A Study on Glycopeptide-Resistant Genotypes among Clinical Isolates of Enterococcus with Van B Phenotype.

Abstract

Background: Enterococci, although remarked as harmless commensals of the intestinal tract of humans and animals, have become a significant source of infection in hospitalized patients worldwide.The present study aimed to isolate and identify enterococci from clinical samples and to determine the genotypic characteristics of vancomycin-resistant enterococcus isolates.

Materials and methods: A total of 774 isolates of enterococci from clinical samples were identified to the species level, and their anti-microbial susceptibility pattern was determined by Kirby Bauer Disk Diffusion method and Vitek 2 automated system. Screening for vancomycin resistance was performed by using brain heart infusion agar containing 6 micrograms/ml of vancomycin. The minimum inhibitory concentration (MIC) of vancomycin was determined by the agar dilution method and Epsilometer test (E test). Genotyping was carried out for resistant isolates by multiplex polymerase chain reaction.

Results: Thirty (3.88%) isolates were resistant to vancomycin by agar screen method. Five isolates showed intermediate resistance with anMIC of 8-16 micrograms/ml for vancomycin by agar dilution. By the E test, two isolates displayed an MIC of ≥32 micrograms/ml for vancomycin and one isolate showed an MICof ≥32 micrograms/ml for teicoplanin.Van A was the common genotype isolated. The present study reports isolates of Enterococcus faecalis with a susceptible MIC for glycopeptide and the presence of the Van A gene.

Conclusion: Heterogeneous resistance among clinical isolates of Enterococcus faecalis was observed in our study. The predominant phenotype and genotype detected among clinical isolates were Van A.