Phenotypic speciation of clinical isolates of Enterococci with special reference to Vancomycin susceptibility by Broth Micro-dilution method

Abstract

Background: Enterococci, once regarded as a commensal in the gastrointestinal tract, are now emerging as an important nosocomial pathogen. By intrinsic and acquired mechanisms of resistance, they pose a significant therapeutic challenge. Objectives: This study aims to characterize Enterococci up to species level based on their phenotypic characters and study their antibiogram with special mention to Vancomycin susceptibility. Materials and Methods: A cross-sectional descriptive study was conducted in the Department of Microbiology, Andhra Medical College. A total of 47 Enterococci isolates recovered from clinical specimens like Urine & Pus are included in this study. Specimen processing and speciation were done according to standard protocols. Kirby–Bauer disc diffusion technique was used to study antimicrobial susceptibility pattern with recommended drugs including high-level aminoglycoside resistance, whereas the minimum inhibitory concentration of vancomycin was determined by the Broth Microdilution method, with reference to the Clinical and Laboratory Standards Institute guidelines (CLSI). Results: Two different species of Enterococci were isolated, E. faecalis and E. faecium accounting 86% and 14% each. All the strains were sensitive to Vancomycin, Linezolid and Teicolplanin, while all the urine isolates are also sensitive to Nitrofurantoin. Disparities were not observed between the disc diffusion technique and Broth Microdilution method in determining vancomycin resistance. Conclusion: E.faecalis and E. faecium were the predominant species in causing Enterococcal infections. To maintain the low level of resistance, improvement of antibiotic policies and hospital infection control is essential.