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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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  • 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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  • 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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  • Half-Fraser broth is a selective enrichment broth for the identification and isolation of Listeria spp, primarily from food and environmental samples. The antibiotics, nalidixic acid and acriflavine, are already included in the formulation so only ferric ammonium citrate (LS5004) need be added to make the complete Half-Fraser broth. The peptones provide carbon, nitrogen and vitamins, sodium chloride provides osmotic balance and the phosphate buffer system maintains pH. Lithium chloride inhibits enterococci and the antibiotics make the medium highly selective. Listeria spp hydrolyse aesculin to aesculetin which forms a confirmatory dark brown or black complex with Fe3+ ions.
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  • Cetrimide agar is a selective medium for the isolation and detection of Pseudomonas aeruginosa from pharmaceutical, clinical and cosmetic samples. The formulation is complaint with the requirements of the Harmonised USP/EP/JP. Detection is achieved using the unique ability of P. aeruginosa to produce the water soluble, bright green pigment pyocyanin. The production of this pigment is stimulated by the presence of magnesium chloride and di-potassium sulphate in the medium. The addition of glycerol (10ml/l) is required as this compound serves as an energy source. Cetrimide, a quaternary ammonium compound, is also present to suppress the growth of other Pseudomonas spp. as well as Gram-negative and Gram-positive organisms. Pancreatic digest of gelatin provides the required nitrogen, carbon and vitamins. Related Supplements :
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  • Lowenstein-Jensen medium is based on the original formulation of Lowenstein that was subsequently modified by Jensen. It is used with fresh egg and glycerol for the isolation and presumptive identification of Mycobacterium spp., particularly Mycobacterium tuberculosis, from clinical samples. L-Asparagine and Potato starch are sources of nitrogen and vitamins in the medium. Potassium hydrogen phosphate and magnesium sulphate enhance organism growth and act as buffers. Sodium citrate and malachite green are selective agents that have inhibitory effects on organisms other than the mycobacteria. Malachite green is also incorporated into the medium to provide a colour contrast between the colonies and the medium. The required addition of egg emulsion provides the fatty acids and protein required for the metabolism of mycobacteria. Glycerol is also added which is said to enhance the growth of Mycobacterium tuberculosis however other strains of mycobacteria, particularly Mycobacterium bovis, may be inhibited by its presence. Subsequently, sodium pyruvate (12.5 g/600ml) may be used as an alternative to glycerol to encourage the growth of Mycobacterium bovis.  
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  • R2A agar is used for the enumeration and cultivation of bacteria from drinking water. R2A agar developed by Reasoner and Geldreich is a low nutrient medium that can used in pour plate, spread plate, and membrane filtration methods for heterotrophic plate counts. In combination with a lower incubation temperature and longer incubation period R2A agar stimulates the growth of stressed and chlorine-tolerant bacteria. Traditionally nutritionally rich media have been used for this purpose but these media support the growth of fast-growing bacteria and may suppress slow growing or stressed bacteria found in treated water. Enzymatic digest of casein, proteose peptone, acid hydrolysate of casein and yeast extract provide the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. Dipotassium hydrogen phosphate is a buffering agent. Magnesium sulphate is a source of divalent cations and sulphate. Starch and sodium pyruvate aid in the recovery of stressed organisms.  
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