Objectives: this study was devoted to detect the plasmid-mediated quinolone resistance (PMQR) mechanisms (qnr, qepA and aac(6')-Ib-cr ) and its association withAmpC- Beta-lactamase production in E. coli strains from different sources.
Methods: Twenty-nine E. coli isolates from food-producing animals (chicken and sheep) and their by-products, collected from Sharkia province, Egypt were tested for their susceptibilities for different antimicrobial groups. Uniplex PCR was applied using specific primer sets for screening the presence of PMQR and AmpC β –lactamases genes in strains under study.
Results: Out of 29 E. coli strains, only 9 isolates were positive for  qnrA gene (31.03%) and associated with the amp < /em>C β -lactamase genes ( MOX, DHA, ACC,  EBC) whereas only one qnrB and qnrS-like genes (3.45 %) were detected. A qnrB gene as well as qnrS was detected in  (DHA , EBC) isolate. qepA and aac(6')-Ib-cr were detected in 41.38% and 3.45% of the  E .coli isolates, respectively alone or in combination with qnr genes. The amp < /em>C β -lactamase genes were detected in 75.86 % of all strains and in 100% and 66.66 %of the PMQR determinant-positive and -negative strains, respectively, gave amplicons range from 302 bp to 520 bp, that easily distinguished by gel electrophoresis.
Conclusions: A high prevalence of PMQR determinants among AmpC β-lactamase producing E. coli isolates from chicken mainly and their by-products was detected in Egypt. Their effect may slightly increase the MIC of quinolone and may relate to the development of full resistance to quinolone.