title: Clinical significance and outcome of polymicrobial Staphylococcus aureus bacteremia.
abstract: OBJECTIVE
  The clinical significance of polymicrobial Staphylococcus aureus bacteremia (SAB) remains unclear. We therefore compared the clinical features and outcomes of polymicrobial and monomicrobial SAB.
  
  
  METHODS
  A prospective cohort study of patients with SAB was performed during a 20-months. Polymicrobial SAB was defined as the simultaneous isolation of S. aureus and other microorganisms from blood cultures. However, Corynebacterium spp., Bacillus spp., and coagulase-negative staphylococci were considered contaminants unless they were related to device infection and grew in two or more blood cultures.
  
  
  RESULTS
  During the study period, 44 (10%) patients had polymicrobial and 412 (90%) had monomicrobial SAB. A total of 54 microorganisms were isolated from the former, with Enterococcus spp. (22%) being the most common. Independent risk factors for polymicrobial SAB included neutropenia (odds ratio [OR] 3.5, p = 0.02), biliary tract catheters (OR 5.0, p = 0.001), and intra-abdominal infection (OR 10.3, p < 0.001). Clinical outcomes were significantly worse among patients with polymicrobial than monomicrobial SAB, including bacteremia-related and 7-day mortality rates. Independent predictors of bacteremia-related mortality were solid tumors (HR 2.0, p = 0.03) and polymicrobial SAB (HR 2.8, p = 0.007).
  
  
  CONCLUSIONS
  Polymicrobial SAB is associated with more severe illness than monomicrobial SAB, with neutropenia, biliary tract catheters and intra-abdominal infection being significant risk factors for polymicrobial SAB.
authors.affiliation: Department of Infectious Diseases, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Seong Yeon
authors.initials: SY
authors.lastname: Park
authors.forename: Ki-Ho
authors.initials: KH
authors.lastname: Park
authors.forename: Kyung Mi
authors.initials: KM
authors.lastname: Bang
authors.forename: Yong Pil
authors.initials: YP
authors.lastname: Chong
authors.forename: Sung-Han
authors.initials: SH
authors.lastname: Kim
authors.forename: Sang-Oh
authors.initials: SO
authors.lastname: Lee
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Choi
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Jeong
authors.forename: Jun Hee
authors.initials: JH
authors.lastname: Woo
authors.forename: Yang Soo
authors.initials: YS
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000382:microbiology / Q000473:pathology*; D001769:Blood / Q000382:microbiology; D015331:Cohort Studies; D060085:Coinfection / Q000382:microbiology / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000382:microbiology / Q000473:pathology*; D013211:Staphylococcus aureus / Q000302:isolation & purification*; D016896:Treatment Outcome; D055815:Young Adult