title: Association of blaOXA-23 and bap with the persistence of Acinetobacter baumannii within a major healthcare system.
abstract: OBJECTIVE
  Acinetobacter baumannii is an emerging opportunistic nosocomial pathogen. Two factors that may enhance persistence in healthcare settings are antimicrobial resistance and biofilm-forming ability. The aim of this work was to determine whether A. baumannii isolates that persist in healthcare settings (endemic), can be differentiated from sporadic isolates based upon their ability to resist antibiotics and their biofilm-forming capability.
  
  
  METHODS
  Two hundred and ninety A. baumannii isolates were isolated over 17 months in the Detroit Medical Center (DMC). The isolates were genotyped using repetitive extragenic palindromic-PCR (REP-PCR). REP-types appearing greater than 10 times during active surveillance were considered endemic. The in vitro biofilm-forming ability and antibiotic resistance profile of each isolate were evaluated. Isolates were tested for the presence of two genetic markers-one implicated in biofilm formation (bap) and the other in antibiotic resistance (blaOXA-23).
  
  
  RESULTS
  Of the 290 isolates evaluated, 84% carried bap and 36% carried blaOXA-23 . Five unique REP-PCR banding-types were detected >10 times (endemic) and constituted 58% of the 290 isolates. These five endemic REP-PCR types were 5.1 times more likely than sporadic isolates to carry both bap and blaOXA-23 . Furthermore, endemic isolates were resistant to 3 more antibiotic classes, on average, than sporadic isolates and four of the five endemic REP-PCR types formed denser biofilms in vitro than sporadic isolates.
  
  
  CONCLUSIONS
  Endemic A. baumannii isolates are more likely than sporadic isolates to possess factors that increase virulence and enhance survival within a large healthcare system.
authors: Department of Epidemiology, School of Public Health, University of Michigan Ann Arbor, MI, USA.
authors: Ting L
authors: TL
authors: Luo
authors: Department of Epidemiology, School of Public Health, University of Michigan Ann Arbor, MI, USA.
authors: Alexander H
authors: AH
authors: Rickard
authors: Department of Epidemiology, School of Public Health, University of Michigan Ann Arbor, MI, USA.
authors: Usha
authors: U
authors: Srinivasan
authors: Division of Infectious Diseases, Wayne State University Detroit, MI, USA.
authors: Keith S
authors: KS
authors: Kaye
authors: Department of Epidemiology, School of Public Health, University of Michigan Ann Arbor, MI, USA.
authors: Betsy
authors: B
authors: Foxman
keywords: OXA-23; REP-PCR; antibiotic resistance; bap; biofilms; molecular epidemiology