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363 Community-Associated Methicillin-Resistant Staphylococcus aureus (CA-MRSA) Colonization in High-Risk Cohorts of HIV-Infected Patients

Sunday, April 3, 2011: 10:45 AM
Cortez Ballroom (Hilton Anatole)
Kyle J. Popovich, MD , Rush University Medical Center, Chicago, IL
Kimberly Smith, MD , Rush University Medical Center, Chicago, IL
Bala Hota, MD , Stroger Hospital of Cook County/Rush University Medical Center, Chicago, IL
Alla Aroutcheva, MD, PhD , Rush University Medical Center, Chicago, IL
Thana Khawcharoenporn, MD , Rush University Medical Center, Chicago, IL
Cj Thurlow, MD , Rush University Medical Center, Chicago, IL
Guajira Thomas, MD , Stroger Hospital of Cook County, Chicago, IL
John Lough , Rush University Medical Center, Chicago, IL
Chad Zawitz, MD , Stroger Hospital of Cook County/Rush University Medical Center, Chicago, IL
Patricia Herrera, MD , Stroger Hospital of Cook County/Rush University Medical Center, Chicago, IL
Robert A. Weinstein, MD , Stroger Hospital of Cook County/Rush University Medical Center, Chicago, IL
Background: The CA-MRSA and HIV epidemics have intersected, i.e., a disproportionate number of HIV patients have had CA-MRSA infections.  Possible community exposures in some patient populations may increase risk for CA-MRSA colonization and potentially amplify the epidemic.

Objective: To examine the CA-MRSA nasal colonization prevalence among 3 cohorts of HIV patients.

Methods:

We assessed the prevalence of nasal MRSA colonization in 3 clinics at a 6000-outpatient HIV/AIDS center in Chicago -- Clinic A: female patients, Clinic B: recently incarcerated patients, and Clinic C: Hispanic patients.  We determined risk factors associated with MRSA colonization and typed available isolates by pulsed-field gel electrophoresis (PFGE).  Chi-square and t-test were used for uni- and bivariate analyses of categorical and continuous variables, respectively.  Relative prevalence was calculated using poisson regression.  Logistic regression was used for multivariable analysis.

Results:

We enrolled 360 HIV patients: 231 (64%) were African-American, 106 (29%) were Hispanic, and 230 (64%) were women.  179 (50%) of the study population had been incarcerated; 108 of 230 (47%) women had been incarcerated.  130 of 360 (36%) patients had a history of a prior skin/soft tissue (SSTI) or MRSA infection. 

Of the 360 patients, 33 (9.2%) were colonized with MRSA.  Clinic A had the highest colonization prevalence (25/207, 12.1%) followed by Clinic B (6/58, 10.3%); Clinic C had the lowest prevalence (2/95, 2.1%).  Clinic A’s rate was significantly higher than Clinic C’s (relative prevalence=5.74; 95% CI, 1.4, 24; p=0.017).  Of 29 isolates that had PFGE performed, 23 (79%) were USA300, the predominant CA-MRSA USA strain.

Significant MRSA colonization factors on uni- or bivariate analysis included: race/ethnicity, history of incarceration, and being an African-American women. CD4 count (81% of patients had a CD4 count ≥ 200 cells/mm3) and trimethoprim/sulfamethoxazole exposure (22% of patients were on prophylaxis) were not significantly different between those with and without MRSA colonization.  On multivariate analysis, being an African-American woman (OR=2.3; 95% CI, 1.05, 4.96; p=0.038) was associated with MRSA colonization.  There was a trend (OR=1.9; 95% CI, 0.9, 4; p=0.09) toward history of incarceration as a colonization risk factor.  114 of 130 (88%) patients with a history of prior SSTI or MRSA infection did not have MRSA nasal colonization, suggesting that some of these individuals were intermittent S. aureus carriers or had extra-nasal MRSA colonization.

Conclusions:

In our HIV/AIDS center, we found CA-MRSA nasal colonization rates much higher than those for the general population; study enrollment continues which may increase our ability to distinguish risk factors.  Detection and prevention strategies may be improved by targeting those at highest risk of colonization.