Dehydrated Culture 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
  • A general purpose and nutritious medium for the non-selective enrichment of non-fastidious and some fastidious organisms. Tryptone and soy peptone are the nitrogen and vitamin source in the medium. Glucose is the carbon energy source that facilitates organism growth and sodium chloride maintains osmotic balance. Di-potassium hydrogen phosphate is a buffering agent to prevent auto-sterilisation due to acid production during the growth of some organisms. Tryptone Soya Broth is also commonly referred to as Soybean-Casein Digest Medium or Tryptic Soya Broth and is abbreviated as TSB. TSB conforms to the Harmonized United States Pharmacopoeia (USP), European Pharmacopoeia (EU), and Japanese Pharmacopoeia (JP).  
  • Tryptone yeast extract salts (TYES) agar is a culture medium that can be used as the primary isolation medium for Flavobacterium columnare (1) and F. psychrophilum. Growth of Flavobacterium spp. requires a culture media with a lower nutrient content than that used in general-purpose mediums such as brain heart infusion agar andtryptone soya agar. The tryptone and yeast extract provide the required carbon, nitrogen and vitamins. Calcium chloride and magnesium sulphate provide the required minerals. Agar is a solidifying agent.
  • KM8011-1

    Tryptose

    Tryptose is a mixed enzymatically digested protein. This product can be used in preparing microbiological culture media providing unique nutritional properties useful for cultivating fastidious microorganisms.  
  • A modification of Christensen’s medium by Maslen this medium is generally used to detect rapid urease activity of Proteus spp. It can also be used to detect urease activity of other enterobacteriaceae including urease producing Salmonella spp. and Shigella spp. When used for the latter purpose it is necessary to increase the incubation time to as long as 48 hours. The peptone provides the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. The potassium dihydrogen phosphate is a buffer and sodium chloride maintains osmotic balance. Phenol red is a pH indicator. Related Supplements : BM3000 Urea 40% Solution
  • A modification of Christensen’s medium by Maslen this medium is generally used to detect rapid urease activity of Proteus spp. although it can be used to detect urease activity of other enterobacteriaceae including urease producing Salmonella spp. and Shigella spp. Unlike Christensen’s medium when used for the later purpose it is not necessary to increase the incubation time. The peptone provides the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. The disodium phosphate and potassium dihydrogen phosphate are buffers and sodium chloride maintains osmotic balance. Phenol red is a pH indicator. Related Supplements : BM3000 Urea 40% Solution
  • Violet Red Bile Agar is a medium for the enumeration of coliform organisms in food and dairy products and conforms to American Public Health Association (APHA). Yeast extract and enzymatic digest of gelatin provides the required carbon, nitrogen and vitamins. Sodium chloride maintains the osmotic balance. The medium is made selective by the inclusion of bile salts and crystal violet to inhibit Gram-positive and non-enteric organisms. Lactose is a fermentable carbohydrate and neutral red is a pH indicator. Lactose fermenters produce red/purple colonies often surrounded by a halo of the same colour. Non lactose fermenters produce pale colonies. Selectivity can be increased by incubation at 42-44ºC.  
  • Violet Red Bile Glucose Agar (VRBGA) is a selective medium for the isolation and enumeration of Enterobacteriaceae in food products. It is a modification of the original Violet Red Bile Agar with the lactose being replaced with glucose. As all Enterobacteriaceae ferment glucose VRBGA allows for a wider range of organisms to be detected. This medium conforms to the requirements of the Harmonised USP/EP/JP. Yeast extract and pancreatic digest of gelatin provide the required carbon, nitrogen and vitamins. Glucose is a fermentable carbohydrate and neutral red is a pH indicator. Sodium chloride maintains the osmotic balance. The medium is made selective by the inclusion of bile salts and crystal violet to inhibit Gram-positive and non-enteric organisms.
  • Xylose Lysine Deoxycholate (XLD) agar is used for the isolation and detection of Salmonella and Shigella spp. Developed by Taylor, xylose lysine agar base was used for isolating and differentiating Gram-negative enteric bacilli. The addition of sodium thiosulfate, ferric ammonium citrate, and sodium deoxycholate created the more selective medium, XLD agar. This medium was found to be satisfactory for the isolation of Shigella and Providencia spp., as well as proving to be an effective differential media. The yeast extract is the source of the required nitrogen, carbon and vitamins. Lactose, sucrose and xylose are fermentable carbohydrates. Sodium deoxycholate, sodium thiosulphate and ferric ammonium citrate are selective agents. Phenol red acts as a pH indicator. Sodium chloride maintains the osmotic balance. Most enteric bacteria including Salmonella spp., can ferment xylose to produce acid. Shigella spp. are unable to do this and thus the colonies remain red. Once xylose has been completely utilized Salmonella spp. will decarboxylate lysine resulting in a pH increase to alkaline. Salmonella and Shigella spp. are differentiated as Salmonellae spp. are able to metabolise thiosulphate producing hydrogen sulphide resulting in colonies with black centres. Stool specimens or rectal swabs may be plated directly onto XLD agar. Selective enrichment broths, such as Selenite Broth or Tetrathionate Broth, may be used prior to streaking. For specific procedures refer to appropriate references.  
  • KM8003

    Yeast Extract

    Yeast extract is obtained from selected autolyzed Saccharomyces cerevisiae cells. This product can be used in preparing microbiological culture media providing readily available soluble vitamins (notably B-complexes), amino acids, peptides, and other essential growth factors. Yeast extract is observed as an animal free source and is therefore used extensively in many non-animal cell culture formulations.  
  • Yeast extract agar is a nutrient rich medium for the cultivation of non-fastidious bacteria, yeasts and moulds. Recommended for the plate count of microorganisms in water and dairy products. The yeast extract and peptone acts as a source of nitrogen, amino acids, carbon and vitamins. Related Supplements : LS0019 Oxytetracycline Selective Supplement
  • This is a selective medium for the isolation and enumeration of yeasts and moulds in dairy products. It is in according to a typical formulation of The International Organisation for Standardisation (ISO). Yeast extract acts as a source of nitrogen, carbon and vitamins in this medium. Glucose is a fermentable carbohydrate. Although the medium has a low pH it is made more selective by the inclusion of chloramphenicol, an antibiotic selective agent.  
  • In vitro diagnostic. Dehydrated KM0179 Yersinia Selective Agar Base powder can be reconstituted to form a selective plated medium for the isolation and enumeration of Yersinia species from clinical and food samples.