Proficiency of determination of vancomycin susceptibility in enterococci by clinical laboratories in Taiwan.

Eighty clinical microbiology laboratories in Taiwan were evaluated for proficiency in the determination of vancomycin susceptibility of enterococci. Each laboratory was given 1 vancomycin-sensitive isolate and 3 vancomycin-resistant enterococci (VRE) isolates to determine the levels of vancomycin resistance. Among a total of 240 tests performed, 153 (63.8%) correctly determined the levels of vancomycin resistance of the survey isolates. Seventy eight (98%) of the 80 laboratories accurately identified the high level of vancomycin resistant isolates [Enterococcus faecalis; minimum inhibitory concentration (MIC) >256 microg/mL]. Seventy two laboratories (90%) correctly determined the level of vancomycin resistance of another VRE with a vancomycin MIC of 64 microg/mL. Only 3 of the 80 laboratories correctly determined the intermediate-level vancomycin resistant isolates (Enterococcus casseliflavus; MIC = 8 microg/mL). Eight laboratories reported the vancomycin-susceptible isolate as being vancomycin-resistant or of intermediate susceptibility. This survey demonstrated that clinical microbiology laboratories in Taiwan are proficient in detecting high-level but not low-level VRE, suggesting a need to improve their proficiency in VRE detection.