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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 -
Hektoen enteric agar was developed by King and Metzger as a differential selective medium for the isolation of Shigella spp. and Salmonella spp. species from enteric pathological samples. The meat peptone and yeast extract provide the required nitrogen, carbon and vitamins. Lactose, sucrose and salicin are fermentable carbohydrates. Bromothymol blue is added as a pH indicator in order to identify carbohydrate fermenting organisms. The combination of ferric ammonium citrate and sodium thiosulfate allows the production of hydrogen sulphide. Hydrogen sulphide positive colonies produce black centred colonies. Sodium chloride maintains the osmotic balance. The bile salts and acid fuchsin inhibit Gram-positive organisms.
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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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Hoyles agar is selective culture medium for the isolation and differentiation of Corynebacterium diphtheriae types. Hoyles agar allows for rapid growth of the organisms and normally 18 hours incubation should be sufficient for a diagnosis. As the medium is highly selective, inoculation should be by rubbing the swab (or other material) over the entire surface of the agar, there is no need to spread the inoculum with a loop indeed doing so can cause the organism to be missed especially when they are present only in small numbers. The Elek method can be used to determine the toxigenicity of any C. diptheriae strains. The beef extract and peptone act as a source of nitrogen, carbon and vitamins. The sodium chloride maintains osmotic balance. This medium should be used in conjunction with two supplements: lysed horse blood at 50 ml/l and 10ml/l of potassium tellurite 3.5% solution (BM2230). Lysed horse blood provides added nutrients to the medium and potassium tellurite inhibits Gram-negative and several Gram-positive microorganisms. Related Supplements : BM2290 3.5% Potassium Tellurite Solution, Horse Blood Lysed
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Kligler iron agar is used to differentiate between some of the enterobacteriacae on the basis of three reactions: fermentation of lactose and glucose and the production of hydrogen sulphide. Kligler iron agar is a modification of the original formulation developed by Kligler. It incorporates the principles of Russell’s double sugar agar with Kligler ‘s lead acetate agar. The peptone provides the required nitrogen, carbon and vitamins. Lactose and glucose are carbohydrates. Acid production from their fermentation is detected by the phenol red pH indictor. Sodium thiosulphate is reduced to hydrogen sulphide which is detected by the ferric citrate indicator. Sodium chloride maintains the osmotic balance.
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Thiosulphate citrate bile salts sucrose (TCBS) agar is a selective medium used in microbiology laboratories to isolate Vibrio spp. The formulation was developed by Kobayashi et al. which was modified from Nakanishi’s formulation. The yeast extract and peptone are the source of the required nitrogen, carbon and vitamins. TCBS agar contains high concentrations of sodium thiosulphate, sodium citrate and ox bile to inhibit the growth of Gram-positive organisms and suppress coliforms. Sucrose is included as a fermentable carbohydrate for the metabolism of Vibrio spp. Sodium chloride maintains the osmotic balance in the medium. Sodium thiosulphate also serves as a sulphur source and, in combination with ferric citrate, detects hydrogen sulphide production. Thymol blue and bromothymol blue are included as indicators of pH changes.
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Lactalbumin hydrolysate is obtained through enzymatic hydrolysis of lactalbumin protein in milk whey. This product is rich in essential amino acids as well as providing a source of nitrogen, carbon and vitamins. It is commonly utilized in media for tissue culture and for the production of vaccines as well as being useful for bacterial and fermentation media.
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Lactose broth is used for the performance and confirmation of the Presumptive Test for coliforms in water and dairy samples. This medium is also frequently used as a pre-enrichment medium when testing foods, water samples and dairy products for Salmonella spp. Beef extract and gelatin peptone provide the required carbon, nitrogen and vitamins in this medium. Lactose is a fermentable carbohydrate. Fermentation of lactose is detected by the production of gas
