gyrA mutations associated with fluoroquinolone resistance in eight species of Enterobacteriaceae
gyrA mutations associated with fluoroquinolone resistance in eight species of Enterobacteriaceae
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DOI：
10.1128/aac.42.10.2661
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发表时间：
1998-10-01
影响因子：
4.9
通讯作者：
Tenover, FC
中科院分区：
文献类型：
--
作者：
Weigel, LM;Steward, CD;Tenover, FC
近年来，肠杆菌科细菌临床分离株对氟喹诺酮类药物耐药(FQ-R)的报道日益增多。在革兰氏阴性菌中，已经确定了FQ-R的两种机制：DNA旋转酶的突变和减少细胞内的药物积累。GyrA基因的单点突变已被证明可降低对氟喹诺酮类药物的易感性。为了确定肠道细菌GyrA基因FQ-R突变的程度，从大肠埃希菌和肺炎克雷伯菌的喹诺酮耐药决定区(QRDR)两侧的保守序列中筛选出一套寡核苷酸引物，对8株肠杆菌科细菌和60株耐氟喹诺酮类临床分离株的QRDR进行了扩增和测序。虽然7个物种的核苷酸序列相似性在80.8%~93.3%之间，但与E.Coli相比，Gyra QRDR的氨基酸序列高度保守。在敏感的弗劳地、E、产气菌、催产克雷伯菌(Ser-83对Thr)和斯氏假单胞菌(Asp-87到Glu)的QRDR中检测到保守的氨基酸替换，环丙沙星MIC为2mUg/ml的菌株主要在Gly-81、Ser-83或Asp-87位表达氨基酸替换，而具有相同gyrA突变的菌株的氟喹诺酮MIC有显著差异，表明gyrA以外的突变与耐药有关。在这六个属中，氨基酸改变的类型和位置也不同，高水平的FQ-R经常与本研究中除大肠杆菌以外的所有肠杆菌科物种中的单个gyrA突变相关。
Fluoroquinolone resistance (FQ-R) in clinical isolates of Enterobacteriaceae species has been reported with increasing frequency in recent years. Two mechanisms of FQ-R have been identified in gram-negative organisms: mutations in DNA gyrase and reduced intracellular drug accumulation. A single point mutation in gyrA has been shown to reduce susceptibility to fluoroquinolones. To determine the extent of gyrA mutations associated,vith FQ-R in enteric bacteria, one set of oligonucleotide primers was selected from conserved sequences in the flanking regions of the quinolone resistance-determining regions (QRDR) of Escherichia coli and Klebsiella pneumoniae, This set of primers was used to amplify and sequence the QRDRs from 8 Enterobacteriaceae type strains and 60 fluoroquinolone-resistant clinical isolates of Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, E. coli, K. pneumoniae, Klebsiella oxytoca, Providencia stuartii, and Serratia marfescens. Although similarity of the nucleotide sequences of seven species ranged from 80.8 to 93.3%, when compared with that of E, coli, the amino acid sequences of the gyrA QRDR were highly conserved. Conservative amino acid substitutions were detected in the QRDRs of the susceptible type strains of C. freundii, E, aerogenes, K. oxytoca (Ser-83 to Thr), and P. stuartii (Asp-87 to Glu), Strains with ciprofloxacin MICs of >2 mu g/ml expressed amino acid substitutions primarily at the Gly-81, Ser-83, or Asp-87 position, Fluoroquinolone MICs varied significantly for strains exhibiting identical gyrA mutations, indicating that alterations outside gyrA contribute to resistance. The type and position of amino acid alterations also differed among these six genera, High-level FQ-R frequently was associated with single gyrA mutations in all species of Enterobacteriaceae in this study except E. coli.