Department of Veterinary Microbiology and Preventive Medicine, 1116 Veterinary Medicine Complex, Iowa State University, Ames, IA 50011, USA.
Appl Environ Microbiol. 2011 Oct;77(20):7128-33. doi: 10.1128/AEM.00763-11. Epub 2011 Aug 5.
Salicylate, a nonsteroidal anti-inflammatory compound, has been shown to increase the resistance of Campylobacter to antimicrobials. However, the molecular mechanism underlying salicylate-induced resistance has not yet been established. In this study, we determined how salicylate increases antibiotic resistance and evaluated its impact on the development of fluoroquinolone-resistant Campylobacter mutants. Transcriptional fusion assays, real-time quantitative reverse transcription-PCR (RT-PCR), and immunoblotting assays consistently demonstrated the induction of the CmeABC multidrug efflux pump by salicylate. Electrophoretic mobility shift assays further showed that salicylate inhibits the binding of CmeR (a transcriptional repressor of the TetR family) to the promoter DNA of cmeABC, suggesting that salicylate inhibits the function of CmeR. The presence of salicylate in the culture medium not only decreased the susceptibility of Campylobacter to ciprofloxacin but also resulted in an approximately 70-fold increase in the observed frequency of emergence of fluoroquinolone-resistant mutants under selection with ciprofloxacin. Together, these results indicate that in Campylobacter, salicylate inhibits the binding of CmeR to the promoter DNA and induces expression of cmeABC, resulting in decreased susceptibility to antibiotics and in increased emergence of fluoroquinolone-resistant mutants under selection pressure.
水杨酸是一种非甾体类抗炎化合物，已被证明能提高弯曲杆菌对抗生素的耐药性。然而，水杨酸诱导耐药的分子机制尚未确定。在这项研究中，我们确定了水杨酸如何增加抗生素耐药性，并评估了它对氟喹诺酮耐药弯曲杆菌突变体发展的影响。转录融合测定、实时定量 RT-PCR 和免疫印迹分析一致表明水杨酸诱导 CmeABC 多药外排泵的表达。电泳迁移率变动分析进一步表明，水杨酸抑制 CmeR（TetR 家族转录抑制剂）与 cmeABC 启动子 DNA 的结合，提示水杨酸抑制 CmeR 的功能。培养基中存在水杨酸不仅降低了弯曲杆菌对环丙沙星的敏感性，而且在环丙沙星选择压力下，氟喹诺酮耐药突变体的出现频率增加了约 70 倍。总之，这些结果表明，在弯曲杆菌中，水杨酸抑制 CmeR 与启动子 DNA 的结合，并诱导 cmeABC 的表达，导致对抗生素的敏感性降低，并在选择压力下增加氟喹诺酮耐药突变体的出现。
