title: Community-associated methicillin-resistant Staphylococcus aureus and HIV: intersecting epidemics.
abstract: BACKGROUND
  Single-site studies have suggested a link between human immunodeficiency virus (HIV) and community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA).
  
  
  METHODS
  Population-level incidence of HIV-infected patients with CA-MRSA versus community-associated methicillin-susceptible S. aureus (CA-MSSA) infection was assessed in the Cook County Health and Hospitals System (CCHHS), a multi-hospital and ambulatory care center. Rates in zip codes, including those with a high density of individuals with prior incarceration (ie, high-risk zip codes), were calculated. We did a nested case-control analysis of hospitalized HIV-infected patients with S. aureus skin and soft-tissue infections (SSTIs).
  
  
  RESULTS
  In CCHHS, the incidence of CA-MRSA SSTIs was 6-fold higher among HIV-infected patients than it was among HIV-negative patients (996 per 100,000 HIV-infected patients vs 157 per 100,000 other patients; P < .001). The incidence of CA-MRSA SSTIs among HIV-infected patients significantly increased from 2000-2003 (period 1) to 2004-2007 (period 2) (from 411 to 1474 cases per 100,000 HIV-infected patients; relative risk [RR], 3.6; P<.001), with cases in period 1 clustering in an area 6.3 km in diameter (P=.035) that overlapped high-risk zip codes. By period 2, CA-MRSA SSTIs among HIV-infected patients were spread throughout Cook County. USA300 was identified as the predominant strain by pulsed-field gel electrophoresis (accounting for 86% of isolates). Among hospitalized HIV-infected patients, the incidence of CA-MRSA increased significantly from period 1 to period 2 (from 190 to 779 cases per 100,000 HIV-infected patients; RR, 4.1; P<.001). Risks for CA-MRSA by multivariate analysis were residence in alternative housing (eg, shelters), residence in high-risk zip codes, younger age, and infection in period 2.
  
  
  CONCLUSIONS
  HIV-infected patients are at markedly increased risk for CA-MRSA infection. This risk may be amplified by overlapping community networks of high-risk patients that may be targets for prevention efforts.
authors.affiliation: Rush University Medical Center, Chicago, Illinois 60612, USA. kyle_popovich@rush.edu
authors.forename: Kyle J
authors.initials: KJ
authors.lastname: Popovich
authors.forename: Robert A
authors.initials: RA
authors.lastname: Weinstein
authors.forename: Alla
authors.initials: A
authors.lastname: Aroutcheva
authors.forename: Thomas
authors.initials: T
authors.lastname: Rice
authors.forename: Bala
authors.initials: B
authors.lastname: Hota
mesh_terms: D000328:Adult; D016000:Cluster Analysis; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000821:virology; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005260:Female; D005843:Geography; D015658:HIV Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000821:virology; D006801:Humans; D015994:Incidence; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008875:Middle Aged; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D018461:Soft Tissue Infections / Q000453:epidemiology / Q000382:microbiology / Q000821:virology; D013207:Staphylococcal Skin Infections / Q000453:epidemiology*