title: Mutational and transcriptomic changes involved in the development of macrolide resistance in Campylobacter jejuni.
abstract: 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.
authors.affiliation: 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.
authors.forename: Haihong
authors.initials: H
authors.lastname: Hao
authors.forename: Zonghui
authors.initials: Z
authors.lastname: Yuan
authors.forename: Zhangqi
authors.initials: Z
authors.lastname: Shen
authors.forename: Jing
authors.initials: J
authors.lastname: Han
authors.forename: Orhan
authors.initials: O
authors.lastname: Sahin
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Qijing
authors.initials: Q
authors.lastname: Zhang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D016123:Campylobacter jejuni / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects* / Q000235:genetics; D004917:Erythromycin / Q000494:pharmacology; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D020459:Genes, rRNA; D018942:Macrolides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D012338:RNA, Ribosomal, 23S / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome; D015645:Tylosin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004917:Erythromycin; D018942:Macrolides; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; D015645:Tylosin