Wednesday Ploskirev (Bactoagar F): description. Medical Microbiology

Ploskirev's medium (also called Bactoagar G) is a nutrient medium for the cultivation of certain microorganisms, mainly Shigella and Salmonella. As a source for her use of infected materials: urine, bile, bowel movement.

History

Nikolai Ivanovich Ploskirev is a Soviet microbiologist and Honored Doctor of the RSFSR. He was born in 1869 and died in 1948, most of his life working in his native city - Tomsk.

In 1888, he, a future scientist, did not finish the sixth grade of the school, entered the military service. He finished his studies only in 1892, after which he passed exams for admission to the Imperial Tomsk University, he studied at the Medical Faculty. In 1898 he received the title of physician.

Ploskirev participated in the Russo-Japanese War, and after that he worked in the Tomsk hospital. In 1910 he was appointed head of the Tomsk Dermatovenerologic Hospital and for thirty years was its permanent head. Similarly, the scientist was one of the founders of the dermatovenerologic dispensary in Tomsk.

Nikolai Ivanovich Ploskirev wrote a series of works devoted to the fight against venereal diseases.

Composition

Wednesday Ploskirev - a material for the cultivation of intestinal bacteria, and therefore, must contain several types of nutrients. It is produced in dry form.

Pancreatic hydrolyzate of sprat (10.4 g / l) has a rather large share in its total mass. Slightly less is necessary for disodium hydrogen citrate (8.5 g / l). It also contains dry nutrient broth and milk sugar (8.62 and 7.3 g / l).

The second name for Ploskirev's medium is Bactoagar J. It contains agar in the amount of 6.94 g / l. The content of anhydrous sodium sulfate is 5.1 g / l. There is the presence of dehydrated phosphate disodium - 2.1 g / l, sodium salts of bile acids about 3.46 g / l, and soda ash - 2.4 g.

Less gram contains indicators - neutral red (0.05) and brilliant green (0.0002). The iodine content is 0.13.

Application

The study of the biochemical processes of bacteria plays a very important role in the diagnosis of diseases that cause anaerobic organisms. The species included in this family are hundreds. They are almost identical in morphology and cultural properties, and the most reliable way to distinguish them from each other is to study biochemistry.

The study begins with the sowing of pathological material in the nutrient medium. It is differential-pathological for the intestinal group of bacteria, and its composition, in addition to meat-agaric agar, includes an indicator and lactose. The ability to process lactose is an important sign of differentiation of enterobacteria. If this is detected, the pH shifts towards acidity and an indicator that stains the colony is triggered.

In other countries, other nutrient media can be used, but the mechanism of their action corresponds to the three most common in Russia - the environments of Endo, Levina, and Ploskirev's environment.

Description of the method

Abroad, the analogue of Ploskirev's environment is the so-called MacConkey Agar. In the finished form, the solution is transparent, has a light pinkish-yellow hue. Colonies that are able to process lactose are given red (cowberry) color in Ploskirev's medium . If the bacterium can not process it, the colony is either colorless or weak in color.

In view of the fact that Ploskirev's medium contains inhibitory substances (brilliant green, bile salts, iodine), it virtually completely suppresses the growth of gram-positive flora, and on the first day significantly inhibits the growth of the eshechiria, as well as the other usually accompanying microflora.

Second phase

Next, the selection of the colony of interest takes place, and it is sown to the primary differentiation and accumulation media. The media on which seeding occurs must contain several substrates. Bacterial culture should detect enzymatic activity in relation to them, besides the media are located in test tubes so that there are two areas:

• The one on which the agar is skewed;
• With a column.

The colony that interests the researcher is populated on the sloping part with a dense stroke, and in the column - with a prick. At this stage, the media of Russell, Kligler or Olkenitsky are used. As a differential-diagnostic, Ploskirev's medium is also used.

Microbiology and pathogens

Ploskirev's agar is an important factor in the detection of infections caused by enterobacteria. So, for example, it grows and differentiates colonies of microorganisms, which are the causative agents of bacterial dysentery. These are anaerobic organisms that enter the genus Schigella.

Like all who are part of the family of intestinal bacteria, Shigella are the kind of rods, the size of two micrometers. They do not form capsules and spores, do not have flagella - this allows them to be distinguished from Salmonella, which in turn is mobile. They perfectly grow on the simplest environments, at a temperature just above room temperature (35-37 ° C) and 7.4 pH. By the nature of growth, the colonies do not differ from salmonella.

As mentioned above, microorganisms can have practically no morphological differences, but they differ significantly in biochemical processes of vital activity. So, except Shigella Newcastle, the fermentation of carbohydrates is the formation of acid without gas. With the exception of shigella Sonne, they can not ferment lactose, but break down glucose. Also, to their key characteristics can be attributed to the fact that they can reduce niracy to nitrites. Their colonies do not cleave urea, and in the nutrient medium there is no liquefaction of gelatin.

Collection and preparation of inoculum

To detect pathogens of dysentery, microbiological studies of infected media, that is, patient's bowel movements, are necessary. After receiving the material, it is necessary to sow as soon as possible. If this is not possible, the source must be placed in a preservative - a phosphate buffer mixture or glycerol. At a temperature of 4 ° C they can be stored for no more than a day. Collection of material should be done with a rectal glass tube, which is inserted into the rectum.

For investigation of the material purulent-slimy pieces are selected, which must be washed in two or three tubes of isotonic sodium chloride solution.

The application of pathogenic bacteria to Ploskirev's medium is made with a glass spatula. It is necessary in a small area to rub it into agar, then tear off the spatula from the medium, and the residual material should be rubbed into the unsealed surface. If sowing is done in several cups, each of them needs to be sowed with a new portion.

If there are no mucopurulent pieces in the excreta taken for analysis, this does not mean that pathogenic microorganisms are not present there. In such a case, it is necessary to emulate feces in 10 ml of sodium chloride solution (concentration 0.85%), then sow one or two drops on the Ploskirev medium. The emulsified stool can be sown in the selenite broth. It is also used if there are vomit or wash water instead of feces.

Microbiological diagnostics

At the first stage of microbiological research, pathogenic bacteria are seeded into two cups, then to observe how the shigella grows. On Ploskirev's medium, one crop is produced, the second is on Levin or Endo's medium.

In view of the emergence of Shigella strains resistant to antibiotics, levomycetin is added to the media. Then, during the day, incubation takes place in a thermostat at a temperature of 37 ° C.

On the second day you need to study the grown up colonies. Those that do not grow colorless on a differential diagnostic environment must be weeded out to Russell's medium or a short "motley series." Further research is carried out according to the algorithm of primary crops on them. Colonies of shigellas on Ploskirev's medium grow in the form of transparent, colorless and small columns. They are of two types:

• Flattened with jagged edges;
• Rounded, convex, with a characteristic moist luster.

Three or four colonies must be microscopized and examined for mobility. In case the latter is not found, they are moved to Olkenitsky's environment in order to single out a pure culture. In the absence of characteristic colonies of shigella, or if there is no growth at all, it is necessary to make seeding from the selenite broth on Endo or Ploskirev agar. If typical colonies are present in sufficient quantities, an approximate agglutination reaction is put. Used a mixture of sera Sonne and Flexner, the reaction takes place on the glass.

Further research

On the third day, the changes that occurred in the colonies on the Russellian environment are noted. If there is a culture that does not decompose lactose, and glucose ferments with the formation of acid, it is separated and examined, microscopy is carried out, and also sowing is carried out on the "motley series", but this time it is deployed. In the same way, an agglutination test is performed for the purposes of serological identification.

On the last day you can make a conclusion on the basis of changes in the "motley series" (whether there is fermentation of carbohydrates), as well as summed up the agglutination reaction.

Storage and preparation

The preparation of Ploskirev agar proceeds in this way:

1. 55 g of dry substance is stirred in liter of distilled water.
2. Boil for two to three minutes, until the agar is completely melted.
3. Pour into Petri dishes (sterility is optional) with a layer of 5-6 mm.
4. The cups are left open for an hour and a half at room temperature (18-25 degrees). At the end of this time, the medium will freeze and dry sufficiently.

The environment of Ploskirev is light sensitive and hygroscopic. The powder must be stored in a sealed package, the relative humidity of the air in the room should not exceed 60%. The optimum storage temperature is from 2 ° C to 25 ° C. It is necessary to comply with the above storage rules, otherwise inaccurate research results are possible.