-
This is a modification of the original Nitrate Reduction Broth which is generally used as one of a series of identification tests for the enterobacteriaceae group of organisms. In addition to allowing the testing of Nitrate Reduction this formulation also contains Agar making it possible to concurrently determine motility. The medium is recommended for use in the confirmatory testing of Clostridium perfringens in water samples. The medium is inoculated by “stabbing” the test organism into the medium, using an inoculating needle or straight wire, and after appropriate incubation motility is demonstrated by diffusion of the organism from the line of inoculation into the medium. The Nitrate Reduction Test is a test for the presence of the enzyme nitrate reductase which, in the presence of an appropriate electron donor, reduces nitrate to nitrite. Following incubation “Nitrate Reagent” is added to the medium and a positive reaction is indicated by the formation of a red colour. For full details of the test method reference should be made to appropriate publications. -
This is a modification of the traditional liquid media used to differentiate and identify micro-organisms. It consists of a Buffered Tryptose base containing Lactose and solidified with Gelatin which permits detection of Gelatin Liquefaction where appropriate. Phenol Red Indicator is also included as an indicator of pH change. -
This is best described as a multi-purpose medium for differentiation of enterobacteriacae that combines three individual tests into a single medium. For use the medium is inoculated by making a single stab into the medium with a straight wire (or equivalent) using a pure culture (or discrete single colony) of the test organism. Following incubation it is recommended that the medium should first of all be examined to determine whether or not the organism is motile. The presence of motility is apparent by the organism tracking out from the line of inoculation and often turning the medium turbid. Non-motile organisms generally grow within the stab line leaving the surrounding medium clear. Urease positive organisms (e.g. Proteus spp) turn the medium bright red due to the hydrolysis of the Urea in the presence of the Phenol Red Indicator often making it difficult to determine the other parameters.Indole is tested for by layering a small amount of Indole Reagent (Erlich’s or Kovac’s appear to work equally well) onto the surface of the medium and allowed a few minutes to react. A positive result is indicated by the formation of a red line at the interface of the reagent and the medium.
