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Selenite cystine broth is a modification of selenite F broth and is for the selective enrichment of Salmonellae spp. from clinical, food and environmental specimens. The peptone acts as a nitrogen, carbon and vitamin source. Lactose is a fermentable carbohydrate and sodium phosphate is a buffer. L-cystine is used to enhance the recovery of Salmonellae spp. in low numbers. The medium is made selective by the addition of sodium biselenite (KM8021). Following overnight incubation subculture(s) are usually made on to one or more of the many selective enteric solid media. -
Developed by Leifson, selenite F broth is a medium for the selective enrichment of Salmonella spp. from both clinical and food samples. The peptone acts as a nitrogen, carbon and vitamin source. Lactose is a fermentable carbohydrate and sodium phosphate is a buffer. The medium is made selective by the addition of sodium biselenite (KM8021). Following overnight incubation subculture(s) are usually made on to one or more of the many selective enteric solid media.
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Selenite mannitol broth is a modification of selenite broth and is for the selective enrichment of Salmonellae spp. from clinical, food and environmental specimens. Comparisons have shown that mannitol selenite broth is better than other enrichment broths for the isolation of Salmonellae spp. The peptone acts as a nitrogen, carbon and vitamin source. Mannitol is a fermentable carbohydrate and sodium phosphate is a buffer. The medium is made selective by the addition of sodium biselenite (KM8021). The fermentation of mannitol by Salmonellae spp. is said to correct the alkaline pH swing which can occur during incubation. Following overnight incubation subculture(s) are usually made on to one or more of the many selective enteric solid media.
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Sheep Blood Agar Base has been developed to provide a nutrient rich medium compatible with sheep blood for the cultivation of many bacteria, especially fastidious Streptococcus spp., without affecting haemolytic reactions. Alternative culture mediums, such as Blood agar base No. 2, can results in mixed haemolytic reactions for some Streptococcus spp. This is thought to occur due to the trace amounts of fermentable carbohydrates in yeast extract and the physiological difference between sheep and horse blood. The tryptone, peptone, and yeast extract provide the required nitrogen, carbon and vitamins in the medium. Sodium chloride maintains the osmotic balance. Related Supplements : LS0008 Staph/Strep Selective Supplement
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For in vitro diagnostic use. KM0159 SIM Medium is a multi-purpose medium for the differentiation of Enterobacteriaceae. This is best described as a multi-purpose medium for the differentiation of Enterobacteriaceae that combines three individual tests into a single medium (hydrogen sulphide production, indole formation and motility). 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. H₂S positive organisms turn the medium black due to the formation of hydrogen sulphide in the presence of the sodium thiosulfate and ferric ammonium citrate often making it difficult to determine the other parameters. Indole production is tested for by layering a small amount of Indole Reagent (Kovac’s) onto the surface of the medium. A positive result is indicated by the formation of a pink colour at the interface of the reagent and the medium. The enzymatic digest of casein and enzymatic digest of animal tissue provide the required carbon, nitrogen, and vitamins in this medium. Ferric ammonium citrate and sodium thiosulfate are used to detect hydrogen sulphide production. The low concentration of agar allows for a semisolid media which is used for motility detection.
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This medium can be used as a screening method for the differentiation of enterobacteriaceae based on the ability of some species to utilise citrate as a sole source of carbon. It is often used as a screening test for Klebsiella pneumoniae (positive reaction) while Escherichia coli is negative. Species that metabolize citrate as their sole source of carbon and ammonium as the sole source of nitrogen cause an increase in alkalinity of the medium resulting in a colour change from green to blue due to the presence of the pH indicator bromthymole blue.
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This medium was originally described by Slanetz and Bartley(1) for the enumeration of enterococci from water samples using membrane filtration. The medium has also become useful as a direct plating medium. Tryptose and yeast extract provide the required carbon, nitrogen and vitamins. Glucose is a fermentable carbohydrate. The di-potassium hydrogen phosphate acts as a buffer. Selectivity is achieved through the addition of sodium azide which is used to suppress the growth of Gram-negative organisms. The medium contains tetrazolium chloride, which is reduced by enterococci to the insoluble red dye formazan resulting in dark red colonies of enterococci on the agar. It should be noted that this reaction is not exclusive to enterococci and colonies should be confirmed by additional testing e.g. aesculin hydrolysis.
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Sorbitol MacConkey agar is a differential medium for the isolation of Escherichia coli 0157:H7 based on the formulation by Rappaport and Henig. It differs from other MacConkey mediums in that lactose has been replaced by sorbitol. As Escherichia coli 0157:H7 does not ferment sorbitol it produces pale translucent colonies whereas most other strains of Escherichia coli are sorbitol positive and produce pink colonies. Although it should be noted that colonies that are sorbitol positive can revert and possibly be mistaken as sorbitol negative. Tryptone and meat peptone provide the required carbon, nitrogen and vitamins. Sorbitol is a fermentable carbohydrate and neutral red is a pH indicator. Bile Salts no.3 and crystal violet are selective agents and together inhibit Gram-positive cocci. Sodium chloride maintains the osmotic balance. If required, the selectivity of the medium may be increased by the addition of cefixime (0.05mg/L) and potassium tellurite (2.5mg/L). Related Supplements : LS0013 Escherichia coli 0157 Selective Supplement
