Prevalence and dissemination of oqxAB in Escherichia coli isolates from animals, farmworkers, and the environment.
OqxAB has recently been identified as one of the mechanisms of plasmid-mediated quinolone resistance (PMQR). Compared to what is observed for other PMQR determinants, there is a paucity of data with regard to the prevalence and epidemiology of OqxAB and its contribution to resistance to different antimicrobials. In this study, the prevalence and dissemination of oqxAB and other PMQR genes in Escherichia coli isolates from animals, farmworkers, and the environment in 2002 in China were investigated. Of the 172 E. coli isolates, 39.0% carried oqxA, while only 4.1%, 2.9%, and 0.6% carried qnr (1 qnrB6 isolate, 5 qnrS1 isolates, and 1 qnrD isolate), qepA, and aac(6')-Ib-cr, respectively. Among the 33 isolates from farmworkers, 10 (30.3%) were positive for oqxA. oqxAB was associated with IS26 and was carried on the 43- to 115-kb IncF transferable plasmid. Transconjugants carrying oqxAB showed 4- to 16-fold increases in the MICs of quinolones, 16- to 64-fold increases in the MICs of quinoxalines, 8- to 32-fold increases in the MICs of chloramphenicol and trimethoprim-sulfamethoxazole, and 4- to 8-fold increases in the MICs of florfenicol compared to the levels for the recipient. The pulsed-field gel electrophoresis (PFGE) analysis showed that the high levels of prevalence and dissemination of oqxAB in E. coli in animal farms were primarily due to the transmission of plasmids carrying oqxAB, although clonal transmission between human and swine E. coli isolates was observed. It is concluded that oqxAB was widespread in animal farms in China, which may be due to the overuse of quinoxalines in animals. This study warrants the prudent use of quinoxalines in food animals.
Zhao
Jingjing
J
College of Veterinary Medicine, National Reference Laboratory of Veterinary Drug Residues SCAU, South China Agricultural University, Guangzhou 510642, China.
Chen
Zhangliu
Z
Chen
Sheng
S
Deng
Yuting
Y
Liu
Yahong
Y
Tian
Wei
W
Huang
Xianhui
X
Wu
Congming
C
Sun
Yongxu
Y
Sun
Yan
Y
Zeng
Zhenling
Z
Liu
Jian-Hua
JH
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D015363:Quinolones / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D015363:Quinolones