Shiga toxin-producing Escherichia coli (STEC) strains: Its impact on public health in and around Murarai, West Bengal, India

Abstract

The purpose of the present study is to conduct a comprehensive investigation on shiga toxin-producing Escherichia coli (STEC) responsible for the hemolytic uremic syndrome (HUS) in surface water samples in and around the study area and calculate a probable risk conferred by them due to their existence. To assess the impact of this bacterium on public health, water samples were analysed on the basis of bacteriological and physiochemical parameters. Bacteriological parameters include Most Probable Number (MPN) count, isolation, microscopy, biochemical characterization, 16 s rDNA sequencing, heavy metal and antibiotic resistance pattern of the strains; whereas physiochemical parameter include calculation of TDS, pH, hardness, temperature and conductivity of water samples. Total thirty water samples were collected randomly and these were found contaminated with human excreta. The water bodies of the area have high TDS, high conductivity, and high saline condition with alkaline pH. The biochemical analysis and 16 s rDNA sequencing undoubtedly prove the identity of the isolated strains as STEC strains of E. coli. They are highly sensitive to Cadmium, moderately sensitive to Cobalt but less sensitive to Copper and Nickel and do not have any significant resistance to any one of the antibiotics used in this study. The risk estimation of the study area was calculated on the basis of epidemiological data and findings of Payment and Hurst as well as in accordance with the principles and guidelines for the conduct of microbiological risk assessment developed by Codex Alimentarious. The principles and guidelines for the conduct of microbiological risk assessment developed by Codex Alimentarious estimate the annual risk of infection in Murarai is nearly 18 % which is more accurate and higher than that of the findings of Payment and Hurst. The assessment indicates that the resident of this area are living under high risk of infection of the HUS. This is the first confirmed risk assessment report of Shiga toxin-producing E. coli (STEC) and its impact on public health from this area of West Bengal. The study highlights that the contamination is predominantly anthropogenic in nature.