The Determination of the Presence of Coliform Bacteria from Selected Sources by Means of the Most Probable Number MPN Method

Coliform bacteria are good indicator organisms for the presence of pathogenic bacteria due to their realtionship with these pathogenic bacteria, their relative ease of determination by simple methods, and by their occurrence in large quantities in human feces.The MPN method used in this experiment is one of the prescribed techniques for the determination of these coliform bacteria from the Standard Methods for the Examination of Water and Wastewater as prescribed by the EPA.It consists of three stages, each of which necessitates a positive result for the previous stage.Thefirst stage (presumptive test) determines the gas-producing coliform characteristic during lactose-fermentation.The second stage (confirmed test), determines the gram-reaction and also the lactose fermentation abilities of the organism, while the last stage (completed test) determines the endospore presence to determine if the organisms in the sample indeed are coliforms.The number of coliforms or bacteria present is readily seen with the use of a special table and then the statistically estimated numbers are determined.The samples, however, did not produce positive results for the presence of coliforms.Enventhough there was a large MPN value for one of the samples, about 1100 MPN per 100 ml, the sample still tested negative in the last stage.It is therefore suffice to say that the samples did not present any health risks for humans.Future researchers should, however, device or perform other more specific procedures due to the fact that there might have been still coliforms present but these may have been negated by possible endospore-forming relatives.
Human health has always been a hard condition to preserve and the detection and control of pathogens in the environment have been the very key to the success of the human race.Although microbial pathogens are relatively few in comparison to the total number of microorganisms, their detection hav…

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