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Increasing rates of CA-MRSA occurring among HIV patients
Risk factors for CA-MRSA in people living with HIV include history of syphilis infection and recent use of beta-lactam antibiotics.
TORONTO — Rates of community-acquired methicillin-resistant Staphylococcus aureus infections are not only increasing worldwide in the general population, but also are rapidly increasing among people living with HIV, according to research presented at the XVI International AIDS Conference.
“HIV patients appear to have up to an 18-fold higher risk of these infections than the general population. Whether this is due to the role of immunosuppression, some of their behaviors or an increased use of antibiotics in this population remains unclear,” said lead researcher Nancy F. Crum-Cianflone, MD, MPH, of the TriService AIDS Clinical Consortium in San Diego.
Studies have indicated that outbreaks of CA-MRSA have occurred in San Francisco and New York, where there have been multiple reports of severe disease due to these community-acquired strains among prison inmates, athletes, post-partum women, military trainers and men who have sex with men (MSM). Proposed risk factors for CA-MRSA infection among people living with HIV include low current CD4 counts, history of MSM, drug use, absence of trimethoprim sulfamethoxazole prophylaxis, antibiotic use, contact with sexual partners who have skin infections and the use of public saunas and baths.
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“HIV infection is a known risk factor for both MRSA colonization and infection; however, few studies have actually examined the incidence and risk factors of CA-MRSA among HIV infected people,” she said at the conference.
Crum-Cianflone and colleagues conducted a retrospective study of the incidence of CA-MRSA infections between 1993 through 2005 in a large HIV clinic located in California. They found that recent use of beta-lactam antibiotics and having sexually transmitted diseases, specifically syphilis infections, are two statistically significant risk factors.
Incidence of CA-MRSA
The researchers defined an incidence of CA-MRSA as a patient who had a positive MRSA culture but no recent hospitalizations. In order to identify risk factors, they compared the demographics, diabetic status, CD4 counts, HIV viral loads, history of STDs, and antibiotic and antiretroviral use between HIV patients with CA-MRSA and HIV patients without CA-MRSA.
The researchers found that of 425 HIV patients, 25 (5.9%) had confirmed CA-MRSA infections, all of which occurred after 2002. From 2003 and 2005, CA-MRSA incidence increased by 17-fold. The incidence rate last year among patients with HIV was 40 cases per 1,000 person year, compared with 2.28 cases per 1,000 person year for the general population. This indicated an 18-fold increased risk among those living with HIV, according to Crum-Cianflone.
All CA-MRSA infections involved the skin and soft tissue. Sixty-seven percent had a positive nares culture and 16% required hospitalization for one to 13 days.
“We did not see any cases of bacteremia, severe disease or death due to CA-MRSA in our cohort, but what we did see was a very high rate of recurrent infections despite adequate treatment of the infection,” Crum-Cianflone said.
None of the patients were taking TMP-SMX prophylaxis, 56% were on highly active antiretroviral therapy, and despite appropriate initial antibiotics, 16% had MRSA infection relapses.
“Community-acquired MRSA increasingly was diagnosed over the time period of this study and in fact during 2005, 37% of all wound cultures taken among our patients were community-acquired MRSA,” Crum-Cianflone said. “Community-acquired MRSA also accounted for an increasing percentage of S. aureus infections.”
Between 2004 and 2005, 65% of staph infections were CA-MRSA, according to Crum-Cianflone. Updated study results presented at the conference indicated that during the same study period, 29 of the 435 HIV patients followed (with more than 12,000 person years of follow-up) developed CA-MRSA.
Risk factors for infection
There was no association between demographics, diabetes, HAART use and duration of HIV to CA-MRSA infection among patients living with HIV, according to Crum-Cianflone. Participants’ ages ranged from 19 to 73 years (mean age of 40 years). Ninety-two percent were male, 50% were white and 4% had diabetes.
Multivariate analysis showed that HIV patients with CA-MRSA recently used beta-lactam antibiotics and perhaps had a history of documented sexual risk activity, as demonstrated by increased syphilis infections, according to Crum-Cianflone. Lower CD4 count and high viral load were also predicative of CA-MRSA.
“The most common presentation was abscess of the scrotum or buttocks. In our population, most patients present with an abscess, followed by a carbuncle, followed by cellulitis and finally folliculitis,” Crum-Cianflone said. “Regarding the site, most commonly this is the scrotum or the buttocks region followed by lower extremity, then trunk and upper extremity.”
Most patients were in the military, so her group could not consider the effect of sexual preference or practices, or the role of drug use because of military policies, she said.
“We advocate further studies among HIV patients to help develop preventative guidelines and treatment guidelines in this population,” Crum-Cianflone concluded. – by Tara Grassia
For more information:
- Crum-Cianflone N, Hale B, Burgi A, et al. Increasing rates of community-acquired MRSA infections among HIV-infected persons. Abstract MOAB0304. Presented at: The XVI International AIDS Conference; August 13-18, 2006; Toronto.