Chemical Sterlization and it's types.pptx

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1. Chemical sterilizatio n Presented by M.S. Swetha I st M .S c. Microbiology

2. Sterilization P rocess of making surface or medium is free of all living organisms. It is the process of killing of microorganisms. It was carried out by two methods 1. P hysical method 2. C hemical method

3. Chemical methods of sterilization (disinfection) P rocess of killing of many microorganisms, but not all microorganisms. It is the chemical method of sterilization. Chemicals used for disinfection are called as Disinfectants.

4. Chemical methods( disinfection ) Disruption of cell membrane (alcohol, detergents and phenols) Modification of proteins ( Chlorine, Iodine, Heavy metals, Hydrogen peroxide, Aldehydes, Ethylene oxide and Acids) Modification of Nucleic acids ( crystal violet and Malachite green)

5. (a) DISRUPTION OF CELL MEMBRANE 1. Alcohols a. W idely used to clean the skin before immunization or venipuncture . b. A cts mainly by disorganizing the lipid structure in membranes, and also denatures proteins as well(presence of water activity is high) . c. 70% ethanol is often used as an antiseptic to clean the skin prior to venipuncture .

6. 2. Detergents a. Detergents are “surface-active “ agents composed of long-chain, lipid-soluble, hydrophopc portion and polar hydrophilic group . b. It interact s with lipid in the cell membrane through their hydrophopic chain .

7. 3. Phenols a. F irst disinfectant used in the operating room . b. I t is rarely used as a disinfectant today because it is too caustic c. Hexachlorophene, which is a bi-phenol with six chlorine atoms, is used in germicidal soaps, but concern over possible neurotoxicity has limited its use.(active ingredient is Lysol). d. Phenols not only damage membranes but also denature proteins.

8. (b) MODIFICATION OF PROTEINS 1.Chlorine a . U sed as a disinfectant to purify the water supply and to treat swimming pools. b. It is also the active component of hypochlorite which is used as a disinfectant in the home and in hospitals. c. P owerful oxidizing agent that kills by cross-linking essential sulfhydryl groups in enzymes to form the inactive disulfide.

9. 2. Iodine a. Iodine is the most effective skin antiseptic used in medical practice and should be used prior to obtaining a blood culture and installing intravenous catheters because contamination with skin flora such as staphylococcus epidermis can be a problem. b. Iodine can be supplied in two forms: 1. Tincture of Iodine 2. Iodophors

10. 3. Heavy metals a. M ercury and silver have the greatest antibacterial activity of the heavy metals and the most widely used in medicine. b. A ct by binding to sulfhydryl groups, thereby blocking enzymatic activity. c . S ome of the heavy metals are Silver nitrate , S ilver sulfadiazine

11. 4. Hydrogen peroxide a. U sed as an antiseptic to clean wounds and to disinfect contact lenses. b. It is an oxidizing agent that attacks sulfhydryl groups, therby inhibiting enzymatic activity.

12. 5. Aldehydes a. Formaldehyde, which is available as a 37% solution in water(formalin), denatures proteins and nucleic acids. b. B oth proteins and nucleic acids contain essential-NH2 and –OH groups, which are the main sites of alkylation by the hydroxymethyl group of formaldehyde. c. G lutaraldehyde, which has two reactive aldehyde groups, is 10 times more effective than formaldehyde and is less toxic.

13. 6. Ethylene oxide a. E thylene oxide gas is used extensively in hospitals for the sterilization of heat sensitive materials such as surgical instrumentations and plastics. b. I t kills by alkylating both proteins and nucleic acids. 7. Acids a. S trong acids and alkalis kill by denaturing proteins. b. W eak acids, such as benzoic, propionic, and citric acids, are frequently used as food preservatives because they are bacteriostatic .

14. (C) MODIFICATION OF NUCLEIC ACIDS A variety of dyes not only stain microorganisms but also inhibit their growth. 1. C rystal violet a. U sed as a skin antiseptic. b. Its action is based on binding of the positively charged dye molecule to the negatively charged phosphate groups of the nucleic acids.

15. 2. M alachite green a. A triphenylamine dye- like crystal violet ,is a component of Lowenstein-Jensen’s medium, which is used to grow mycobacterium tuberculosis b. T he dye inhibits the growth of unwanted organisms in the sputum during the 6 week incubation period.

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