Open AccessCharacterization of antimicrobial resistance among Escherichia coli isolates from chickens in China between 2001 and 2006
Author(s) -
Dai Lei,
Lu LiMing,
Wu CongMing,
Li BeiBei,
Huang SiYang,
Wang ShaoChen,
Qi YongHua,
Shen JianZhong
Publication year - 2008
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2008.01272.x
Subject(s) - florfenicol , microbiology and biotechnology , biology , broth microdilution , antimicrobial , escherichia coli , amikacin , antibiotic resistance , minimum inhibitory concentration , antibiotics , gene , biochemistry
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 μg 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≥32 μg 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 μg mL −1 and one with MIC=64 μg mL −1 were negative for the floR gene.