Drinking water is often contaminated with microorganisms. Common microorganisms found in drinking water are Cryptosporidium, Anabaena species, copepods, rotifers, E. coli, Rhizopus stolinifer, Naegteria fowleri, Legionella Pneumophila, Chaetomium species, Salmonella Enterica. Coliform bacteria, part of Enterobacteriaceae family, can be found in human and animal waste, known as faecal coliform bacteria and E. coli is sub group of faecal coliform bacteria (University of Wisconsin, n.d.). Escherichia coli (E. coli) is pathogenic bacteria found in the digestive tracts of human and animals and plant and soil material.
Water is contaminated with coliform bacteria from different sources. Anthropogenic sources such as failing septic tanks, leaking sewer lines, wastewater treatment plants, and combined sewer overflow (CSOs), urban storm water runoff and animal sources such as manure spread on land, livestock in runoff or in streams, improperly disposed farm animal wastes, pet and bird wastes are potential sources of E. coli in drinking water (University of Wisconsin, n.d.).
Biological quality of drinking water is tested by total coliform test. The absence of coliform bacteria in water is considered as bacterially safe. However, presence of E. coli indicates faecal contamination with human or animal wastes. Cellular functions such as protein synthesis, mitochondrial function, cytoskeletal function, cell division, ion secretion, transcription and apoptosis are affected by E. coli (Kaper et al., 2004).
Different types of E. coli can be found contaminated with water. Kaper et al. (2004) categorised intestinal E. coli into six categories as enteropathogenic E.coli (EPEC), entrohaemorrhagic E. coli (EHEC), enterotoxigenic E. coli (ETEC), enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC) and diffusively adherent E. coli (DAEC). Enterohaemorrhagic Escherichia coli (EHEC) causes abdominal cramps and diarrhoea and more dangerous among other types of E. coli.
Department of Environmental Services (2010) Interpreting the Presence of Coliform Bacteria in Drinking Water. [Online] Available at http://des.nh.gov/[Accessed on 14 July 2013].
Kaper, J.B., Nataro, J.P., Mobley, H.L.T. (2004) Pathogenic Escherichia Coli. Nature Reviews: Microbiology. Vol 2.
University of Wisconsin (n.d.) Bacteria and Water Quality. [Online] Available at www.uwex.edu [Accessed on 15 July 2013].