Gastrointestinal colonisation of vancomycin-resistant enterococcus in a Singapore teaching hospital

Vancomycin-resistant enterococcus (VRE) has become an important nosocomial pathogen in many countries but is still rare in Singapore. A study was conducted from January to March 1997 at a 900-bed teaching hospital to determine the prevalence of intestinal colonisation of VRE in the patient population. A total of 299 consecutive stool specimens received by the microbiology laboratory for routine testing were plated onto two different selective media for comparison. VRE isolated were phenotypically characterised using minimum inhibitory concentrations (MICs) to vancomycin and teicoplanin and then typed using pulsed-field gel electrophoresis (PFGE) with SmaI digestion of DNA. VRE were detected in the stool of 35 patients (12.3%). This group consisted of four isolates with VanB (one Enterococcus faecalis and three E. faecium) and 31 isolates with VanC (30 E. casseliflavus and one E. gallinarum). Two patients (0.7%) carried isolates (both VanB) with high level resistance to vancomycin (MIC = 256 mug/ml) while the rest had isolates of low level resistance (MIC = 8 mug/ml). Except for isolates from the same patients, PFGE patterns were diverse, suggesting that the VRE isolates were genotypically different and possibly introduced from many sources. This study demonstrates that VRE colonisation is not uncommon in the Singapore patient population.