title: Outbreak of vancomycin-susceptible Enterococcus faecium containing the wild-type vanA gene.
abstract: Accurate detection of vancomycin-resistant enterococci (VRE) is essential in preventing transmission in health care settings. Chromogenic media are widely used for screening VRE because of fast turnaround times (TAT) and high sensitivity. We report an outbreak of Enterococcus faecium bearing vanA yet susceptible to vancomycin (vancomycin-variable Enterococcus [VVE]). Between October 2009 to March 2011, clinical and screening specimens (n=14,747) were screened for VRE using VRE-selective medium and/or PCR. VVE isolates were genotyped to determine relatedness. Plasmids from these isolates were characterized by sequencing. Overall, 52 VVE isolates were identified, comprising 15% of all VRE isolates identified. Isolates demonstrated growth on Brilliance VRE agar (Oxoid) at 24 h of incubation but did not grow on brain heart infusion agar with 6 μg/ml vancomycin (Oxoid) or bile esculin azide agar with 6 μg/ml vancomycin (Oxoid) and were susceptible to vancomycin. Genotyping of 20 randomly selected VVE isolates revealed that 15/20 were identical, while 5 were highly related. PCR of the VVE transposon confirmed the presence of vanHAXY gene cluster; however, vanS (sensor) and vanR (regulator) genes were absent. The outbreak was controlled through routine infection control measures. We report an emergence of a fit strain of E. faecium containing vanA yet susceptible to vancomycin. Whether this new strain represents VRE has yet to be determined; however, unique testing procedures are required for reliable identification of VVE.
authors: Brant Community Healthcare System-Brantford General Hospital, Brantford, Canada.
authors: Tom A
authors: TA
authors: Szakacs
authors: Lindsay
authors: L
authors: Kalan
authors: Michael J
authors: MJ
authors: McConnell
authors: Alireza
authors: A
authors: Eshaghi
authors: Dea
authors: D
authors: Shahinas
authors: Allison
authors: A
authors: McGeer
authors: Gerry D
authors: GD
authors: Wright
authors: Donald E
authors: DE
authors: Low
authors: Samir N
authors: SN
authors: Patel
mesh_terms: D000362:Agar; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D003470:Culture Media; D004196:Disease Outbreaks; D016984:Enterococcus faecium / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification*; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics*; D005838:Genotype; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D014640:Vancomycin / Q000494:pharmacology*; D020713:Vancomycin Resistance / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003470:Culture Media; D014640:Vancomycin; D000362:Agar