MRSA Skin and Soft Tissue Infection in a Cohort of Otherwise Healthy Adults Infected with HIV Type 1

July 2009

Colonization and Subsequent Skin and Soft Tissue Infection Due to Methicillin-Resistant Staphylococcus aureus in a Cohort of Otherwise Healthy Adults Infected with HIV Type 1
Shet A, et al. J Infect Dis 2009;200:88-93. [PubMed Abstract]

Background: MRSA has evolved as possibly the most important bacterial pathogen presumably due to the explosive epidemic of strains with the Panton-Valentine Leukocidin (PVL) gene. Patients with infections involving this organism are often colonized with this agent, and some studies have shown that patients with HIV infection have increased rates of both MRSA carriage and infection. The purpose of this study was to determine the carriage rate of S. aureus and MRSA in patients with HIV infection and no evidence of immune suppression.

Methods: Participants were asymptomatic persons with HIV infection and uninfected controls. Cultures were done of nares and axilla three times separated by 1 month with follow-up to determine incidence of S. aureus infection in a 1 year period.

Results: The sample size was 107 HIV-infected patients with a mean age of 37 years, a mean CD4 cell count of 599 cell/mm³ and a mean of HIV viral load of 1500 c/mL; 69% were receiving ARV and 61% had no detectable virus. These results showed that 67 of the HIV-infected participants (59%) had at least one positive culture for S. aureus and 9 (8%) had at least one positive culture for MRSA. These results were significantly greater than carriage for each of these two categories in 52 controls. Of the 21 MRSA isolates recovered from HIV infected patients, 19 were PVL positive. These results are summarized in the following Table (1):

TABLE 1

Colonization with S. aureus and MRSA Based

on Nasal and Axillary Cultures x 3

HIV

n=107

Controls

n=52

S. aureus

MRSA

67 (51%)

18 (17%)*

18 (35%)

3 (6%)

2.7

3.3

0.004

0.04

*15/21 MRSA isolates were PVL positive — 10 in this group developed soft tissue abscesses in the 1 year of study.

During the 1 year course of study there were 10 HIV-infected patients with MRSA infections of skin and soft tissue, all in the 18 patients who were colonized with MRSA. PFGE profiles showed that the colonizing and infecting strains were identical in each of 4 with this analysis. There were no infections in the control group.

Conclusions: Asymptomatic patients with HIV infections have relatively high rates of MRSA colonization and infection.

Comment: The data in this report are quite striking in terms of the high frequency of colonization by S. aureus (59%) and the frequency of colonization of MRSA (17%) associated with HIV infection without clinically important immunosuppression based on CD4 cell count. In fact, there appears to be minimal data that immunosuppression per se predisposes to S. aureus or MRSA infection. Instead, this seems to be more correlated with risk categories of MSM and IDU. Particularly impressive and worrisome in this study is the high rate of infection among the 18 patients colonized with MRSA.