Sterilization and Disinfection.pptx.....

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1. Sterilization and Disinfection

2. Sterilization is the killing or removal of all microorganisms, including bacterial spores. It is an absolute germ free state. Disinfection is the killing of many but not all, microorganisms. Specially bacterial spores are not killed. Disinfectant is a chemical agent that is used for disinfection.

3. Methods of sterilization: I. Heat II. Ionizing radiations III. Filtration IV. Chemicals I. Heat : It can be again a. Dry heat b. Moist heat c. Pasteurization

4. a. Dry Heat : Sterilization by dry heat requires temperatures in the high range. Used primarily for glassware. Used less frequently than autoclaving. Dry heat can be applied by i . Red heat: The article to be sterilized is directly held in the flame and heated till it becomes red hot. e.g. S terlizing wire loop in flame of the burner. ii. Hot air oven: Articles are sterilized in hot air oven at temp range of 160 C-180 C.

5. Uses: Glassware, sealed containers. etc are sterilized by this method.

6. b. Moist heat : It can be applied by Boiling Steaming 1. Boiling : Simple boiling is used to sterilize some glassware. Boiling done for 20-30 minutes for three consecutive days is called Tyndalization . The process involves boiling cooling, incubating for consecutive three days and finally boiling again.

7. The three incubation periods are to allow heat-resistant spores to germinate to form the heat-sensitive vegetative stage, which can be killed by the next boiling step. Now a days not commonly used. It is used for materials which can not withstand prolonged boiling.

8. 2. Steaming Most common method to be used. It is normally applied above 100 C under high pressures. The instrument used for it is called autoclave. Principle of autoclaving : In autoclave steam or moist heat is produced at a temp of 115- 121 C. Water boils at 100 C. At this temp vapour pressure equals the atmospheric pressure i.e. 760 mm Hg. When water is heated in a closed vessel the vapour pressure rises with a subsequent rise in boiling point. The boiling point rises to 115 C- 121 C.

9. Thus steam produced at this temp is super heated. This steam when condenses on the articles thermal energy is released from it and along with moisture this heat denatures the microbial proteins. The objects are sterilized for 15-20 minutes Autoclave is used to sterilize most of the instruments and culture media.

10. Different types of autoclaves

11. c. Pasteurization : It is used primarily for milk. It consists of heating the milk to 62°C for 30 minutes followed by rapid cooling OR heating it at 72 C for 20 seconds. This is sufficient to kill the vegetative forms of the milk-borne pathogens, e.g. Mycobacterium bovis , Salmonella, Streptococcus etc

12. II. Ionizing radiations : The three types of radiations are used to kill microorganisms (kill by damaging DNA) . 1.Ultraviolet (UV) light 2. X-rays. 3.Gamma rays Used in industry to sterilize disposable syringes, gloves, catheters etc. III. Filtration : Filtration is the preferred method of sterilizing certain solutions, e.g. IV fluids. Antibiotic solutions.

13. Cellulose acetate membrane filter most commonly used. Pore size 0.02-1 µm. Removes bacteria. High-efficiency particulate air (HEPA) filters remove almost all microorganisms larger than 0.3 micron in diameter. They are used to remove microorganisms from air. Used specially in TB labs.

14. Filter sterilization with a disposable, presterilized plastic unit.

15. IV. Chemicals : They can be Gases like Ethylene oxide used in plastic industry. Highly toxic inflammable ,potentially explosive gas . Liquids like Glutraldehyde used to disinfect endoscopes. Chemical agents act primarily by one of the three mechanisms: Disruption of the lipid-containing cell membrane Modification of proteins Modification of DNA

16. Methods of Disinfection : Disinfectants are strong chemicals used for disinfecting non living articles. They are toxic and corrosives for living tissues. Antiseptics : Disinfectants which are less irritant and can be applied to living tissues are called antiseptics e.g. methylated spirit, Alcohol, Iodine, Chloroxylenol ( dettol ) etc.

17. Types of Disinfectants: 1. Phenol and Phenolic compounds . Phenol (carbolic acid) and phenolics are good disinfectants. Phenolics are derivatives of Phenol. Phenol was first disinfectant used in 1860. Cresols are derived from coal tar form an important group of phenolics . 2. Bisphenols : Bisphenols are derivatives of phenol.

18. Hexachlorophene and Triclosan are important bisphenols . 3. Biguanides : The best known biguanide is chlorhexidine used for microbial control on skin and mucous membranes. Hibiscrub ( chlorhexidine + cetrimide ) Hibisol ( chlorhexidine + glycerine )

19. 4. Halogen compounds: The halogens, particularly iodine and chlorine, are effective antimicrobial agents. The most common commercial preparation of Iodine is povidone -iodine ( Pyodine ). A liquid form of compressed chlorine gas used extensively for disinfecting municipal drinking water, water in swimming pools, and sewage.

20. 5. Aldehydes : Formaldehyde as gas used to sterilize operation theatres and other spaces. Glutaraldehyde a chemical relative of formaldehyde less irritating and more effective than formaldehyde. Glutaraldehyde used to disinfect hospital instruments, including endoscopes and respiratory therapy equipment

21. 6. Alcohol : Alcohols effectively kill bacteria and fungi but not spores and non enveloped viruses. Most commonly used alcohols are ethanol and Isopropanol . The recommended conc. of ethanol is 70% Isopropanol is slightly superior to ethanol as an antiseptic and disinfectant However, alcohols are unsatisfactory antiseptics when applied to wounds.

22. Bactericide: A substance that kills bacteria but does not kill their spores. Sporicide : A substance that kills spores of bacteria as well e.g. Glutraldehyde , formaldehyde,chlorine and Iodine. A   virucide  is an agent (physical or chemical) that deactivates or destroys viruses e.g. Lysol.

23. Antiseptic is a disinfectant which inhibits growth of microorganisms when applied in lesser potency to human tissues. Sanitation: The process by which microbial contamination is brought to a "safe" level. This process refers primarily to the process of "cleaning" inanimate objects