1. 1. DISINFECTION BY, Dr.M.Malathi I year PG- M.D. Microbiology Chengalpattu medical college chengalpattu
2. 2. Definition: The selective elimination of certain undesirable organisms in order to prevent their transmission, achieved by action on their structure or metabolism, irrespective of their functional state. (European committee) Disinfection does not necessarily kill all microorganisms but reduces them to a level acceptable for a defined purpose. (British standards)
3. 3. An ideal disinfectant should: Have a wide spectrum of activity Be active in the presence of organic matter Have speedy action High penetrating power Be stable Not be toxic Not corrosive inexpensive
4. 4. Factors determining the potency of disinfectant: Concentration of the substance Time of action pH of the medium Temperature Nature of the organisms Presence of extraneous material
5. 5. Chemical agents 1. Alcohols: Ethyl, isopropyl, methyl 2. Aldehydes: Formaldehyde, Glutaraldehyde 3. Dyes 4. Halogens 5. Phenols 6. Surface active agents 7. Metallic salts 8. Gases: Ethylene oxide, Formaldehyde, Beta propiolactone.
6. 6. HIGH: Kills all the organisms except high number of Spores, Prions Eg. Aldehydes, ethyleneoxide INTERMEDIATE: Kills Mycobacteria, most viruses and bacteria, fungi but not spores Eg. Iodine, ethanol, chlorine LOW: Kills some viruses and bacteria but not mycobacteria, spores Eg. Quarterly ammonium compounds, mercurials. LEVELS OF DISINFECTION:
7. 7. ALCOHOLS: Ethyl alcohol Methyl alcohol Isopropyl alcohol Bactericidal, tuberculocidal, fungicidal, virucidal. Donot act on spores Optimum concentration is 60 90 % Mechanism of action: denaturation of proteins
8. 8. Microbicidal activity: Pseudomonas 10 sec 30 100% E.coli, S.typhi 10 sec 40 100 % S.aureus, Strep. pyogenes 10 sec 60 95%
9. 9. Ethyl alcohol (60 80%) is virucidal for all lipophilic viruses and hydrophilic viruses except hepatitis A and polio virus Isopropanol is active against all lipophilic viruses. 70% ethanol is active against cryptococcus, blastomyces, coccidiodes 20% isopropanol is used for killed
10. 10. Uses: Oral thermometers Scissors Sthethescopes Disadvantages: As they lack sporicidal action, they are not recommended for equipments and surgical materials. They damage the lensed instruments and tonometer tips. Methyl alcohol is toxic and not used nowadays.
11. 11. CAVI WIPES:
12. 12. Low alcohol (17% isopropanol) surface disinfectants: non abrasive towelettes easy to use ideal for operating rooms, surgical centres, neonatal centres saves time and convenient
13. 13. ALDEHYDES: Formaldehyde Glutaraldehyde Ortho phthalaldehyde Formaldehyde: Bactericidal, sporicidal, virucidal Used to preserve specimens For destroying anthrax spores in hair and wool 10% formalin containing 0.5% sodium tetraborate is used to clean metal
14. 14. Formalin:
15. 15. Glutaraldehyde: High level disinfectant & chemical sterilant In aqueous solutions not sporicidal if activated by using alkalinising agents to change the pH to 7.5 to 8.5 becomes sporicidal
16. 16. Disadvantage of activation: Once activated the shelf life of glutaraldehyde is only 14 days and after that polymerisation of the glutaraldehyde molecules takes place and it blocks the active aldehyde groups. To overcome the above problem: Glutaraldehde phenol sodium phenate or stabilised alkaline glutaraldehyde can be used.
17. 17. Mechanism of action: Alkylation of sulfhydryl, hydroxyl, carboxyl and amino groups of micro organisms which alter the RNA,DNA and protein synthesis
18. 18. > 2% aqueous solution of glutaraldehyde buffered to alkaline pH with sodium bicarbonate kills: Vegetative bacteria