ABSTRACT
Enterococci are important nosocomial pathogens. Multiple drug resistance [MDR] is common among Enterococci and presents difficulties for treatment. High level gentamicin resistance [HLGR] in enterococci, is a significant therapeutic problem. Bactericidal antimicrobial activity usually is obtained by the synergistic combination of a cell wall active agent such as penicillin or glycopeptide with an aminoglycoside. Enterococci can acquire aminoglycoside resistance genes that mediate production of aminoglycoside-modifying enzymes, which eliminate this synergistic bactericidal effect. The most clinically important HLGR genes is aac [6']-le-aph [2"]-la. In the present study, a total of 437 clinical samples from 5 hospital and 3 private laboratory in Tehran, from azar 1384 to Tir 1385, were collected and 300 enterococcal isolates recovered all of the strains were identified to the species level by conventional biochemical tests and assayed for their susceptibility to 11 antibiotics, ampicillin, tetracycline, erythromycin, ciprofloxacin, high dose gentamicin, vancomycin, cotrimoxazole, quinopristin -daifopristin [synercid], linezolid, teicoplanin and nitrofurantoin by disk diffusion method. Gentamicin MIC was accomplished for HLGR strains. The most frequent species was E. faecalis [81.3%] and then E. faecium [18.7%]. MDR strains were detected in 50% and 95% of E.faecalis and E.faecium, respectively. The number of HLGR strains for E.faecalis and E.faecium were found to be 19.5% and 23.5%, respectively. All HLGR strains showed MIC>1024 microg/mL The PCR results showed that 83% and 100% of E.faecalis and E.faecium strains carried aac[6']-le-aph[2"]-la gene as detected by PCR. The present study indicates high rate dissemination of aac[6']-le-aph[2"]-la gene, suggesting the possible mechanism of transfer of gentamicin resistant genes within the enterococcal population and in this case probable need to new aminoglycosides or other antibiotics would be predictable