Abstract
The majority of people in developing nations rely on untreated or minimally treated surface and shallow groundwater sources which are prone to faecal contamination. This study evaluated the utility of EC 3M Petrifilm and sanitary inspection forms (SIFs) as tools to assess 47 water sources and identify hazards of contamination in two rural Ugandan villages (90% were surface sources). Water samples were cultured on EC 3M Petrifilm, which are intended for the enumeration of E. coli and total coliforms following 24 h incubation at 37°C. Isolated bacteria were cultured on MacConkey agar and identified using standard biochemical tests, while selected isolates were verified by sequencing 16S rRNA genes. From 105 Petrifilms, 110 presumptive E. coli were isolated and identified to genus level. However, only 33 presumptive E. coli isolates from 14 water sources (representing 27 distinct strains as determined by PFGE) were confirmed E. coli. The other presumptive E. coli isolates were identified as Citrobacter, Enterobacter, Proteus, Salmonella and Yersinia species. SIFs used an adapted survey designed for urban water sources of Uganda. The form yielded an SIF score based on binary data and characterized potential sources of contamination. SIF scores alone offered little information to distinguish between contamination levels of surface water sources, but the information collected in the surveys could be used to identify ways to improve sources. The results of this study suggest that the use of sanitary surveys may assist in identifying potential pollution sources that may be targeted to protect water sources. Bacterial monitoring using EC 3M Petrifilms may be effective for the screening of relative levels of contamination of source waters, including surface sources.
Highlights
The quality of drinking water is dependent on the initial quality of the source water used and the level of treatment provided
No E. coli in a 100 ml sample is the standard of The World Health Organization and of Uganda for drinking water (WHO, 1993; Howard et al, 2003); the absence of E. coli does not ensure that water is safe for consumption (WHO, 2006)
The application of sanitary inspection forms (SIFs) and bacterial monitoring to assess sources in tandem may aid in drinking water source selection and in development of protection strategies for those sources
Summary
The quality of drinking water is dependent on the initial quality of the source water used and the level of treatment provided. The authors suggest that Petrifilms were suitable for screening water sources that exceed recreation standards for bacterial contamination. The purpose of the current study was to evaluate the potential to use a low-tech method for enumerating E. coli in potential drinking water sources (EC 3MTM PetrifilmTM; hereafter Petrifilms) and to evaluate the appropriateness of sanitary surveys of surface water sources in Uganda.
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