Antimicrobial Resistance, Extended-Spectrum beta-Lactamase Productivity, and Class 1 Integrons in Escherichia coil from Healthy Swine

作者：Changkaew Kanjana; Intarapuk Apiradee; Utrarachkij Fuangfa; Nakajima Chie; Suthienkul Orasa; Suzuki Yasuhlko^*

来源：Journal of Food Protection, 2015, 78(8): 1442-1450.

DOI：10.4315/0362-028X.JFP-14-445

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 beta-lactamase (ESBL) producing strains and to characterize class 1 integrons in Escherichia coil 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. coil isolates were confirmed as ESBL-producing strains. Among them, bla(CTX-M) (45 isolates) and bla(TEM) (41 isolates) were detected. Of the bla(CTX-M)-positive E. coli isolates, 37 carried the bla(CTX-M-1) cluster, 12 carried the bla(CTX-M-9) cluster, and 5 carried both clusters. Sequence analysis revealed bla(TEM-1), bla(TEM-135), and bla(TEM-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 (aadAl, aadA2, aadA22, or aadA23), trimethoprim (dfrA5, dfrAl2, or dftA17), and lincosamide (linF). Genes encoding beta-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. coil strains.

• 出版日期2015-8