Comparative Studies of Enterococci and Escherichia coli as Indices of Pollution.

The presence of coliform bacteria in water and in or on other foods depends on many environmental factors, each of which must be determined separately for each item of food in question. When a correlation is found to exist between insanitary methods of food production and the presence of Escherichia coti in the finished product, the presence of confirmed fecal strains of coliform organisms can be interpreted as having sanitary significance. Under these circumstances, however, if environmental factors tend to permit or promote multiplication of the normal flora of organisms, together with the coliform contaminants, an interpretation of the sanitary significance of E. coli becomes involved. Despite these limitations, the coliform bacteria have long been considered "the only bacterial group which can be used with even a reasonable degree of accuracy as a measure of pollution" (Hunter, 1939). It is not improbable that intestinal microorganisms, other than E. coli, have not been investigated because of technical difficulties. With the development of "SF" medium (Hajna and Perry, 1943) and the application of a few taxonomic requirements (Sherman, 1937), the enterococci represent a group of intestinal microorganisms which can now be readily isolated and identified. The applicability of the enterococci as an index of pollution thus merits consideration. It has been demonstrated that enterococci are normally present in the intestinal tract of man and many warm-blooded animals (Sherman, 1937; Ostrolenk and Hunter, 1946). The work of the latter demonstrated that, in. 37 per cent of 51 fecal specimens examined, enterococci occurred in equal or in greater numbers than E. coli. In the remaining-63 per cent of the specimens, E. coli exceeded enterococci numerically by from one to five decimal dilutions. The lower number of enterococci, as compared with E. coli, in human and animal feces does not in itself necessarily minimize the potential sanitary significance of fecal streptococci. It does, in fact, support the group as a more reliable index of pollution, provided there is a significant relationship between the presence of the organism and recognized pollution sources. Other factors that must be considered include distribution and reproductivity in nature, survival of temperature and chemical treatments, and longevity.