Antibiotics

Antibiotics are substances of microbial, animal or vegetable origin, selectively inhibit the viability of microorganisms. Most of the antibiotics used in medical practice, derived from the actinomycete (radiant fungus).
Antibiotics are very effective in the treatment of many infectious diseases caused by bacteria, fungi, protozoa, the spirochaetes, by Rickettsia, large viruses. The doctrine of antibiotics is closely connected with the problem of antagonism of different microbial species. Currently, described more than 2000 antibiotics, studied all or part of the structure of more than 600, of which a number of synthesized. However, in practice used about 50 drugs because many antibiotics are toxic to humans.
Antibiotics are classified depending on the origin, chemical structure, spectrum. For clinical practice is an important indicator for use of a medication is action spectrum is the range of micro-organisms in respect of which the active given an antibiotic. There are antibiotics narrow-spectrum antibiotics (penicillin), broad-spectrum antibiotics (tetracyclines), intermediate-spectrum (macrolides). In addition, there are drugs that have antifungal activity (polyene antibiotics), antitumor effect (the aktinomitinov, mitomitina and others).
The mechanism of action of antibiotics can be divided into: 1) violating the formation and function of membranes of microorganisms, 2) violates the synthesis of ribonucleic and deoxyribonucleic acid and protein microbial cells.
Medicinal value of antibiotics (if you are sensitive to it of the causative agent) largely depends on the nature of absorption of antibiotics and drug distribution in the body, and on ways and dynamics of its removal from the body. Of great importance in establishing the maximum concentration in a particular organ and tissue has a method of drug administration.
When using antibiotics may cause various side effects. Special attention deserves the emergence of multiple antibiotic-resistant forms of microorganisms, which is associated with excessive and often unjustified use of antibiotics. Resistance of microorganisms to antibiotics develops selectively. An important factor is the emergence of resistant microbes to multiple antibiotics (polyresistance, cross-drug resistance).
Diseases caused by resistant forms of microorganisms are recommended new drugs, as well as combined treatment of multiple antibiotics.
Production of antibiotics is biological, synthetic and semi-synthetic ways. Great attention is paid to the receiving antibiotics by a semi. So managed to get a large number of derivatives of penicillin, differing from it in their pharmacological and antibacterial properties (oxacillin, methicillin, ampicillin and other). Preparations of antibiotics - see articles on the name of the drug.

Antibiotics (from the Greek. anti - against and bios - life) - products of metabolism of microorganisms, especially of lower plants with the capacity to suppress the activity of other microorganisms or the development of some cells of malignant tumors. In a broader sense antibiotics called and antimicrobial substances, which are part of higher plants or animals. A relatively small number of natural antibiotics can have a specific effect of the sick organism, i.e. to serve drugs. In this sense, antibiotics are very close to synthesized chemotherapy means, differing from them only way to obtain.
Classification. Antibiotics can be classified not only by producing their microorganisms, but also spheres of action and chemical structure.
For example, decided to allocate the antibiotic anticancer, antiviral, antibiotic active against pathogenic fungi, against Mycobacterium tuberculosis, etc., On chemical structure antibiotics are divided into the following groups: 1) A. of acyclic structure, of which the most important polyene antifungals such as nystatin, 2) A. alicyclic structure, 3) tetracyclines, 4) A. aromatic structure, 5) chloramphenicol (chloramphenicol), 6) quinones, 7) oxygen-containing heterocyclic compounds, of which the most important griseofulvin, active against dermatophytes, 8) macrolide antibiotics, including erythromycin, oleandomitin, minomycin and others, 9) streptomycin and streptomitsetov A., including neomycin, micurin, monomitsin, kanamycin, paromomycin and others, 10) nitrogen-containing heterocyclic compounds, including cycloserine and one of the first anti-cancer A. - puromycin, And) penicillins, 12) polypeptides and proteins, which include gramicidines, bacitracin, polimiksin, lysozyme, colimycin, Grisey, Albaicin and others, 13) depsipeptide, 14) aktinomitinov with mainly antineoplastic properties, and 15) streptothricin.
Receiving. Higher plants produce large amounts of antibiotic substances, however, due to low efficiency in the infected organism they are almost never applied in the clinic, with the exception of several special position of quinine. Antibiotic substances of animal origin - lysozyme, akmolin and Eritrean - are of limited use. The main producers of antibiotics used in medicine, are microbes - microscopic fungi and bacteria.
The selection of microorganisms these antibiotics based on the phenomenon of antagonism of germs (see Antagonism). To obtain natural antibiotic industrial way it should be accumulated in a nutrient medium in large quantities. For this purpose, as a rule, required preliminary work on the selection of the most active strains - producers and on the preparation of a nutrient medium, which would provide a higher production of antibiotics. At the end of the period of fermentation culture fluid is separated from the mycelium and purified. Production of some antibiotics relatively simple structure (for example, levomitsetina and cycloserine) is also carried out by chemical synthesis.
The effect of antibiotics on the microbial cell can be bacteriostatic or bactericidal. Character of action of antibiotics on the microbial cell depends not only on the nature of matter, but also on the state of the cells, which is determined by its genetic characteristics and physiological activity. Hereditary fixed increased resistance of germs to A. is called drug resistance and is the result of changes of the genetic properties of the organism as a result of its interaction with A. especially Ability to quickly develop drug resistance differ staphylococci.


Application. The choice of antibiotic for the treatment of infectious diseases should primarily be based on information about the antibiotic sensitivity of the causative agent; it is necessary to take into account also of chemotherapy and pharmacological properties of the drug and peculiarities of the patient. It is best to define the sensitivity of the causative agent by the laboratory, which you can use special disks containing basic antibiotics in concentrations close to those that can be created in the blood with the introduction of conventional doses. It should be noted that the local introduction A. in the focus of infection can be created much higher concentrations, and in these cases, the antibiotic can be effective against germs with a higher level of sustainability. When difficulties allocation of the pathogen, and in urgent cases you can choose an antibiotic for the treatment based on indirect data, allowing most likely to assume a particular pathogen. It is very important before treatment to determine which A. is already introduced to the patient and not have it at that, side effects, especially allergic. In doubtful cases can be recommended to produce a skin test.
Side effects of antibiotics on macro can be direct, unique for each of the antibiotic, and indirect, can be caused by the sensitivity of the organism to antibiotics (especially it is typical of penicillin, low-toxic in other ways) or dysbacteriosis. Dysbacteriosis can occur as a result of suppression A. normal microflora. Insensitive to this A. microbes that were in the body or fallen from the outside, can cause new disease process, such as candidiasis. Complications of this type are especially frequent during treatment with broad-spectrum antibiotics, such as tetracycline. To avoid such complications, it is recommended to apply tetracycline with nystatin. It should not be too long to apply the same antibiotic, if the clinical course of the disease shows its inefficiency. In this case, or to re-verify the sensitivity of the causative agent, or on the basis of indirect data about its nature and sensitivity to apply other drug.
Individual A. - see related articles.