title: Emergence of multidrug-resistant, community-associated, methicillin-resistant Staphylococcus aureus clone USA300 in men who have sex with men.
abstract: BACKGROUND
  Infection with multidrug-resistant, community-associated, methicillin-resistant Staphylococcus aureus (MRSA) has been reported but seems to be isolated.
  
  
  OBJECTIVE
  To determine the incidence of a multidrug-resistant MRSA clone (USA300) in San Francisco, and to determine risk factors for the infection.
  
  
  METHODS
  Population-based survey and cross-sectional study using chart review.
  
  
  METHODS
  9 hospitals in San Francisco (population-based survey) and 2 outpatient clinics in San Francisco and Boston (cross-sectional study).
  
  
  METHODS
  Persons with culture-proven MRSA infections in 2004 to 2006.
  
  
  METHODS
  Annual incidence, spatial clustering, and risk factors for multidrug-resistant USA300 infection. Pulsed-field gel electrophoresis, polymerase chain reaction assays, and DNA sequencing were used to characterize MRSA isolates.
  
  
  RESULTS
  The overall incidence of multidrug-resistant USA300 infection in San Francisco was 26 cases per 100,000 persons (95% CI, 16 to 36 cases per 100,000 persons); the incidence was higher in 8 contiguous ZIP codes with a higher proportion of male same-sex couples. Male-male sex was a risk factor for multidrug-resistant USA300 infection (relative risk, 13.2 [CI, 1.7 to 101.6]; P < 0.001) independent of past MRSA infection (relative risk, 2.1 [CI, 1.2 to 3.7]; P = 0.007) or clindamycin use (relative risk, 2.1 [1.2 to 3.6]; P = 0.007). The risk seemed to be independent of HIV infection. In San Francisco, multidrug-resistant USA300 manifested most often as infection of the buttocks, genitals, or perineum. In Boston, the infection was recovered exclusively from men who had sex with men.
  
  
  CONCLUSIONS
  The study was retrospective, and sexual risk behavior was not assessed.
  
  
  CONCLUSIONS
  Infection with multidrug-resistant USA300 MRSA is common among men who have sex with men, and multidrug-resistant MRSA infection might be sexually transmitted in this population. Further research is needed to determine whether existing efforts to control epidemics of other sexually transmitted infections can control spread of community-associated, multidrug-resistant MRSA.
authors.affiliation: University of California, San Francisco, San Francisco, CA 94110, USA. bdiep@epi-center.ucsf.edu
authors.forename: Binh An
authors.initials: BA
authors.lastname: Diep
authors.forename: Henry F
authors.initials: HF
authors.lastname: Chambers
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Graber
authors.forename: John D
authors.initials: JD
authors.lastname: Szumowski
authors.forename: Loren G
authors.initials: LG
authors.lastname: Miller
authors.forename: Linda L
authors.initials: LL
authors.lastname: Han
authors.forename: Jason H
authors.initials: JH
authors.lastname: Chen
authors.forename: Felice
authors.initials: F
authors.lastname: Lin
authors.forename: Jessica
authors.initials: J
authors.lastname: Lin
authors.forename: Tiffany HaiVan
authors.initials: TH
authors.lastname: Phan
authors.forename: Heather A
authors.initials: HA
authors.lastname: Carleton
authors.forename: Linda K
authors.initials: LK
authors.lastname: McDougal
authors.forename: Fred C
authors.initials: FC
authors.lastname: Tenover
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Cohen
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Mayer
authors.forename: George F
authors.initials: GF
authors.lastname: Sensabaugh
authors.forename: Françoise
authors.initials: F
authors.lastname: Perdreau-Remington
mesh_terms: D021821:Communicable Diseases, Emerging / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission; D003153:Community Health Services; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission; D003430:Cross-Sectional Studies; D024901:Drug Resistance, Multiple, Bacterial; D006716:Homosexuality; D006801:Humans; D015994:Incidence; D008297:Male; D016106:Methicillin Resistance; D012189:Retrospective Studies; D012307:Risk Factors; D012495:San Francisco / Q000453:epidemiology; D015231:Sexually Transmitted Diseases, Bacterial / Q000453:epidemiology / Q000382:microbiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000635:transmission; D013211:Staphylococcus aureus