Abstract:
Edwardsiella species and pathogenic strains of Escherichia coli are members of the
Enterobacteriaceae family that are frequently reported as causes of illness in fish and other
mammals. A cross-sectional study was conducted from April 2022 to November2022 with the
objectives of estimating the prevalence E. tarda, E. ictaluri, and E. coli O157:H7 in fish and
determining the antimicrobial susceptibility pattern of the isolates. Thus, a total of 768 tissue
samples comprising intestine, liver and kidney were collected from 256 apparently healthy fish
originated from Lake Abaya and Gilegele gibe-3 dam, southern Ethiopia. Standard
microbiological methods and procedure (ISO, 2003) were employed to isolate and identify target
organisms using biochemical tests. The disc diffusion test was employed to determine the
susceptibility pattern of isolates against seven standard antimicrobial discs. The findings were
presented using descriptive statistics, while the association of categorical variables with the
occurrence of bacterial species was computed using Chi-square and logistic regression analysis.
The overall prevalence of E. coli O157:H7, E. tarda, and E. ictaluri among fishes were 14.1%,
8.6% and 4.7% respectively. Whereas, the overall prevalence of E. coli O157:H7, E. tarda, and
E. ictaluri among organs (intestine, liver and kidney) were 5.34%, 4.01% and 1.95%
respectively. The maturity of fish and Lake showed significant association (P<0.05) with the
occurrence of E.tarda. Thus, immature fish and fishes from Gilgel-Gibe-3 had 2.6 (95%CI=1.0-
6.5) and 6.7 times (95%CI=1.3-35.7) respectively the odds of being positive to E. tarda than
their counter categories. Resistance to tetracycline was noted in all of the isolates. All the
isolates were 100% sensitive to gentamycin, sulfamethoxazole and trimethoprim. The results of
the present study concluded that the intestines of fish have been found to be harboring E. tarda,
E. ictaluri and E. coli O157:H7that may be a resident or transient microorganism. Moreover,
the current findings create momentum for more research work to establish the occurrence and
prevalence of E. tarda, E. ictaluri and E. coli O157:H7 in Lakes to determine cost effective
measures that should be taken to reduce fish mortality.
