| 摘要: |
| 【目的】了解牛源大肠杆菌对氟喹诺酮类药物的耐药特征，为临床合理用药提供理论依据。【方法】从不同牛场采集腹泻犊牛粪样分离鉴定大肠杆菌，采用微量肉汤稀释法测定大肠杆菌对环丙沙星、恩诺沙星和诺氟沙星3种氟喹诺酮类药物的最小抑菌浓度（MIC），PCR检测质粒介导的喹诺酮类耐药（PMQR）基因（qnrA、qnrB、qnrD、qnrS、aac（6′）Ib和qepA基因）及喹诺酮耐药决定区（QRDR）突变（gyrA和parC基因），并选择2株携带PMQR基因的大肠杆菌经恩诺沙星诱导后检测QRDR的gyrA和parC基因突变。【结果】分离鉴定得到75株大肠杆菌，其中60.00%的菌株对至少2种FQs耐药，40.00%的菌株对环丙沙星、恩诺沙星和诺氟沙星均耐药,且对恩诺沙星的耐药程度较为严重。75株大肠杆菌均未检测到qnrA、qnrD和qepA基因，但检测出qnrS、aac(6′)Ib亚型aac(6′)-Ib-cr和qnrB基因，61.33%的菌株至少携带1个PMQR基因，其中以qnrS和aac(6′)-Ib-cr最为常见。58.67%的大肠杆菌发生了QRDR突变，主要突变方式为GyrA:(Ser83Leu＋Asp87Asn)＋ParC:Ser80Ile，发生突变且携带PMQR基因的大肠杆菌对环丙沙星、恩诺沙星和诺氟沙星均耐药。恩诺沙星诱导后，PMQR阳性菌的gyrA基因发生5处碱基突变，PMQR阴性菌无碱基突变。【结论】大肠杆菌耐氟喹诺酮类药物主要与QRDR突变密切相关，因此兽医临床上应合理使用氟喹诺酮类药物来减缓大肠杆菌的耐药性。 |
| 关键词: 牛源大肠杆菌 氟喹诺酮类药物 PMQR基因 QRDR突变 耐药性 |
| DOI： |
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| 基金项目:陕西省农业重点研发项目（2017ZDXM-NY-079）；中国农业大学-新疆农业大学科研合作基金项目(2019TC167) |
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| Resistance of Escherichia coli from dairy to fluoroquinolones |
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WANG Lijuan,WANG Ningning,WANG Le,et al
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| Abstract: |
| 【Objective】The resistance characteristics of E. coli from feces of diarrhea calves to fluoroquinolones isolated were investigated to improve its clinical rational use.【Method】E. coli was collected from fecal samples of diarrhea calves in different cattle farms. Their MICs to three fluoroquinolones of ciprofloxacin,enrofloxacin and norfloxacin were determined by the micro-broth dilution method.PMQR genes (qnrA,qnrB,qnrD,qnrS,aac（6′）-Ib and qepA genes) and QRDR mutations (gyrA and parC genes) were detected by PCR.Two E. coli strains with PMQR gene were selected to detect mutation of QRDR after enrofloxacin induction.【Result】 Seventy-five E. coli isolates were identified with 60.00% resistant to two or more fluoroquinolones (FQs) and 40.00% resistant to ciprofloxacin,enrofloxacin and norfloxacin simultaneously.The qnrA,qnrD and qepA genes were not detected in any of the 75 E. coli strains,while qnrS,aac(6′)-Ib subtypes aac(6′)-Ib-cr and qnrB were detected.At least one PMQR gene was detected in 61.33% strains,and qnrS and aac (6′)-Ib-cr were the most common.QRDR mutations were detected in 58.67% isolates,and main mutations were GyrA:(Ser83Leu＋Asp87Asn)＋ParC:Ser80Ile.All E. coli isolates with QRDR mutation and PMQR genes were resistant to ciprofloxacin,enrofloxacin and norfloxacin.Five base mutations occurred in gyrA of PMQR positive bacteria under enrofloxacin pressure,while no base mutations occurred in PMQR negative bacteria.【Conclusion】The resistance of E. coli to fluoroquinolones was closely related to QRDR mutations,so fluoroquinolones should be reasonably used in veterinary clinic to reduce the resistance of E. coli. |
| Key words: bovine E. coli fluoroquinolones PMQR gene QRDR mutation resistance |
