title: Impact of USA300 methicillin-resistant Staphylococcus aureus on clinical outcomes of patients with pneumonia or central line-associated bloodstream infections.
abstract: BACKGROUND
  The USA300 methicillin-resistant Staphylococcus aureus (MRSA) strain, which initially emerged as a cause of community-associated infections, has recently become an important pathogen in healthcare-associated infections (HAIs). However, its impact on patient outcomes has not been well studied. We evaluated patients with invasive MRSA infections to assess differences in outcomes between infections caused by USA100 and those caused by USA300.
  
  
  METHODS
  Population-based data for invasive MRSA infections were used to identify 2 cohorts: (1) nondialysis patients with central line-associated bloodstream infections (CLABSIs) and (2) patients with community-onset pneumonia (PNEUMO) during 2005-2007 from 6 US metropolitan areas. Medical records of patients with confirmed MRSA USA100 or USA300 infection were reviewed. Logistic regression and, when appropriate, survival analysis was performed to evaluate mortality, early and late complications, and length of stay.
  
  
  RESULTS
  A total of 236 and 100 patients were included in the CLABSI and PNEUMO cohorts, respectively. USA300 was the only independent predictor of early complications for PNEUMO patients (odds ratio [OR], 2.6; P = .02). Independent predictors of CLABSI late complications included intensive care unit (ICU) admission before MRSA culture (adjusted OR [AOR], 2.1; P= .01) and Charlson comorbidity index (AOR, 2.6; P = .003), but not strain type. PNEUMO patients were significantly more likely to die if they were older (P = .02), black (P < .001), or infected with USA100 strain (P = .02), whereas those with CLABSI were more likely to die if they were older (P < .001), had comorbidities (P < .001), or had an ICU admission before MRSA culture (P = .001).
  
  
  CONCLUSIONS
  USA300 was associated with early complications in PNEUMO patients. However, it was not associated with mortality for either PNEUMO or CLABSI patients. Concerns regarding higher mortality from HAIs caused by USA300 may not be warranted.
authors.affiliation: Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. flessa@cdc.gov
authors.forename: Fernanda C
authors.initials: FC
authors.lastname: Lessa
authors.forename: Yi
authors.initials: Y
authors.lastname: Mu
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ray
authors.forename: Ghinwa
authors.initials: G
authors.lastname: Dumyati
authors.forename: Sandra
authors.initials: S
authors.lastname: Bulens
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Gorwitz
authors.forename: Gregory
authors.initials: G
authors.lastname: Fosheim
authors.forename: Aaron S
authors.initials: AS
authors.lastname: DeVries
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.forename: Joelle
authors.initials: J
authors.lastname: Nadle
authors.forename: Kenneth
authors.initials: K
authors.lastname: Gershman
authors.forename: Scott K
authors.initials: SK
authors.lastname: Fridkin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology* / Q000401:mortality; D055499:Catheter-Related Infections / Q000453:epidemiology* / Q000382:microbiology* / Q000401:mortality; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000382:microbiology / Q000401:mortality; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology / Q000401:mortality; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007902:Length of Stay / Q000706:statistics & numerical data; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000302:isolation & purification / Q000472:pathogenicity; D008875:Middle Aged; D011023:Pneumonia, Staphylococcal / Q000453:epidemiology* / Q000382:microbiology* / Q000401:mortality; D016019:Survival Analysis; D016896:Treatment Outcome; D055815:Young Adult