Prevalence of vancomycin and high level aminoglycoside resistant enterococci among high-risk patients

Abstract

Enterococci have been recognized as clinically important pathogens in high-risk populations of hospitalized patients. The role of enterococci in nosocomial infections is being recognized with increasing frequency. The main source of these infections is usually fecal carriage of the microorganisms. In this study, gastrointestinal colonization with vancomycin resistant enterococci (VRE) and high-level aminoglycoside resistant enterococci among 316 high-risk hospitalized patients were investigated. One hundred and ninety-eight enterococci strains were isolated from stool specimens. All strains were identified to species level and 90 of the isolates were identified as Enterococcus faecalis (45%), 85 as E. faecium (21.5%), 14 as E. avium (7%), 7 as E. raffinosus (3.5%), 1 as E. durans (0.5%) and 1 as E. hirae (0.5%). Eleven of 198 strains were found to be moderately sensitive to vancomycin (MIC: 8-16 ?g/ml) by the agar dilution method according to the National Committee for Clinical Laboratory Standards (NCCLS) recommendations, and the rest of these strains were found to be sensitive (MIC?4 ?g/ml). Twenty-eight strains showed high-level resistance to streptomycin (2,000 ?g/ml) and 26 strains were found to have high-level resistance to gentamicin (500 ?g/ ml). Twelve of these strains had high-level resistance to both aminoglycosides. By the disk diffusion tests, 53 of 198 strains were found to be resistant to erythromycin, 51 to penicillin, 37 to ampicillin, 18 to ciprofloxacin, 14 to norfloxacin and 3 to nitrofurantoin. No beta-lactamase production was detected in 198 studied strains.