title: Dissemination of the rmtB gene carried on IncF and IncN plasmids among Enterobacteriaceae in a pig farm and its environment.
abstract: OBJECTIVE
  To investigate the prevalence and characterization of 16S rRNA methylase-producing bacteria in a pig farm and its environment in East China.
  
  
  METHODS
  Enterobacteriaceae isolates and metagenomic DNA from 102 pig faecal samples from a pig farm and 97 soil samples taken in or around the farm were screened for the presence of 16S rRNA methylase genes. The clonal relationships of 16S rRNA methylase-positive isolates, plasmid content and other associated resistance genes were also characterized.
  
  
  RESULTS
  Fifty-six rmtB-positive Enterobacteriaceae isolates, including 54 Escherichia coli, 1 Morganella morganii and 1 Proteus mirabilis, were recovered from 55 pig faecal samples. Nineteen rmtB-positive bacteria, including 13 E. coli, 2 M. morganii, 2 Leclercia adecarboxylata, 1 Enterobacter aerogenes and 1 Enterobacter cloacae, were recovered from 16 soil samples. Among the 75 rmtB-positive isolates, 31 and 25 also carried the qepA and bla(CTX-M) genes, respectively. The qepA gene co-localized with rmtB on the F2:A-:B1 plasmids and the bla(CTX-M-65) gene co-localized with rmtB on the F33:A-:B- plasmids. The rmtB gene was also found to be associated with the IncN plasmids. Clonal transmission of rmtB-positive E. coli isolates was observed between different pig groups and soil samples.
  
  
  CONCLUSIONS
  Both horizontal gene transfer and clonal spread could be responsible for the dissemination of the rmtB gene in the pig farm and its environment. To our knowledge, this study is the first report of rmtB-positive bacteria from farmland soils and indicates that these antibiotic-resistant bacteria and/or resistance genes could be acquired by humans through the food chain.
authors.affiliation: College of Veterinary Medicine, National Reference Laboratory of Veterinary Drug Residues (SCAU),  South China Agricultural University, Guangzhou,  People's Republic of China.
authors.forename: Qiongfen
authors.initials: Q
authors.lastname: Yao
authors.forename: Zhenling
authors.initials: Z
authors.lastname: Zeng
authors.forename: Jianxia
authors.initials: J
authors.lastname: Hou
authors.forename: Yuting
authors.initials: Y
authors.lastname: Deng
authors.forename: Liangying
authors.initials: L
authors.lastname: He
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.forename: Hongqing
authors.initials: H
authors.lastname: Zheng
authors.forename: Zhangliu
authors.initials: Z
authors.lastname: Chen
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Liu
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012988:Soil Microbiology; D034421:Sus scrofa
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D012336:RNA, Ribosomal, 16S; D008780:Methyltransferases; C540682:RmtB protein, E coli