title: Prevalence and molecular characterization of CTX-M β-lactamase-producing Escherichia coli isolated from healthy swine and cattle.
abstract: The purpose of this study was to determine the prevalence and characteristics of CTX-M β-lactamases in Escherichia coli among healthy swine and cattle in Korea. A total of 1212 fecal samples obtained from healthy pigs (n=558) and cattle (n=654) were screened for CTX-M-type extended spectrum β-lactamase (ESBL)-producing E. coli isolates. One hundred and twenty-one E. coli that produced ESBL were subjected to phenotypic and genotypic characterization. A high number (120/558, 21.5%) of swine fecal samples showed the presence of CTX-M β-lactamase-producing E. coli compared to cattle samples (1/654, 0.2%). The most predominant CTX-M-type identified was CTX-M-14 (n=82), followed by CTX-M-15 (n=16). Isolates producing CTX-M-3, CTX-M-27, CTX-M-55, and CTX-M-65 were also identified. Overall, the bla(TEM-1) gene was associated with CTX-M β-lactamase in 55 E. coli isolates. Transfer of bla(CTX-M) gene was demonstrated from 76 out of 121 bla(CTX-M)-positive E. coli isolates to the recipient E. coli J53 by conjugation. Plasmid DNA isolation from the transconjugants revealed a large (90-120 Kb) conjugative plasmid. ISEcp1 and IS903 were detected upstream and downstream of bla(CTX-M) genes in 117 and 91 E. coli isolates, respectively. Our results demonstrated that a combination of clonal expansion and horizontal transmission is spreading bla(CTX-M) genes among swine E. coli. The horizontal dissemination of bla(CTX-M) genes among E. coli was mostly mediated by IncF or IncI1-Iγ plasmids. To the best of our knowledge, this study represents the first report of CTX-M-3, CTX-M-27, CTX-M-55, and CTX-M-65 β-lactamases in bacterial isolates from food animals in Korea. This study revealed that the CTX-M β-lactamase-producing E. coli are widely disseminated among healthy pigs but very rare in cattle in Korea. Increasing prevalence of bla(CTX-M) genes in intestinal E. coli of food animals is a matter of concern and should be carefully monitored.
authors.affiliation: Bacterial Disease Division, Animal, Plant, and Fisheries Quarantine and Inspection Agency, Anyang, Gyeonggi-do, Korea.
authors.forename: Migma Dorji
authors.initials: MD
authors.lastname: Tamang
authors.forename: Hyang-Mi
authors.initials: HM
authors.lastname: Nam
authors.forename: Su-Ran
authors.initials: SR
authors.lastname: Kim
authors.forename: Myung Hwa
authors.initials: MH
authors.lastname: Chae
authors.forename: Geum-Chan
authors.initials: GC
authors.lastname: Jang
authors.forename: Suk-Chan
authors.initials: SC
authors.lastname: Jung
authors.forename: Suk-Kyung
authors.initials: SK
authors.lastname: Lim
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000382:microbiology*; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D005838:Genotype; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D015995:Prevalence; D056910:Republic of Korea / Q000453:epidemiology; D013045:Species Specificity; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology / Q000382:microbiology*; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D001618:beta-Lactamases