Phylogenetic characterization and determination of antibiotic susceptibility of avian pathogenic Escherichia coli strains isolated from broiler visceral organs

Abstract

The study aims to identify phylogenetic groups and antibiotic susceptibility of poultry Escherichia coli (APEC) isolates. E. coli was phenotypically and biochemically characterized. Isolates from 8/30 (26.66%) liver, 7/30 (23.33%) heart, and 4/30 (13.33%) spleen of 37-42 days old vaccinated broiler chickens were assessed. Then the E. coli isolates (19/90; 21.11%) were phylogrouped by quadruplex genotyping based on the presence or absence of arpA, chuA, yjaA genes, and TspE4.C2 DNA fragment.The majority of APEC strains belonged to phylogenetic group C, followed by groups A, E, and F. Phylogroup C was observed in the liver, phylogroup A in both liver and heart samples, phylogroup E in the heart and spleen, and phylogroup F in the liver. The highest antibiotic resistance was observed in Amoxicillin-Clavulanic acid and Ampicillin (100%) predominantly in groups A and E according to antibacterial susceptibility tests. Multiple antibiotic resistance (MDR) for APEC strains was also found at 68.42% (13/19). Of the 19 isolates tested, only 13 (68%) were susceptible to high levels of gentamicin. APEC strains belonging to phylogroups C, A, and E are of epidemiological importance for broilers. It would be beneficial to investigate new phylogroups by performing more detailed genotypic analyzes in APEC strains.