HIV, Community-Associated Methicillin-Resistant Staphylococcus aureus Epidemics Intersect

People with HIV have a heightened risk of community-associated methicillin-resistant Staphylococcus aureus infection (CA-MRSA), according to a report published recently.

In this retrospective study (2000 to 2007), population-level incidence of CA-MRSA and methicillin-susceptible S. aureus in HIV patients was assessed. The team used medical records to study HIV patients with CA-MRSA in the Cook County Health and Hospitals System (CCHHS), a multi-hospital and ambulatory care center.

The rate of skin and soft-tissue CA-MRSA infections was six times higher among people with HIV than others, or 996 cases per 100,000 population versus 157 cases per 100,000, found Dr. Kyle Popovich and colleagues at Rush University Center and Stoger Hospital of Cook County. The incidence of CA-MRSA infections significantly rose during the study, which was divided into two periods: 2000 to 2003 (period 1) and 2004 to 2007 (period 2).

Incidence among HIV patients increased from 411 cases per 100,000 in period 1 to 1,474 cases per 100,000 (relative risk 3.6, P less than 0.001) in period 2. In addition, cases in period 1 clustered in an area, 6.3 kilometers in diameter, overlapping high-risk ZIP codes (where there was a high density of individuals with prior incarceration). By period 2, CA-MRSA cases were spread throughout Cook County. Incidence increased significantly among hospitalized HIV patients, from 190 cases per 100,000 patients in period 1 to 779 cases per 100,000 in period 2.

"Risks for CA-MRSA by multivariate analyses were residence in alternative housing (e.g., shelters), residence in high-risk ZIP codes, younger age, and infection in period 2," according to the authors.

"Our study shows an association between HIV and CA-MRSA," said Popovich, adding that his team wants to study factors behind the link. The risk may be amplified by "overlapping community-based social networks of high-risk patients," he said.

In an earlier study by some of the same researchers, CA-MRSA had grown overall in much of the same area, though methicillin-susceptible strains remained stable.

The full report, "Community-Associated Methicillin-Resistant Staphylococcus aureus and HIV: Intersecting Epidemics," was published in Clinical Infectious Diseases (2010;50:979-987).

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