Inexpensive, disposable presence-absence test for coliforms and Escherichia coli in water
1989
Lee, R.M. | Hartman, P.A.
Six-ounce (151-g) Whirl-Pak bags containing 3.05 g of dehydrated Presence-Absence (P-A) Broth and 5 mg of 4-methyl-umbelliferyl-beta-D-glucuronide (MUG) were pasteurized with 10 kGy of gamma irradiation. To conduct a "bag" P-A test, 100 ml of water sample were added to a bag. The bag was closed, the medium was dissolved by massaging the bag for about 15 sec, and the bag was then placed in a rack for incubation. The bag method was compared with P-A tests conducted in 160-ml glass bottles and 200-ml polysulfone bottles, as well as with a 5-tube Lauryl Tryptose Broth (LTB) most-probable-number (MPN) method. Twenty-nine surface-water samples (11 streams, 7 rivers, and 11 lakes), 9 well-water samples, and 2 sewage effluents were examined. Chi-square analyses of the results revealed that no significant difference (P less than or equal to 0.1) existed among the different P-A tests. The hydrolysis of MUG provided excellent Escherichia coli detection and was easiest to determine in the bags.
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