Bacteriological examination

Bacteriological examination, investigation, intended for selection of bacteria and study their properties with the purpose of registration of microbiological diagnosis.
The material should be collected aseptically into a sterile vessel and transported to the laboratory as soon as possible. If necessary, samples should be stored in the cold. Methods of sampling depends on the object, the nature of the disease and properties of the microorganism. One of the common methods of bacteriological study is to smear.
To study the flow of bacteria are two methods: crushed (between subject and integumentary glass) drops and drops hanging. It should be remembered that the drugs flow contagious bacteria.
For smear microscopy fixed drug use strokes. For their preparation drop investigated liquid spread over the surface of the slide, and then dried. The most common method of fixation of the drug is proexecution it through a gas flame. In some cases, use the locking compositions. Fixed drugs, as a rule, paint (see the Colour of microorganisms). Among the most important elements of bacteriological research include the culture and subcultures bacterial culturesproduced by bacterial loop or the Pasteur pipette. The loop is sterilized by burning in the flames, then its cool touch of the plot early years of the agar or polaskova in a sterile liquid. When using a Pasteur pipette it breaks off the tip tweezers, several times sneaked the eyedropper through a flame and allow to cool down. When crops are using the liquid and solid nutrient media. If planted on sloping agar culture of bacteria pound a loop on the surface of the agar. When planting in thickness agar or gelatin column nutrient medium pierce to the bottom of the tube loop or a special needle. When planting in a liquid environment, it is necessary to watch that the liquid was poured and didn't wet the edges of the test tubes and tube. The culture and subcultures should be near a gas flame, the tubes should not remain open loop or Pasteur pipette with culture should not to touch nothing; before closing the tube, the edges of her be burned. Sown tubes must immediately to label.
The most important stage of bacteriological research is identification - identification of species or standard facilities of bacteria obtained in pure culture. When identifying bacteria is the study of physiological and biochemical properties, coccinobaphi. Widely used serological methods for the identification of bacteria (reaction agglutination and precipitation). In many cases, effective biological method of identification of microorganisms based on the infection of laboratory animals of the studied material, or received by bacteria culture and identification of animals characteristic pathological changes.
To obtain pure cultures use of mechanical and biological methods. An example of a mechanical method: drop investigated material grind the same sterile spatula or bacterial loop on the surface of the dense medium, sequentially in the first, second and third Petri dishes. Allocation of net culture is grown from isolated colonies and is in their research and dropout rates on fresh medium. Biological methods obtain pure cultures based on a particular property allocated microbe that distinguish it from other microbes contained in the material studied.
When the biological method use this kind of medium, which created conditions favorable for development of a certain species of microbes. Among the biological methods is also infected laboratory animals, sensitive allocated mind bacteria.
The cultivation of bacteria produce in thermostats, in which the temperature is kept constant, usually 37 degrees. In most cases, growing continue for about a day, but depending on the type of bacteria are required and other terms of cultivation. Different types of bacteria needed for growing different amounts of oxygen. To maintain the required oxygen concentrations in the environment are various methods of aeration. Cm. also Nutrient medium.

Bacteriological testing is a complex of methods for detection of pathogenic microorganisms in a patient, the media or on the objects of the external environment. Bacteriological tests are also used to detect opportunistic and sanitary-representative of microbes, characterizing the degree of environmental pollution, to study the microbial landscape of a specific environment (object). Bacteriological examination can be used for diagnostics, prophylaxis of infectious diseases, San.-the gig. characteristics of the human environment, for scientific research.
Material and method of bacteriological tests depend on the purpose of the analysis, environmental conditions, pathogenesis and course of the disease. If there bacteremia microbe find with blood cultures. In cases of severe local lesions of the pathogen should be sought in the discharge or discharge of the affected organ (diphtheria, dysentery, gonorrhea, and others). Finally, diseases with complex for when (as, for example, typhoid fever) bacteremia replaced lesions of the small intestines, at each stage, use the appropriate method of investigation: in the first week of the disease produces blood cultures, the second most reliable serological testing, starting from the third week a positive result is obtained when sowing of faeces; the latter method is used and as a follow-up research to detect bakterionositelej among patients and to monitor them.
Performing any of these tasks carried out using methods that are designed to isolate and identify microorganisms. Depending on
characteristics of the germ use the whole complex of methods or part of it.
Smear - most dostupny reception, based on the microscopic examination of material. Microscopic examination of fresh drugs can enjoy some micro-chemical reactions (for example, coloring iodophyllic bacteria Lugol solution) or selective colouring different structural parts of bacteria.
More clearly bacteria can be identified in the painted product. The material is put on a glass slide a thin and even layer. Give the drug to air dry and fix one of the generally accepted methods, but mostly plombirovaniya, i.e., two-, three-fast conduct of the drug over the flame of the burner so that the glass was warm, but not hot. The drug, cooled after fixing, paint simple or differential coloring (see the Colour of microorganisms). When fluorescent microscopy is used both fresh and dried preparations. In this case, the processing of certain dyes is the glow of microbial structures of the body or the whole of the germ in the ultraviolet or short blue rays. In other modification of microbes handle specific serums, labeled fluorescently (dyes). Bacteria, corresponding serum, will be lit, as they will settle labeled serum. Heterologous bacteria will not light up.


By the method of smear microscopy is widely used for bacteriological diagnosis of some infectious diseases (gonorrhea, tuberculosis, and relapsing fever), as well as in the study of the whole complex of the microflora of a body (the amygdala, the vagina), product or other object.
The method of sowing, i.e. the allocation of pure culture of the required microorganism is more accurate and reliable method of bacteriological diagnosis, than smear. Fresh material smear on the surface of the dense medium, poured in Petri dishes. Initial seeding is produced on a regular environment favorable for this microbe, differential or on a selective environment. The choice of a medium (see)as a method of preliminary processing of fresh material for sowing, depends on the degree of contamination associated by other organisms. In 24-48 hours. content in thermostat at optimal for this microbe temperature Cup consider and suspect colonies subcultured on an environment conducive to reproduction of this germ. Thus receive a homogeneous culture of bacteria, which must be identified.
Identification of the germ begins with a study of the morphology painted in the preparation and crushed drop (see) to determine the form of microbes and their mobility. The next step is the study of the enzymatic ability of bacteria on the breakdown of carbohydrates, amino acids, urea defined for each type combinations. In bacteria, the most studied the sugar - and proteolytic enzymes.
Identification of a microbe must be supplemented by the study of other properties, characteristic for each genus and species of microorganisms. These properties include the ability to selectively dissolving erythrocytes of different animals (hemolysis), collapse the blood plasma (plasmahouse), to dissolve fibrin clot (fibrinolysis), etc. these are All characteristics of bacteria can be used in their definition as differential characteristics.
The final determination of germs of some species, mainly of pathogenic bacteria of the family intestinal includes serological identification (see Identification of microbes). Normally that would put an agglutination reaction, i.e., identify a grouping of individuals bacteria under the influence of the same name immune serum. Agglutination of microbes in serum against a certain type indicates belonging to this type. Usually the agglutination reaction tentatively put on the glass and to the final determination in test tubes with dilutions of the serum.
A number of microbes cannot be determined until the end of the described way. Then the identification should be supplemented by infection of laboratory animals, because some bacteria characteristic pathogenicity or toxigenicity, emerging in infected animals. In some cases, the infection of animals is also the method of accumulation of pathogenic microbes.
Only the mapping of all characteristics of the culture gathered in the study of morphological, biochemical, serological, and where necessary and biological properties of it, may provide grounds for identification. The answer with a positive result of the study is no problem if the selected microbe typical. In this case, specify the genus, species, and, if determined, the type of bacteria. At selection of a microbe that are different for some properties from the typical characteristics is given a reply stating on deviant sign. In this case, it is useful to repeat the study, if the disease or condition. It is also beneficial to expose the culture of atypical germs additional study of other, more sophisticated methods.
The negative results of bacteriological tests have relative value and show that in the investigated part of the material found microbes are not held or were not viable. However, they may be present in another serving. This, for example, during examination on presence of bacilli (typhoid fever, dysentery, diphtheria) requires re-examination.