Comparative studies of mutations in animal isolates and experimental in vitro- and in vivo-selected mutants of Salmonella spp. suggest a counterselection of highly fluoroquinolone-resistant strains in the field
Comparative studies of mutations in animal isolates and experimental in vitro- and in vivo-selected mutants of Salmonella spp. suggest a counterselection of highly fluoroquinolone-resistant strains in the field
复制标题
DOI：
10.1128/aac.43.9.2131
复制
发表时间：
1999-09-01
影响因子：
4.9
通讯作者：
Chaslus-Dancla, E
中科院分区：
文献类型：
--
作者：
Giraud, E;Brisabois, A;Chaslus-Dancla, E
研究了体外和体内选择的鼠伤寒沙门氏菌实验突变体以及 138 个耐萘啶酸沙门氏菌野外分离株的旋转酶（gyrA 和 gvrB）和拓扑异构酶 TV parE 和 parC 编码基因中突变的发生情况。对高度氟喹诺酮耐药突变体（MIC 为 4 至 16 μg/ml）中这些基因的喹诺酮耐药决定区进行测序表明，在对应于 Gly-81 或 Ser-83 的密码子处存在 gyrA 突变，其中一些突变与 Asp-87 的突变有关。 gyrB、parC 和 parE 基因未发现突变。开发了一种结合等位基因特异性 PCR 和限制性片段长度多态性的检测方法来快速筛选 gyrA 密码子 81、83 和 87 处的突变。环丙沙星对野外分离株的 MIC 仅达到 2 μg/ml，而一些体外选择的突变体的 MIC 为 16 μg/ml。与体内选择的突变体一样，现场分离株在密码子 83 或 87 处仅具有单个 gvrA 突变。在体外选择的高耐药突变体（环丙沙星的 MIC，8 μg/ml）中也发现了单个 gvrA 突变，这表明除了细胞内靶标的独特修饰之外的其他机制也可能参与沙门氏菌的氟喹诺酮耐药性。体外选择的实验突变体、田间菌株和体内选择的突变体的比较表明，在没有选择压力的田间条件下，高度氟喹诺酮耐药菌株被反选择。
The occurrence of mutations in the genes coding for gyrase (gyrA and gvrB) and topoisomerase TV parE and parC of Salmonella typhimurium experimental mutants selected in vitro and in vivo and of 138 nalidixic acid-resistant Salmonella field isolates was investigated. The sequencing of the quinolone resistance-determining region of these gen es in highly fluoroquinolone-resistant mutants (MICs of 4 to 16 mu g/ml) revealed the presence of gyrA mutations at codons corresponding to Gly-81 or Ser-83, some of which were associated with a mutation at Asp-87. No mutations were found in the gyrB, parC, and parE genes. An assay combining allele-specific PCR and restriction fragment length polymorphism was developed to rapidly screen mutations at codons 81, 83, and 87 of gyrA. The MICs of ciprofloxacin for the field isolates reached only 2 mu g/ml, versus 16 mu g/ml for some in vitro-selected mutants. The field isolates, like the mutants selected in vivo, had only a single gyrA mutation at codon 83 or 87. Single gvrA mutations were also found in highly resistant in vitro-selected mutants (MIC of ciprofloxacin, 8 mu g/ml), which indicates that mechanisms other than the unique modification of the intracellular targets could participate in fluoroquinolone resistance in Salmonella spp. A comparison of experimental mutants selected in vitro, field strains, and mutants selected in vivo suggests that highly fluoroquinolone-resistant strains are counterselected in field conditions in the absence of selective pressure.