Chromid vre agar plate

Rectal samples were transferred onto a blood agar plate (Columbia Agar +5% sheep blood, bioMérieux, Nürtingen, Germany) as well as a ChromID VRE agar plate (bioMérieux, Nürtingen, Germany). All pathogens cultivated on selective culture media were identified down to species level using VITEK2 (bioMérieux, Nürtingen, Germany). Antimicrobial susceptibility testing was also performed with VITEK2. Enterococci were classified as susceptible or resistant to glycopeptides based on minimal inhibitory concentrations according to the breakpoints of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) [19 ], [20 (link)]. Non-susceptibility was regarded as resistance. Very experienced laboratory personnel performed the laboratory testing. Any conflicting results were resolved by multiplex VanA/B-PCR [20 (link)], [21 (link)].

For selective culture of Vancomycin Resistant Enterococcus faecalis or Enterococcus faecium (VRE,) rectal swabs were incubated for 2 nights at 35 °C in Brain Heart Infusion broth with 2% NaCl and 16 mg/l gentamicin plus 16 mg/l vancomycin. Subcultures were made on chromID VRE agar plate (bioMérieux). VRE confirmation was done by VanA/ VanB PCR using GeneXpert (Cepheid).

Chromogenic medium (ChromID VRE agar plate, Biomerieux) was used for detection and differentiation of VRE from screening swabs. Identification of Enterococci in bloodstream isolates was based on VITEK 2 (Biomerieux). Genetic testing for vanA and vanB were not routine during the study period. Clinical isolates were deemed to be vanB if phenotypically susceptible to teicoplanin and resistant to vancomycin by VITEK 2 (Biomerieux) using Clinical and Laboratory Standards Institute (CLSI) guidelines (CLSI 2015, version M100-S25). Isolates resistant to teicoplanin were confirmed to be vanA by PCR (Xpert vanA/vanB, Cepheid, Sunnyvale, USA).