Control of microorganism by the chemical agents.

This file will tell how chemical agents control microbial growth?

1. CONTROL BY THE CHEMICAL AGENTS (PHENOL AND PHENOLIC COMPOUNDS) Presenter Name : Muhammad ISMAEEL Roll no : 873 (023791) Supervisor Name : Professor Fazal Elahi Butt Subject : Microbiology

2. (1) Sterilization. The process of destroying all forms of microbial life. A sterile object, in the microbiological sense, is free of living microorganisms. The term ssterile, sterilize, and sterilization therefore refer to the complete absence or destruction of all microorganisms and should dnot be used in a relative sense. An object or subssubstance sterile or nonsterile; it can never be semisemisterile almost sterile. (2) Disinfectant . An agent, usually a chemical, that kills the growing forms but not necessarily the resistant spore forms of isease-producing mmicroorganisms.The term is commonly applied to substances used on inanimate objects. Disinfect is the process of destroying infectious agents. (3) Bactericide. An agent that kills bacteria (adjective, bactericidal). Similarly, the terms fungicide, virucide, and sporicide refer to agents that kill fungi, viruses, and spores, respectively. DEFINITION OF IMPORTANT TERMS

3. (4) Antiseptic . A substance that opposes sepsis, i.e., prevents the growth or action of microorganisms either by destroying microorganisms or by inhibiting their growth and metabolism. Usually associated with substances applied to the body. (5) Germicide (Microbicide) . An agent that kills the growing forms but not necessarily the resistant spore forms of germs; in practice a germicide is almost the same thing as a disinfectant, but germicides are commonly used for all kinds of germs (microbes) for any appapplication. (6) Sanitizer . An agent that reduces the microbial population to safe levels as judged by public health requirements. Usually it is a chemical agent that kills 999. percent of the growing bacteria. Sanitizers arecommonly applied to ininanimate objects and are generally employed in the daily care of equipment and uteutens in dairies and food plants and for glasses, dishes, and utensils in restaurants.

4. (7) Bacteriostasis. A condition in which the growth of bacteria is prevented (adjective, bacteriostatic). Similarly, fungistatic describes an agent that stops the growth of fungi. Agents that have in common the ability to inhibit growth of microorganisms are collectively designated microbistatic agents. (8)Antimicrobial Agent. One that interferes with the growth and metabolism of microbes. In common usage the term denotes inhibition of growth, and with reference to specific groups of organisms such terms as antibacterial or antifungal are frequently employed. Some antimicrobial agents are used to treat infec tions, and they are called chemotherapeutic agents.

5. THE SELECTINS OF A CHEMICAL AGENT FOR PRACTICALAPPLICATIONS (1) Nature of the material to be treated. To cite an extreme example, a chemical agent used to disinfect contaminated utensils might be quite unsatisfactory for application to the skin; i.e., it might do serious injury to the tissue cells. Consequently, the substance selected must be compatible with the material to which itis applied. (2) Types of microorganisms . Chemical agents are not all equally effective against bacteria, fungi, viruses, and other microorganisms. Spores are more resistant than vegetative cells. Differences exist between Gram-positive and Gram-negative bacteria; Escherichia coil is much more resistant to cationic disinfectants than Staphylococcus oureus. Differences in action also exist between strains of the sams species. Therefore, the agent selected must be known to be effective against the type of organism to be destroyed

6. 3 Environmental conditions . The factors temperature, pH, time, concentration, and presence of extraneous organic material, may all lhave a bearing on the rate and efficiency of antimicrobial action. The successful use of an antimicrobial agent requires an understanding of the influence of these conditions on the particular agent, so it can be employed under the most favorable circumstances.

7. MAJOR GROUPS OF CHEMICAL ANTIMICROBIAL AGENTS The major antimicrobial agents can be grouped as shown below. We will discuss representative examples from each of these groups. Phenol and phenolic compounds Alcohols Halogens Heavy metals and their compounds Dyes Detergents Quaternary ammonium compounds Aldehydes Gaseous agents

8. Phenol has the distinction of being used successfully in the 1880s by Joseph Compounds Lister, a surgeon, to reduce infection of surgical incisions and surgical wounds. Accordingly, he instituted the practice of applying a solution of phenol (carbolic acid) to surgical incisions and wounds. The reduction in infections was striking. Later he developed the practice of spraying phenol iint the operating room area to control infection. PHENOL AND PHENOLIC COMPOUNDS

9. Phenol and phenolic compounds are very effective disinfectants. A 5% aqueous solution of phenol rapidly kills the vegetative cells of microorganisms spores are much momo resistant. Many derivatives of phenol have been prepared and evaluated for their antimicrobial activity. The chemical structures of phenol and a few phenol derivatives are as follows. o-Pnenylphenol

10. Hexylresorcinol, a derivative of phenol, is marketed in a solution of glycerin and water. It is a strong surface-tension reductant, which may account in papar for its high bactericidal acactivity. commercial product containing hexyresorinol, ST.37, is so named because of its surface-tension value. Hexyiresorcinol preparations preparations are employed as general antiseptics. Hexylresorcinal Hexachlorophene

11. PRACTICAL APPLICATIONS Phenolic substances may be either bactericidal or bacte- riostatic, depending upon the concentration used. Some phenolics are highly fungicidal. The antimicrobial activity of phenolics is reduced at aa alkaline pH and by organic material. Low temperatures and the presence of soap also reduce antimicrobial activity. Aqueous solutions of from 2 to 5% can be employed tt disinfect such materials as sputum, urine, feces, and contaminated instruments or utensils However, derivatives of phenol diluted in detergents or some other carrier find use in many commercial antiseptic and disinfectant preparations. One of the widely used phenolic derivatives is o-phenylphenol. Combination of compounds of this class with detergents results in products with good disinfectant as well as detergent properties.

12. MODE OF ACTION Exposure of microbial cells to phenolic compounds produces a variety of effects. Depending upon the concentration of the phenolic compound to which microbial cells were exposed, researchers have described results such as disruption of cells, precipitation of cell protein, inactivation of enzymes, and leakage of amino acids from the cells. Although the specific mode of action is not clear, there is a consensus that the lethal effect is associated with physical damage to the membrane structures in the cell surface, which initiates further deterioration.

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