Enterococcal infections with special reference to phenotypic characterization & drug resistance.

BACKGROUND & OBJECTIVES Enterococci, classified as group D streptococci, are the second leading cause of nosocomial infections. The incidence of enterococcal infections and species prevalent in India is not thoroughly investigated. The present study was undertaken to isolate and characterize enterococci from clinical specimens and determine the antimicrobial susceptibility pattern of these isolates. METHODS Clinical specimens (blood, urine and swabs) were cultured on bile esculin azide agar (BEAA) for isolation of enterococci. The phenotype based scheme included Gram staining of growth on BEAA and subculturing of cocci on sheep blood agar plates for vancomycin disk diffusion and hydrolysis of L-pyrrolidonyl-beta-napthylamide (PYR) testing. The phenotypic method was used to surveillance cultures that yielded growth on BEAA. Enterococcal strains were further identified to the species level by conventional biochemical tests. PYR positive isolates were further characterized into vancomycin resistant enterococci (VRE) and nonVRE depending upon vancomycin inhibition zone size. The isolates were characterized into vanA, vanB and vanC depending upon minimum inhibitory concentration (MIC) values. Conventional method was used to study the antibiogram of isolates. RESULTS A total of 52 isolates of enterococci (10 Enterococcus faecalis, 42 E. faecium) were isolated from 534 clinical specimens. Of the 52 isolates, 12 isolates were resistant to vancomycin with an MIC > 4 microg/ml but sensitive to teicoplanin (vanB isolates). INTERPRETATION & CONCLUSION Our study reveals the problem of multiple drug resistant enterococci and emergence of VRE. Better susceptibility tests need to be used to measure the vancomycin resistance accurately.