Isolation and molecular characterization of pathogenic strains, their antibiogram and associated risk factors of Escherichia coli isolates from diarrheic calves in bahir dar city dairy farms, north western ethiopia

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