title: Molecular characterization of CTX-M β-lactamase and associated addiction systems in Escherichia coli circulating among cattle, farm workers, and the farm environment.
abstract: A total of 84 extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates from cattle, farm workers, and the farm environment isolated from February to September 2008 in the Republic of Korea were investigated. All 84 ESBL-producing isolates carried blaCTX-M genes that belonged to the CTX-M-1 (n = 35) or CTX-M-9 (n = 49) family. The most predominant CTX-M type identified was CTX-M-14 (n = 49), followed by CTX-M-32 (n = 26). The blaCTX-M genes were identified most commonly in E. coli isolates from feces (n = 29), teats (n = 25), and milk (n = 14). A blaCTX-M-14 gene was also detected in an E. coli isolate from a farmer's hand. Transfer of the blaCTX-M gene from 60 blaCTX-M-positive E. coli isolates to the recipient E. coli J53 strain by conjugation was demonstrated. Plasmid isolation from blaCTX-M-positive transconjugants revealed a large (95- to 140-kb) conjugative plasmid. Almost all (82/84) blaCTX-M genes possessed an insertion sequence, ISEcp1, upstream of the blaCTX-M gene. Only in the case of the CTX-M-14 genes was IS903 downstream of the gene. The blaCTX-M genes were associated with seven kinds of addiction systems. Among them, pndAC, hok-sok, and srnBC were the most frequently identified addiction systems in both wild strains and transconjugants. The spread of blaCTX-M genes was attributed to both clonal expansion and horizontal dissemination. Our data suggest that a combination of multiple addiction systems in plasmids carrying blaCTX-M genes could contribute to their maintenance in the host cells. To our knowledge, the blaCTX-M-32 gene has not previously been reported in animal isolates from the Republic of Korea.
authors.affiliation: Bacterial Disease Division, Animal, Plant, and Fisheries Quarantine and Inspection Agency, Anyang, Republic of Korea.
authors.forename: Migma Dorji
authors.initials: MD
authors.lastname: Tamang
authors.forename: Hyang-Mi
authors.initials: HM
authors.lastname: Nam
authors.forename: Mamata
authors.initials: M
authors.lastname: Gurung
authors.forename: Geum-Chan
authors.initials: GC
authors.lastname: Jang
authors.forename: Su-Ran
authors.initials: SR
authors.lastname: Kim
authors.forename: Suk-Chan
authors.initials: SC
authors.lastname: Jung
authors.forename: Yong Ho
authors.initials: YH
authors.lastname: Park
authors.forename: Suk-Kyung
authors.initials: SK
authors.lastname: Lim
mesh_terms: D000383:Agriculture; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field / Q000662:veterinary; D004783:Environmental Microbiology; D004926:Escherichia coli / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D005260:Female; D006801:Humans; D008321:Mammary Glands, Animal / Q000382:microbiology; D008892:Milk / Q000382:microbiology; D010957:Plasmids / Q000235:genetics; D056910:Republic of Korea / Q000453:epidemiology; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*
chemical_list: C055184:beta-lactamase TEM-3; D001618:beta-Lactamases