Abstract:
Escherichia coli is recognized as one of the major causes of neonatal calf diarrhea with
severe lethal outcome and major damage to the livestock industry worldwide. A crosssectional study was conducted from January 2019 - Jun 2019 to isolate & identify
pathogenic Escherichia coli strains, their antibiogram and associated risk factors from
diarrheic calves in Bahir Dar city dairy farms. A total of 112 fecal samples were collected
directly from the rectum of diarrheic calves and processed using standard microbiological
procedures. Accordingly, 57 (50.89%) samples were positive for E. coli. The multivariable
logistic regression analysis indicates that, the isolation rate of E. coli was significantly (p <
0.05) affected by factors such as age, breed, herd size and first colostrum feeding time.
Genomic DNA extracted from the isolates was amplified using polymerase chain reactions
to detect pathogenic strains. Furthermore, stx2, stx1, eaeA and hlyA genes were detected
from the isolates at the rates of 10/57 (17.54%), 5/57 (8.77%), 3/57 (5.26%) and 3/57
(5.26%), respectively. Based on the genes detected three pathotypes/strains of E. coli were
identified: STEC 11(19.3%), EHEC 4(7.02%) and aEPEC 1(1.75%). In vitro antimicrobial
sensitivity testing showed susceptibility rates ranging from 0% up to 85.96% and
resistance rates ranging 8.77% and 100%. All pathogenic E. coli strains were susceptible
to chloramphenicol but all of the pathogenic strains showed resistance to Neomycin. In
conclusion, the occurrence of E. coli isolates, their pathogenic strains and Frequent use of
limited antibiotics were found at high frequency. Hence, Identifying pathogenic strains
and strict control measures such as treatment of positive cases using effective drugs are
vitally important as effective control and prevention strategies.
