Isolation, Identification and Determination of Antibiogram Characteristics of Escherichia Coli from Calves in West Shewa Zone, Oromia, Ethiopia

A cross-sectional study, conducted from December 2022 to April 2024 in West Shewa, Oromia, Ethiopia aimed to isolate and identify Escherichia coli from calves and determine its antimicrobial susceptibility patterns. Diarrheic calves were purposively sampled, while non-diarrheic calves were randomly sampled. Escherichia coli was isolated using standard bacteriological methods. Stx1 and eaeA virulence genes were detected by PCR. Escherichia coli susceptibility to 11 antibiotics was assessed via disk diffusion. The study data was analyzed using SPSS version 20. A total of 162 rectal fecal samples were collected 84 from diarrheic calves and 78 from non-diarrheic calves aged 0-4 months. Escherichia coli was isolated in 48.1% (78/162; 95% CI: 40.2–56.1%). Escherichia coli was more common in diarrheic calves (56%) than non-diarrheic ones (40%) (p = 0.039). Season, age, health, house hygiene, first colostrum feeding, and feeding technique all significantly impact on the occurrence of Escherichia coli (p < 0.05). 10 of the 78 isolates were PCR-tested for eaeA and stx1 genes. The PCR results showed 30% had eaeA, 60% had stx1, and 10% had both genes. Isolates from diarrheic (n=24) and non-diarrheic (n=16) calves showed resistance to ampicillin, amoxicillin, tetracycline, and amoxicillin/clavulanic acid, but were susceptible to gentamicin, norfloxacin, nitrofurantoin, and streptomycin. The 54.2% of isolates from diarrheic calves and 50% from non-diarrheic calves were multidrug resistant. It was concluded that Escherichia coli may cause calf diarrhea, influenced by season, age, health, and colostrum feeding timing. The effective antibiotics identified were gentamicin, nitrofurantoin, norfloxacin, and streptomycin. Further characterization of Escherichia coli in calves is needed to improve calf health and antibiotic stewardship.