What are coliforms? Why are they important in assuring water quality? Why is E. colithe indicator bacterium for fecal contamination?

Answer:

Coliform bacteria are rod shaped Gram-negative non-spore forming and motile or non-motile bacteria which can ferment lactose with the production of acid and gas when incubated at 35-37°C. Due to the limited ability of certain coliform bacteria to ferment lactose, the definition has changed to bacteria containing the enzyme B-galactosidase. They are used as indicator of sanitary quality of food and water. Since they are universally present in large numbers in the feces of warm-blooded animals. They not normally causes serious illness, but they are easy to culture, and their presence is used to indicate that other pathogenic organism if fecal origin may be present. Such pathogens include disease-causing bacteria, viruses, protozoa and multicellular parasites (e.g. Citrobacter, Enterobacter, Hafnia, Klebsiella and Escherichia).

E. coli are almost exclusively of fecal origin and their presence is thus an effective confirmation of fecal contamination (recent contamination in most cases). E. coli cannot live long outside the host, for this reason, their presence is water is evidence that water was recently contaminated. If contaminated animal meat (such as beef) is consumed (not cooked properly) it can cause the consumer to become ill. Most strains of E. coli are harmless, but other can cause bloody diarrhea, stomach cramps, vomiting and fever, as well as pneumonia, other respiratory illnesses, and urinary tract infections.