Colibacillosis, which is caused by Escherichia coli (E. coli), is one of the most common infectious diseases affecting poultry and causes the great economic losses to poultry production worldwide. The present study investigated the presence of E. coli in broiler chickens affected by colibacillosis and reared at various locations in Tiaret Province as well as evaluated the susceptibility of isolated E. coli strains to various antimicrobial agents. A total of 110 samples collected from 55 broiler chickens representing liver (n=55) and spleen (n=55) showing lesions suspected to be colibacillosis were analyzed by conventional methods, and 33 E. coli isolates were tested on a panel of seven antimicrobial agents using the disk diffusion method. The overall isolation rates of E. coli were 60% (33/55) and 50.9% (56/110) in whole chickens and organs, respectively. There was no variation in the isolation rate between organs: 50% (28/56) for liver and 50% (28/56) for spleen. All E. coli isolates tested showed 100% resistance to Nalidixic acid and Ofloxacine, followed by 93.93%, 90.90%, and 51.51% resistance to Tetracycline, Trimethoprim-sulfamethoxazole (Co-trimoxazole), and Chloramphenicol, respectively. However, low resistance to Gentamycin was observed (12.12%), whereas all E. coli isolates were susceptible to Colistin sulfate. Multidrug resistance was observed in 96.96% (32/33) of the isolates tested. We conclude that E. coli was largely present in broiler chickens affected by colibacillosis in Tiaret Province, and multidrug-resistant E. coli isolates showed high resistance to multiple antibiotics.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    Sample collection
    Isolation and identification of E. coli
    Antimicrobial susceptibility determination
RESULTS
    Necropsy finding
    Bacteriological and Biochemical Examination
    Antimicrobial resistance profiles of E. coli isolates
    Multidrug resistance patterns for E. coli isolates
DISCUSSION
CONCLUSIONS
REFERENCES

• Rachid Merati(Laboratoty of Hygiene and Animal Pathology, University of Tiaret) Corresponding Author.
• Abdellatif Boudra(Department of Animal Health, Veterinary Science Institute, University of Tiaret)
• Abdelhamid Hammoudi(Laboratoty of Hygiene and Animal Pathology, University of Tiaret)
• Hebib Aggad(Laboratoty of Hygiene and Animal Pathology, University of Tiaret)