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BACTERIAL ACTION (bacterium[a] + lat. to kill with caedere) — ability of various physical, chemical and biological agents to kill bacteria. Concerning other microorganisms use the terms «virotsidnost», «amebotsidnost», «fungicidity» etc.

To the physical factors operating bakteritsidnoh, high temperature belongs. The majority of asporogenic bacteria perishes at t ° 60 ° within 60 min., and at t ° 100 ° is instant or the first minutes. At t ° 120 ° full sterilization of material is observed (see. Sterilization ). Besides, B. possess nek-ry not ionizing (ultraviolet rays) and the ionizing types of radiations (x-ray and gamma-rays). Under the influence of ultraviolet rays microorganisms have a damage of DNA which consists in formation of dimer between the next pirimidinovy bases. Thereof DNA replication is blocked. Sensitivity of microorganisms to ionizing radiation is connected with specific accessory. Gram-negative microorganisms are more sensitive to gamma-rays, than gram-positive. Disputes and viruses have the highest resistance to them. The mechanism of bactericidal action of ionizing radiation is connected with damage of nucleic acids — gaps in a polynucleotide chain, chemical changes of nitrogen bases etc. The bactericidal effect of ultraviolet rays received practical application, in particular for disinfecting of rooms. The question of use of gamma-rays for sterilization is intensively studied.

Among the chemical agents possessing B., big specific weight is occupied by poverkhnostnoaktivny substances (phenol, quaternary ammonium compounds, fatty acids etc.). Many of them belong to to desinfectants (see). The bactericidal effect can be caused by the general denaturation of proteins, disturbance of permeability of membranes and an inactivation of nek-ry enzymes of a cell. Data that the bactericidal effect of many disinfecting connections can be connected with blockade of the enzymes participating in processes of breath (oxidases, dehydrogenases, a catalase etc.) collect. Many connections (proteins, phospholipids, nucleic acids etc.) can form complexes with poverkhnostnoaktivny substances that reduces them B a little.

Bactericidal action of a number of chemical connections is widely used in medicine, the industry and agriculture.

Among biol, the agents acting bakteritsidno it should be noted β-lysines, a lysozyme, antibodies and a complement. Generally bactericidal effect of blood serum, saliva, tears, milk etc. on microbes depends on them.

The bactericidal effect of a lysozyme is connected with effect of this enzyme on glucosidic bonds in glycopeptide of a cell wall of bacteria. Action of antibodies and a complement is caused probably by disturbance of a cell wall of microorganisms and emergence of impractical protoplasts or spheroplasts. Bactericidal action of properdinovy system, antibodies, a lysozyme and so forth plays an extremely important role in protection of an organism against an infection.

It should be noted that the nek-ry antibiotics relating to poverkhnostnoaktivny substances (gramicidin, polymyxin etc.) render not bacteriostatic, but bactericidal effect on microorganisms.

Bactericidal effect of radiation it is caused by impact of ionizing radiation on the vital macromolecules and intracellular structures of microorganisms. It depends on radio stability of this species of microbes, initial concentration of cells in the irradiated volume, existence or lack of oxygen in a gas phase of the irradiated object, heating environments, extent of hydration, conditions of keeping after radiation. In the general form spore-formers (their disputes) several times more radiorezistentna, than asporous or vegetative forms. In the presence of oxygen radio sensitivity of all bacteria increases by 2,5 — 3 times. Change of temperature in a radiation time within 0 — 40 ° has no significant effect on bactericidal effect of radiation; reduction of temperature below zero (— 20 — 196 °) reduces effect for the majority of the studied objects. Reduction of extent of hydration irradiated a dispute increases their radiation resistance.

Because initial concentration of bacteria in the irradiated volume defines quantity of the individuals who remained viable after radiation in this or that dose, the bactericidal effect of radiation is estimated on curves «dose effect» with definition of fraction of not inactivated individuals. So, e.g., the high bactericidal effect providing almost absolute sterilization (remain not inactivated 10^-8 a dispute of the majority of the most radio resistant forms), it is reached at radiation in doses of 4 — 5 million I am glad. For a dispute of the most widespread anaerobe bacterias sterilization of this degree is reached at doses of 2 — 2,5 million is glad. For typroid bacteria and stafilokokk this figure is equal to 0,5 — 1 million is glad. Sterilization of various objects depending on conditions and tasks is carried out at the different modes providing the most often accepted factor of sterilization equal 108 (exposure doses of 2,5 — 5 million I am glad). See also Sterilization (cold).

Bibliography: Tumanyan M. A. and To hey-shansky D. A. Radiation sterilization, M., 1974, bibliogr.; Radiosterilization of medical products and recommended code of practice, Vienna, 1967, bibliogr.

B. V. Pinegin; P. V. Petrov (I am glad.).