Isolation and molecular characterization of escherichia coli from selected drinking water sources in Njoro sub county, Kenya

Abstract

Contamination of drinking water sources remains a big challenge and many people lack access to safe potable water. In Njoro Sub-county the main water sources are rivers, man-made wells (protected and unprotected), boreholes, rainwater and springs (protected and unprotected). Although Escherichia coli (E. coli) is an indicator organism for fecal contamination of water, some E. coli strains have acquired the ability to cause intestinal (gastroenteritis) and extra intestinal diseases in humans. This study aimed at determining the Physico-chemical parameters and microbiological quality (using E. coli as indicator organism) in water used for drinking in Njoro Sub-county. Water samples were collected from drinking water sources and household storage containers. E. coli was isolated and quantified using the Compartmental Bag Test kit (CBT). The Physico-chemical properties were measured to determine water quality at points of collection and use, respectively. Characterization of pathogenic E. coli strains was done using a published multiplex-PCR protocol (mPCR). All data was imported into SAS 9.1 statistical software package for analysis. Numerical variables were summarized using arithmetic means and frequencies. The means were subjected to One way ANOVA and compared using Least Significant difference (LSD) at p= 0.05. Turbidity and electrical conductivity were above the WHO recommended levels in the water samples. E. coli was detected in 62.36% (n=111) of all the sampled drinking water in the sources and household storage containers. In total, 53.15% (n=59) of the E. coli positive samples were positive for pathogenic strains. However, only 38.98% (n=23) of the samples had different combinations of virulence strains. This indicated that the majority of drinking water were contaminated with the organic and inorganic matter at sources, during storage and handling and hence the need for frequent water quality monitoring and treatment to minimize contamination