Detection of vancomycin resistance in enterococcus species isolated from clinical samples and feces of colonized patients by phenotypic and genotypic methods.

Abstract

The aim of this study was to find out the clinical correlation between the presence of vancomycin-resistant genes (van A and van B) and their expression as detected by phenotypic tests in colonized patients and in clinical isolates. Enterococci were isolated from various clinical samples and also from fecal specimens of colonized patients at the time of admission, after 48 h and after 5 days of admission. Identification to species level was done using standard methods. Vancomycin susceptibility in Enterococci was detected by disc diffusion test. Minimum inhibitory concentration was determined by agar dilution method. Multiplex polymerase chain reaction (PCR) was used to detect the presence of van genes. Out of all the clinical and fecal samples processed, 12.0% isolates were either vancomycin resistant or vancomycin intermediate. Further, these isolates carried van A or van B genes as confirmed by PCR methods. Expression of van A gene was found to be more in Enterococcus faecalis (28.3%) as compared to Enterococcus faecium (25.0%) in both clinical and fecal isolates. 16.6% strains of E. faecium and 15.0% strains each of E. faecalis and Enterococcus gallinarum were found to carry van B genes. The overall prevalence of vancomycin resistant Enterococci (VRE) in colonized patients was about 9.6%. Prior administration of antibiotics had significant effect (P = 0.001) on VRE carriage. Urinary tract infection was the most common infection caused by vancomycin susceptible Enterococci (VSE), 105/214 (49.0%) and VRE, 13/36 (36.1%). There was no significant difference (P = 0.112) in the distribution of VRE and VSE in different infection types. Both clinical and fecal VRE showed maximum resistance to penicillin, ampicillin, and piperacillin. Resistance to linezolid was 2.8% in clinically isolated VRE. VRE in our study were found to be resistant to a number of commonly used antibiotics. The frequency of isolation of vancomycin resistant E. faecalis (VRE.fs), which is highly virulent, and the number of strains harboring van A gene in our hospital setup is high and needs to be addressed.