Sterilization


Chemical Sterilization

Chemical agents can exert bactericidal or bacteriostatic
effect. The bactericidal agents in lower concentrations exert
bacteriostatic effect. The bactericidal effect is probably
because of enzyme inactivation either by protein denaturation,
oxidation or by a combination of the antibacterial
agent with specific groups of enzyme proteins.

Chemicals Used

Various chemicals used are

1 Chloroform (volatile antiseptic): Used in preservation
of serum for culture media at 0.25% concentration.
Can be removed by heating to 56oC.
 2Phenol group: Cresol, lysol (strong antiseptics) are mainly
employed for surgical instruments,
discarded routine
cultures, and pipettes, slides, etc. and disinfecting hands.
Phenol 0.5% is used for preserving sera and vaccines.

3Metallic salts: Perchloride of mercury in 1:10000
strength solution.

4. Glycerol: A 50% solution is used for preservation of
certain viruses. Glycerol also kills contaminating
organisms

 5.Formalin: It is the only method for sterilizing Perspex
or polythene and for killing cultures on plates. Can also
be used for fumigation purposes.

6. Sulfur: Burning in air forms sulfur dioxide (SO2) for
fumigation.

7. Halogens: Chlorine and iodine. Chlorine for water
disinfection and iodine for skin.

8. Acids and alkalies: Most bacteria grow in pH range of 5
to 9 and many grow at pH 7. Strong acids and alkalies
can be used to disinfect contaminated materials.

9. Alcohols: These are used for disinfecting skin before
injecting and before operations. Alcohols act by
protein denaturation.

10. Two groups of dyes (a) the aniline dyes, and
(b) the acridines have been widely used as skin and
wound disinfectants.

11. Quaternary ammonium compounds are active against
both gram-positive and gram-negative species but are
not effective against spores and mycobacteria. They
are used for sterilizing food utensils in restaurants and
hotels and for disinfecting blankets in hospitals.

12. Glutaraldehyde (Cidex) affects even spores and
mycobacteria. It is employed as 2% solution and is
recommended for sterilizing cystoscopes, etc.

13. Ethylene oxide gas is being widely used to sterilize
disposable plastic syringes, petri dishes, etc.

تعليقات

إرسال تعليق

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