title: Antimicrobial Resistance, Extended-Spectrum β-Lactamase Productivity, and Class 1 Integrons in Escherichia coli from Healthy Swine.
abstract: Administration of antimicrobials to food-producing animals increases the risk of higher antimicrobial resistance in the normal intestinal flora of these animals. The present cross-sectional study was conducted to investigate antimicrobial susceptibility and extended-spectrum β-lactamase (ESBL)-producing strains and to characterize class 1 integrons in Escherichia coli in healthy swine in Thailand. All 122 of the tested isolates had drug-resistant phenotypes. High resistance was found to ampicillin (98.4% of isolates), chloramphenicol (95.9%), gentamicin (78.7%), streptomycin (77.9%), tetracycline (74.6%), and cefotaxime (72.1%). Fifty-four (44.3%) of the E. coli isolates were confirmed as ESBL-producing strains. Among them, blaCTX-M (45 isolates) and blaTEM (41 isolates) were detected. Of the blaCTX-M-positive E. coli isolates, 37 carried the blaCTX-M-1 cluster, 12 carried the blaCTX-M-9 cluster, and 5 carried both clusters. Sequence analysis revealed blaTEM-1, blaTEM-135, and blaTEM-175 in 38, 2, and 1 isolate, respectively. Eighty-seven (71%) of the 122isolates carried class 1 integrons, and eight distinct drug-resistance gene cassettes with seven different integron profiles were identified in 43 of these isolates. Gene cassettes were associated with resistance to aminoglycosides (aadA1, aadA2, aadA22, or aadA23), trimethoprim (dfrA5, dfrA12, or dfrA17), and lincosamide (linF). Genes encoding β-lactamases were not found in class 1 integrons. This study is the first to report ESBL-producing E. coli with a class 1 integron carrying the linF gene cassette in swine in Thailand. Our findings confirm that swine can be a reservoir of ESBL-producing E. coli harboring class 1 integrons, which may become a potential health risk if these integrons are transmitted to humans. Intensive analyses of animal, human, and environmental isolates are needed to control the spread of ESBL-producing E. coli strains.
authors.affiliation: Division of Bioresources, Research Center for Zoonosis Control, Hokkaido University, Sapporo, Japan.
authors.forename: Kanjana
authors.initials: K
authors.lastname: Changkaew
authors.affiliation: Department of Clinic, Faculty of Veterinary Medicine, Mahanakorn University of Technology, Bangkok, Thailand.
authors.forename: Apiradee
authors.initials: A
authors.lastname: Intarapuk
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, Bangkok, Thailand.
authors.forename: Fuangfa
authors.initials: F
authors.lastname: Utrarachkij
authors.affiliation: Division of Bioresources, Research Center for Zoonosis Control, Global Station for Zoonosis Control, Hokkaido University, Sapporo, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Nakajima
authors.affiliation: Department of Microbiology, Faculty of Public Health, Mahidol University, Bangkok, Thailand. orasa.sut@mahidol.ac.th.
authors.forename: Orasa
authors.initials: O
authors.lastname: Suthienkul
authors.affiliation: Division of Bioresources, Research Center for Zoonosis Control, Global Station for Zoonosis Control, Hokkaido University, Sapporo, Japan. suzuki@czc.hokudai.ac.jp.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000617:Aminoglycosides / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000890:Anti-Infective Agents; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects* / Q000201:enzymology*; D004927:Escherichia coli Infections; D006801:Humans; D032023:Integrons / Q000235:genetics*; D055231:Lincosamides / Q000494:pharmacology; D010641:Phenotype; D013552:Swine / Q000382:microbiology*; D013785:Thailand; D014295:Trimethoprim / Q000494:pharmacology; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D055231:Lincosamides; D014295:Trimethoprim; D001618:beta-Lactamases