Dehydrated Culture Media

Dehydrated Culture Media

Dehydrated Culture Media products are formulated to supply the required nutrients to allow for the growth of microorganisms. Used in combination with a variety of selective agents and incubation conditions a wide range of specific organisms can be isolated. With careful raw material selection of the various media components E&O can ensure a consistent level of quality and performance. For each formulation the necessary ingredients are accurately weighed, combined and blended together to produce a homogenous powdered product.

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  • Alkaline peptone water is generally used as an enrichment medium in the isolation of Vibrio spp. from faeces. This medium may also be used for the enrichment of Vibrio spp. from food and water samples. First developed by Shread, Donovan and Lee as an enrichment broth for the growth of Aeromonas spp., Cruickshank showed that with a higher pH the medium can be used for the enrichment of Vibrio spp. The peptone is the source of the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance. The high pH of the medium inhibits most enteric organisms for at least 24 hours.
  • Bacillus cereus (MYP) agar is intended for the selective enumeration of Bacillus cereus in food samples. This medium utilizes two reactions namely mannitol fermentation and lecithinase production to differentiate Bacillus cereus from other related species. As B. cereus is mannitol negative the colonies are pink in colour due to the presence of the phenol red pH indicator. Lecithinase production (from the addition of egg yolk) is indicated by a white precipitate around the colonies. This medium meets the requirements of ISO 7932:2004. Beef extract and peptone provide the required carbon, nitrogen and vitamins. Sodium chloride helps maintain the osmotic balance and phenol red is the pH indicator. Mannitol is a fermentable carbohydrate. The medium is made selective by the inclusion of polymyxin B sulphate (LS0020). NB: This is a basic medium only and contains no additional supplement. It should be noted that some Proteus spp. and Gram-positive cocci may grow on this medium. Related Supplements : LS0020 Bacillus cereus Selective Supplement, BM0140 Egg Yolk Emulsion
  • Bacillus cereus agar (PEMBA) is used for the selective isolation and enumeration of Bacillus cereus in food samples. It is said to be particularly suitable for the detection of small numbers of Bacillus cereus particularly in the presence of other contaminating organisms. Bacillus cereus agar (PEMBA) is based on the formulation developed by Holbrook and Anderson. The peptone provides the required carbon, nitrogen and vitamins. Mannitol is a fermentable carbohydrate. Bromothymol blue is a pH indicator used to detect mannitol fermentation. Sodium chloride maintains the osmotic balance. Magnesium sulphate provides divalent cations and sulphate. Di-sodium hydrogen phosphate and potassium dihydrogen phosphate are buffering agents. Egg yolk emulsion (BM0140) must be added to this media to assess lecithinase production. Sodium pyruvate is present to improve egg yolk precipitation and enhance B. cereus sporulation. The medium is made selective by the inclusion of polymyxin B sulphate (LS1051).
  • Bacteriological peptone is an economical source of nutrients provided by a balanced mixture of meat peptones and tryptone.The growth requirements of most non fastidious organisms will be fulfilled by the range of amino acids, peptides and proteoses in this mixture.  
  • Baird Parker agar is a selective medium for the isolation and presumptive identification of coagulase-positive staphylococci. This medium is used extensively for detecting Staphylococcus aureus in foods, dairy products, and other materials. Enzymatic digest of casein, meat extract and yeast extract provide the required carbon, nitrogen and vitamins. The medium is made selective by the inclusion of lithium chloride and the addition of potassium tellurite. Glycine and sodium pyruvate are included as growth enhancers while the pyruvate also acts as a neutraliser of toxic peroxides. Coagulase positive staphylococci are differentiated by the addition of egg yolk tellurite (BM0530) due to their ability to break down the egg yolk. Clear zones around colonies form due to the proteolytic action of lecithinase. A secondary opaque zone, surrounding presumptive positive colonies, may also form due to lipase activity. Potassium tellurite is reduced by staphylococci giving rise to blackening of colonies. NB: Any black colonies (with halo (typical) or without the halo (atypical)) on this medium must be confirmed as Staphylococcus aureus by further tests (e.g. coagulase test or latex agglutination etc.) Related Supplements : BM0530 Egg Yolk Tellurite
  • KM8006

    Beef Extract

    Beef extract is sourced from bovine tissue and supports the nutritive needs of microorganisms. Providing a mixture of amino acids, peptides, minerals and vitamins this product is recommended for use in microbiological culture media for the examination of water, milk and other materials.  
  • Bile Aesculin Medium is generally used for the differentiation and presumptive identification of Group D streptococci (enterococci). Enterococci hydrolyse aesculin forming, amongst other products, aesculetin which in turn combines with Ferric ammonium citrate producing a dark brown or black complex. The presence of Bile salts in the medium inhibits gram positive organisms other than enterococci. The medium can also be used for the presumptive identification of certain organisms within the Enterobacteriaceae group such as Klebsiella spp., Enterobacter spp., etc.
  • Blood agar base No. 2 is a general-purpose medium enriched with various concentrations of horse or sheep blood and is suitable for the isolation of most organisms including many fastidious anaerobes of clinical significance. Haemolysis observations may vary with the type of blood being used. Previous studies have shown that sheep blood provides the most reliable colony and haemolysis characteristics. The peptone, yeast extract and liver digest act as nitrogen, carbon and vitamin sources in this medium. Sodium chloride maintains osmotic balance. Related Supplements : Defibrinated Sheep Blood, Defibrinated Horse Blood, LS0008 Staph/Strep Selective Supplement, LS0017 Neomycin Selective Supplement