquired (i.e., outside a hospital) infection with methicillin-resistant Staphylococcus aureus (MRSA) bacteria is a growing problem in many areas. S. aureus causes soft tissue abscesses, boils, and wound infections, and may lead to more severe conditions including necrotizing fasciitis (so-called "flesh-eating" bacterial infection). MRSA is a concern because resistant bacteria cannot be treated with standard drugs.

At the recent XVI International AIDS Conference in Toronto, researchers reported on a study of the incidence of MRSA infection at the TriService AIDS Clinical Consortium, a large San Diego HIV clinic that serves many military personnel, from 1993 through 2005. Infections were considered community-acquired if they occurred in individuals who had not been hospitalized during the prior year.

The researchers compared HIV positive individuals with and without MRSA, looking at factors including demographic variables, history of antibiotic and antiretroviral use, CD4 cell count, viral load, and history of sexually transmitted diseases.

Results

Among 425 HIV positive patients at the clinic, 25 (5.9%) developed community-acquired MRSA infection.

All cases occurred after 2002, with a 17-fold increase from 2003 to 2005 (Chi-square test of trend 15.7; P < 0.001).

In 2005, the annual incidence rate among HIV positive patients was 40 cases per 1000 person-years (PY), compared with 2.3 per 1000 PY among HIV negative individuals in the general population - an 18-fold higher rate.

All HIV positive patients with MRSA developed soft tissue infections (often on the scrotum and/or buttocks), 16% required hospitalization, and 67% had S. aureus cultured from their nostrils.

16% experienced relapsing MRSA infection despite appropriate initial antibiotic therapy.

More than half of patients with MRSA (56%) were on HAART, but none were receiving opportunistic infection prophylaxis using TMP/SMX (Septra, Bactrim).

In a univariate analyses, lower current CD4 count, CDC stage C HIV disease, history of syphilis, and use of B-lactam antibiotics during the past year were predictive of MRSA; there were no associations with demographics, diabetes, or use of HAART.

In a multivariate analysis, only recent use of B-lactam antibiotics (P = 0.04) and history of syphilis (P = 0.02) remained independent predictors of MRSA.

Conclusion

"Community-acquired MRSA infections are rapidly increasing among HIV-infected patients," the researchers concluded. "HIV patients have a 18-fold higher risk for community-acquired MRSA than the general population."

They added that, "Risk factors for community-acquired MRSA include recent use of B-lactam antibiotics and high-risk sexual activity as demonstrated by syphilis infection."

At the conference, presenter Nora Crum-Cianflone noted that they did not ask directly about sexual activity or drug use due to the potential negative ramifications if military personnel disclosed such information.

09/01/06

Reference
N Crum-Cianflone, B Hale, A Burgi, and others. Increasing rates of community-acquired MRSA infections among HIV-infected persons. XVI International AIDS Conference. Toronto, August 13-18, 2006. Abstract MOAB0304/5672.