[The incidence of high-level aminoglicoside and high-level beta-lactam resistance among enterococcal strains of various origin].

Abstract

Introduction: Intensive use of broad-spectrum antibiotics is responsible for conversion of enterococci from commensal bacteria to opportunistic nosocomial pathogenes. The serious infections caused by them are often treated with synergistic bacteriocidal combination of beta-lactam and aminoglycoside. The presence of high-level aminoglikosyde (HLAR) and/or beta-lactam (HLPR) resistance makes this treatment ineffective.

Methods: This study investigated the differences in occurance of HLAR and/or HLPR among groups of enterococi isolated from: rectal swabs of healthy volunteers, samples of food and clinical specimens. Enterococci were identified by 6.5% NaCl tolerance and growth on bile-esculin agar with esculin hydrolysis. Species-level identification was made on the basis of motility, pigmentation, arginine hydrolysis, growth on tellurite and formation of acid in mannitol, sorbitol, sucrose, arabinose, raffinose and sorbose broth (according to the Facklam's and Sahm's scheme). High-level resistance were determined to penicillins (> 100 microg/ml), gentamycin (> 500 microg/ml) and streptomycin (> 2000 microg/ml).

Results: Although differences in species prevalence varied by source, E. faecalis was the common enterococcal species in all samples (> 70%), followed by E. faecium (10%-20.4%) and E. durans (4.2%-8.45%). E. faecalis varians, E. pseudoavium and E. raffinossus were isolated rarely. Analysis of 452 enterococcal strains revealed the presence HLAR in all groups, but HLPR was not present in samples of food. In community the HLR was greatest for streptomycin, but among hospital isolations-HLR both to streptomycin and gentamycin were most common. Such resistance was more frequent in E. faecium than in E. faecalis. HLR to kanamycin was not found.

Conclusions: This study shows that high-level resistance to aminoglycoside and/or beta-lactam of enterococci may play an important role in public health. Little is known about the prevalence, risk factors and reservoirs for resistance enterococci outside of the hospital. A comparison of the resistance determinants in isolates from healthy volunteers with the genes responsible for resistance in isolates from patients.