Assay of extracellular proteinases using a colorimetric collagen substrate for the differentiation of Serratia in the tribe Klebsielleae.

The gelatin test has been utilized for many years as a characteristic to separate the genus Serratia from other members of the tribe Klebsielleae. Gelatin is a large protein matrix that cannot diffuse into bacterial cells. Microbes that attack gelatin do so by producing extracellular proteinases. The measurement of gelatinase has suffered from the lack of a definable endpoint and the inability to quantitate the enzyme. A method was developed utilizing an azo-dye-labelled collagen substrate that could measure the extracellular proteinase of serratia. The test was easy to perform, inexpensive, and potentially quantifiable. The azo-dye test corresponded completely with the gelatinase tests.