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CLED SI Agar Cystine Lactose Electrolyte Deficient Single Indicator (CLED SI) Agar is based on Mackey and Sandys 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. -
Bevis modified Mackey and Sandys 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 Andrades 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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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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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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Selenite mannitol broth is a modification of selenite broth and is for the selective enrichment of Salmonellae spp. from clinical, food and environmental specimens. Comparisons have shown that mannitol selenite broth is better than other enrichment broths for the isolation of Salmonellae spp. The peptone acts as a nitrogen, carbon and vitamin source. Mannitol is a fermentable carbohydrate and sodium phosphate is a buffer. The medium is made selective by the addition of sodium biselenite (KM8021). The fermentation of mannitol by Salmonellae spp. is said to correct the alkaline pH swing which can occur during incubation. Following overnight incubation subculture(s) are usually made on to one or more of the many selective enteric solid media.
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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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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.
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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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Luria Bertani (LB) agar (Miller) is used for the cultivation and maintenance of recombinant strains of Escherichia coli and is based on the formulation stated by Miller. This medium is typically used in molecular biology procedures such as the detection of phage or plasmid transformed bacteria. LB agar (Miller) is prepared using 10 g/L of sodium chloride and this level varies from that described by Lennox. Enzymatic digest of casein provides the required nitrogen and carbon for organism growth. Vitamin B complex required by recombinant strains of E. coli are supplied by the yeast extract. Sodium chloride maintains the osmotic balance and provides sodium ions for membrane transport. Related Supplements : LS0035 Ampicillin Selective Supplement, LS0037 Kanamycin Selective Supplement
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LB agar (Lennox) is used for the cultivation and maintenance of recombinant strains of Escherichia coli and is based on the formulation stated by Lennox. This medium is typically used in molecular biology procedures such as the detection of phage or plasmid transformed bacteria. LB agar (Lennox) is prepared using 5 g/L of sodium chloride and this level varies from that described by Miller. This allows for additional sodium chloride to be added at the point of preparation if required. Enzymatic digest of casein provides the required nitrogen and carbon for organism growth. Vitamin B complex required by recombinant strains of E. coli are supplied by the yeast extract. Sodium chloride maintains the osmotic balance and provides sodium ions for membrane transport. Related Supplements : LS0035 Ampicillin Selective Supplement, LS0037 Kanamycin Selective Supplement
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Selenite cystine broth is a modification of selenite F broth and is for the selective enrichment of Salmonellae spp. from clinical, food and environmental specimens. The peptone acts as a nitrogen, carbon and vitamin source. Lactose is a fermentable carbohydrate and sodium phosphate is a buffer. L-cystine is used to enhance the recovery of Salmonellae spp. in low numbers. The medium is made selective by the addition of sodium biselenite (KM8021). Following overnight incubation subculture(s) are usually made on to one or more of the many selective enteric solid media.
