Meios de Cultura Desidratados
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Bcp Glucose Agar
Enterobacteriaceae Confirmatory Agar ISO 21528:2
For the differentiation and enumeration of Enterobacteriaceae
- BCP GLUCOSE AGAR, also known as Enterobacteriaceae Confirmatory Agar ISO 21528:2, is used for the differentiation of Enterobacteriaceae in urine, water and food.
- It differentiates species on the basis of dextrose fermentation.
- Tryptone and Yeast extract provide nitrogen, vitamins, minerals and amino acids essential for growth.
- D-glucose is the fermentable carbohydrate providing carbon and energy Sodium chloride supplies essential electrolytes for transport and osmotic balance.
- Bromocresol purple is a pH indicator.
- Bacteriological agar is the solidifying agent.
- Inoculate and incubate at 35 ± 2°C for 18 – 24 hours. The glucose-fermenting microorganisms produce yellow colonies (acid) and the non-fermenting ones, purple colonies. ISO 21528:2 recommends this medium for glucose fermentation testing. Inoculate oxidase-negative colonoes in tubes containing BCP Glucose Agar and incubate at 37ºC for 24 ± 2 hours. A yellow color indicates a positive reaction. Colonies that are oxidase negative and glucose-positive are confirmed as Enterobacteriaceae.
Azide Dextrose Broth (ACC. TO ROTHE)
Azide Dextrose Broth (Rothe) is used for the enumeration of enterococci in drinking water, frozen foods and other food products by the most probable number method.
This sodium azide glucose broth is prepared according to the formula of Rothe. It was recommended by Malmann and Seligman for the enumeration of fecal streptococci in waste water and foods. Malmann, Botwright and Churchill showed the bacteriostatic action of sodium azide on Gram-negative flora, thereby favoring the growth of enterococci.
The high nutritive capacity of Azide Dextrose Broth is due to the presence of a high concentration of polypeptone and glucose. Sodium chloride maintains the osmotic equilibrium. Potassium phosphates buffer the medium. Sodium azide inhibits the growth of Gram-negative bacteria by its bacteriostatic action and favors that of fecal streptococci. After observing cultures in tubes (presumptive test), it is necessary to carry out a confirmation in Ethyl violet Azide Broth (Litsky broth).
Bacillus Cereus Agar (ACC. TO MOSSEL)
Enumeration Of Bacillus Cereus
Bacillus cereus Agar is used for the detection and enumeration of spores and vegetative cells of Bacillus cereus in food products.
The typical composition corresponds to the MYP agar (mannitol, egg yolk, polymyxin agar) described in the standards NF EN ISO 7932 and NF EN ISO 21871.
In 1967, Mossel et al. recommended the use of a mannitol-phenol red-egg yolk medium, whose principles were based on two factors : the lack of mannitol fermentation by Bacillus cereus and the presence of a lecithinase in majority of tested strains. The authors showed that satisfactory selectivity was obtained with polymyxin B at 10 mg / liter.
Tryptone and meat extract favor the growth of Bacillus cereus. Sterile egg yolk emulsion is used to detect the presence of lecithinase present in most Bacillus cereus strains. Insoluble breakdown products of egg yolk lecithin accumulate around the colonies, forming a whitish precipitate. Mannitol is used to differentiate contaminating microorganisms which ferment it, causing phenol red to turn yellow. Polymyxin is used to inhibit accompanying microflora when the tested sample is heavily contaminated.
Baird-Parker Agar With Egg Yolk Tellurite
Enumeration Of Coagulase Positive Staphylococci
Baird-Parker Agar with egg yolk and potassium tellurite is a selective medium for the detection and enumeration of Staphylococcus aureus in animal origin biological samples, pharmaceutical products, cosmetics, foods and water.
The formula with egg yolk, developed by Baird-Parker in 1962, was found to be particularly appropriate for the enumeration of coagulase positive staphylococci. In 1964, Smith and Baird-Parker showed that adding sulfamethazine to the medium inhibited the growth of Proteus and in 1971, Tardio and Baer observed, that among 18
selective isolation media tested, that the Baird-Parker formulation was less inhibitory than Vogel-Johnson medium, used previously with some frequency.
The growth of staphylococci is favored by sodium pyruvate and glycine. Accompanying microflora is inhibited by lithium chloride and potassium tellurite (added extemporaneously), as well as a high concentration of glycine. The addition of sulfamethazine (optional) after autoclaving inhibits most Proteus and thus limits the invasion of the medium by this species. Enrichment with egg yolk aids in identification by showing the action of lecithinase. Staphylococcus aureus presents black colonies (due to the reduction of tellurite to telluride), surrounded by clearing zones in the cloudy egg yolk medium. In principle, other microorganisms are inhibited. However it is possible to observe brown or greenish micrococci, white yeast colonies or brown Bacillus or Proteus. Coagulase negative staphylococci are nearly totally inhibited and if a culture does develop, it will not be surrounded by clearing zones.
Bea Agar (BILE, ESCULIN & AZIDE)
Confirmation Of Enterococci
Bile Esculin Azide Agar (BEA agar) is a selective medium used to isolate and enumerate enterococci in food and pharmaceutical products. It is also used for the enumeration of enterococci animal feed.
Rochaix first showed the interest of esculin hydrolysis for the identification of enterococci. Meyer and Schoefeld then showed that this hydrolysis in medium containing bile was an excellent test for the detection of group D streptococci. The first formulations described by Swan were subsequently modified by Isenberg, who obtained a medium which was both more selective and at the same time favored the rapid growth and good recovery of the bacteria sought. The current formula is described in standards as a confirmation media for intestinal enterococci in water, when the enumeration is carried out by membrane filtration.
Sodium azide inhibits contaminating Gram-negative bacteria. Bacteriological bile inhibits the growth of Gram-positive microorganisms. Enterococci hydrolyze esculin to glucose and esculetin. The esculetin produced forms a black complex in the presence of ferric ions arising from ferric citrate in the medium
Bismuth Sulfite Agar
Detection Of Salmonella Typhi and Other Salmonellae
Bismuth Sulfite (modified Wilson Blair agar) Agar is a selective medium used to isolate Salmonella Typhi and other salmonellas in pathological products of animal origin, water, dairy and other food products. Bismuth Sulfite agar can be used in the normalized methods for Salmonella detection as the second isolation media.
In 1926, Wilson and Blair combined bismuth and sodium sulfite in a medium destined to isolate Salmonella of the typhi and paratyphi groups. In 1956, Hajna and Damon described a modified formula which was recommended by the United States Pharmacopoeia.
The concentrations of brilliant green and bismuth sulfite inhibit accompanying Gram-positive flora and most enterobacteria, except for Salmonella and several Shigella. Using the sulfur compounds in the medium, Salmonella releases hydrogen sulfide which produces a metallic precipitate in the presence of ferrous sulfate, giving the colonies a black or sometimes green color. It is particularly recommended to first enrich using Tetrathionate, Selenite or Rappaport-Vassiliadis Broths and to simultaneously inoculate onto other less selective media : MacConkey, XLD or Hektoen Enteric Agars, for example. Because of its elevated inhibitory power, this medium enables a highly contaminated inoculum to be used.
BRILLIANT GREEN AGAR (KRISTENSEN)
DETECTION OF SALMONELLA
Brilliant Green Agar of Kristensen is a highly selective medium used to isolate salmonella, except for Salmonella Typhi, in biological samples of animal origin and food products.
The agar can also be used as the second media of choice in the normalized standards for the research and detection of Salmonella.
BRILLIANT GREEN BILE BROTH (BGBB)
CONFIRMATION OF COLIFORMS
Brilliant Green Bile Broth (BGBB) is used for the confirmation of coliforms and thermotolerant coliforms in food products, water used for watering food products and for effluent / run-off water testing. It can also be used as an enumeration media for coliforms in frozen dairy and ice cream products.
Research and development of a culture medium inhibiting microorganisms other than coliform bacteria has long interested bacteriologists. In 1926, Dunham and Schoenlein studied the proportions of bile and brilliant green which could give good results. Jordan showed that this medium was better than Lactose Broth for the detection of coliform bacteria in water. For the control of milk pasteurization, MacCrady and Langevin satisfactorily used Brilliant Green Bile Broth for the detection of coliform bacteria. Mackenzie verified that the brilliant green concentration was sufficient to effectively inhibit the culture of lactose-fermenting anaerobes, in particular Clostridium perfringens. . 3 PRINCIPLES The simultaneous presence of ox bile and brilliant green inhibit almost all Gram-positive organisms and Gramnegative bacteria other than coliforms. The brilliant green concentration was specifically determined in order to prevent the growth of lactose-fermenting anaerobes at 44°C, which avoids false positives. Development of coliform bacteria is shown by turbidity and gas production in the Durham tubes, as a result of lactose fermentation.
BUFFERED PEPTONE WATER
DILUENT ENRICHMENT BROTH
Buffered Peptone Water is a general use diluent destined for numerous operations and standards including sample preparation, the preparation of stock suspensions and serial dilutions of samples.
This media is also used for the pre-enrichment of Salmonella and for Cronobacter sakazakii, by allowing the resuscitation of microorganisms having undergone sublethal treatments as in the case of spray drying, pasteurization, action of conservators, elevated osmotic pressure and high acidity.
It is used as a suspension and resuscitation media for the enumeration of Listeria monocytogenes.
Sodium chloride maintains the osmotic balance. The medium is buffered with sodium and potassium phosphates.
CHLORAMPHENICOL GLUCOSE AGAR
ENUMERATION OF YEASTS AND MOLDS
Chloramphenicol Glucose Agar is destined for the detection and enumeration of yeasts and molds in food products.
Yeast extract and glucose favor the growth of yeasts and molds. The presence of chloramphenicol, a heat-stable antibiotic, inhibits the growth of contaminating bacteria.
BCP DEXTROSE AGAR
ENUMERATION OF SPORES
BCP Dextrose Tryptone Agar (also known as BCP Glucose agar) is used to enumerate mesophilic and thermophilic aerobic bacterial spores (especially Bacillus stearothermophilus, responsible for flat sour) in raw materials and in ingredients used in canning non-acid products (pH > 4,5). It is also used in surface samples and canning process water.
The medium was developed by the National Canners Association laboratories for the enumeration of mesophilic and thermophilic aerobic bacteria in the sugar used in canned food.
Soluble starch, a protective agent, favors spore germination. Bacteria which acidify the medium by metabolizing glucose result in the pH indicator, bromocresol purple, turning yellow. Non-acidifying colonies are blue.
DETECTION OF ENTEROBACTERIACEAE
MacConkey agar is a selective medium for the isolation of enterobacteria in water, food, pharmaceutical products and biological samples of animal origin and in cosmetic products.
The formulation of MacConkey for the isolation of enterobacteria has been modified a number of times since its inception. The present medium is the “classical” formula used for many years by authors such as Block and Ferguson, who found the medium satisfactory for the isolation of fastidious Shigella.
Bile salts and crystal violet inhibit the growth of Gram positive bacteria. The dye inhibits primarily the development of enterococci and staphylococci. The fermentation of lactose to acid is revealed in presence of neutral red by the formation of red or pink colonies. Lactose-negative colonies form colorless colonies.