Клиническая микробиология и антимикробная химиотерапия (Feb 2018)
Detection of vancomycin-resistant enterococci using chromogenic selective medium
Abstract
Objective. To detect vancomycin-resistant enterococci (VRE) using chromogenic selective medium CHROMagar™VRE (CHROMagar, France). Materials and Methods. In the first part of the study, a total of 39 vancomycin-resistant and 20 vancomycinsusceptible Enterococcus spp. isolated from blood culture with known susceptibility profiles were incubated on the CHROMagar™VRE (CHROMagar, France) and examined after 24 h and 48 h of incubation. In the second part of the study, a total of 110 rectal swabs were taken from patients with hematological malignancies and incubated on the CHROMagar™VRE. The vancomycin susceptibility of isolates grown on the selective medium was further evaluated by the broth microdilution method (CLSI, 2017). Glycopeptide resistance genes were detected by PCR. Results. Using the CHROMagar™VRE, a total of 36 (92.3%) vancomycin-resistant isolates were detected after 24 h and additional two isolates – after 48 h of incubation. The sensitivity of the selective medium for detection of VRE obtained from blood culture was 92% and 97% after 24 h and 48 h of incubation, respectively. All 20 vancomycin-susceptible enterococci did not grow on the CHROMagar™VRE (specificity – 100%). Of 110 rectal swabs, 35 (31.8%) samples were positive for Enterococcus spp. on the CHROMagar™VRE (33 – E. faecium и 2 – E. faecalis). Resistance to vancomycin was detected in 32/33 (97%) E. faecium isolates, of them 28 and 4 strains were isolated after 24 h and 48 h of incubation; all VRE strains carried vanA gene. The proportion of false positive isolates was 3.4% after 24 h of incubation and 8.6% after 48 h of incubation on the CHROMagar™VRE medium for screening of VRE from rectal swabs. Conclusions. The chromogenic selective media CHROMagar™VRE has a high sensitivity and specificity for the detection of VRE and can be used for screening in laboratory practice.
