中国部分地区产超广谱-β内酰胺酶大肠埃希菌和肺炎克雷伯菌qnrA基因的检测  

The study of qnrA gene in Escherichia coli and Klebsiella pneumonia producing extended-spectrumβ-lactamase in part of China

作　　者：钱英[1] 裘云庆[2] 周志慧[2] 俞云松[2] 李兰娟[2] 

机构地区：[1]杭州师范大学医学院,310041 [2]浙江大学医学院附属第一医院传染科

出　　处：《中华传染病杂志》2007年第10期601-606,共6页Chinese Journal of Infectious Diseases

基　　金：973课题资助项目(2005CB523101);浙江省自然科学基金(Y206123)

摘　　要：目的明确我国部分地区产超广谱-β内酰胺酶(ESBL)大肠埃希菌和肺炎克雷伯菌中qnrA基因的存在状况。方法PCR扩增产ESBL菌株,包括263株大肠埃希菌和99株肺炎克雷伯菌的qnrA基因;测序分析其基因序列。琼脂稀释法测定10种抗菌药物对qnrA基因阳性菌株的最低抑菌浓度(MIC)。接合实验和Southern杂交进行基因定位。脉冲场凝胶电泳(PFGE)分析qnrA基因阳性株的同源性。结果263株大肠埃希菌中有5株检出qnrA基因,占1.9%;99株肺炎克雷伯菌中有8株检出qnrA基因,占8.1%。13株qnrA阳性株中qnrA基因均位于可接合性质粒上。13株菌株同时携带CTX-M基因(1株CTX-M-9、5株CTX-M-14和7株CTX-M-24)。qnrA基因阳性的接合菌与受体菌J53相比,环丙沙星对前者的MIC较后者提高了4～133倍。11株环丙沙星耐药株(MIC≥4 mg/L)均存在GyrA亚基的83位氨基酸和(或)87位氨基酸改变,其中8株对环丙沙星高水平耐药株(MIC≥16 mg/L)同时存在ParC亚基的80位氨基酸改变。2株MIC分别为4 mg/L和2 mg/L的菌株GyrA和ParC两亚基均未发生改变。结论肺炎克雷伯菌中qnrA基因的携带率高于大肠埃希菌。qnrA基因单独作用仅导致低水平喹诺酮类耐药,合并gyrA和(或)parC突变导致喹诺酮类高水平耐药。Objective To detect qnrA gene in Escherichia coli and Klebsiella pneumonia producing extended-spectrum β-lactamases（ESBL） in part of China. Methods Polymerase chain reaction （PCR） was used to amplify qnrA gene and ESBL gene in 263 Escherichia coli isolates and 99 Klebsiella pneumonia isolates, minimal inhibitory concentration（MIC） of ten antimicrobial agents were determined by agar dilution method. Conjugation experiments and Southern blot hybridization were employed to determine if qnrA gene was located on the plasmid. PFGE was performed to analyze the homologic isolates in which qnrA was positive. Results The qnrA gene was detected in 5 of 263 （1.9%） Escherichia coli isolates and 8 of 99 （8. 1%） Klebsiella pneumonia isolates. The CTX-M gene presented in all 13 qnrA-positive strains （including CTX-M-9. CTX-M-14 and CTX-M-24）. Transfer of the qnrA determinant by conjugation could be detected from all 13 qnrA-positive strains. The MICs of ciprofloxacin for transconjugants were 0.06-2 /Lg/mL, representing an increase of 4- to 133- fold compared to the recipient. Mutations of amino acid 83 and（or） 87 in GyrA were found in 11 ciprofloxacin resistant isolates（MIC ≥ 4 mg/L）, while mutations of amino acid 80 in ParC were also found in 8 of 11 isolates with high-level resistance to ciprofloxacin（MIC ≥ 16 mg/L）. There was no mutation in 2 isolates with low-level resistance to ciprofloxacin. Conclusions The positive rate of qnrA gene in Klebsiella pneumonia strains is higher than that in Escherichia coli strains. The co presence of qnrA gene and mutation of GyrA and（or） ParC results in the higher-level resistance to quinolones, qnrA gene and CTX-M gene can be co transferred by the same plasmid.

关 键 词：喹诺酮类 Β内酰胺酶 qnrA基因 抗药性 细菌 克雷伯菌 肺炎 大肠埃希菌 

分 类 号：R450[医药卫生—治疗学]