VPE 511: Environment and Environmental Hygiene (2+1)

COLIFORM BACILLI

• The coliform bacilli constitute a group of organisms of diverse origin.
• The most important member is Escherichia coli whose natural habitat is the human and animal intestine .
• The other member E. aerogenes and E. cloacae are found in soil and on vegetation and they are regarded as saprophytes. All these microbes may be found in sewage.
• The first type is dominant organisms found in faeces and for this reason is commonly referred to as faecal coli whilst the other two referred to as non faecal coli.
• The E. coli  does not normally live for any length of time outside the intestinal tract of man and animals, the presence of this organism in water can be regarded as almost certain evidence of recent excretal pollution of human or animal origin.
• There is no very satisfactory method at present for distinguishing between faecal coli of human origin on the one hand and those of animal origin on the other. But the topographical circumstances relevant to the water supply may sometime help in assigning faecal coli to their probable source.