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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  • Columbia agar is a general-purpose, non-selective medium capable of supporting the growth of most micro-organisms based on the original Columbia agar formulation described by Ellner et al. from Columbia University. With further enrichment using blood, most fastidious organisms can be isolated and their β-haemolytic reactions can be determined in order to aid identification. The peptone is the source of the required nitrogen, carbon and vitamins. Starch increases growth of Neisseria spp., and enhances the haemolytic reactions of some streptococci. This medium is relatively free of reducing sugars, which have been reported to adversely influence the haemolytic reactions of β-haemolytic streptococci . Supplementation of the base medium with blood (5- 10%) will provide additional growth factors for fastidious microorganisms, and aids in determining haemolytic reactions. It should be noted that the haemolytic patterns of isolates may vary with the source of animal blood and the type of basal medium used. Related Supplements : Defibrinated Horse Blood, Defibrinated Sheep Blood, Horse Blood Lysed, LS0008 Staph/Strep Selective Supplement, LS0017 Neomycin Selective Supplement, LS0022 Clostridium difficle Selective SupplementLS0012 Bacitracin Selective Supplement, LS0011 Campylobacter Growth Supplement, LS0009 Campylobacter (Skirrow) Selective Supplement
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  • Sabouraud Dextrose Agar is one of several media available for theisolation of yeasts and fungi suitable for use in all areas of mycology. Sabouraud Dextrose Agar is a modification of a medium originally described by Sabouraud. The tryptone and meat peptone provide the nitrogen and vitamins required for organism growth in Sabouraud Dextrose Agar. The high concentration of dextrose is included as an energy source and in tandem with the acidic pH (5.6) facilitates the growth of fungi whilst providing limited selective properties. Higher levels of selectivity can be achieved against bacterial species by the addition of chloramphenicol. NB: This is a basic medium only and contains no additional supplements. Related Supplements : LS0050 Chloramphenicol Selective Supplement
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  • CLED SI Agar Cystine Lactose Electrolyte Deficient Single Indicator (CLED SI) Agar is based on Mackey and Sandy’s formulation and is popular for culturing urine specimens in the clinical laboratory. The reduced number of electrolyte level prevents swarming of Proteus spp. The peptone and beef extract is the source of the required nitrogen, carbon and vitamins. Lactose is a carbohydrate. The inclusion of bromothymol blue as a pH indicator allows easy differentiation of lactose and non-lactose fermenting organisms. L-Cystine is also present to benefit those organisms that have a particular cystine requirement.  
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  • Bevis modified Mackey and Sandy’s original medium by introducing a double indicator to improve the differentiation of lactose and non-lactose fermenting coliforms, staphylococci and streptococci spp. Cystine Lactose Electrolyte Deficient Double Indicator (CLED DI) is popular for urine culture in the clinical laboratory. The reduced number of electrolytes prevents swarming of Proteus spp. The peptone and beef extract is the source of the required nitrogen, carbon and vitamins. Lactose is a carbohydrate. The inclusion of bromothymol blue and Andrade’s as indicators allows easy differentiation of lactose and non-lactose fermenting organisms. L-Cystine is also present to benefit those organisms that have a particular cystine requirement. Streptococcus pyogenes and many other fastidious organisms that do not require the presence of blood can grow on this medium.  
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  • Fastidious Anaerobe Agar is intended as a primary isolation medium capable of supporting most clinically significant anaerobes. The formulation is complex and includes detoxification agents (starch and sodium bicarbonate), growth enhancing agents (L-Cysteine, arginine, vitamin K, sodium succinate, glucose and pyrophosphate), as well as haemin to encourage pigment production in Bacteroides melaninogenicus. The peptone is the source of the required nitrogen, carbon and vitamins. Glucose also acts as a carbon source and sodium pyruvate as an energy source. Sodium chloride maintains the osmotic balance in the medium. Sodium pyrophosphate acts as a buffering agent and sodium succinate improves the growth of organisms such Bacteroides spp. Supplementation of the base medium with blood (5 - 10%) will provide additional growth factors for the more fastidious microorganisms, and aids in determining any haemolytic reactions. Related Supplements : LS0015 Actinomycete Selective Supplement, LS0017 Neomycin Selective Supplement, LS0022 Clostridium difficile Selective Supplement, LS0023 Clostridium perfringens Selective Supplement, BM0140 Egg Yolk Emulsion
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  • 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 with the aim of simplifying the differentiation and presumptive identification of the main organisms usually found in Urinary Tract Infections (UTI). The peptone is the source of the required nitrogen, carbon and vitamins. Based on the traditional CLED medium, to prevent the swarming of Proteus spp., two chromogens are present in the medium. One allows the detection of enterococci giving rise to blue colonies whilst the second results in purple colonies of E. coli. Phenylalanine and tryptophan are also included as indicators of tryptophan deaminase activity producing brown colonies of Proteus spp. Related Supplements : SHS500 Sterile Horse Serum 500ml
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  • This is a selective medium for the isolation of Helicobacter pylori from clinical samples. The medium is based on a modification of Campylobacter CCDA Blood Free Medium with charcoal, ferrous sulphate and sodium pyruvate replacing the horse blood. The medium is made selective by the addition of vancomycin and cefsulodin, to suppress other bacteria, and amphoteracin to inhibit yeasts. Horse serum (10%) is also added to promote optimum growth of Helicobacter spp. Related Supplements : LS0031 Helicobacter pylori Selective Supplement, SHS500 Sterile Horse Serum 500ml
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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
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  • This medium was first introduced by MacConkey in 1905 for the isolation and differentiation of lactose and non-lactose fermenting enteric bacteria containing swarming strains of Proteus spp. MacConkey agar without salt and crystal violet is a differential medium that restricts swarming of Proteus spp. as sodium chloride is omitted from the medium to provide an electrolyte deficient medium. The omission of crystal violet permits the growth of Staphylococcus spp. and Enterococcus spp. The peptone is the nitrogen, carbon and vitamin source in this medium. Lactose is the fermentable carbohydrate. Lactose fermentation causes a local pH drop around the colonies which will react with the pH indicator, neutral red, and hence aids in differentiation. Bile salts act as the selective agent. Related Supplements : LS0189 Cefotaxime Supplement (1mg/L)
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  • Xylose Lysine Deoxycholate (XLD) agar is used for the isolation and detection of Salmonella and Shigella spp. Developed by Taylor, xylose lysine agar base was used for isolating and differentiating Gram-negative enteric bacilli. The addition of sodium thiosulfate, ferric ammonium citrate, and sodium deoxycholate created the more selective medium, XLD agar. This medium was found to be satisfactory for the isolation of Shigella and Providencia spp., as well as proving to be an effective differential media. The yeast extract is the source of the required nitrogen, carbon and vitamins. Lactose, sucrose and xylose are fermentable carbohydrates. Sodium deoxycholate, sodium thiosulphate and ferric ammonium citrate are selective agents. Phenol red acts as a pH indicator. Sodium chloride maintains the osmotic balance. Most enteric bacteria including Salmonella spp., can ferment xylose to produce acid. Shigella spp. are unable to do this and thus the colonies remain red. Once xylose has been completely utilized Salmonella spp. will decarboxylate lysine resulting in a pH increase to alkaline. Salmonella and Shigella spp. are differentiated as Salmonellae spp. are able to metabolise thiosulphate producing hydrogen sulphide resulting in colonies with black centres. Stool specimens or rectal swabs may be plated directly onto XLD agar. Selective enrichment broths, such as Selenite Broth or Tetrathionate Broth, may be used prior to streaking. For specific procedures refer to appropriate references.  
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  • Legionella agar was designed for the isolation of Legionella spp. and is used primarily in water and environmental laboratories. Since Legionella spp. are fastidious organisms, the medium contains yeast extract as a source of nitrogen, carbon and vitamins. Charcoal is also included to neutralise growth-inhibiting substances and agar is the solidifying agent. The medium requires supplementation with ferric pyrophosphate as a source of iron, L-cysteine, an essential amino acid for the growth of Legionella spp. and α-ketoglutaric acid, which acts as a growth stimulant. ACES buffer/potassium hydroxide is also added to maintain the optimal pH of 6.9 for growth of Legionella spp. Omission of the L-cysteine produces a confirmation medium that can be used to test presumptive Legionella spp. as isolates will not be able to grow. Selective versions of the medium can also be created by the addition of various selective agents. GVPC is the most popular for water testing and BMPA for clinical testing. Related Supplements : LS7044 Legionella BCYE Supplement, LS7045 BCYE without Cysteine
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  • GC Agar when used with blood and other enrichment is for the isolation of Neisseria gonorrhoeae but is also capable of supporting the growth of most fastidious micro-organisms. This medium is based on the modified formulation described by Thayer and Martin that was based on the original formulation stated by Johnson. Enrichment is usually attained using lysed blood but haemoglobin powder or chocolated blood are suitable alternatives. Additional enrichment can be provided by the addition of Suplex supplement (BM0478) which consists of yeast extract and glucose. Selective variants of GC Agar can be prepared through the addition of various selective supplements such as VCAT (LS0002) or LCAT (LS0001). These supplements will suppress most of the background flora likely to be present in specimen and will restrict the swarming of Proteus spp. The peptone is the source of the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance in the medium. Starch is present to absorb toxic metabolites and phosphate buffers prevent pH changes during incubation. Related Supplements : BM0478 Suplex, LS0001 GC LCAT Selective Supplement, LS0002 GC VCAT Selective Supplement
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  • A general purpose and nutritious medium for the non-selective enrichment of non-fastidious and some fastidious organisms. Tryptone and soy peptone are the nitrogen and vitamin source in the medium. Glucose is the carbon energy source that facilitates organism growth and sodium chloride maintains osmotic balance. Di-potassium hydrogen phosphate is a buffering agent to prevent auto-sterilisation due to acid production during the growth of some organisms. Tryptone Soya Broth is also commonly referred to as Soybean-Casein Digest Medium or Tryptic Soya Broth and is abbreviated as TSB. TSB conforms to the Harmonized United States Pharmacopoeia (USP), European Pharmacopoeia (EU), and Japanese Pharmacopoeia (JP).  
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  • This is a selective medium for the isolation and enumeration of yeasts and moulds in dairy products. It is in according to a typical formulation of The International Organisation for Standardisation (ISO). Yeast extract acts as a source of nitrogen, carbon and vitamins in this medium. Glucose is a fermentable carbohydrate. Although the medium has a low pH it is made more selective by the inclusion of chloramphenicol, an antibiotic selective agent.  
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  • Tryptone Soya Agar (TSA) is a general-purpose, non-selective medium capable of supporting the growth of most micro-organisms. This medium meets the requirements of the Harmonised USP/EP/JP and is based on the original formulation described by Leavitt et al. in 1955. TSA is commonly referred to as Soybean-Casein Digest Agar. TSA supplemented with lecithin and Tween 80® is widely used in environmental monitoring. With further enrichment using 5-10% sheep or horse blood, most fastidious organisms can be isolated and their haemolytic reactions can be determined in order to aid identification. It should be noted that the haemolytic patterns of isolates may vary with the source of animal blood and the type of basal medium used. The tryptone and soy peptone are the source of the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance in the medium. Related Supplements : Defibrinated Sheep Blood, Defibrinated Horse Blood
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  • MacConkey agar No. 3 is a selective medium primarily for the isolation of Enterobacteriacae from waters and sewage. This media differs from the original MacConkey formulation in that as well as bile salts, crystal violet has been included as an additional selective agent. This has the effect of inhibiting Gram-positive organisms. The peptone acts as a nitrogen, carbon and vitamin source. Sodium chloride maintains osmotic balance. Lactose is a carbohydrate and during its fermentation causes a confined pH drop around the bacterial colony. This causes a colour change in the pH indicator, neutral red and bile precipitation.  
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  • Eosin Methylene Blue agar (EMB) is a selective medium primarily for the isolation of coliforms from clinical, food and environmental samples. This is the modified formulation of EMB proposed by Levine with a higher concentration of lactose and the sucrose omitted. The peptone provides the required carbon, nitrogen and vitamins. Lactose is a fermentable carbohydrate and di-potassium phosphate is a buffer. Eosin Y and methylene blue are indicators. Methylene blue is also a selective agent. During strong acidic conditions, the dyes impart a metallic sheen to certain lactose fermenters, such as Escherichia coli.  
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  • Mannitol Salt Agar is selective medium for the isolation of pathogenic staphylococci. The medium conforms to the requirements of the Harmonised USP/EP/JP. Chapman showed that adding a high level of sodium chloride to Phenol Red Mannitol Agar allowed for the recovery of pathogenic staphylococci. Pathogenic staphylococci produced yellow colonies whereas non-pathogenic staphylococci produced small red colonies. Pancreatic digest of casein, peptic digest of animal tissue and beef extract provide the required nitrogen, carbon and vitamins. The high level of sodium chloride inhibits most organisms other than staphylococci. Mannitol is a carbohydrate that is fermented by coagulase positive staphylococci. Phenol red is the pH indicator.
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  • 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
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  • 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
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  • 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)
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  • 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.  
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  • Formulated to ISO 6887-1, Maximum Recovery Diluent (MRD) is a diluent designed to maintain organisms by protecting the cells from unnecessary physiological shock that may occur using other aqueous solutions. MRD is used extensively in food and environmental testing. The low level of peptone provides a protective effect but does not allow for multiplication during the short residence time in the diluent, 45 minutes. The sodium chloride prevents osmotic shock as the sample is initially diluted.  
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  • Nutrient Broth No.2 is used for the cultivation of fastidious pathogens and other microorganisms. This general use medium, rich in nutrients, allows the growth of bacteria when there is a low level of cells. The medium is particularly suitable as a secondary growth medium for staphylococci to be tested for coagulase production and also be used for sterility testing of aerobic organisms. Beef extract and peptone provide the required carbon, nitrogen and vitamins. Sodium chloride maintains osmotic balance.