Total Coliforms|Fecal Coliforms|E- Coli-Defines

Total Coliforms:Coliforms are a group of gram-negative, rod-shaped bacteria that are nonpathogenic and nonspore forming. The most common coliform genera are Escherichia, Enterobacter, Citrobacter,Serratia, and Klebsiella, with E. coli being the most abundant in the gut of humans and other warm-blooded animals. Coliform bacteria are identifiable by their ability to ferment lactose to produce acid and gas within 48 h, when incubated at 35 DegC.

However,the development and use of media and commercial kits to detect coliformsTotal Coliforms based on specific enzymes (b-galactosidase) have expanded the definition of coliforms to include many genera of bacteria, some of which live primarily in the environment rather than in the gut of warm-blooded animals.Because they are found in the intestines of humans, domestic animals, and wild animals, coliforms are shed in feces along with pathogenic organisms present in the gut of infected animals, and can be detected in water with relative ease; total coliforms have been used by the US Public Health Service since 1914 as the standard for sanitary quality of water. However, because some coliforms occur naturally in soils, aquatic environments including drinking water distribution systems, and plant matter where they can proliferate, and because pathogenic organisms do occur in water and disease outbreaks have occurred even when coliforms are not present, they are neither reliable indicators of fecal contamination nor indicators for the presence of pathogenic microorganisms.

Fecal Coliforms:Fecal coliforms (FC) are a subgroup of total coliforms consisting mainly of E. coli,Enterobacter, and some Klebsiella. They inhabit the intestines of warm-blooded animals.Because they can grow and ferment lactose at a relatively high temperature (Approximate 45.08 Deg C),

Escherichia Coli:Escherichia coli is found in the intestines of humans and other warm-blooded animals where it performs important physiological functions. They are not normally found living in other environments, but have been reported to multiply in E-coli surface waters, especially in tropical environments. Several strains of E. coli are usually non disease causing, although illnesses such as septicemia and urinary tract infections have been reported, especially in immuno compromised individuals. Some E. coli strains (e.g., E. coli O157:H7) produce toxins that may cause diarrhea or even death in humans, particularly in elderly people and children
A historical account of the use of E. coli as an indicator bacterium for fecal contamination can be found in Feng et al. E. coli was first proposed as an indicator species in 1892. But, it was only after the development of newer methods for rapid identification and differentiation of the species from the other members of the fecal coliform group that it officially came into use as an indicator species.

 

Author: T.P.Sivanandan

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