Define the Criteria for an Indicator Organism?

Following criteria are suggested for an indicator organism:

i. It should be suitable for the analysis of all types of water, i.e., tap, river, ground, impounded, recreational, estuary etc.

ii. It should be present whenever enteric pathogens are present.

iii. It should survive longer than the hardiest enteric bacterium.

 iv. It should not reproduce in the contaminated water and produce an inflated value.

v. Testing procedure should be easy, specific, have high sensitivity and can detect even low levels of indicator.

vi. It should be harmless to human.

vii. Level of indicator organism in contaminated water should have some direct relationship to the degree of faecal pollution.