摘要:Klebsiella pneumoniae(K.pneumoniae)is one of the main gram-negative bacilli in clini- cal practice.Nosocomial infections caused by K.pneumoniae producing extended-spectrumβ-lactama- ses(ESBLs)are very difficult to treat.This paper investigated the resistant characteristics of K.pneu- moniae producing ESBLs and their aminoglycoside-modifying enzyme gene expressions including N- acetyhransferases and O-adenyhransfemses.Bacteria identification and ESBLs confirmatory tests were performed by Phoenix^(TM)-100 system.And minimum inhibitory concentrations(MICs)of gentamicin, amikacin,kanamycin,tobramycin,netilmicin and neomycin in 53 K.pneumoniae isolates were de- tected by agar dilution.In addition,six aminoglycoside-modifying enzyme genes were amplified by polymerase chain reaction(PCR)and verified by DNA sequencer.It was found that imipenem and meropenem against 120 K.pneumoniae isolates produced powerful antimicrobial activities.The resis- tant rates of gentamicin and amikacin were 55.0% and 46.7%,respectively.Except neomycin, MIC_(50)and MIC_(90)of gentamicin,amikacin,kanamycin,tobramycin and netilmicin in 53 K.pneumoni- ae were all>128μg/ml,and the resistant rates were 83.0%,52.3%,75.5%,81.1% and 69.8%,respectively.However,neomycin was only 39.6%.In addition,five modifying enzyme genes,including aac(3)-Ⅰ,aac(3)-Ⅱ,aac(6')-Ⅰb,ant(3″)-Ⅰ,ant(2″)-Ⅰgenes,were found in 53 isoahes except aac(6')-Ⅱ,and their positive rates were 11.3%,67.9%,47.2%, 1.9% and 39.6%,respectively.It was also confirmed by nucleotide sequence analysis that the above resistant genes shared nearly 100% identities with GenBank published genes.The results obtained in the present study indicated that K.pneumoniae producing ESBLs strains are rapidly spreading in our hospital,and their resistance to aminoglycosides may be associated with aminoglycoside-modifying enz- yme gene expressions.