Abstract
Objectives: 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.
Highlights
Acinetobacter baumannii is a Gram-negative coccobacillary bacterium that is environmentally ubiquitous
A similar trend was observed at the Detroit Medical Center (DMC) in Michigan where imipenem-resistant A. baumannii isolates increased from 1% to 58% between 2003 and 2008 (Reddy et al, 2010)
From January 2010 to May 2011, a total of 426 clinical A. baumannii isolates were collected from DMC hospitals and facilities. 136 of these isolates were cultured from patients residing at a nursing home that is physically located within DMC
Summary
Acinetobacter baumannii is a Gram-negative coccobacillary bacterium that is environmentally ubiquitous. It is capable of causing severe nosocomial infections, especially among patients who are immunocompromised (due to underlying medical conditions or age), have medical devices, or are frequently exposed to antibiotics (Bergogne-Berezin, 2001; Maragakis and Perl, 2008). A. baumannii is intrinsically tolerant to many antimicrobials and is capable of rapidly acquiring antibiotic resistances. It is not unusual to observe considerable and unexpected increases in the number of resistant isolates within a healthcare facility over short periods of time. A similar trend was observed at the Detroit Medical Center (DMC) in Michigan where imipenem-resistant A. baumannii isolates increased from 1% to 58% between 2003 and 2008 (Reddy et al, 2010)
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