Prevalence and characteristics of β-lactamase and plasmid-mediated quinolone resistance genes in Escherichia coli isolated from farmed fish in China.
OBJECTIVE
To determine the molecular epidemiology of extended-spectrum β-lactamases (ESBLs) and plasmid-mediated quinolone resistance (PMQR) in Escherichia coli isolated from farmed fish in China.


METHODS
E. coli was isolated from fish gut samples from fish farmed throughout Guangdong province and tested for the presence of the β-lactamase genes and PMQR-encoding genes using PCR and DNA sequence analysis. Co-transfer of plasmids encoding for ESBLs as well as PMQR determinants was explored by conjugation into E. coli.


RESULTS
A total of 218 non-duplicate E. coli were recovered from fish gut samples. β-Lactamase genes were identified in 19 (17%) of 112 strains with reduced susceptibility to ampicillin, and PMQR genes were identified in 59 (73.8%) of 80 strains with reduced susceptibility to ciprofloxacin. Only three ESBL genes were identified in three isolates: bla(CTX-M-14), bla(CTX-M-79) and bla(SHV-27). PMQR gene screening identified qnr genes (n = 59) as the most common, including qnrB (n = 33), qnrS (n = 21) and qnrD (n = 5), with aac(6')-Ib-cr (n = 6) being rarely found. The co-carriage of two or three PMQR genes in one strain was found in 7 (11.9%) isolates. The ESBL gene bla(CTX-M-79) was found to be co-carried with qnrS. Co-transfer of qnrS was observed with bla(CTX-M-79).


CONCLUSIONS
Our study is the first to demonstrate the existence of high levels of mobile genes conferring reduced susceptibility to fluoroquinolones as well as the presence of ESBL genes in fish produced in China, and identifies a significant reservoir of antibiotic resistance genes relevant to human medicine.
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.
Hong-Xia
HX
Jiang
Dian
D
Tang
Ya-Hong
YH
Liu
Xiao-Hua
XH
Zhang
Zhen-Ling
ZL
Zeng
Li
L
Xu
Peter M
PM
Hawkey
D000667:Ampicillin / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017756:Aquaculture; D002681:China; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology / Q000662:veterinary*; D005399:Fishes; D041981:Gastrointestinal Tract / Q000382:microbiology*; D005796:Genes; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D010957:Plasmids; D016133:Polymerase Chain Reaction; D015363:Quinolones / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D015363:Quinolones; D000667:Ampicillin; D001618:beta-Lactamases