National Reference Laboratory of Veterinary Drug Residues (HZAU)/MOA Key Laboratory for Detection of Veterinary Drug Residues in Foods, Huazhong Agricultural University, Wuhan, People's Republic of China.
Antimicrob Agents Chemother. 2013 Mar;57(3):1369-78. doi: 10.1128/AAC.01927-12. Epub 2012 Dec 28.
Macrolide antibiotics are important for clinical treatment of infections caused by Campylobacter jejuni. Development of resistance to this class of antibiotics in Campylobacter is a complex process, and the dynamic molecular changes involved in this process remain poorly defined. Multiple lineages of macrolide-resistant mutants were selected by stepwise exposure of C. jejuni to escalating doses of erythromycin or tylosin. Mutations in target genes were determined by DNA sequencing, and the dynamic changes in the expression of antibiotic efflux transporters and the transcriptome of C. jejuni were examined by real-time reverse transcription-PCR, immunoblotting, and DNA microarray analysis. Multiple types of mutations in ribosomal proteins L4 and L22 occurred early during stepwise selection. On the contrary, the mutations in the 23S rRNA gene, mediating high resistance to macrolides, were observed only in the late-stage mutants. Upregulation of antibiotic efflux genes was observed in the intermediately resistant mutants, and the magnitude of upregulation declined with the occurrence of mutations in the 23S rRNA gene. DNA microarray analysis revealed the differential expression of 265 genes, most of which occurred in the intermediate mutant, including the upregulation of genes encoding ribosomal proteins and the downregulation of genes involved in energy metabolism and motility. These results indicate (i) that mutations in L4 and L22 along with temporal overexpression of antibiotic efflux genes precede and may facilitate the development of high-level macrolide resistance and (ii) that the development of macrolide resistance affects the pathways important for physiology and metabolism in C. jejuni, providing an explanation for the reduced fitness of macrolide-resistant Campylobacter.
大环内酯类抗生素对治疗空肠弯曲菌引起的感染具有重要作用。空肠弯曲菌对这类抗生素的耐药性发展是一个复杂的过程，其涉及的动态分子变化仍未得到明确界定。通过逐步暴露于递增剂量的红霉素或泰乐菌素，选择出了多种大环内酯类耐药突变体谱系。通过 DNA 测序确定了靶基因突变，通过实时逆转录-PCR、免疫印迹和 DNA 微阵列分析检测了抗生素外排转运蛋白的动态变化和空肠弯曲菌的转录组。核糖体蛋白 L4 和 L22 中的多种类型突变在逐步选择的早期发生。相反，介导对大环内酯类药物高度耐药的 23S rRNA 基因突变仅在晚期突变体中观察到。在中度耐药突变体中观察到抗生素外排基因的上调，并且随着 23S rRNA 基因突变的发生，上调幅度下降。DNA 微阵列分析显示了 265 个基因的差异表达，其中大多数基因发生在中间突变体中，包括核糖体蛋白编码基因的上调和参与能量代谢和运动性的基因的下调。这些结果表明：（i）L4 和 L22 的突变以及抗生素外排基因的时间过度表达先于并可能促进高水平大环内酯类耐药性的发展；（ii）大环内酯类耐药性的发展影响空肠弯曲菌生理和代谢途径的重要性，为空肠弯曲菌的耐药性降低提供了解释。
