Evaluation of Methods for Coliform Counts in Farm Pond Waters

Abstract

In an effort to determine the most accurate method for estimating the density of coliform organisms in untreated farm pond water, 46 samples were analyzed in parallel by: the membrane filter technique; the MPN method with confirmation on BGB broth; the MPN‐BGB method, followed by the SMC test on all positive BGB tubes; and, the SMC test alone. If it is assumed that the MPN‐BGB‐SMC method gave the closest approximation of the true coliform population, then, in terms of both average and individual results, the SMC method was most accurate. MF results tended to be somewhat high, and the MPN‐BGB method showed a definite bias toward high values. The results emphasize the need for exercising care in the choice of method for determining coliform density of moderately polluted water in small impoundments, such as farm ponds. The BGB‐confirmed test should not be employed unless it is certain that results from this method are in accord with results from the completed test on a particular water source.

Coliforms, Enterococci, Thermodurics, Thermophiles, and Psychrophiles in Untreated Farm Pond Waters

“…The specific procedure was initial inoculation into lactose, three tubes per dilution, with confirmation in brilliant green lactose bile broth (BGB). All positive BGB tubes were streaked on eosin methylene blue (EMB) agar, followed by transfer of colonies to secondary lactose broth and agar slant (Malaney et al, 1961).…”