Publication

Abstract : Background: Enterococcus has become an important nosocomial pathogen by virtue of their versatile genetic machinery enabling them to exhibit intrinsic, as well, acquired resistance to several antimicrobials. The aminoglycoside resistant enterococci may exhibit versatility in their genetic mechanism to encode resistance to a single antimicrobial in more than one way; hence genotypic analysis helps in detecting the genetic basis of antimicrobial resistance. Objectives: The aim of this study is: to detect antimicrobial resistance and to study the molecular epidemiology, with reference to high-level aminoglycoside resistance, of enterococci. Methods: In the present study, a total of 396 enterococci were isolated from various clinical specimens in the Department of Microbiology, in a tertiary care hospital in south India, during the period from September 2003 to August 2004. The isolates were identified to the species level by conventional biochemical and microbiological tests, and assayed for their susceptibilities to antimicrobial agents. The genetic diversity of antimicrobial resistant strains was evaluated by pulsed-field gel electrophoresis (PFGE) analysis of Sma I restricted chromosomal DNA. Results: The most frequent species was Enterococcus faecalis (79.79%). Other species identified were: E. faecium (11.11%), and 3% each of E. gallinarum, E. hirae and E. casseliflavus. The overall prevalence of isolates with high-level resistance (HLR) to aminoglycosides was 56%. No strains with acquired resistance to vancomycin were found. PFGE analysis showed the predominance of clonal group A, comprising strains isolated from different clinical specimens. Conclusion: These results suggest an intrahospital dissemination of one predominant clonal group of E. faecalis isolates with HLR to gentamicin in the hospitals.