¹Department of Microbiology, Faculty of Veterinary Medicine, Mehmet Akif Ersoy University, TR-15030 Burdur - TURKEY DOI : 10.9775/kvfd.2019.23541 AmpC type beta-lactamase enzyme production by Escherichia coli confers resistance to penicillin and cephalosporins including oxyiminocephalosporin, cephamycin and aztreonam (variably). Screening of AmpC beta-lactamase determinants in both commensal and pathogenic E. coli isolates in livestock is important to reveal the resistance status of the bacteria. Therefore, we aimed to investigate the AmpC beta-lactamase producing E. coli isolates in cattle and sheep populations in Burdur, Turkey. The fecal samples were collected from 250 Holstein cows, older than 12 months of age and apparently healthy, and from 225 sheep from different breeds, older than 6 months of age and apparently healthy. After selective isolation and identification of the agent in coliform/E. coli selective medium supplemented with cefotaxime (2 μg/mL) or ceftazidim (2 μg/mL), the cefoxitin resistant E. coli isolates were determined by agar disc diffusion test (ADDT). Then, pAmpC beta-lactamase genes were determined by multiplex polimerase chain reaction (PCR) as gold standart test for pAmpC beta-lactamase producing E. coli. Finally, the isolates were characterized by PCR for phylogeny and Enterohemorrhagic/Shiga toxin producing E. coli (EHEC/STEC) related virulence genes. Totally 17 (6.8%) cattle fecal samples were found positive for pAmpC beta-lactamase producing E. coli. None of the sheep fecal samples yielded culture positive results for the bacteria of interest. Among the E. coli isolates, only CIT (origin, Citrobacter freundii) family pAmpC gene was found. The predominant phylogenetic group was found as group A and only eae gene was detected in only one E. coli isolate. Multidrug resistance (MDR) was observed in 7 (41.2%) isolates. Consequently, the present study revealed that pAmpC beta-lactamase producing E. coli, with MDR and low phylogenetic group diversity, exists in cattle population, but not in sheep population. Keywords : Beta-lactamase, Escherichia coli, intimin, pAmpC, Phylogeny, Ruminant