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The effect of antimicrobial chemicals on microorganisms
In addition to nutrient chemicals that have a positive effect on microorganisms, there are a number of chemicals that inhibit or completely stop their growth. Chemicals cause either microbicidal (death of microorganisms) or microbostatic effect (they stop their growth, but after removal of this substance, growth resumes again). The nature of the action (microbicidal or microbostatic) depends on the dose of the substance, the time of its exposure, also temperature and pH. Small doses of antimicrobial agents often stimulate the development of microorganisms. With increasing temperature, the toxicity of many antimicrobial substances, as a rule, increases. Temperature affects not only the activity of the chemical itself, but also microorganisms. At temperatures exceeding the maximum for a given microorganism, even small doses of such substances cause their death. The pH of the medium also has a similar effect.
For different antimicrobial substances, the same microorganism exhibits a different degree of resistance. One and the same substance can have a different effect on different types of microorganisms — some cause rapid death, others stop their development, and others may have no effect at all. It depends on the presence of spores and capsules that are resistant to chemicals. Antimicrobial substances act much more strongly on vegetative cells than on spores.
Of inorganic substances, salts of heavy metals (mercury, copper, silver), oxidizing agents - chlorine, ozone, iodine, hydrogen peroxide, bleach, potassium permanganate), alkali and acid (sodium hydroxide, sulfur dioxide, hydrogen fluoride, have a strong antimicrobial effect) acids), some gases (hydrogen sulfide, carbon monoxide, sulphurous, carbon dioxide). Organic substances (alcohols, phenols, aldehydes, especially formaldehyde) also have a detrimental effect on microorganisms. The mechanism of the destructive effect of antimicrobial substances is different and depends on their chemical nature. For example, alcohols, ethers dissolve CPM lipids, as a result of which they easily penetrate the cell and interact with its various components, which disrupts the normal functioning of the cell. Heavy metal salts, formalin cause rapid coagulation of “cytoplasmic proteins, phenols — inactivation of respiratory enzymes, acids and alkalis — protein hydrolysis. Chlorine and ozone, which have a strong oxidizing effect, also inactivate enzymes. Antimicrobial chemicals are used as disinfectants and antiseptics.
Disinfectants cause rapid (within a few minutes) death of bacteria, they are more active in environments that are poor in organic substances, destroy not only vegetative cells, but also spores. They do not cause the appearance of resistant forms of microorganisms. The microbicidal action of antiseptics, unlike disinfectants, manifests itself after 3 hours or more. The greatest activity is manifested in media containing organic substances. Antiseptics destroy only vegetative cells and cause the formation of resistant forms of microorganisms.
Antimicrobial substances such as phenols, chloramine, formalin, in high concentrations (2-5%) are disinfectants, but their solutions, diluted 100-1000 times, can be used as antiseptics. Many antiseptics are used as food preservatives (sulphurous, benzoic, sorbic acid, yuglon, plumbagin, etc.).
Disinfectants in the food industry are used to process the working surfaces of apparatuses and other technological equipment, implements, containers, utensils and rooms. In the food industry, you can use only those drugs that do not have a toxic effect on the human body, have no smell and taste.
They must have antimicrobial activity at a minimum concentration, dissolve in water and be effective for short periods of action. Of great importance is their storage stability. Preparations should not have a destructive effect on the equipment material, should be cheap and convenient for transportation.
To process equipment at food enterprises, chlorine-containing substances are mainly used, the disinfecting effect of which is due to the release of active chlorine. Usually, solutions containing 150-200 mg of active chlorine per liter are used for disinfection. The most vulnerable places in the sense of bacterial contamination are treated with solutions containing 400 mg of active chlorine per 1 liter. The processing time of the equipment should be at least 15 minutes. Inorganic chlorine-containing disinfectants include: bleach, antiformin (a mixture of bleach, soda ash and caustic soda), sodium hypochlorite; to organic ones, chloramine B, new synthetic preparations (dichlorodimethylhydantoin) and complex combinations of new chloroactive compounds with surfactants (for example, sulfochlorantin, which has both a wetting, washing and high antimicrobial effect). Formalin (an aqueous solution of formaldehyde), milk of lime, soda ash and caustic soda are also used as disinfectants.
Organic antibacterial disinfectants — the so-called quaternary ammonium compounds — possess high antimicrobial activity in small doses. Their advantage ”over existing antimicrobial agents is that they are readily soluble in water, have no smell, taste, low toxicity to the human body, do not cause corrosion of metals, and do not irritate the skin of the hands of personnel. Among domestic drugs of this group, cetozol and catamine-AB can be called. The mechanism of action of this class of compounds on microorganisms is not yet entirely clear. It is believed that they damage the cell wall of bacteria, resulting in a sharp increase in cell permeability, denaturation of proteins, inactivation of enzyme systems, and lysis (dissolution) of microorganisms.
Many gaseous substances (formaldehyde, sulfur dioxide, ethylene oxide and b-propiolactone) have a strong bactericidal effect.
When using disinfectants for processing equipment, the following general rules must be observed: apply them only after thorough mechanical washing of the equipment; disinfectant solutions should be freshly prepared; after disinfection, all processed equipment and communications are thoroughly washed until the disinfectant is completely removed.
Drinking water, as well as industrial water, is usually disinfected in a variety of ways — using strong oxidizing agents (a large amount of water — chlorine, a small amount — chlorine compounds, iodine, heavy metal ions), by ozonation, irradiation with ultraviolet rays with a wavelength of 200-295 nm, processing by gamma radiation, ultrasound.
For air disinfection, chlorine preparations and triethylene glycol in the form of their fumes or aerosols are most often used. These disinfectants reduce the total number of microorganisms in the air by more than 90%. Good results for air disinfection of production halls and cold rooms are provided by ozonation and ultraviolet irradiation. Periodic use of physical (ventilation, filtering) and chemical methods of disinfection, cleaning and disinfection of air and their combination with wet cleaning of rooms can significantly reduce the bacterial contamination of air in industrial and domestic premises.
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The effect of antimicrobial chemicals on microorganisms
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- The influence of environmental conditions on microorganisms.
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