Transcript of Disinfection
- 1. DISINFECTION BY, Dr.M.Malathi I year PG- M.D. Microbiology
Chengalpattu medical college chengalpattu
- 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. 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. 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. 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. 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. 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. Microbicidal activity: Pseudomonas 10 sec 30 100% E.coli,
S.typhi 10 sec 40 100 % S.aureus, Strep. pyogenes 10 sec 60
95%
- 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. 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. CAVI WIPES:
- 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. 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. Formalin:
- 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. 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. Mechanism of action: Alkylation of sulfhydryl, hydroxyl,
carboxyl and amino groups of micro organisms which alter the
RNA,DNA and protein synthesis
- 18. > 2% aqueous solution of glutaraldehyde buffered to
alkaline pH with sodium bicarbonate kills: Vegetative bacteria