title: Prevalence of 16S rRNA Methylase Gene rmtB Among Escherichia coli Isolated from Bovine Mastitis in Ningxia, China.
abstract: The aim of this study is to understand the prevalence and molecular characterization of 16S rRNA methylase gene, rmtB, among Escherichia coli strains isolated from bovine mastitis in China. A total of 245 E. coli isolates were collected from bovine mastitis in China between 2013 and 2014 and were screened for 16S rRNA methylase genes (armA, rmtA, rmtB, rmtC, rmtD, rmtE, and npmA) by polymerase chain reaction. About 5.3% (13/245) of the isolates carried the rmtB gene; the isolates were highly resistant to amikacin. Thirteen rmtB-positive strains were analyzed for the presence of extended-spectrum β-lactamase genes (bla(TEM), bla(CTX-M), bla(OXA), and bla(SHV)). All the isolates harbored both bla(TEM-1) and bla(CTX-M-15) genes and two of the isolates were also positive for bla(OXA-1). Pulsed-field gel electrophoresis (PFGE) analysis indicated that the nine rmtB-positive strains belonging to ST10 from one farm showed the similar PFGE pattern, indicating a clonal expansion in this farm. S1-PFGE and Southern blotting showed that 12 isolates harbored the rmtB gene in plasmids of two different sizes (≈45 kb [n=10] and ≈48 kb [n=2]), while only 1 strain harbored the rmtB gene in the chromosome. These plasmids were transferable by conjugation studies, and two isolates from two respective farms carried the same size of plasmid, suggesting that the horizontal transmission of plasmids also contributed to the spread of rmtB gene. This is the first report of prevalence of the 16S rRNA methylase gene rmtB among E. coli isolated from bovine mastitis in China, and rmtB-carrying E. coli may pose a threat to the treatment of bovine mastitis.
authors.affiliation: 1 College of Agriculture, Ningxia University , Yinchuan, China .
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.affiliation: 2 Key Laboratory of Development and Evaluation of Chemical and Herbal Drugs for Animal Use, College of Veterinary Medicine, China Agricultural University , Beijing, China .
authors.forename: Tao
authors.initials: T
authors.lastname: He
authors.affiliation: 2 Key Laboratory of Development and Evaluation of Chemical and Herbal Drugs for Animal Use, College of Veterinary Medicine, China Agricultural University , Beijing, China .
authors.forename: Hong
authors.initials: H
authors.lastname: Yao
authors.affiliation: 1 College of Agriculture, Ningxia University , Yinchuan, China .
authors.forename: Jin-Bao
authors.initials: JB
authors.lastname: Zhang
authors.affiliation: 1 College of Agriculture, Ningxia University , Yinchuan, China .
authors.forename: Xiao-Na
authors.initials: XN
authors.lastname: Li
authors.affiliation: 2 Key Laboratory of Development and Evaluation of Chemical and Herbal Drugs for Animal Use, College of Veterinary Medicine, China Agricultural University , Beijing, China .
authors.forename: Rong-Ming
authors.initials: RM
authors.lastname: Zhang
authors.affiliation: 1 College of Agriculture, Ningxia University , Yinchuan, China .
authors.forename: Gui-Qin
authors.initials: GQ
authors.lastname: Wang
mesh_terms: D000818:Animals; D002417:Cattle; D002681:China; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000032:analysis*; D005260:Female; D008414:Mastitis, Bovine / Q000382:microbiology*; D008780:Methyltransferases / Q000032:analysis*; D010957:Plasmids / Q000032:analysis / Q000235:genetics; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012336:RNA, Ribosomal, 16S; D001618:beta-Lactamases / Q000032:analysis
chemical_list: D029968:Escherichia coli Proteins; D012336:RNA, Ribosomal, 16S; D008780:Methyltransferases; C540682:RmtB protein, E coli; D001618:beta-Lactamases