Beijing Key Laboratory for Prevention and Control of Infectious Diseases in Livestock and Poultry, Institute of Animal Husbandry and Veterinary Medicine, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China.
Queensland Alliance for Agriculture and Food Innovation, The University of Queensland, St. Lucia, Australia.
Microb Drug Resist. 2021 Sep;27(9):1290-1300. doi: 10.1089/mdr.2020.0348. Epub 2021 Mar 19.
, the etiological agent of porcine pleuropneumonia, is increasingly resistant to antibiotics. However, little is known about the mechanisms of antibiotic resistance in this pathogen. In this study, we experimentally evolved the reference strain of both serovar 1 and serovar 7, the most prevalent serovars worldwide, to quinolone resistance by sequential exposure to subinhibitory concentrations of ciprofloxacin. The adaptive ciprofloxacin-resistant mutants of serovar 1 and serovar 7 had a minimum inhibitory concentration (MIC) increment from 0.004 to 1 or 2 μg/mL, respectively. Adaptation to ciprofloxacin was shown to confer quinolone resistance with a 32- to 512-fold increase (serovars 1 and 7, respectively) as well as cross-resistance to ampicillin with an increased MIC by 16,384- and 64-fold (serovars 1 and 7, respectively). The genetic analysis of quinolone resistance-determining region mutations showed that substitutions occurred in (S83A) and (D84N) of serovar 1, and (D87N) of serovar 7. The ciprofloxacin-resistant mutants showed significantly reduced bacterial fitness. The mutants also showed changes in efflux ability and biofilm formation. Notably, the transcription and secretion levels of Apx toxins were dramatically reduced in ciprofloxacin-resistant mutants compared with their wild-type strains. Altogether, these results demonstrated marked phenotypic changes in ciprofloxacin-resistant mutants of . The results stress the need for further studies on the impact of both the genotypic and phenotypic characteristics of following exposure to subinhibitory concentrations of antibiotics.
猪传染性胸膜肺炎放线杆菌是猪传染性胸膜肺炎的病原体，其对抗生素的耐药性日益增强。然而，人们对这种病原体的抗生素耐药机制知之甚少。在这项研究中，我们通过连续暴露于低浓度环丙沙星来实验性地使世界上最流行的血清型 1 和 7 的参考菌株进化为对喹诺酮类药物的耐药性。血清型 1 和 7 的适应性环丙沙星耐药突变株的最小抑菌浓度（MIC）分别从 0.004 增加到 1 或 2μg/mL。对环丙沙星的适应被证明赋予了喹诺酮类耐药性，分别增加了 32 到 512 倍（血清型 1 和 7）以及交叉耐药性，使氨苄西林的 MIC 增加了 16384 到 64 倍（血清型 1 和 7）。对喹诺酮类药物耐药决定区突变的遗传分析表明，血清型 1 中的 （S83A）和 （D84N）以及血清型 7 中的 （D87N）发生了取代。环丙沙星耐药突变株的细菌适应性显著降低。突变株还表现出外排能力和生物膜形成的变化。值得注意的是，与野生型菌株相比，环丙沙星耐药突变株的 Apx 毒素转录和分泌水平显著降低。总之，这些结果表明，环丙沙星耐药突变株的表型发生了明显变化。这些结果强调了需要进一步研究在抗生素亚抑菌浓度暴露后，猪传染性胸膜肺炎放线杆菌的基因型和表型特征的影响。
