title: Identification of ribosomal RNA methyltransferase gene ermF in Riemerella anatipestifer.
abstract: Riemerella anatipestifer is a major bacterial pathogen of waterfowl, globally responsible for avian septicaemic disease. As chemotherapy is the predominant method for the prevention and treatment of R. anatipestifer infection in poultry, the widespread use of antibiotics has favoured the emergence of antibiotic-resistant strains. However, little is known about R. anatipestifer susceptibility to macrolide antibiotics and its resistance mechanism. We report for the first time the identification of a macrolide resistance mechanism in R. anatipestifer that is mediated by the ribosomal RNA methyltransferase ermF. We identified the presence of the ermF gene in 64/206 (31%) R. anatipestifer isolates from different regions in China. An ermF deletion strain was constructed to investigate the function of the ermF gene on the resistance to high levels of macrolides. The ermF mutant strain showed significantly decreased resistance to macrolide and lincosamide, exhibiting 1024-, 1024-, 4- and >2048-fold reduction in the minimum inhibitory concentrations for erythromycin, azithromycin, tylosin and lincomycin, respectively. Furthermore, functional analysis of ermF expression in E. coli XL1-blue showed that the R. anatipestifer ermF gene was functional in E. coli XL1-blue and conferred resistance to high levels of erythromycin (100 µg/ml), supporting the hypothesis that the ermF gene is associated with high-level macrolide resistance. Our work suggests that ribosomal RNA modification mediated by the ermF methyltransferase is the predominant mechanism of resistance to erythromycin in R. anatipestifer isolates.
authors.affiliation: a Research Center of Avian Diseases , College of Veterinary Medicine of Sichuan Agricultural University , Sichuan , P.R. China.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Luo
authors.forename: Mafeng
authors.initials: M
authors.lastname: Liu
authors.forename: Lanying
authors.initials: L
authors.lastname: Wang
authors.forename: Wangshu
authors.initials: W
authors.lastname: Zhou
authors.forename: Mingshu
authors.initials: M
authors.lastname: Wang
authors.forename: Anchun
authors.initials: A
authors.lastname: Cheng
authors.forename: Renyong
authors.initials: R
authors.lastname: Jia
authors.forename: Shun
authors.initials: S
authors.lastname: Chen
authors.forename: Kunfeng
authors.initials: K
authors.lastname: Sun
authors.forename: Qiao
authors.initials: Q
authors.lastname: Yang
authors.forename: Xiaoyue
authors.initials: X
authors.lastname: Chen
authors.forename: Dekang
authors.initials: D
authors.lastname: Zhu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017963:Azithromycin; D001426:Bacterial Proteins / Q000235:genetics*; D002681:China; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D004917:Erythromycin; D004926:Escherichia coli; D008034:Lincomycin; D018942:Macrolides / Q000494:pharmacology; D008780:Methyltransferases / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D060494:Riemerella / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D015645:Tylosin
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D018942:Macrolides; D004917:Erythromycin; D017963:Azithromycin; D008034:Lincomycin; D008780:Methyltransferases; C437393:ErmF protein, Bacteroides; C035181:rRNA (adenosine-O-2'-)methyltransferase; D015645:Tylosin