| 摘要 |
The general method involves contacting a bacterial colony with a .beta.-D-ga lactosidase substrate and a carbon source (e.g. adonitol , esculin, salicin, amygdalin, cellobiose, etc.) metabolizable by a plurality of coliform species but not metabolizable by E. coli, an d detecting reaction product signals of the substrate and carbon source. The absence of both reaction product signals indicates the presence of non- coliform bacteria, the presence of both reaction product signals indicates t he presence of non-E. coli coliform bacteria; and the pr esence of the .beta.-D-galactosidase substrate reaction product signal and absence of the carbon source reaction product signal indicates the presence of E. coli. A signal may identify a reaction product per se (e.g. a colored pro duct derived from a chromogenic form of the substrate or from a chromogenic reagent which interacts with the product, etc.), or an effect of a reaction product on or at the colony (e.g. catabolite repression, growth, localized pH change, etc.). In a preferred embodiment, the .beta.-D- galactosidase substrate reaction product signal is provi ded directly by a .beta.-D-galactosidase reaction product and the carbon source reaction product signal is provided by carbon source reaction pro duct-induced catabolite repression of the .beta.-D-galactosidase substrate reaction produ ct signal at a portion of the colony.
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