M. Miller and colleagues at Columbia University studied 502 subjects from a community-based cohort of drug users between February 1999 and March 2000. They found that increased antimicrobial use by HIV patients might heighten their risk of methicillin-resistant Staphylococcus aureus infection.

"HIV-infected individuals, especially those with a history of injecting drug use, are at high risk of Staphylococcus aureus infection," the researchers noted. "Moreover, the use of antimicrobial agents for opportunistic infections may increase nasal colonization by antimicrobial-resistant Staphylococcus aureus in this population and, subsequently, levels of infection with multidrug-resistant Staphylococcus aureus in the community." Test results revealed that 24 percent of the subjects had Staphylococcus aureus infections, and "only HIV infection and homelessness were associated with Staphylococcus aureus colonization," according to the study. Ten isolates (8 percent) were methicillin- resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus isolates were found among 14 percent of HIV-infected subjects, vs. 3 percent of HIV- uninfected subjects. Among those colonized and HIV- infected, the mean number of resistant isolates was higher for those currently reporting antibiotic use and for those with CD4 counts equal to or less than 200/microliter.

"The increased use of antimicrobial agents in HIV-infected individuals colonized with Staphylococcus aureus may be an underlying mechanism that contributes to the presence of multidrug-resistant Staphylococcus aureus in the community," the researchers reported.

Miller and coauthors published their study, "Staphylococcus Aureus Colonization in a Community Sample of HIV-Infected and HIV-Uninfected Drug Users," in the European Journal of Clinical Microbiology & Infectious Diseases (2003;22(8):463- 469).

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