Serogroups and antibiotics susceptibility pattern of avian pathogenic Escherichia coli strains responsible for colibacillosis in broiler breeding farms in the east of Algeria

In East Algeria, 100 Escherichia coli strains were isolated from livers and spleens of 120 broiler carcasses that presented colibacillosis lesions at autopsy. Serogrouping of these strains demonstrated that 83% of their serogroups belong to the most pathogenic serogroups of Avian Pathogenic Escherichia coli (APEC): O1 (14%), O2 (53%) and O78 (16%). In vitro susceptibility to antimicrobials of veterinary significance was determined by disc diffusion test. Antibiogram demonstrated a high level of resistance to enrofloxacin (82%), trimethoprim-sulfmethoxazole (82%), ampicillin (89%) and amoxicillin/ Ac clavulanic (90%), nalidixic acid (99%) and tetracycline (100%). There were moderate levels of resistance to neomycin (49%) and nitrofurantoin (53%). There were low levels of resistance to gentamicin (2%), chloramphenicol (13%) and no resistance to colistin sulfate (0%). All strains were multi-drug resistant and more than half (58%) of the isolates were resistant to seven antibiotics at least. Thus, thirty one antibiotic resistant patterns of E. coli strains were detected, of which 11 were present significantly. Co-resistance was found in eight of the eleven most common multidrug resistant patterns, 62% of the strains expressed this co-resistance. E. coli strains isolated expressed resistances to molecules that are routinely used in the field. It is clear that these are less effective against colibacillosis. It is more than ever necessary to perform antibiotic susceptibility testing prior to treatment in order to prescribe the molecule of choice, and set up a monitoring program in Algeria to monitor antimicrobial resistance in pathogenic bacteria that could be potentially transmitted to humans from animal food. Key words: Algeria, antibiotic resistance, colibacillosis, Escherichia coli, serogroups.