Identification, antimicrobial susceptibility and virulence factors of Enterococcus species isolated from clinical specimens at an Indian tertiary care hospital

Abstract

Purpose: Enterococcus species have increasingly emerged as important pathogens in serious nosocomial and community acquired infections. The objective was to determine species identification, evaluate current susceptibility pattern and characterize various virulence determinants among clinical isolates of enterococci at an Indian hospital. Methods & Materials: Consecutive isolates from clinical specimens (April to September 2017) were included. Species identification was performed by conventional biochemical tests. Antimicrobial susceptibility testing was as per CLSI guidelines, including detection of high-level gentamicin resistance (HLGR), high-level streptomycin resistance (HLSR) and glycopeptide resistant enterococci (GRE). All screen-positive GRE isolates were investigated by PCR for species confirmation and presence of vanA/ vanB genes. Virulence genes asa1, esp, hyl, cyl, and gelE were investigated by molecular methods. Haemolysin and biofilm production were studied phenotypically. Results: Of 71 strains isolated, 57 (80.3%), 9 (12.7%) and 5 (7.0%) were from urine, pus and blood respectively consisting of E. faecalis (45, 63.4%), E. faecium (20, 28.2%), E. durans (3, 4.2%), and E. avium, E. hirae, E. mundtii (1, 1.4%). Six (8.4%) were GRE (5 E. faecium, 1 E. faecalis), all vanA phenotypically and genotypically. HLGR and HLSR was observed in 41 (57.7%) and 23 (32.4%) isolates respectively, higher in E. faecium compared to E. faecalis (85.0% and 40.0% vs 46.6% and 28.8%). Resistance to other antibiotics was also higher in E. faecium. All were susceptible to daptomycin. Hemolysin activity was significantly higher in E. faecalis compared to E. faecium (55.5% vs 0%). Biofilm production was observed in 23 (32.4%) isolates. Virulence genes detected were asa1 (9, 45%), gel (9, 45%), esp (7, 35%), cyt (6, 30%) and hyl (1, 5%). Frequency of asa, gel, and cyl was higher in E. faecalis than E. faecium (7, 7, 5 vs 2, 2, 1), whereas esp and hyl was more in E. faecium compared to E. faecalis (5, 1 vs 0, 0). Conclusion: Prevalence of a wide variety of Enterococcus species in clinical samples together with their variable antimicrobial susceptibility pattern and virulence traits emphasizes the need for their routine speciation and susceptibility testing which may help control the spread of multidrug resistant Enterococcus species.