Chronological study of antibiotic resistances and their relevant genes in Korean avian pathogenic Escherichia coli isolates.
Antibiograms and relevant genotypes of Korean avian pathogenic Escherichia coli (APEC) isolates (n = 101) recovered between 1985 and 2005 were assessed via disc diffusion test, PCR, restriction enzyme analysis, and sequencing. These isolates were highly resistant to tetracycline (84.2%), streptomycin (84.2%), enrofloxacin (71.3%), and ampicillin (67.3%), and most of the tetracycline, streptomycin, enrofloxacin, and ampicillin resistances were associated with tetA and/or tetB, aadA and/or strA-strB, mutations in gyrA and/or parC, and TEM, respectively. Class 1 integrons were detected in 40 isolates (39.6%), and a variety of gene cassettes conferring streptomycin (aadA), gentamicin (aadB), and trimethoprim (dfr) resistances were identified: aadA1a (27.5%), dfrV-orfD (2.5%), aadB-aadA1a (2.5%), dfrI-aadA1a (47.5%), dfrXVII-aadA5 (12.5%), and dfrXII-orfF-aadA2 (7.5%). In addition, several types of common promoters (P(ant)) of the gene cassettes (hybrid P1, weak P1, or weak P1 plus P2) and single-nucleotide polymorphisms in aadA1a were identified. The results of a chronological analysis demonstrated significant and continuous increases in the frequencies of resistances to several antibiotics (tetracycline, streptomycin, enrofloxacin, ampicillin, and trimethoprim-sulfamethoxazole) and of the relevant resistance genes (tetA, strA-strB, and TEM), mutations in gyrA and parC, and multidrug-resistant APEC strains during the period 2000 to 2005.
Kim
Tae-Eun
TE
Laboratory of Avian Diseases, Seoul National University, San 56-1, Shillim-Dong, Gwanak-Gu, Seoul, 151-742, Korea.
Jeong
Yong-Wun
YW
Cho
Sun-Hee
SH
Kim
Sun-Joong
SJ
Kwon
Hyuk-Joon
HJ
D000818:Animals; D002645:Chickens / Q000382:microbiology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D004927:Escherichia coli Infections / Q000662:veterinary*; D008826:Microbial Sensitivity Tests; D020641:Polymorphism, Single Nucleotide; D011201:Poultry Diseases / Q000382:microbiology*; D011401:Promoter Regions, Genetic; D013997:Time Factors