Dehydrated Culture Media

  • Sabouraud dextrose agar with chloramphenicol is a selective media for the isolation 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.(1) The tryptone and meat peptone provides the required nitrogen, carbon and vitamins. 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.(2) Chloramphenicol is included to increase the selectivity of the media inhibiting a range of Gram-positive and Gram-negative bacteria. References (1) Sabouraud, R. 1892. Ann. Dermatol. Syphilol. 3:1061. (2) Jarett, L., and A. C. Sonnenwirth (eds.). 1980. Gradwohl’s and parasitic infections, 7th ed. American Public Health Association, Washington, D.C.
  • Sabouraud liquid medium USP is used in sterility testing for the detection of moulds, yeasts and acidophilic microorganisms in pharmaceutical products. This medium is also used for non-sterile testing and for the determination of fungistatic activity. Sabouraud liquid medium USP conforms to the USP and Harmonised Pharmacopeia. The peptic digest of animal tissue and pancreatic digest of casein provides the required nitrogen, carbon and vitamins. 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.
  • This is a selective medium for the isolation of Salmonella spp. and Shigella spp. from clinical specimens and food samples. SS agar is a modification of the original DCA medium described by Leifson. The formulation for SS agar was later modified to improve the growth of Shigella spp. SS agar modified differs from SS agar in that it has an alternation to the bile salts mixture, peptone, pH value, and total g/litre. The peptone provides the required carbon, nitrogen and vitamins. Lactose is a fermentable carbohydrate and neutral red is a pH indicator. Sodium thiosulphate and ferric citrate are used to detect hydrogen sulphide production indicated by the black centred colonies of hydrogen sulphite positive organisms. Bile salts, sodium citrate and brilliant green inhibit Gram-positive bacteria and a number of different coliform bacteria.
  • 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.  
  • Developed by Leifson, selenite F broth is a medium for the selective enrichment of Salmonella spp. from both clinical and food samples. The peptone acts as a nitrogen, carbon and vitamin source. Lactose is a fermentable carbohydrate and sodium phosphate is a buffer. 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.  
  • 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.
  • Sheep Blood Agar Base has been developed to provide a nutrient rich medium compatible with sheep blood for the cultivation of many bacteria, especially fastidious Streptococcus spp., without affecting haemolytic reactions. Alternative culture mediums, such as Blood agar base No. 2, can results in mixed haemolytic reactions for some Streptococcus spp. This is thought to occur due to the trace amounts of fermentable carbohydrates in yeast extract and the physiological difference between sheep and horse blood. The tryptone, peptone, and yeast extract provide the required nitrogen, carbon and vitamins in the medium. Sodium chloride maintains the osmotic balance. Related Supplements : LS0008 Staph/Strep Selective Supplement
  • This medium can be used as a screening method for the differentiation of enterobacteriaceae based on the ability of some species to utilise citrate as a sole source of carbon. It is often used as a screening test for Klebsiella pneumoniae (positive reaction) while Escherichia coli is negative. Species that metabolize citrate as their sole source of carbon and ammonium as the sole source of nitrogen cause an increase in alkalinity of the medium resulting in a colour change from green to blue due to the presence of the pH indicator bromthymole blue.
  • This medium was originally described by Slanetz and Bartley(1) for the enumeration of enterococci from water samples using membrane filtration. The medium has also become useful as a direct plating medium. Tryptose and yeast extract provide the required carbon, nitrogen and vitamins. Glucose is a fermentable carbohydrate. The di-potassium hydrogen phosphate acts as a buffer. Selectivity is achieved through the addition of sodium azide which is used to suppress the growth of Gram-negative organisms. The medium contains tetrazolium chloride, which is reduced by enterococci to the insoluble red dye formazan resulting in dark red colonies of enterococci on the agar. It should be noted that this reaction is not exclusive to enterococci and colonies should be confirmed by additional testing e.g. aesculin hydrolysis.
  • 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
  • KM8007

    Soy Peptone

    Soy peptone is manufactured from the enzymatic hydrolysis of soybean. This product provides a good source of nitrogen, carbohydrates, and vitamins. It is recommended for use in microbiological media for the detection and isolation of a wide variety of bacteria and fungi.  
  • Trichomonas medium is based on the formula described by Kupferburg, Johnson and Sprince for the selective isolation of Trichomonas spp. (1) The tryptone and liver extract act as carbon, nitrogen and vitamin sources in this medium. Maltose is a fermentable carbohydrate. The agar and cysteine HCl reduce the oxygen tension in the medium which aids the growth of trichmonads. Methylene blue is a redox indictor and allows for the visualisation of any significant oxygen diffusion in the medium. The addition of selective agents such as chloramphenicol is recommended to inhibit bacterial species that may be present in specimens. References 1) Kupferberg, A.B. Johnson, G., and Sprince, H. 1948. Proc. Soc. Exper. Biol. Med., 67:304-308
  • Triple sugar iron agar is used to differentiate between some of the enterobacteriacae on the basis of four reactions: fermentation of lactose, glucose and sucrose and the production of hydrogen sulphide. Beef extract, yeast extract and peptone provide the required nitrogen, carbon and vitamins. Lactose, sucrose 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 osmotic balance.  
  • KM8002

    Tryptone

    Tryptone is obtained by pancreatic digestion of casein. Casein is the main protein of milk and is a rich source of amino acid and nitrogen. This product can be used in preparing microbiological culture media providing nitrogen, vitamins, minerals and amino acids. Due to the high tryptophan content in tryptone it can be used in detecting indole production.  
  • 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 as a selective medium for the isolation and enumeration of Escherichia coli without the need for membranes or pre-incubation. Based on the formulation of Tryptone Bile Agar it incorporates a chromogenic substrate, X-Glucuronide, to detect the ß-glucuronidase enzyme which is specific for the majority of E. coli strains. Approximately, 3-4% of E. coli are glucuronidase negative including E. coli O157.(1) The advantage of the chromogenic substrate is that the reaction is concentrated within the colony resulting in distinctive blue/green colonies of E. coli while the other coliforms produce cream colonies. The tryptone provides the required carbon, nitrogen and vitamins. Bile salts No.3 is a selective agent against Gram-positive bacteria. X-glucuronide is a chromogenic substrate. Agar is solidifying agent.
  • 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