Prevalence of plasmid-mediated quinolone resistance qnr genes in poultry and swine clinical isolates of Escherichia coli.
The prevalence of qnr genes was investigated in veterinary clinical isolates of Escherichia coli in Guangdong province, China, and the aac (6')-Ib gene and the mutations in QRDRs of gyrase and topoisomerase IV were examined in qnr-positive strains. A total of 232 E. coli strains isolated from pig and poultry were screened for the presence of the qnrA, qnrB and qnrS genes by PCR and sequencing. The aac (6')-Ib gene was detected in qnr-bearing strains by PCR and sequencing. For all strains carrying qnr, MICs for six quinolones were determined. Mutations within the gyrase and topoisomerase were analyzed by PCR and sequencing for all the QRDRs of gyrA, gyrB, parC and parE. Among 232 E. coli isolates, 14 (6%) isolates were positive for the qnr gene, including one for qnrB, 13 for qnrS, but no qnrA was identified in this population. Detection of the aac (6')-Ib gene showed that one qnrS-positive isolate from pig and one qnrB-positive isolate from duck carried aac (6')-Ib gene, and both were the cr variant allele of aac (6')-Ib. All of the 14 isolates had MICs of ciprofloxacin more than 0.25 mg/L. Mutations in the QRDR of gyrA mutations were observed in 5 (35.7%) of the 14 strains. Three fluoroquinolone-resisting strains showed one mutation S83L of gyrA, while one S83I. One high-level resistance strains harboured gyrA S83L and A87N of gyrA. A singe mutation in site 58 of parC was detected in 3 (21.4%) strains. None mutations were found in QRDRs of gyrB and parE. The emergence of qnr genes in veterinary clinical E. coli isolates is described for the first time. This is also the first report of aac (6')-Ib-cr gene in E. coli isolates from food-producing animals.
College of Veterinary Medicine, Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou 510642, People's Republic of China.
Lei
L
Yue
Hong-Xia
HX
Jiang
Xiao-Ping
XP
Liao
Jian-Hua
JH
Liu
Shu-Juan
SJ
Li
Xue-Ying
XY
Chen
Chao-Xi
CX
Chen
Dian-Hong
DH
Lü
Ya-Hong
YH
Liu
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002645:Chickens; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids / Q000235:genetics*; D011201:Poultry Diseases / Q000382:microbiology; D015363:Quinolones / Q000494:pharmacology; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology
D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; C485384:Qnr protein, E coli; D015363:Quinolones