• coli is a normal inhabitant of the large intestine in humans and other warm-blooded animals.
  • This species may have a role in vitamin synthesis in the intestinal tract, particularly in the case of vitamin K.
  • coli is present in large numbers in the faeces due to the ideal warm, moist conditions and the abundance of food.

Pathogenic (disease-causing) E. coli strains 

  • Although most strains of coli are non-pathogenic and restricted to the large intestine, some strains are capable of adhering to the small intestine.
  • Pathogenic strains of coli include enteropathogenic, enteroinvasive, enterotoxigenic and enterohemorrhagic strains.
  • These pathogenic strains release toxins that induce fluid loss from the cells of the small intestine, causing symptoms of diarrhea.
  • Hemorrhagic colitis (HC) is the acute disease caused by coli. HC results in severe abdominal cramps, watery diarrhea, and lower intestinal bleeding; with occasional vomiting and fever. Particularly in the case of E. coli0157:H7, hemolytic uremic syndrome or renal failure can also occur.
  • Although not life threatening to healthy adults, pathogenic strains of coli can be fatal to young children, the elderly, and immunocompromised persons.

    Water Lab

E coli as an indicator organism

  • It is not economically feasible or warranted to examine water for the presence of all possible pathogens.
  • Routine monitoring of pathogens which can cause serious diseases such as cholera, typhoid, salmonellosis, and dysentery, is unreliable since these organisms are difficult to detect
  • It is universally accepted that a group of microorganisms that came from the same source as human pathogens (i.e., the gastrointestinal tract) can be used to indicate the presence of pathogens.
  • If “indicator” microorganisms are detected in a water source, it indicates the presence of faecal contamination and therefore possible presence of pathogenic microorganisms in the water.
  • coli is the most reliable indicator of fecal contamination in water.
  • It follows that coli can be used as an “indicator” for the possible presence of other faecal microorganisms of public health significance such as Azotobacter sp, Campylobacter sp, Helicobacter sp, Salmonella sp, Shigella dysenteriae, Vibrio cholerae, Yersinia sp, Adenoviruses, and Enteroviruses

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