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目的 调查肺炎克雷伯菌临床分离株aac(6’)-Ib-cr基因存在情况.方法 收集2006年1月至2007年9月从临床分离的337株非重复的肺炎克雷伯菌.挑选64株对庆大霉素、阿米卡星和妥布霉素任何一种耐药的肺炎克雷伯菌临床分离株进行aac(6’)-Ib-cr基因检测,采用PCR法检测aac(6’)-Ib和Ⅰ类整合酶基因(intll),通过DNA直接测序确定aac(6’)-Ib-cr.抗生素MIC值测定采用琼脂稀释法.ESBLs检测采用双纸片扩散法,通过接合试验检测质粒是否可以发生转移.结果 337株肺炎克雷伯菌临床分离株中,对庆大霉素、阿米卡星和妥布霉素的耐药率分别为19.0%(64/337)、8.3%(28/337)和16.3%(55/337).共有24株细菌经PCR证实aac(6’)-Ib基因阳性,经测序证实全部为aac(6’)-Ib-cr基因,阳性率为37.5%(24/64).24株aac(6’)-Ib-cr基因阳性株中,有13株对环丙沙星耐药(MIC≥2 mg/L)和11株环丙沙星敏感(MIC≤0.25～1.0 mg/L).aac(6’)-Ib-cr基因在环丙沙星耐药菌株和环丙沙星敏感菌株中的检出率分别为54.2%(13/24)和27.5%(11/40),经X2检验,差异具有统计学意义(X2=11.056,P＜0.01).24株aac(6’)-Ib-cr基因阳性株中,ESBLs和intl1基因的阳性率分别为79.2%(19/24)和91.7%(22/24).13株aac(6’)-Ib-cr基因阳性菌株的质粒成功转移至受体菌,以受体菌质粒DNA为模板进行aac(6’)-Ib-cr检测,13株受体菌质粒全部为aac(6’)-Ib-cr基因和intl基因阳性,全部为ESBLs阳性株.结论 aac(6’)-Ib-cr基因广泛存在于肺炎克雷伯菌临床分离株中,aac(6’)-Ib-cr可能通过Ⅰ类整合子和ESBL基因同时位于可转移的质粒上造成传播.“,”Objective To investigate the prevalence of aac(6’)-Ib-cr in clinical isolates of Klebsiella pneumoniae.Methods A total of 337 isolates of Klebsiella pneumoniae were isolated from clinical specimens in our hospital from Jan,2006 to Sep,2007.Gentamycin,amikacin or tobramicin was used to screen the isolated with aac(6’)-Ib-cr.aac(6’)-Ib and class 1 interase gene(intl1)was determined by PcR All PCR products of aac(6’)-Ib were sequenced for determination of aac(6’)-Ib-cr. MICs of antibiotics were determined by agar dilution method.The ESBLs-producing isolates were determined by the CLSI-recommended confirmatory tests.Conjugation test was used to detect the transfer of plasmid.Results Of the 337 clinical isolates of Klebsiella pneumoniae,64(19.0%),28(8.3%)and 55(16.3%)isolates were resistant to gentamycin,amikacin and tobramycin,respectively.Among 64 gentamycin-resistant isolates,24(37.5%)were positive for aac(6’)-Ib-cr,including 13 ciprofloxacin-resistant isolates and 11 ciprofloxacinsusceptible isolates.The prevalence of aac(6’)-Ib-cr in ciprofloxacin-resistant and-susceptible isolates were 54.2%(13/24)and 27.5%(11/40).The positive rates of ESBLs and intl1 in the 24 isolates carrying aac(6’)-Ib-cr were 79.2%(19/24)and 91.7%(22/24).Plasmids carrying aac(6’)-Ib-cr of 13 isolates were successfully transferred to E.coli J53.Plasmids of all transconjugants were positive for aac(6’)-Ib-cr and intl1.All transconjugants were ESBL producing strains.Conclusions aac(6’)-Ib-cr exists widely in clinical isolates of Klebsiella pneumoniae.aac(6’)-Ib-cr and ESBL gene usually coexist in a selftransmissible conjugative plasmid by class 1 integron.