Occurrence of Shiga-toxigenic and enteropathogenic E. coli contaminations and assessment of water quality in the southern coastal belt in Sri Lanka.

The contamination of coastal water with Shiga-toxin-producing Escherichia coli (STEC) and Enteropathogenic Escherichia coli (EPEC) poses a significant risk to human health as they are causing severe gastroenteritis diseases. This study focused on detecting Enterohaemorrhagic E. coli (EHEC) and STEC in coastal waters along the southern coastal belt in Sri Lanka. Water samples (n=66) from 22 sampling locations were collected, and the virulent genes, eae, stx1 and stx2, were selected for the screening of EHEC and STEC. Amplification was done through optimized PCR protocols. Further, the water quality was measured in terms of N-NO^-₃, N-NO^-₂, N-NH₃, Total Nitrogen, Total Phosphate and COD in selected locations following the APHA standard methods. The findings indicate the presence of EHEC and STEC in some locations of the southern coast belt, which are popular for tourism and recreational activities. STEC were detected at 45.45% of sampling locations in the southern coastal belt of Sri Lanka, while EHEC was detected at 54.54%. Further, the recorded water quality values for N-NO₃^-, N-NO₂^-, N-NH₃⁺, Total Nitrogen, Total Phosphate and COD ranged from 0.30 to 3.48 mg/L, 0 to 0.64 mg/L, 0.03 to 2.39 mg/L, 0.48 to 4.31mg/L, 0.06 to 3.17mg/L and 584 to 679mg/L, respectively.