Antimicrobial Resistance and Virulence Genes of Shiga Toxin-producing Escherichia coli (STEC) Isolated from Tilapia and Mullet and its Public Health Significance

Abstract

Shiga toxin-producing Escherichia coli (STEC) is responsible for several food-borne outbreaks worldwide. In this study, tissue samples of finfish (tilapia, n = 100) and (mullet, n = 100), and twenty human hand swabs from fish sellers and fishermen were tested bacteriologically for STEC presence. Isolates were tested for their antibiotic susceptibility and examined for the presence of the eaeA, stx1, and stx2 genes. E. coli and STEC were identified from the tissues (36.5% and 12.5%) of the examined tilapia and mullet, respectively; however, E. coli and STEC from human hand swabs were as high as (60% and 40%), respectively. Of the recovered E. coli isolates, 25 presumptive STEC (17 from finfish and 8 from humans) yielded characteristic mauve-colored colonies on CHROMagar STEC medium. The highest prevalence of STEC was in mullet and tilapia from freshwater of Nile tributaries at 24% and 48%, followed by fish from freshwater fish farms at 16% and 12%, respectively. No STEC was isolated from fish from Suez Canal water and saltwater fish farms. Recovered STEC isolates from fish belonged to 14 serotypes belonging to (O121: