Study on virulence and antibiotic susceptibility of Escherichia coli isolated from diarrheic dairy calves

Abstract

Diarrhea in the calves during the suckling period caused by E. coli results in high economic losses for farmers. Seventy-four fecal samples of the diarrheic dairy calves were collected from Duc Trong district, Lam Dong province for determining the pathogenicity and antibiotic susceptibility of E. coli. The studied results showed that the biochemical characteristics of 73 isolated strains of E. coli were fully similar to the descriptions in the reference publications. By using PCR technique to check for toxic genes of the isolated E. coli strains, there were 15 strains carried toxic genes, of which 13/15 E. coli strains carried eae gene (17.80%); 3/15 strains carried Stx2 gene (4.10%); 1/15 E. coli strains carried both eae and Stx2 genes (1.37%). 10/15 strains carried high virulence, killed 100% of the experimental mice within 6 to 20 hours. Highly virulent E. coli strains were extremely susceptible to enrofloxacin (90%), gentamicin (80%) and ceftiofur (80%), but resistant to amoxicillin, doxycyclin and oxytetracyclin with the ratio of 50, 70 and 90%, respectively. The studied results also revealed that, E. coli strains carrying toxic genes were the causative agents of diarrhea in the dairy calves, therefore it is necessary to periodically test the antibiotic
susceptibility of the E. coli to improve the treatment effectiveness and limit antibiotic resistance.