阴沟肠杆菌临床分离株中3类质粒介导喹诺酮类药物耐药基因的检测

Detection of plasmid-mediated quinolone resistance determinants in clinical isolates of Enterobacter cloacae

目的了解3类质粒介导喹诺酮类药物耐药基因在阴沟肠杆菌中流行情况。方法采用聚合酶链反应检测2005年1—12月本院临床分离的101株阴沟肠杆菌中qnrA、qnrB、qnrS、aac(6′)-Ib以及qepA基因,对aac(6′)-Ib基因阳性菌株采用FokI酶切确认aac(6′)-Ib-cr基因,同时检测ESBLs及AmpC酶的产生情况。结果101株阴沟肠杆菌对环丙沙星的耐药率为32.7%。41.6%(42/101)菌株携带qnr基因和(或)aac(6′)-Ib-cr基因,其中39株(38.6%)携带qnr基因,7株(6.9%)携带aac(6′)-Ib-cr基因,4株同时携带qnrB4和aac(6′)-Ib-cr,未检测到qepA基因。qnr基因阳性菌株中qnrA19株、qnrB18株、qnrS3株(其中1株同时含有qnrB和qnrS)。环丙沙星耐药与敏感菌株中qnr基因检出率分别为48.5%(16/33)和32.8%(21/64),经卡方检验两组差异无统计学意义(P=0.22)。产与非产ESBLs菌株中qnr基因检出率分别为62.7%(32/51)和14.0%(7/50),两者差异有统计学意义(P<0.01)。结论临床分离的阴沟肠杆菌中质粒介导的喹诺酮类药物耐药基因检出率高,在环丙沙星敏感阴沟肠杆菌中qnr基因的检出率与耐药株中的检出率相仿。

Objective To investigate the prevalence of three types of plasmid-mediated quinolone resistance （PMQR） determinants in Enterobacter cloacae clinical isolates. Methods qnrA, qnrB, qnrS, aac（6＇）-Ib and qepA were detected by PCR in 101 clinical strains isolated from Huashan Hospital from January to December in 2005. Positive PCR products of aac（6＇）-Ib were digested with FokI to identify aac（6＇） -Ib-cr. ESBLs and ArnpC genes were also detected by PCR. Results Of the 101 E. cloacae isolates, 32.7% were resistant to ciprofloxacin. PMQR determinants were present in 41.6% （42/101） of the isolates, evidenced by amplicon of qnr and/or aac（6＇）-Ib-cr. The qnr gene was identified in 39 （38.6%） strains and aac（6＇）-Ib-cr in 7 （6.9 % ） strains. The qepA gene was not identified in any of the strains. The 39 qnr gene-positive strains included 19 （18.8 %） qnrA, 18 （17.8%） qnrB and 3 （3.0%） qnrS （one strain harbored both qnrB and qnrS）. The prevalence of qnr genes was 48.4% （16/33） in ciprofloxacin resistant strains and 32.8% （21/64） in ciprofloxacin susceptible strains. The prevalence between these two groups was not significantly different （P = 0.22）. The prevalence of qnr genes was 62.7% （32/51） in ESBL-producing strains and 14.0% （7/50） in non-ESBL-producing strains （P〈0.01）. Conclusions PMDR determinants are highly prevalent in Enterobacter cloacae clinical isolates. The prevalence of qnr genes in ciprofloxacin susceptible strains is similar to that in ciprofloxacin resistant strains.