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
  • Brain heart infusion agar is very nutritious general-purpose medium and is suitable for the isolation of most micro-organisms including many fastidious organisms. The formulation is a modification of that from Rosenow and Hayden. The medium is not recommended for the determination of haemolytic reactions because of the glucose content. The nitrogen, vitamin and carbon sources are supplied by the Brain-Heart infusion solids and peptone. Glucose serves as the carbohydrate source and sodium chloride aids in maintaining the osmotic balance. A phosphate buffer, disodium hydrogen phosphate, is incorporated to help neutralize any acids produced as a result of glucose utilization and thus maintain viability of the organisms. NB: Organisms that produce large amounts of acid in the medium may overwhelm the buffering system and as a result may ‘auto-sterilize’ the culture.
  • Brain heart infusion broth is very nutritious isotonic medium with a low concentration of glucose to stimulate early growth. The formulation is a modification of that from Rosenow and Hayden. Brain heart infusion broth is suitable for the isolation of most micro-organisms including many fastidious organisms and, with the appropriate enrichment, is suitable as a base for blood culture medium. The nitrogen, vitamin and carbon sources are supplied by the Brain-Heart infusion solids and peptone. Glucose serves as the carbohydrate source and sodium chloride aids in maintaining the osmotic balance. A phosphate buffer, disodium hydrogen phosphate, is incorporated to help neutralize any acids produced as a result of glucose utilization and thus maintain viability of the organisms. NB: Organisms that produce large amounts of acid in the medium may overwhelm the buffering system and as a result may ‘auto-sterilize’ the culture.  
  • Brain-heart infusion solids is a dehydrated infusion of porcine brains and heart. This product can be used in preparing microbiological culture media providing nitrogen, vitamins, minerals and amino acids.  
  • Brilliant green agar is for the selective isolation of Salmonella spp., other than S. typhi. Brilliant green agar was first cited by Kristensen et al. in 1925 but was subsequently modified by the Netherlands Institute for Public Health. Brilliant green agar is generally used in conjunction with XLD agar (KM0013) as a secondary plating medium for subculture from selective enrichment media in food and environmental testing. It should be noted that the medium is highly selective and therefore not suited to the isolation of Salmonella spp. from samples where the numbers may be low. Beef extract, peptone and yeast extract provide the required carbon, nitrogen and vitamins. Di-sodium hydrogen phosphate and sodium di-hydrogen phosphate are buffering agents. Lactose and sucrose are fermentable carbohydrates. Phenol red is a pH indicator and turns the medium yellow during lactose and/or sucrose fermentation. Brilliant green inhibits Gram-positive bacteria and Gram-negative bacilli other than Salmonella spp. NB: It is not recommended that this medium be used for the isolation of Salmonella typhi or Shigella spp. Related Supplements : LS0024 Novobiocin Supplement (20mgs/L)
  • Brucella broth is a non-selective medium for the cultivation of Brucella spp. and other fastidious microorganisms. Brucella broth has been developed from the APHA formulation for Albimi broth. (1&2) The enzymatic digest of casein, enzymatic digest of animal tissues and yeast extract provide the necessary carbon, nitrogen and vitamin sources for this medium. Glucose is a fermentable carbohydrate and sodium chloride maintains the osmotic balance of the medium. Sodium bisulfite is added to enhance growth. References (1) Hausler, W. J. (ed.). 1976. Standard methods for the examination of dairy products, 14th ed. American Public Health Association, Washington, D.C. (2) ISO 10272-1:2006. Microbiology of food and animal feeding stuffs – Horizontal method for detection and enumeration of Campylobacter spp.
  • Brucella Medium Base is a general purpose medium for the cultivation of Brucella spp. and other fastidious microorganisms. Brucella Medium Base has been developed from the APHA formulation for Albimi broth. The peptones act as carbon, nitrogen and vitamin source in this medium. Glucose is a fermentable carbohydrate and sodium chloride maintains the osmotic balance of the medium.
  • Formulated to ISO 6579, Buffered Peptone Water (BPW) is a pre-enrichment medium designed to help sub-lethally damaged Salmonella spp. recover before introducing them into a selective enrichment medium. Enzymatic digest of casein is the source of the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance in the medium. Di-sodium hydrogen phosphate and potassium di-hydrogen phosphate act as buffers in the medium. This nutritious medium is free from inhibitors and is well buffered to maintain pH 7.0 for the incubation period. Sub-lethal injury to Salmonella spp. occurs in many food processes and this pre-enrichment step greatly increases the chance of their recovery, especially if a low number of cells are present in a sample.  
  • Burkholderia cepacia agar base is a selective medium for the detection and isolation of Burkholderia cepacia from cystic fibrosis (CF) patients. This is an important opportunistic pathogen in CF patients and can lead to fatal infection in approximately 20% individuals that have been colonised with B. cepacia complex organisms. This medium is based on the PC medium described by Gilligan et al. Magnesium sulphate, ammonium sulphate and ferrous ammonium sulphate supports the growth of B. cepacia. Potassium di-hydrogen phosphate and di-sodium hydrogen phosphate are buffering agents, used to maintain the pH the medium. The phenol red is used as a pH indicator. If the sodium pyruvate in the medium is metabolised by B. cepacia alkaline by-products are produced which raises the pH. This causes the colour of the medium to turn pink/red around sections of heavy growth on the medium. Bile salts and crystal violet are selective agents. The associated selective supplement for this medium, LS0125, contains ticarcillin and polymyxin B which further improves the selectivity, particularly with the inhibition of Pseudomonas spp. Related Supplements : LS0125 B.cepacia Selective Supplement, LS0026 Pseudomonas CFC Selective Supplement