Diarrheagenic toxins in stool correlate to drinking water from improved water sources in Ethiopia

Abstract

Escherichia coli toxins are the most common types found in association with disease in E. coli bacteria. They are found in nearly all pathogenic E. coli bacteria either released from the bacteria or E. coli cell or both transmitted via the orofecal route. The present study evaluated the relationship between E. coli toxins detected in ‘improved’ drinking water sources and toxins found in stool samples from individuals with diarrhea that consumed the water. Improved water is defined as the water source, by the nature of their construction or through active intervention, are protected from external contamination, particularly with fecal matter. A correlation between toxins in the water with toxins in the stools suggests that contaminated drinking water is a potential infection source. Stool samples were collected from people with diarrhea (248 stool samples) and their drinking water at their home (248 water samples). Only diarrhea patients that reported use of improved drinking water sources as per the definition of the WHO/UNICEF Joint Monitoring Programme were included in the study. E. coli isolates were analysed for 5 major toxins (enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1), heat-stable enterotoxin a (Sta); shiga-like toxin 1 (Stx1), shiga-like toxin 2 (Stx2), and heat-liable enterotoxin (LT)) using a multiplex polymerase chain reaction (mPCR). Descriptive statistics, Chi-square (χ2) test, Fisher's exact, logistic regression, and bivariate Pearson correlation coefficients were used to examine the association and correlation of toxins in the drinking water with those in the stool samples. Of the 248 households, 24% had positive results in both water and stool samples, 63% [Confidence Interval (CI): 55–67%] had positive results in water samples only and 46% [CI: 37- 49%] were found to be positive for toxins in stool samples only. EAST1 was the most frequently detected from the 5 toxins evaluated, with 33% in the water and 38% in the stool. ESAT1, Stx1, and LT toxins were the most commonly found contaminants in water from improved water sources. The prevalence of toxins in household water samples was higher than that obtained from yard connections (51%) and piped systems connected to public stands (42%), compared to the other types of water sources. Both a positive correlation (P < 0.05; r = 0.412) and statistically significant association (P=0.0001) was found between the toxins in the water and toxins in the stool. EAST1 in the stool was significantly correlated with overall toxins in water (r = 0.378) and increased the probability of the occurrence of EAST1 in water (odds ratio (OR)=4.96, 95% CI, 2.81–8.74; P=0.000). E. coli toxins have been found to be effective biomarkers for detecting possible drinking water contamination in households with diarrhea. Long-term planning for the protection and/or treatment of stored household drinking water to ensure toxins free water at the point of use are required.