The recovery of coliform from food or water above a certain numerical limits implies that diseases causing organism may be present and the food is potentially dangerous for human consumption.
Differentiation of faecal from non faecal coliform:- In many laboratories differentiation of faecal coliforms from non faecal coliform is considered of limited value in determining the suitability of water or food for human consumption, as contamination with either type renders water or food potentially dangerous and unsafe from a sanitary stand point. However, differentiation may be advantageous under some conditions where the identity of specific members of the group present may indicate the source of pollution. Coliform such as a aerogenes and E. freundui only occessionally found in the intertinal contents of man and animans (6%). They are normally found in soil. Therefore, there presence in food or water is of doubtful sanitary significance. On the other hand E.coli, rarely found in the soil but constitute the predominant organisms in the intestinal contents of man and animals. Therefore, isolation E.coli in food may strongly suggest the food has been polluted with feaces than isolation of A.aerogenes or E.freundii.