• This is one of several selective media available for the isolation of Campylobacter spp. in clinical, food and environmental laboratories. Campylobacter agar base is based on the formulation from Bolton and Robertson. The peptone is the source of the required nitrogen, carbon and vitamins. Sodium chloride maintains the osmotic balance in the medium. The medium is enriched with lysed horse blood and made selective by the addition of cefoperazone, to suppress other enteric organisms, and amphotericin to suppress yeast and fungal growth (Preston supplement LS0010). Related Supplements : LS0009 Campylobacter (Skirrow) Selective Supplement, LS0010 Campylobacter (Preston) Selective Supplement, Lysed Blood
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  • Rappaport-Vassiliadis Soya Broth is used for the enrichment and selective isolation of Salmonella spp. This medium is a modification of the original formulation by Rappaport et al. and has been formulated to exploit the full characteristics of Salmonella spp. These characteristics include the ability to survive at relatively high osmotic pressure, to multiply at low pH values and greater resistance to malachite green. This formulation also has the correct amount of magnesium chloride as previous formulations did not take into account the volume of displacement caused by dissolving large amounts of magnesium chloride in water. This formulation has been shown to be superior to tetrathionate broth and selenite broth for the isolation of Salmonella spp. from meat products. Soya peptone provides the required carbon, nitrogen and vitamins. Potassium dihydrogen phosphate and di-potassium hydrogen phosphate act as buffers. Magnesium chloride raises the osmotic pressure in the medium. Malachite green is an inhibitory substance. NB: This formulation is very hygroscopic and will produce a slight exothermic reaction when mixed with water.  
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  • Malt extract agar is used for the detection, isolation and enumeration yeasts and moulds. The high carbohydrate content of the medium ensures rapid growth of yeasts and moulds. Malt extract and mycological peptone provide the carbon, protein and nutrient sources required by the organisms. The acidic nature of this medium allows for optimal growth of moulds and yeasts while restricting bacterial growth. Malt extract agar can also be used for the cultivation of fungi, although with the prolonged incubation necessary, cultures may become overgrown by bacteria. The selectivity of the medium can be increased by lowering the pH to 3.5-4.0 or by the addition of selective agents such as chloramphenicol. Related Supplements : LS0050 Chloramphenicol Selective Supplement
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  • DNase agar is used primarily in clinical laboratories to differentiate pathogenic Staphylococcus aureus from other staphylococci based on deoxyribonuclease (DNase) activity. The tryptone provides the required carbon, nitrogen and vitamins. Sodium chloride maintains the osmotic balance. The addition of DNA to the base medium provides a simple method to check for DNase activity. Following incubation of the inoculated medium, the surface of the medium is flooded with a small quantity of 1M hydrochloric acid to precipitate the DNA. This results in the medium turning opaque. Organisms that can produce sufficient quantity of a DNase enzyme will hydrolyse the DNA resulting in a clear area around the colonies. Whereas DNase negative organisms will not produce clearing. NB: As with most tests of this type a positive result should not be taken in isolation and other appropriate tests, e.g. coagulase test, latex agglutination etc., should be carried out.  
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  • Mycological agar is a selective medium for the isolation of pathogenic fungi, particularly dermatophytes, from clinical specimens. Enzymatic digest of soybean meal provides the required carbon, nitrogen and vitamins. Glucose is an energy source for the metabolism of fungi. The addition of chloramphenicol further reduces the risk of bacterial contamination when processing material that may be heavily contaminated with coliforms. Cycloheximide should also be added (0.4g/L) to suppress the growth of commensal yeasts and saprophytic fungi.  
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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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  • Campylobacter Blood-Free Selective Medium (CCDA) is one of several media formulations available for the selective isolation of Campylobacter spp., primarily C. jejuni and C. coli. CCDA was described by Bolton et al. and formulated to replace blood with a combination of charcoal, ferrous sulphate, and sodium pyruvate. CCDA is recommended for food testing. CCDA with the addition of yeast extract and cefoperazone is used in the isolation of Campylobacter spp. from foodstuffs and swabs in the FDA/BAM method. This product complies with the requirements of ISO 10272-1:2006. Bolton et al. recommended incubating inoculated plates at 37°C to improve isolation rates but incubation at 41.5°C is recommended for the isolation of the commonly encountered thermophilic species (C. jejuni and C. coli). The meat peptone, beef extract and tryptone provide the required nitrogen, carbon and vitamins. Bacteriological charcoal absorbs toxic compounds and metabolites. Ferrous sulphate and sodium pyruvate are oxygen scavengers. Sodium desoxycholate is a selective agent. Through the addition of campylobacter (Preston) supplement (LS0010), which consists of cefoperazone and amphotericin B, enteric flora is suppressed. Related Supplements : LS0010 Campylobacter (Preston) Selective Supplement
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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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