Isolation and molecular detection of E. coli isolated from feces of sheep

Articles in Press

Document Type : Research Paper

Authors

1 Department of Microbiology, College of Veterinary Medicine, University of Baghdad, Iraq.

2 Department of Pathology, College of Veterinary Medicine, University of Baghdad, Iraq.

10.22103/jab.2026.27393.1945

Abstract

Objective
Escherichia coli is one of the most significant pathogens that cause infections in the digestive systems of animals, especially sheep, causing huge economic losses due to deaths, decreased productivity, and expenses on treatment. Moreover, Escherichia coli is a zoonosis which can be dangerous for people. Therefore, the identification of this pathogen is extremely important. The goal of this research was the isolation and identification of Escherichia coli from feces of diarrhetic sheep in Abu Ghraib city, Baghdad, Iraq, by bacteriological, VITEK 2, and PCR techniques (uidA and uspA genes). Also, pathogenicity of the isolates was assessed in experimentally infected mice.
Materials and methods
Fecal samples of forty sheep suffering from diarrhea were cultured in MacConkey and Eosin Methylene Blue (EMB) agars. Presumptive identification of bacteria isolated was done using cultural and biochemical tests followed by VITEK 2 automated test for confirmation. DNA isolation from the bacterial isolates was done while polymerase chain reaction (PCR) techniques using uidA and uspA primers were employed. Pathogenicity testing of E. coli was done through oral infection in mice using a dose of 1 × 10⁸ CFU/ml. Tissue fixation was done, and histopathology tests of intestinal and gastric tissues were done after that.
Results
Out of forty samples, seventeen (42.5%) were found to be positive for E. coli. Isolated bacteria formed typical pink colonies in MacConkey agar and metallic green sheen colonies in EMB agars. The isolates were identified as Escherichia coli using the automated VITEK 2 system with 97% confidence level. PCR results showed amplicon formation at the expected sizes of 623 bp (uidA gene) and 884 bp (uspA gene). Histopathology tests showed that infection resulted in severe lesions in the intestines and stomach of experimentally infected mice. Lesions included villous degeneration, inflammatory cells infiltration, disruption of the mucosa, congestion of blood vessels, and necrosis of gastric glands and gastric epithelium.
Conclusion
The results of the study show that a significant number of E. coli are associated with diarrheic sheep, and the importance of using a combination of conventional and molecular techniques for the identification of the isolate is evident.

Keywords

References

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Articles in Press, Accepted Manuscript
Available Online from 03 July 2026

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