Nutrient media in microbiology are substrates on which microorganisms and tissue cultures are grown. They are used for diagnostic purposes, isolation and study of pure cultures of microorganisms, production of vaccines and drugs, and for other biological, pharmaceutical and medical purposes.

Classification of microbiological culture media

In microbiology, nutrient media are divided into:
- environments of definite and indefinite composition;
- natural, semi-synthetic and synthetic;
- basic, diagnostic, elective;
- dense, semi-liquid, liquid, dry, granular.

Natural nutrient media are those that are obtained from natural materials: blood, meat, proteins, animal organs, plant extracts and plant materials. Examples of such media include meat broth, whey, beer wort, hay infusions, agar-agar, blood, and bile. Natural environments refer to environments with an uncertain composition, which at different times may have different amounts of certain components.

Semi-synthetic media are also considered media of uncertain composition. They are prepared on the basis of natural nutrient media, but substances are added to them that guarantee active reproduction of the crops. Crops are grown on semi-synthetic media to produce vitamins, amino acids, and antibiotics for industrial pharmaceuticals.

Synthetic media are prepared from ingredients of known composition, in known concentrations and ratios, therefore these media belong to media of a certain composition. With their help, they study the metabolism of microorganisms, their biological and physiological properties, and the possibility of obtaining substances that suppress or, conversely, stimulate their development.

Basic, elective and diagnostic culture media

Basic media are used for growing various microbial cultures, as well as as a basis for obtaining elective and diagnostic media. Basic media, for example, include meat broth, meat agar, wort, and Hottinger broth. For different crops, some components are added to the basic media to stimulate growth - these can be vitamins, amino acids, and natural extracts. Thus, the causative agent of whooping cough is grown on a medium with the addition of blood.

Elective media - media for selective (selective) cultivation of biological crops. The composition of the medium is selected so as to be optimal for one species or group of closely related bacteria and suppress the development of bacteria of other species. For example, adding sodium chloride to the medium in a certain concentration inhibits the growth of all bacteria except staphylococci. With the help of elective crops, pure cultures are obtained for further propagation and accumulation.

Diagnostic media are used to identify microorganisms. Based on changes in the medium and its chemical composition (changes in the color of the medium, the appearance of gas bubbles, etc.), the type of bacteria is determined. Chemical indicator dyes such as crystal violet, malachite green, methylene blue, fusin and others are often added to such media. They help separate close cultures. For example, in the pink Endo medium, tinted with fusin, E. coli forms red colonies, and typhoid and dysentery colonies of bacteria are colorless.

There is a significant number of nutrient media used for the cultivation and maintenance (preservation) of microorganisms. In microbiology, a nutrient medium is a medium containing various compounds of complex or simple composition that are used for the propagation of microorganisms in laboratory or industrial conditions. Back in 1930, at least two thousand items were classified, but the number of ingredients that are their integral components is relatively small, and their compositions are created on certain general principles. For any bacteria to reproduce, it is necessary to provide a suitable biophysical environment and biochemical nutritional components. Any nutrient medium must meet the following requirements: contain all the nutrients necessary for growth in an easily digestible form; have optimal humidity, viscosity, pH, be isotonic, balanced with high buffer capacity and, if possible, transparent. For the growth of autotrophic bacteria, the nutrient requirements are quite simple: water, carbon dioxide and appropriate inorganic salts. For example, bacteria of the genus Nitrobacter assimilate CO 2 and obtain energy by oxidizing nitrites into nitrates. Heterotrophic bacteria obtain energy from the oxidation (dissimilation) of reduced carbon compounds.

Heterotrophic bacteria use organic compounds for two purposes: 1) as a source of energy; in this case, the organic matter is oxidized or broken down with the release of energy and the formation of a number of end products such as CO 2, organic acids, etc.; 2) as substrates that are assimilated directly into the formation of cellular components or for their synthesis in reactions that require energy. So, E.coli capable of growth on a simple medium containing only glucose and inorganic salts. Lactic acid bacteria grow in complex media containing as additives a number of organic compounds (vitamins, amino acids, etc.), which cells are not able to synthesize on their own. Such connections are called growth factors. Organisms that require their addition to the growth medium are called auxotrophic via the appropriate connections. Another group of organisms, capable of growth on simple media containing a source of carbon and energy, as well as a set of basic nutrients, is called prototrophic. It should also be taken into account that in nature there are bacteria that are able to multiply in places with a low food carbon flow - up to 0.1 mg/l per day. They got the name oligotrophic, the opposite group for them are bacteria copiotrophic– capable of growing on rich food substrates.

The choice of nutrient medium depends largely on the goals of the experiment, and the existing classification of nutrient media takes into account the characteristics of their following features.

By composition nutrient media are divided into natural And synthetic. Natural media are those that consist of products of plant or animal origin that have an uncertain chemical composition. Examples of nutrient media of this type are media that are a mixture of protein breakdown products (casein, mammalian muscles) formed during their hydrolysis. Acid (HCl) hydrolysis of proteins is used to prepare complete hydrolysates. The action of enzymes such as trypsin, pancreatin, papain leads only to partial (incomplete) hydrolysis of proteins, resulting in the formation peptones. As a rule, microorganisms grow better on peptone nutrient media than on nutrient media prepared from complete hydrolysates or mixtures of amino acids. Enzymatic hydrolysis probably preserves labile growth factors. In addition, many microorganisms grow better on media containing small peptides, because they can absorb them directly, while missing amino acids cannot. Typically, in the composition of such a medium, an enzymatic protein hydrolyzate provides the need for nitrogen sources such as amino acids, carbohydrates (glucose), is used as a source of carbon and energy, salts satisfy the needs of bacteria for inorganic ions, and yeast extract provides the needs for vitamins. Nutrient media of uncertain composition also include media obtained from plant raw materials: potato agar, tomato agar, decoctions of cereals, yeast, beer wort, infusions of hay and straw, etc. The main purpose of such nutrient media is isolation, cultivation, production of biomass and maintaining microbial cultures.

Media of uncertain composition also include media semi-synthetic. Known compounds are introduced into such an environment as clearly necessary; and small amounts of yeast or corn extract (or any other natural product) are added to meet unknown growth needs. Such media are often used in the case of industrial cultivation of biological objects to obtain metabolic products.

Synthetic media– these are environments of a certain composition, represented by pure chemical compounds taken in precisely specified concentrations and ratios of individual elements. Mandatory components of such media are inorganic compounds (salts) and carbon- and nitrogen-containing substances (typical representatives are glucose and (NH 4) 2 SO 4. Buffer solutions and chelating compounds are often added to such media. Auxotrophic organisms grow on such media only with the addition corresponding growth factors.The main purpose of such nutrient media is to study the characteristics of the physiology and metabolism of microorganisms, isolate genetic recombinants, etc.

By purpose environments are divided into elective And differential diagnostic. Selective environments ensure the preferential development of one or an entire physiological group of microorganisms. For example, for the preferential isolation of gram-negative bacteria, it may be sufficient to add triphenylmethane dyes (crystal violet, malachite green, etc.) to the nutrient medium. To isolate staphylococci, sodium chloride can be added to the medium at a concentration of 7.5%. At this concentration, the growth of other bacteria is inhibited. Elective media are used at the first stage of isolating a pure bacterial culture, i.e., when obtaining an enrichment culture.

Differential diagnostic media are used to quickly identify closely related species of microorganisms, to determine the species, in clinical bacteriology, etc. The principle of constructing differential diagnostic media is based on the fact that different types of bacteria differ in biochemical activity and have a different set of enzymes that break down substrates included in the nutrient medium.

The differential diagnostic environment includes:

a) the main nutrient medium that ensures the proliferation of bacteria;

b) a certain chemical substrate, the relationship to which is a diagnostic sign for a given microorganism;

c) a color indicator, a change in color indicates a biochemical reaction and the presence of a given enzyme system in the microorganism under study.

For example, Endo environment allows you to distinguish clones that ferment lactose from clones that do not have this property. The main components of this medium are nutrient (peptone) agar, carbohydrate and basic fuchsin decolorized with sulfite (Schiff's reagent). The initial nutrient medium is colored pink. Microorganisms that do not ferment lactose form colorless colonies. When lactose is fermented to acetaldehyde, the latter reacts with sulfite and the red color of the corresponding colonies develops.

Medium with eosin and methylene blue (Levine's medium) contains eosin and methylene blue as indicators and is initially colored black-blue. Cells that carry out fermentation form colonies painted black with a metallic sheen, and colonies that do not have this property are colorless. Such color changes occur because dyes are present in the medium not as independent compounds, but in the form of complexes with substances in the nutrient medium. At low pH values, these complexes precipitate, but the original dyes are soluble under these conditions; at high pH, ​​the dye complexes are colorless, while methylene blue acquires a blue color. This medium makes it possible to differentiate bacteria of the genus Escherichia from bacteria of the genus Proteus.

By consistency environments can be liquid, semi-liquid, solid, granular. Liquid nutrient media are obtained by dissolving a certain required set of nutrients, macro- and microelements in water. In composition they can be either natural or synthetic. The growth of microorganisms in a liquid medium can occur in periodic (closed) system, in this case, after inoculation of the medium, there is no addition or removal of any components other than the gas phase (closed system). At flow (continuous) Cultivation is characterized by a constant supply of fresh nutritional components at a rate equal to the rate of medium removal (open system).

Solid state media in the form of dense gels have been used in bacteriology since the time of R. Koch. The most important advantage of using solid media is that they can grow microorganisms in the form of colonies formed from individual cells of the population.

Preparation solid nutrient media is achieved by adding certain sealants to liquid media, which can be agar, gelatin, silica gel, carrageenan. The most common sealant is agar - a polysaccharide isolated from red seaweed and consisting of two polysaccharides - agarose (70%) and agaropectin. It has a number of useful properties, in particular: 1) it is able to form gels in water;

2) melts at a temperature of 100 °C and solidifies at 45 °C; 3) does not break down under the influence of enzymes of most types of microorganisms; 4) thermolabile substances and living microorganisms are not destroyed when added to molten agar heated to 45 ° C, if the mixture is immediately cooled; 5) agar gels have a high degree of transparency; 6) commonly used concentrations
1.5 - 2.0% are relatively low and their use is economical.

Gelatin, a protein made from skin and bones, is now used for special purposes because the gel it forms melts at temperatures of about 25 - 30 °C. In addition, gelatin is liquefied by proteolytic enzymes of many microorganisms. The “thickening” concentration of gelatin is 17 – 20%.

Silica gel is called silicon dioxide (SiO 2). Its sterile sol is prepared from a solution of sodium silicate and before use, in order to cause the formation of a gel, a nutrient medium containing electrolytes is added to it. Silica gel based media
(1.5 – 2.0%) is used to obtain cultures of autotrophic bacteria, since there are no organic substances in the medium. By adding various organic substances to such mineral media, it is possible to study the ability of heterotrophic bacteria to use them as sole carbon sources. Silica gel media can also be used to determine the vitamin requirements of bacteria.

Carrageenan (“vegetable gelatin”) is obtained by extraction from certain types of red seaweed. Potassium salts of some types of carrageenans are capable of forming dense (2%) transparent gels, which can be substitutes for agar. Carrageenan is much cheaper than agar and is not destroyed by most types of bacteria. However, the prepared media should be poured at a high temperature - 55 - 60 ° C.

Semi-liquid the media contain a gel-forming substance in low (0.3 - 0.7%) concentration and have a soft jelly-like consistency. Such media are suitable for studying cell motility and chemotaxis and culturing microaerophiles.

Bulk media are a mass of more or less crushed and moistened raw materials (most often, plant materials). Their main purpose is to use them in the food industry (producing soy sauce or rice vodka), agriculture (forage silage), etc.

In bacteriological practice they are most often used dry nutrient media that are produced on an industrial scale - tryptic hydrolysates of cheap non-food products (fish waste, meat and bone meal, technical casein) and nutrient agar. Dry media can be stored for a long time, are convenient for transportation, and have a relatively standard composition.

MGAVMiB im. K.I. Scriabin

Department of Microbiology and

immunology

Head Burlakova G.I.

ABSTRACT

Nutrient media and their classification

Completed by a student

II year 1st group FVM

Kurinnova S.V.

Moscow-2007

1. Introduction…………………………………………………………….2

2. Cultivation of microorganisms……………………………...2

3. Classification of nutrient media and methods of their preparation………3

4. Cultivation of mushrooms……………………………………………..7

5. Conclusion…………………………………………………………………………………..8

6. List of used literature…………………………………9

1. Introduction.

Microbes, like any other living organisms, carry out their development and growth, renewal of building materials, and provision of energy processes due to constant exchange of substances with the external environment surrounding them, i.e. through nutrition and breathing. Depending on the type of nutrition, microbes are divided into autotrophs(capable of assimilating carbon from CO 2, as well as molecular nitrogen from the air, and minerals through chemo- or photosynthesis) and heterotrophs(capable of assimilating carbon and other substances only from ready-made organic compounds). Autotrophs mainly include many soil bacteria, and heterotrophs (parathotrophs) include microbes of infectious diseases of animals and plants.

Types of nutrition, respiration (aerobes and anaerobes), induction and activity of enzymes, toxins, pigments, growth and reproduction are the main physiological parameters that are taken into account when developing the composition of nutrient media and conditions for cultivating microbes in vitro.

2. Cultivation of microorganisms .

Cultivating microorganisms means artificially creating conditions for them growth and reproduction invitro, interrelated, but not necessarily conjugate processes. Growth and reproduction is a cyclic 4-phase process (latent, logarithmic growth, stationary, death). The period between the formation of new cells and their division is called the generation period, the duration of which, in addition to the characteristics of the microbe, is influenced by the composition of the nutrient medium. The shapes of colonies of different microbes on a nutrient medium of the same composition differ, which is taken into account when differentiating them.

In vitro cultivation requires substrates that microorganisms can use as nutrients for their growth and reproduction. Such nutrient substrates - dense or liquid - are called cultural or nutritional Wednesdays. In most cases, in microbiological laboratories, microorganisms are cultivated invitro, i.e. in glass flasks, test tubes and other vessels.

There are a number of basic requirements for any nutrient medium:

1). Sterility and, if possible, transparency.

2). When compiling nutrient media, the need of microorganisms for nutrients is taken into account (biochemical factors necessary for the life of cells - energy sources, C, N, S, as well as inorganic ions - available for assimilation by microorganisms).

3). Optimal values ​​of a number of biophysical indicators: concentration of hydrogen ions (pH), oxidation-reduction potential (Eh), water activity ( a w), osmotic pressure.

3. Classification of nutrient media and methods of their preparation.

Depending on the species of microbes and the purpose of cultivation, the consistency and composition of culture media are different and vary widely. An environment that meets the biological characteristics of a microbe and ensures its growth and reproduction is called full, not having any component necessary for its life activity – scarce .

Nutrient media are classified depending on:

Chemical composition and starting components;

Consistency;

· intended purpose.

Depending on the chemical composition and starting components The following types of nutrient media are distinguished:

- environments of uncertain chemical composition(natural or natural environments) are environments that consist of products of animal or plant origin, having a complex, uncertain chemical composition:

1) environments of animal origin (initial products - meat, fish, eggs, milk, etc.)

2) media of plant origin (initial products - soybeans, peas, potatoes, carrots, etc.)

Microorganisms develop well in natural media, but these media are unsuitable for controlled studies of the physiology of metabolism of microorganisms and diagnostic studies, since they do not allow taking into account the needs of a number of components of the environment, and on the other hand, determining the substances produced by microorganisms. Natural environments are used mainly for maintaining cultures of microorganisms, accumulating their biomass and for diagnostic purposes.

"Semi-synthetic" environment (hydrolysate), related to media with uncertain composition. They, along with compounds of a known chemical nature, include substances of uncertain composition. They are used in microbiological practice to obtain vitamins, antibiotics, amino acids and other waste products of microorganisms (hydrolysis products of meat, milk, yeast, blood and other protein substances).

Media of known chemical composition (synthetic)– they contain known chemical compounds (salts, carbohydrates, amino acids, vitamins, etc.) in an optimal quantitative ratio. Synthetic media can be simple in composition or have a relatively large set of components. They are used when the grown cell mass needs to be maximally freed from ballast organic compounds that are part of conventional media, for example, when obtaining diagnostic allergens or when studying the metabolic needs of a microorganism for a particular chemical compound. In addition, researchers are trying to determine the minimum nutrient requirements for each microorganism and, based on this, create minimum an environment containing only the chemical compounds necessary for its reproduction.

By consistency nutrient media are differentiated into solid, semi-liquid and liquid.

Liquid culture media. Prepared using extracts, hydrolysates, solutions of initial products.

Semi-liquid and solid nutrient media . They are used to count the number of bacteria, isolate them in the form of a “pure” culture, and for other purposes. The necessary consistency is given to the medium by adding various sealants - agar-agar or gelatin.

Agar-agar (Malay jelly) is a plant colloid obtained from certain seaweeds. It consists mainly of polysaccharides with an insignificant amount of nitrogenous substances. To obtain dense media it is added in an amount of 1.5-2%, semi-liquid – 0.3-0.7%.

Gelatin is an acidic, nitrogen-containing product obtained by boiling down bones and cartilage. Typically, 10-20% gelatin is added to the culture media. But a number of bacteria secrete proteolytic enzymes that decompose gelatin, which makes it inconvenient for use.

By purpose distinguish:

A).Commonly used (basic) environments .

They are used for cultivating relatively unpretentious microorganisms.

Meat water: Preparation - minced meat is poured with tap water 1:2, boiled for 1 hour, then filtered, topped up with water to the original volume, poured into containers, tightly closed and sterilized by autoclaving at 120 O C for 20 minutes.

Hottinger's digest is prepared from meat waste by tryptic hydrolysis. Fat, fascia, tendons are cut, poured with boiling water 1:2, boiled, cooled to 45 ° C, pancreatin is added, alkalized with sodium carbonate solution, shaken, chloroform is added, closed and kept in a warm place for 10 days.

Meat-peptone broth (MPB). Meat broth is used for cooking. To 1 liter of meat broth add 5-10 g of peptone (the first product of protein hydrolysis with high molecular weight) to increase the calorie content of the medium and 5 g of NaCI to create osmotic activity. Then a neutral or slightly alkaline reaction of the medium is established. Boil. Filter through a paper filter, pour into flasks, test tubes and sterilize by autoclaving at 120 0 C for 20 minutes.

Meat peptone agar (MPA): add 15-20 g of finely chopped agar-agar to 1 liter of MPB. The medium is heated until the agar dissolves, the medium is slightly alkaline with a 20% Na 2 CO 3 solution, filtered and poured into test tubes through funnels, sterilized by autoclaving at 120 0 20 min.

Meat-peptone gelatin (MPG). Gelatin is added to 1 liter of MPB to a final concentration of 10-20%, heated, a slightly alkaline pH is established, boiled, filtered, poured into test tubes and sterilized in a Koch boiler with flowing steam for 3 days or once by autoclaving at 120 0 C at 1 atm. for 20 minutes.

Semi-liquid meat-peptone agar (PZA) prepared like MPA, but add 0.25% agar, boil until it melts, set the required pH, filter while hot and sterilize by autoclaving.

Hottinger's broth : Hottinger's main digest is diluted with water 1:5 (1:8), 0.5% NaСI, 0.1 g of potassium hydrogen phosphate are added, the pH is adjusted, boiled for 150-20 minutes, filtered, poured into containers and sterilized by autoclaving at 120 0 20 min.

Hottinger's agar prepared by adding 2% agar-agar to Hottinger broth.

Nutritious broth contains: tryptic hydrolyzate of sprat – 10.05, NaCI – 4.95. 15 g of this broth powder is dissolved in 1 liter of dist. Water is boiled for 2 minutes, filtered, poured into containers and sterilized in an autoclave at 120 0 C for 20 minutes (Ph 7.3).

Culture media- biological preparations used for growing microorganisms and studying cultural, biochemical, antigenic properties, phagolysability and sensitivity to antibiotics.

Nutrient media are widely used in laboratory practice for the diagnosis of infectious diseases, as well as for monitoring the sterility of medicines. In order for microorganisms to grow and develop, nutrient media must meet the following requirements.

1. Optimal composition. They must contain all the necessary components that are needed for the development of microbes: proteins, vitamins, carbohydrates, minerals.

2. Optimal pH value. Most microorganisms develop at pH 7.2...7.4.

3. Sterility. It is necessary in order to avoid competition between microbes.

4. Transparency. To better study the nature of microbial colonies.

5. Humidity. Nutrition and respiration are carried out by osmosis and diffusion, so the nutrient media should be slightly moist.

Classification of media. Nutrient media are divided according to the following characteristics.

1. By consistency: a) dense (solid) - agar 1.2...2% (meat peptone agar); b) semi-liquid - agar 0.2...0.3% (semi-liquid agar); c) liquid - meat-peptone broth.

To give media a dense or semi-liquid consistency, agar-agar, a polysaccharide isolated from seaweed, is most often used. Agar is capable of forming a gel in water that melts at 80...100 °C and hardens at 37...40 °C. Agar's resistance to the liquefying action of most microorganisms, as well as the ability to form strong jellies, have led to its widespread use in bacteriology.

2. By origin: a) artificial: animal (MPA, MPB) and plant origin (beer wort); b) natural: animal (blood, milk) and plant origin (potato pieces).

3. By composition: a) protein; b) protein-free; c) mineral.

4. By purpose: a) media for cultivation (simple, special); b) enrichment media (for the accumulation of microorganisms at their low concentration in the source material); c) preservative media for primary seeding and transportation of pathogens; d) media for identification (differential diagnostic) - microbes of one type form colonies that differ in appearance from colonies of other microorganisms.

If the material is slightly contaminated with foreign microflora, then simple general purpose media (MPA) are used to isolate cultures; in case of heavy contamination with saprophytes, special media are used: selective (for certain species) and differential diagnostic (to facilitate identification).

Media characteristics. Preservative transport media(glycerol mixture, phosphate buffer, thioglycollate medium for anaerobes, etc.). They prevent the death of pathogenic microbes and suppress the growth of saprophytes.

Enrichment media(selective broth, bile broth, Muller's medium, Rappoport, Kaufman's medium, alkaline peptone water). They are used to accumulate a certain group of bacteria by creating conditions that are optimal for some species and unfavorable for others. The most commonly used are various dyes and chemicals - salts, bile acids, potassium tellurite, antibiotics, fuchsin, etc.

Elective (selective environments). They provide more favorable conditions for the isolated microbe while simultaneously suppressing the accompanying microflora. For example, Ploskirev's media and salt agar are used for primary seeding of material or for subculture from preservative or enrichment media in order to obtain a pure culture.

Differential diagnostic environments. Designed to determine the species of the microbe under study, based on the characteristics of its metabolism.

Media for identifying the proteolytic and hemolytic ability of microbes. They contain protein substances (blood, milk, gelatin, etc.).

Media with indifferent chemicals. They serve as a source of nutrition for some types of microbes and are not digestible by other types (Simmons citrate agar).

Media with carbohydrates(monosaccharides, disaccharides, polysaccharides), polyhydric alcohols (sorbitol, mannitol), glycosides (salicin, inositol) to detect the corresponding enzymes.

Media for determining the reducing ability of microbes. They contain paints that become discolored upon reduction (Omelyansky agar with indigo carmine), as well as nitrates to determine the denitrifying ability of microorganisms.

Dry culture media. Bacteriological laboratories mainly use commercial dry media. They are ready-made nutrient media, dried and crushed to a powdery state. Dry media have a number of advantages over conventionally produced media: they can be stored for a long time in a dry, dark room in a hermetically sealed container, they are transportable, easy to use and standard, which makes it easier to obtain comparable results during bacteriological research.

Solid media consist of a nutrient base, agar-agar, indicators and other organic and mineral substances that improve the growth of some microorganisms and inhibit the growth of other microorganisms.

Various protein sources are used as the nutritional basis for dry media. Abroad, dry media is most often made using meat-peptone broth, which requires a large consumption of beef meat. In our country, hydrolysates of sprat, casein, and feed yeast are used as a source of protein.

To package dry nutrient media, orange glass jars (250 g), polyethylene jars (250, 500, 1000 g), as well as bags of three-layer laminated paper (50...200 g) are used. The shelf life in glass and polyethylene jars is 2...4 years, and in bags made of three-layer laminate - from 1 year to 4 years.

The domestic industry produces more than 120 types of various dry nutrient media. The largest producers are the Federal State Unitary Enterprise NPO “Nutrient Media” (Makhachkala) and the State Research Center for Medical Sciences (Obolensk) (M. M. Medzhidov, Handbook of Microbiological Nutrient Media. - M.: Medicine, 2003). The following media are most often used in practical laboratories.

Dry differential diagnostic media. If earlier in the practice of veterinary bacteriological laboratories, Hiss media containing a single carbohydrate was widely used to identify microorganisms, then recently media that make it possible to differentiate microorganisms by two or three characteristics have become increasingly used.

Rossel environment(FSUE NPO “Nutrient Media”). Designed for primary identification of enterobacteria. The prepared medium is green. After sowing the culture, after 18...20 hours of incubation at 37 °C, lactose fermentation is judged by the appearance of a yellow color in the slanted part of the agar, and glucose fermentation is judged by the yellow color of the agar column. Gas formation is indicated by the appearance of bubbles and ruptures in the agar. If the microorganism does not ferment glucose and lactose, the medium remains green or turns blue.

Kligler's medium(FSUE NPO Nutrient Media, Makhachkala and JSC Biomed named after I.I. Mechnikov, Moscow). Designed for primary identification of enterobacteria. The prepared medium is red. It is necessary to mow so that a column 2.5...3 cm high remains. Sowing is done first into the thickness of the medium, and then along the beveled surface. After 18…20 hours of incubation at 37 °C, the results are taken into account. If the microorganism ferments lactose, the slanted part of the agar turns yellow. When glucose is fermented, the medium turns yellow in the column. With gas formation - the appearance of bubbles and ruptures of the agar. If hydrogen sulfide is formed, the medium becomes black. Indole production is determined using special indicator papers.

Double-layer iron-glucosolactose agar with urea. Olkenitsky’s environment (FSUE NPO “Nutrient Media”). These media allow bacteria to be identified by their ability to ferment glucose and lactose, produce hydrogen sulfide, and break down urea. Detailed instructions on preparation, method of inoculating microorganisms and recording the results can be found in the “Handbook of Microbiological Nutrient Media” by M. M. Medzhidov.

Dry elective nutrient media. Selective salt agar(SA) (FSUE NPO "Nutrient Media" and FSUE "Allergen", Stavropol). Designed to isolate staphylococci from the test material. Can serve as a basis for preparing yolk-salt or milk-salt agar. When inoculating material on SA, after 48 hours of incubation at 37 °C, staphylococci grow in the form of round colonies with a diameter of 2...4 mm.

Selective nutrient medium for isolating pneumococcus(pneumococcus-agar) (FSUE NPO “Nutrient Media”). Designed for selective isolation of pneumococcus from pathological material (blood, sputum, pus). The prepared medium is brown in color. 24...48 hours after inoculating the material and incubating it at 36...38 °C in a “candle vessel” conditions, pneumococcus forms convex colonies on the medium up to 1 mm in size, clearly distinguishable from pale pink colonies of staphylococcus.

Nutrient medium for isolating fungi of the genusCandida(candida agar) (FSUE NPO Nutrient Media, Makhachkala). Designed for the isolation of fungi of the genus Candida from infected material and environmental objects. The medium is not autoclavable. Fungi of the genus Candida on this medium after 22...24 hours of incubation at 37 °C form dense convex or flat colonies of creamy consistency with smooth or wavy edges measuring 1...2 mm.

The medium suppresses the growth of accompanying bacterial flora (Escherichia coli, Proteus, staphylococcus).

Selective agar for isolation and preliminary identification of enterobacteria in urine(analogue of MacConkey agar) (FSUE NPO Nutrient Media). It is recommended for the isolation and preliminary identification of enterobacteria from urine, and can also be used for bacteriological examination of food products, feces, and wastewater.

The prepared medium is red-brown in color, transparent, with slight opalescence. After 16...20 hours of incubation of the inoculation at 37 °C, lactose-negative Salmonella form transparent colorless colonies, lactose-positive Escherichia - colonies of bright crimson color. The medium suppresses the “swarming” of proteas, which grow in the form of colorless isolated colonies in the O-form. The growth of staphylococci is completely suppressed.

Nutrient media of other groups. Glycol medium(FSUE NPO Nutrient Media, Makhachkala; JSC Biomed named after I.I. Mechnikov, Moscow). Designed to control the sterility of medical and biological preparations. The results are recorded in accordance with the instructions “Testing of medicinal products for microbiological purity”.

Nutrient media No. 1 and 2 are produced by FSUE NPO Nutrient Media (Makhachkala) and FSUE Allergen (Stavropol).

Nutrient medium for controlling microbial contamination, dry No. 1. Used to determine the total contamination of non-sterile drugs and food products.

Nutrient medium for controlling microbial contamination (Saburo-agar) No. 2. Recommended for cultivating mushrooms, as well as determining the content of fungi in non-sterile medicinal media and other environmental objects.

Erythritol agar And erythritol broth. Designed for the isolation and cultivation of Brucella.

Nutrient medium for isolation and cultivation of anthrax microbe.

Ketoglutar agar. Effective for isolating and culturing the causative agent of tularemia.

AGV environment. Proposed for determining the sensitivity of microorganisms to antibiotics using the disk diffusion method.

Nutrient medium for rapid determination of antibiotic sensitivity of opportunistic bacteria. Proposed for rapid determination of antibiotic sensitivity of gram-negative opportunistic microorganisms. The results can be taken into account after 4…5 hours.

The range of dry nutrient media produced by the domestic industry is constantly expanding. Only a small number of those that can be used in the daily work of veterinary laboratories are given. In addition, it is currently possible to purchase imported nutrient media. Commercial names can be found by ordering the corresponding catalogues. However, their introduction and widespread use in veterinary laboratories of the Russian Federation is possible only in the long term due to their rather high cost. In addition, this chapter does not mention ready-made commercial nutrient media of fairly good quality produced by the Scientific Research Center for Physics (St. Petersburg). They are packaged in 400 ml bottles; shelf life 1 year. Media can certainly be useful when carrying out bacteriological work in the field.

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