title: Mutations in 23S rRNA gene associated with decreased susceptibility to tiamulin and valnemulin in Mycoplasma gallisepticum.
abstract: Mycoplasma gallisepticum is a major etiological agent of chronic respiratory disease (CRD) in chickens and sinusitis in turkeys. The pleuromutilin antibiotics tiamulin and valnemulin are currently used in the treatment of M. gallisepticum infection. We studied the in vitro development of pleuromutilin resistance in M. gallisepticum and investigated the molecular mechanisms involved in this process. Pleuromutilin-resistant mutants were selected by serial passages of M. gallisepticum strains PG31 and S6 in broth medium containing subinhibitory concentrations of tiamulin or valnemulin. A portion of the gene encoding 23S rRNA gene (domain V) and the gene encoding ribosome protein L3 were amplified and sequenced. No mutation could be detected in ribosome protein L3. Mutations were found at nucleotide positions 2058, 2059, 2061, 2447 and 2503 of 23S rRNA gene (Escherichia coli numbering). Although a single mutation could cause elevation of tiamulin and valnemulin MICs, combinations of two or three mutations were necessary to produce high-level resistance. All the mutants were cross-resistant to lincomycin, chloramphenicol and florfenicol. Mutants with the A2058G or the A2059G mutation exhibited cross-resistance to macrolide antibiotics erythromycin, tilmicosin and tylosin.
authors.affiliation: Key Laboratory of Development and Evaluation of the Chemical and Herbal Drugs for Animal Use, Department of Veterinary Pharmacology and Toxicology, College of Veterinary Medicine, China Agricultural University, Beijing, China.
authors.forename: Bei-Bei
authors.initials: BB
authors.lastname: Li
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Shen
authors.forename: Xing-Yuan
authors.initials: XY
authors.lastname: Cao
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Dai
authors.forename: Si-Yang
authors.initials: SY
authors.lastname: Huang
authors.forename: Cong-Ming
authors.initials: CM
authors.lastname: Wu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003470:Culture Media / Q000737:chemistry; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004224:Diterpenes / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D020459:Genes, rRNA; D008826:Microbial Sensitivity Tests; D045686:Mycoplasma gallisepticum / Q000187:drug effects* / Q000235:genetics; D017354:Point Mutation; D012329:RNA, Bacterial / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000235:genetics*; D017422:Sequence Analysis, DNA; D012692:Serial Passage
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D004269:DNA, Bacterial; D004224:Diterpenes; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S; C117845:valnemulin; C014224:tiamulin