Characterization of antimicrobial resistance among Escherichia coli isolates from chickens in China between 2001 and 2006.
Escherichia coli is a common commensal bacterium and is regarded as a good indicator organism for antimicrobial resistance for a wide range of bacteria in the community and on farms. Antimicrobial resistance of E. coli isolated from chickens from 49 farms in China between 2001 and 2006 was studied. A total of 536 E. coli isolates were collected, and minimal inhibitory concentrations (MICs) of eight antimicrobials were determined by the broth microdilution method. Isolates exhibited high levels of resistance to ampicillin (80.2%), doxycycline (75.0%) and enrofloxacin (67.5%). Relatively lower resistance rates to cephalothin (32.8%), cefazolin (17.0%) and amikacin (6.5%) were observed. Strains were comparatively susceptible to colistin (MIC(50) = 1 microg mL(-1)). A marked increase in isolates with elevated MICs for florfenicol was observed over the study period. Therefore, five resistance genes leading to the dissemination of phenicol resistance in the isolates (n = 113) with florfenicol MICs > or = 32 microg mL(-1) were analyzed. The gene floR was the most prevalent resistance gene and was detected in 92% of the 113 isolates, followed by the cmlA (53%), catA1 (23%) and catA2 (10%) genes. catA3 was not detected in these isolates. Eight isolates with florfenicol MICs = 32 microg mL(-1) and one with MIC = 64 microg mL(-1) were negative for the floR gene.
Dai
Lei
L
National Center for Veterinary Drug Safety Evaluation, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Lu
Li-Ming
LM
Wu
Cong-Ming
CM
Li
Bei-Bei
BB
Huang
Si-Yang
SY
Wang
Shao-Chen
SC
Qi
Yong-Hua
YH
Shen
Jian-Zhong
JZ
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002645:Chickens / Q000382:microbiology*; D002681:China; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D005798:Genes, Bacterial; D005838:Genotype; D008826:Microbial Sensitivity Tests
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial