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This is a medium that can be used to differentiate between some of the Enterobacteriacae on the basis of four reactions, fermentation of Lactose, Glucose and Sucrose and the production of H2S. For use the medium is inoculated using a pure culture of the test organism which should be smeared onto the surface of the slope and stabbed into the butt of the medium. For details of the many reactions that may arise during the use of this medium reference should be made to one of the many standard textbooks. -
This is a plate count agar originally suggested by the American Public Health Association for the estimation of total viable counts in food and dairy products.
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This is a general-purpose medium supporting a wide range of organisms. It conforms to the requirements of the United States Pharmacopeia for sterility testing of pharmaceutical products as well as being suitable in all areas of bacteriological investigation. -
Tryptone Soya Broth (Modified) with Novobiocin (20mg/L) This is a selective enrichment broth for the isolation of Escherichia coli 0157, primarily from food and food products, and is capable of detecting the organisms even when they are present in small numbers. It is also increasingly being used in clinical laboratories when screening faecal samples. Based on Tryptone Soya Broth it is made selective for Escherichia coli 0157 by the addition of bile salts and Novobiocin and is also buffered to maintain the pH during incubation. This medium is generally used in conjunction with selective agar subculture (e.g. Sorbitol MacConkey Agar with Cefixime Tellurite – (CT-SMAC)). -
Tryptone Water is an alternative medium to Peptone Water and more reliable for the testing of Indole production. The medium has a high content of Tryptophan that many organisms, particularly coliforms, break down to form Indole. After incubation add a few drops of Indole reagent to determine the Indole reaction (Red colour is Positive). -
Recent developments in culture media have given rise to the use of chromogenic substrates as a means of differentiating bacteria particularly among the coliform group of organisms. This is one such medium and has been developed primarily as a selective medium for the isolation and enumeration of Escherichia coli in food samples. Based on Tryptone Bile Agar it incorporates the chromogenic agent X-glucuronide, which detects glucuronidase activity, the same enzyme as is detected by MUG reagent. Escherichia coli can be differentiated from other coliform organisms by the presence of glucuronidase resulting in the colonies being blue/green while the other coliforms are colourless. For information on the full technical detail as to the functionality of this medium reference should be made to the many publications available. -
Based on Christensen’s Medium this medium is generally used to detect rapid urease activity of Proteus spp although it can be used to detect urease activity of other Enterobacteriaceae. When used for the later purpose it is necessary to increase the incubation time to as long as 48 hours. -
A modification of Christensen’s Medium by Maslen this medium is generally used to detect rapid Urease activity of Proteus spp although it can be used to detect Urease activity of other Enterobacteriaceae including Urease producing Salmonella and Shigella. Unlike Christensen’s Medium when used for the later purpose it is not necessary to increase the incubation time.
