Detection of mutations in the gyrA and parC genes in quinolone-resistant clinical isolates of Enterobacter cloacae
Detection of mutations in the gyrA and parC genes in quinolone-resistant clinical isolates of Enterobacter cloacae
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DOI：
10.1093/jac/40.4.543
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发表时间：
1997-10-01
影响因子：
5.2
通讯作者：
Kawada, Y
中科院分区：
文献类型：
--
作者：
Deguchi, T;Yasuda, M;Kawada, Y
我们已经确定了阴沟肠杆菌型菌株gyrA和parC基因的部分序列，包括与大肠杆菌gyrA基因的喹诺酮耐药决定区相似的区域。推断出阴沟大肠杆菌gyrA和parC基因的65和49个氨基酸序列分别与大肠杆菌gyrA和parC蛋白的相应区域相同。我们对从尿路感染患者中分离的40株阴沟肠杆菌进行了对钠利地酸和环丙沙星的敏感性检测。根据纳利地酸和环丙沙星的mic，将分离株分为喹诺酮类药物敏感株19株（纳利地酸mic为3.13 ~ 25 mg/L；环丙沙星mic为小于或等于0.025 mg/L）和耐药株21株（纳利地酸mic为400 ~ 800 mg/L；环丙沙星mic为0.39 ~ 100 mg/L）。我们分析了5株喹诺酮敏感株和21株喹诺酮耐药株在GyrA和ParC中的变化。5株喹诺酮敏感菌株的GyrA和ParC氨基酸序列与型菌株相同。在21株喹诺酮耐药菌株中，有3株（纳利地酸的mic值为400 ~ 800 mg/L，环丙沙星的mic值为0.39 ~ 3.13 mg/L）在大肠杆菌GyrA蛋白Ser-83位点发生了一个氨基酸变化，ParC位点没有变化；其中一种（钠啶酸的MIC值为bb0 800 mg/L，环丙沙星的MIC值为3.13 mg/L）在GyrA中Ser-83位点发生了单氨基酸变化，在大肠杆菌ParC蛋白中相当于Glu-84位点发生了单氨基酸变化；两组（纳利二酸MIG， bb0 800 mg/L，环丙沙星MIG， 25 mg/L） GyrA Ser-83和Asp-87双氨基酸变化，ParC无变化；15个（纳利二酸，100 ~ 800 mg/L；环丙沙星，25 ~ 100 mg/L）在GyrA中Ser-83和Asp-87位点发生双氨基酸变化，在ParC中Ser-80或Glu-84位点发生单氨基酸变化。本研究提示，在临床分离的阴沟肠杆菌中，DNA gyrase是喹诺酮类药物的主要靶点，GyrA中Ser-83的单个氨基酸变化足以产生对钠地酸的高水平耐药性，并降低对环丙沙星的敏感性，GyrA中氨基酸变化的积累和ParC改变的同时存在在环丙沙星的高水平耐药性中起核心作用。
We have determined partial sequences of the gyrA and parC genes of Enterobacter cloacae type strain including the regions analogous to the quinolone resistance-determining region of the Escherichia coli gyrA gene. The deduced 65- and 49-amino acid sequences of the determined regions of the E. cloacae gyrA and parC genes were identical to the corresponding regions of the E. coli GyrA and ParC proteins, respectively. We examined 40 clinical strains of E. cloacae isolated from patients with urinary tract infection for susceptibilities to nalidixic acid and ciprofloxacin. Based on the nalidixic acid and ciprofloxacin MICs, these isolates were divided into 19 quinolone-susceptible strains (MICs of nalidixic acid, 3.13-25 mg/L; MICs of ciprofloxacin, less than or equal to 0.025 mg/L) and 21 quinolone-resistant strains (MICs of nalidixic acid, 400 to >800 mg/L; MICs of ciprofloxacin, 0.39-100 mg/L). We analysed five quinolone-susceptible and 21 quinolone-resistant strains for alterations in GyrA and ParC. The five quinolone-susceptible strains had amino acid sequences in GyrA and ParC identical to those of type strain. Of the 21 quinolone-resistant isolates, three (MICs of nalidixic acid, 400 to >800 mg/L; MICs of ciprofloxacin, 0.39-3.13 mg/L) had a single amino acid change at the position equivalent to Ser-83 in the E. coli GyrA protein and no alterations in ParC; one (MIG of nalidixic acid, >800 mg/L; MIC of ciprofloxacin, 3.13 mg/L) had a single amino acid change at Ser-83 in GyrA and a single amino acid change at the position equivalent to Glu-84 in the E. coli ParC protein; two (MIG of nalidixic acid, >800 mg/L; MIC of ciprofloxacin, 25 mg/L) had double amino acid changes at Ser-83 and Asp-87 in GyrA and no alterations in ParC; and 15 (MICs of nalidixic acid, >800 mg/L; MICs of ciprofloxacin, 25-100 mg/L) had double amino acid changes at Ser-83 and Asp-87 in GyrA and a single amino acid change at Ser-80 or Glu-84 in ParC. This study suggests, that in clinical isolates of E. cloacae, DNA gyrase is a primary target of quinolones, that only a single amino acid change at Ser-83 in GyrA is sufficient to generate high-level resistance to nalidixic acid and to decrease susceptibility to ciprofloxacin, and that the accumulation of amino acid changes in GyrA and the simultaneous presence of the ParC alterations play a central role in developing high-level resistance to ciprofloxacin.