title: Increased prevalence of plasmid-mediated quinolone resistance determinants in chicken Escherichia coli isolates from 2001 to 2007.
abstract: To evaluate the temporal change in the plasmid-mediated quinolone resistance (PMQR) determinants from 2001 to 2007 in chicken, a total of 532 chicken Escherichia coli isolates were screened for PMQR determinants by polymerase chain reaction and sequencing. The prevalence of qnr genes, aa(6')-Ib-cr, and qepA were 9.8%, 11.7%, and 0.75%, respectively. Among the qnr determinants, qnrA-, qnrB-, and qnrS-type genes were detected in 4 (0.75%), 21 (3.9%), and 27 (5.1%) of the examined isolates, respectively. None of the isolates carried qnrC gene. Ciprofloxacin resistance increased over time (p < 0.01), and a clear trend of increase in the prevalence of qnr and aac(6')-Ib-cr genes among the isolates was shown from 2001 to 2007 (p < 0.01). Pulsed-field gel analysis showed that the PMQR-positive isolates were not clonally related and genetically diverse. Quinolone resistance was transferred by conjugation from qnrB-, qnrS-, and aac(6')-Ib-cr-positive isolates to recipient E. coli. The qnrB and aac(6')-Ib-cr alleles were located on the plasmids with the size of 49 and 50 kb, respectively. However, the qnrS alleles were located on different plasmids with sizes from 57.4 to 88.6 kb, indicating diverse genetic backgrounds. The increasing frequency of ciprofloxacin resistance in E. coli was associated with increasing prevalence of qnr genes and aac(6')-Ib-cr (r(s) = 0.964, p = 0.00045). This survey showed that PMQR determinants were highly prevalent in chicken E. coli isolates in China with a trend of increase from 2001 to 2007. Horizontal transfer and widespread use of quinolone antimicrobials may have contributed to the spread of PMQR determinants in the poultry production system. The widespread dissemination of PMQR could potentially fuel the rapid development of fluoroquinolones resistance.
authors.affiliation: National Center for Veterinary Drug Safety Evaluation, College of Veterinary Medicine, China Agricultural University, Beijing, People's Republic of China.
authors.forename: Si-Yang
authors.initials: SY
authors.lastname: Huang
authors.forename: Lei
authors.initials: L
authors.lastname: Dai
authors.forename: Li-Ning
authors.initials: LN
authors.lastname: Xia
authors.forename: Xiang-Dang
authors.initials: XD
authors.lastname: Du
authors.forename: Yong-Hua
authors.initials: YH
authors.lastname: Qi
authors.forename: He-Bing
authors.initials: HB
authors.lastname: Liu
authors.forename: Cong-Ming
authors.initials: CM
authors.lastname: Wu
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Shen
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens / Q000382:microbiology*; D002681:China; D002939:Ciprofloxacin / Q000494:pharmacology; D015169:Colony Count, Microbial; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000737:chemistry; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D029968:Escherichia coli Proteins / Q000235:genetics; D005243:Feces / Q000382:microbiology; D024841:Fluoroquinolones / Q000494:pharmacology*; D005516:Food Microbiology; D022761:Gene Transfer, Horizontal; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011201:Poultry Diseases / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D024841:Fluoroquinolones; C485384:Qnr protein, E coli; D002939:Ciprofloxacin