Clinical and laboratory data were available from 1,813 subjects with clinical and laboratory data available from at least one visit in 2006 from 16 sites. Fourteen MRSA infections (all culture confirmed) occurred among 1,813 subjects and 1,267 person-years of followup for an incidence of 772 cases per 100,000 persons and an incidence rate of 11.1 infections per 1,000 patient-years (PY) of observation (95% confidence interval (CI): 11.06–11.14). Median follow-up time was 0.79 years for the MRSA-infected case-patients and 0.80 years for the MRSA-uninfected patients. Seven (0.45%) subjects who were perinatally infected with HIV had MRSA infections for an incidence of 6.8 infections per 1,000 PY (95% CI, 1.8–11.8). Six (1.9%) behaviorally HIV-infected subjects had an MRSA infection incidence of 33.3 infections per 1,000 PY (95% CI, 5.6–61). One MRSA-infected case-patient acquired HIV infection in childhood but HIV risk factors were not known; this child was classified as nonbehaviorally HIV infected. In most cases (11/14), MRSA was diagnosed and/or cultured at a visit in 2006 after at least one prior visit without MRSA infection. In the remaining three cases, MRSA was diagnosed and/or cultured at the first abstracted visit for LEGACY, in February, April, and July, respectively.
All MRSA-infected case-patients were non-Hispanic black; eight (57%) were female and six (43%) received HIV care in Maryland. None reported use of intravenous drugs. Median age was 18 years (range, 6–24). Median CD4 cell count and percentage were 383 cells/mm3
and 20%, respectively. Six (43%) subjects were treated with HAART, but only 1 (7%) had a suppressed viral load (<400
copies/mL). Overall, nine (64%) MRSA-infected case-patients had HIV-1 viral loads >10,000
copies/mL. One subject was receiving cotrimoxazole prophylaxis; none were taking systemic steroids.
Four (29%) case-patients were hospitalized at time of MRSA diagnosis, including one subject whose blood culture grew MRSA and whose urine culture grew E. coli
and MRSA. This subject with invasive disease was a 15-year-old, perinatally HIV-infected boy who was taking HAART; the laboratory results from five months prior to onset of his MRSA infection included CD4 values of 524
and 28% but a viral load of 49,411
copies/mL. He did not have an indwelling vascular catheter or neutropenia at the time of hospital admission for his MRSA infection. There was no evidence of endocarditis, and he responded well to intravenous treatment for urinary tract infection with bacteremia. Another subject with severe, chronic cystic lung disease who was admitted for management of a recurrent pneumothorax produced purulent sputum with heavy normal respiratory flora noted on Gram stain and growth of MRSA (at 2 days), Pseudomonas aeruginosa
, and normal respiratory flora. Sputum production and cough improved with piperacillin/tazobactam and tobramycin but without MRSA-active antibiotic treatment. The role of MRSA in this exacerbation of chronic pulmonary disease was uncertain. There were no other cases of bacteremia or other invasive infections. MRSA was cultured from skin and soft tissue infections (SSTIs) in the remaining 12 (71%) case-patients. Two of these SSTIs were associated with viral exanthems (zoster and HSV). All MRSA isolates were susceptible to vancomycin and cotrimoxazole; resistance to erythromycin (11/12 tested) was more common than resistance to clindamycin (one constitutive resistance and one inducible resistance, both from Maryland, detected among 14 tested). Most isolates were susceptible to tetracycline (9/11 tested) and to fluoroquinolones (6/8 tested).
Compared with MRSA-uninfected participants, MRSA case-patients were older (17 versus 14 years, P
< 0.05), more likely to be non-Hispanic black (100% versus 69%, P
= 0.012), to have received care in Maryland (43% versus 7%, P
< 0.0001), and to have been behaviorally HIV infected (43% versus 17%, P
< 0.012) (). MRSA case-patients were also more likely to have had an HIV-1 viral load > 1000 (86% versus 51%, P
= 0.01), a lower mean CD4 percentage (18% versus 27%, P
= 0.0016) and a lower mean CD4 count (391 versus 680
= 0.029). MRSA-infected and MRSA-uninfected subjects were similar (P
> 0.05) with respect to gender (57% versus 55% female), history of eczema (14% versus 13%), presence of ANC < 1500
(30% versus 27%), history of AIDS-defining illness (18% versus 25%), and HAART use (43% versus 45%).
Characteristics of Participants with and without MRSA Infections in the LEGACY Study, 2006.
In multivariate analysis (), Maryland care site, non-Hispanic black race, and HIV-1 viral load >1000
copies/mL remained independently associated with MRSA infection after controlling for age, behavioral mode of HIV transmission, and CD4 count. Because CD4 count and viral load were highly correlated, we tested the model without viral load; the association with CD4 count remained nonsignificant. In the final reduced model, Maryland HIV care site, non-Hispanic black race, and HIV-1 viral load > 1000
copies/mL remained independently associated with MRSA infection.
Factors associated with MRSA infection in multivariable analysis, the LEGACY Study, 2006.