Extensive dissemination of CTX-M-1- and CMY-2-producing Escherichia coli in poultry farms in Tunisia.

We characterized 67 Escherichia coli isolates with reduced susceptibility to cefotaxime obtained from 136 samples of healthy broilers housed in 36 Tunisian farms. All these isolates harboured blaCTX-M-1 and/or blaCMY-2 genes located mostly on self-conjugative IncI1 plasmids. qnrS1, qnrA6 and aac(6')-Ib-cr were detected in six isolates. Considerable genetic diversity was detected among isolates from different farms. To our knowledge, this is the first detailed documentation of a high occurrence of blaCTX-M-1 and blaCMY-2 in E. coli at the poultry farm level in Tunisia as well as the first description of plasmid-mediated quinolone resistance in food animals in Tunisia which may contribute to the dissemination of these genes throughout Tunisia.