title: Diversity of plasmid replicons encoding the bla(CMY-2) gene in broad-spectrum cephalosporin-resistant Escherichia coli from livestock animals in Japan.
abstract: Broad-spectrum cephalosporin (BSC) resistance has increased in Escherichia coli isolates from broiler chickens in Japan since 2004. The purpose of this study was to understand the epidemiology of BSC-resistant E. coli in livestock animals. Among 3274 E. coli isolates from 1767 feces of apparently healthy animals on 1767 farms between 2004 and 2009, 118 ceftiofur (CTF)-resistant isolates (CTF MIC ≥4 μg/mL) were identified on 74 farms. After elimination of apparently clonal isolates from a single animal, 75 selected CTF-resistant isolates (62 isolates from 61 broiler chickens, 10 isolates from 10 layer chickens, two isolates from two cows, and one isolate from a pig) were characterized. The bla(CMY-2) gene was most frequently detected in 50 isolates, followed by bla(CTX-M) (CTX-M-2: six isolates; CTX-M-14: four isolates; CTX-M-25: two isolates; CTX-M-1: one isolate) and bla(SHV) (SHV-12: seven isolates; SHV-2, SHV-2a, SHV-5: one isolate each). In particular, 42 of 62 broiler chicken isolates harbored bla(CMY-2). Pulsed-field gel electrophoresis analyses using XbaI revealed divergent profiles among the BSC-resistant isolates. The incompatibility groups of bla(CMY-2) plasmids from 34 of the 42 broiler chicken isolates belonged to IncIγ (10 isolates), IncA/C (nine isolates), IncB/O (seven isolates) and IncI1 (six isolates), or were nontypeable (two isolates). Co-transmission of resistance to non-β-lactam antibiotics was observed in transconjugants with IncA/C plasmids, but not with IncI1, IncIγ, and IncB/O plasmids except for one isolate with IncB/O. Our findings suggest that the bla(CMY-2) gene is a key player in BSC-resistant E. coli isolates and that coselection is unlikely to be associated with the abundance of bla(CMY-2) plasmids, except for IncA/C plasmids.
authors.affiliation: National Veterinary Assay Laboratory, Ministry of Agriculture, Forestry, and Fisheries, Tokyo, Japan.
authors.forename: Mototaka
authors.initials: M
authors.lastname: Hiki
authors.forename: Masaru
authors.initials: M
authors.lastname: Usui
authors.forename: Akemi
authors.initials: A
authors.lastname: Kojima
authors.forename: Manao
authors.initials: M
authors.lastname: Ozawa
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Ishii
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asai
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002417:Cattle; D018550:Cephalosporin Resistance / Q000187:drug effects / Q000235:genetics; D002511:Cephalosporins / Q000494:pharmacology; D002645:Chickens; D002876:Chromosomes, Bacterial / Q000235:genetics*; D004269:DNA, Bacterial / Q000302:isolation & purification*; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000472:pathogenicity; D005243:Feces; D005506:Food Contamination; D005516:Food Microbiology; D007564:Japan; D058751:Livestock / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D012093:Replicon / Q000235:genetics*; D013552:Swine; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D004269:DNA, Bacterial; C053503:ceftiofur; C103022:beta-lactamase CMY-2; C071167:beta-lactamase CTX-2; C055184:beta-lactamase TEM-3; C048795:AmpC beta-lactamases; D001618:beta-Lactamases