Abstract
Aim/background : Infection by E. coli is a serious reason of neonatal calf diarrhoea, particularly in newly born calves,constitute a theatrical role in the evolution of severe diarrhoea, significant morbidity and mortality rates, and considerable economic concern. Our work designate to determine the isolation rate of E. coli as a primary a etiological agent of diarrhoea in young calves, genetic screening of virulence elements and profile of E. coli strains against common antimicrobial agents. Methods: A total of 120 specimens form diarrhoeic calves were collected in addition to 20 samples from each bedding, animal feed, drinking water, and milking utensils. Results: E. coli was predominate in 20.8% out of total 120 specimens from diarrhoeic calves. In addition, environmental sampling revealed E. coli contamination rates of 45%, 15%, 35%, and 40% in bedding, animal feed, drinking water, and milking utensils, respectively. Sensitivity testing showed broad phenotype resistance to tetracycline (84%), ampicillin (80%), streptomycin (76%), sulphamethoxazole–trimethoprim (70%), and amoxicillin–clavulanic acid (60%), while moderate sensitivity was observed to gentamicin (50%), chloramphenicol (46%), neomycin (44%), and florfenicol (44%). Molecular screening by PCR demonstrated successful detection of the K99, eaeA stx1, and stx2 virulence genes at 248, 314, 614, and 779 bp respectively. Conclusion: These findings suggest a strong association between antimicrobial resistance profiles and virulence gene carriage, which may explain the severity of E. coli–associated diarrhoea encountered in the field. Further studies are required to investigate additional virulence factors and resistance mechanisms to support effective control and prevention strategies.

Key words: antibiogram, young age, diarrhea, E.coli, PCR, virulence.