غلامحسین حبیبی - Department of Clinical Sciences, Faculty of Veterinary Medicine, Kazerun Branch, Islamic Azad University, Kazerun, Iran
محمد ضیائی - Graduated of Faculty of Veterinary Medicine, Kazerun Branch, Islamic Azad University, Kazerun, Iran

Background and aim: Yolk sac infection (YSI) and colibacillosis are the most common infectious diseases that lead to high rates of early chick mortalities (ECMs) in young chicks. In this study, by referring to the Mashhad Veterinary Laboratory, one hundred chicks from different poultry farms sent to the Veterinary Laboratory, were examined and sampling was performed. All specimens without a history of antibiotic use were gradually transferred to a laboratory to be cultured from their yolk sac. Materials and Methods: For this purpose, MacConkey culture medium and eosin methylene blue were used to grow microbes. The morphological status of the microbe was examined by slide preparation and Gram staining. Also, using biochemical culture medium, indole and methyl red index were used to identify Escherichia coli bacteria. Then, antibiogram of the isolated strains was performed to determine the susceptibility and resistance of the microbes. For this purpose, the disk diffusion method was used by Kirby Bauer method and compared with standard drug disks. Finally, based on the results, the extent of microbial contamination and their drug sensitivity were determined. Results: The findings showed that ۴۰% of the samples contained Escherichia coli and the highest microbial susceptibility to Ceftiofur and gentamicin drugs was observed, such that their sensitivity was ۵۷.۵% and ۶۰%, respectively. The three drugs of Colistine, phosphomycin and lincomycin were ۳۰% sensitive. Oxytetracycline, Sultrim, Erythromycin, Fluorophenicol, Tiamulin and Tylosin showed more than ۹۰% drug resistance. Also, other antibiotics had different degrees of drug resistance and in addition, multidrug resistance has been observed in abundance. Conclusion: Since the indiscriminate use of antibiotics has caused high drug resistance in chickens, it is necessary to minimize the occurrence of microbial contamination by observing hygienic conditions and appropriate disinfection. Also, the prescription of drugs should only be done by a veterinarian and based on the antibiogram.

Escherichia coli, Yolk sac infection, Antibiogram, Drug resistance, اشریشیا کلی, عفونت کیسه زرده, آنتی بیوگرام, مقاومت دارویی