MOA Key Laboratory of Food Safety Evaluation, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China.
Int J Food Microbiol. 2011 Nov 15;151(1):52-61. doi: 10.1016/j.ijfoodmicro.2011.08.002. Epub 2011 Aug 11.
Physiologic and phenotypic alterations in the context of antibiotic resistance have been extensively studied in some bacteria. However there are not enough data addressing these alterations due to macrolide resistance in Campylobacter jejuni. The present study examined the fitness cost imposed by different macrolide resistance mutations and the phenotypic alterations due to exposure to macrolides in C. jejuni. C. jejuni was induced with different macrolide agents to obtain different macrolide resistance mutations. The results revealed that the mutations significantly imposed defect variations on the doubling time and the relative fitness in the resistant strains when competed against the susceptible strain. Furthermore macrolides through induction or exposure to sub-MIC concentrations impaired the motility of C. jejuni in 0.4% MH agar plates. Electron microscope analysis revealed the absence of flagellar filaments from strains exposed to macrolides. SDS-PAGE demonstrated that macrolides have no effect on protein synthesis and immunoblotting analysis further confirmed that flagellin was fully synthesized within C. jejuni strains exposed to macrolides. Nevertheless C. jejuni strains exposed to macrolides demonstrated defect in their excreted flagellin into the supernatant compared to strains not exposed to macrolides. Accordingly we speculated that macrolides inhibited flagellar filament formation in the strains exposed to macrolides via affecting the secretion of flagellin without affecting the amount synthesized within the bacteria. Taken together these findings demonstrated that different macrolide resistance mutations imposed different fitness costs and exposure to macrolides resulted in phenotypic alterations such as inhibition of flagellar filament formation and loss of motility in C. jejuni.
在抗生素耐药性的背景下，一些细菌的生理和表型改变已经得到了广泛的研究。然而，由于空肠弯曲菌对大环内酯类的耐药性，针对这些改变的数据还不够充分。本研究检测了不同大环内酯类耐药突变所带来的适应代价，以及大环内酯类暴露对空肠弯曲菌表型的改变。空肠弯曲菌通过不同的大环内酯类药物诱导获得不同的大环内酯类耐药突变。结果表明，这些突变显著改变了耐药菌株的倍增时间和相对适应度，与敏感菌株竞争时更是如此。此外，大环内酯类药物通过诱导或暴露于亚最低抑菌浓度会损害空肠弯曲菌在 0.4% MH 琼脂平板上的运动能力。电子显微镜分析显示，暴露于大环内酯类药物的菌株中没有鞭毛丝。SDS-PAGE 表明大环内酯类药物对蛋白质合成没有影响，免疫印迹分析进一步证实，暴露于大环内酯类药物的空肠弯曲菌中，鞭毛蛋白被完全合成。然而，与未暴露于大环内酯类药物的菌株相比，暴露于大环内酯类药物的空肠弯曲菌菌株分泌到上清液中的鞭毛蛋白存在缺陷。因此，我们推测大环内酯类药物通过影响鞭毛蛋白的分泌而不是影响细菌内合成的量来抑制暴露于大环内酯类药物的菌株中鞭毛丝的形成。总之，这些发现表明，不同的大环内酯类耐药突变带来了不同的适应代价，而大环内酯类药物的暴露导致了空肠弯曲菌表型的改变，如鞭毛丝形成的抑制和运动能力的丧失。
