Sterilization Chemical Method

Sterilization Chemical Method

1. STERILIZATION : CHEMICAL METHOD

Mr. Naresh Pokhrel
M.Sc Clinical Microbiology
Department of Microbiology
Father Muller Medical College, Mangalore

2. CHEMICAL METHODSCHEMICAL METHODS
Alcohols
Aldehydes
Dyes
Halogens
Phenols
Gases
- - Ethylene Oxide
- Formaldehyde gas
- Betapropiolactone (BPL)
Surface active agents

3. Properties of an ideal disinfectant or
antiseptic
Should have wide spectrum of activity and be
effective against all microorganism.
Be active in presence of organic matter.
Have speedy action.
Have high penetrating power.
Stable and non corrosive
Cheap, easy to use
Be effective in acid as well as alkaline media
Be compatible with other antiseptics and
disinfectants
Not cause local irritation or sensitization

4. THE FACTORS THAT
DETERMINE THE POTENCY OF
DISINFECTANTS ARE:
Concentration of the substance ,
Time of action,
pH of the medium ,
Temperature
Nature of organism
Presence of extraneous material

5. CHEMICAL AGENTS ACT IN VARIOUS
WAYS :
Protein coagulation ,
Disruption of cell membrane resulting exposure,
damage or loss of the contents
Removal of free sulphydryl groups essential for the
functioning of the enzymes and
Substrate competition- a compound resembling the
essential substrate of the enzyme diverts or
misleads the enzymes necessary for the
metabolism of the cell and cause cell death.

6. ALCOHOLSALCOHOLS
 Ethanol, methanol, isopropyl alcohol are frequently
used.
 Act by denaturing proteins.
 They have no action on spores.
 To be effective working concentration is 70-80 % in
water..
 Protein Slow its action whereas 1 % mineral acid and
alkali enhances it.

7. CONTD……
 Methyl alcohol is effective against fungal spores.
 Evaporate, leaving no residue
 The inside of the Chambers are wiped with liberal
amounts of methanol.
 A pad moistened with methanol and a dish of
water(to ensure high humidity) are kept inside ,
 And the incubator is left at working temperature
for several hours.

8. CONTD……..
Uses: To disinfect skin prior to injections.
Methyl alcohol is used to clean incubators and
biosafety cabinets
Isopropyl alcohol is preferred as it is better fat
solvent, more bactericidal and less volatile
 Mainly used for disinfection of clinical thermometer.

9. ALDEHYDESALDEHYDES ::
Mechanism: active against the amino group in the
protein molecule.
bactericidal, sporicidial and virucidal
Commonly used aldehydes are Formaldehyde,
glutaraldehyde

10. FORMALDEHYDE GAS
Excellent disinfectant
Formalin(10%) was used extensively to preserve
biological specimens and for destroying anthrax
spores in hair and wool.
 Irritates mucous membranes, strong odour.
10 % formalin containing 0.5 % sodium tetra borate
in water is used to sterilise clean metal instruments
Formaldehyde in gaseous form is used to fumigate
sick rooms, operation theaters, labs

11. Glutaraldehyde:
Less irritating and more effective than
formaldehyde.
 sterilizing agent : 2% solution of glutaraldehyde
(Cidex) which is Bactericidal, tuberculocidal,
virucidal in 10 minutes.
 Sporicidal in 3 to 10 hours

12. CONTD……….
Commonly used to disinfect hospital instruments-
cystoscopes, endoscopes, corrugated rubber tubes,
face masks, metal instruments, polythene tubes

13. ORTHOPHTALALDEHYDE
Has bactericidal activity
Uses to Clean endoscopes between as it is
quick, effective and safe.

14. DYES
ANILINE DYES -Brilliant green, malachite green
and crystal violet
More active against gram+ve than gram-ve bacteria
No activity against tubercle bacilli hence Malachite
green is used in Lowenstein Jensen media
Non irritant, Non toxic
These dyes are used in the microbiology laboratory
as selective agents in culture media.
Lethal effects on bacteria are believed to be due to
their reaction with the acid group in the cell.

15. ACRIDINE DYES
 Are not selective as the aniline dyes.
 Proflavine, acriflavine, euflavine, aminacrine
Impair DNA complexes of organisms and destroy
reproductive capacity of the cell

16. HALOGENS
Iodine:
Tincture of iodine (alcohol solution) was one of
first antiseptics used.
 Combines with amino acid tyrosine in proteins and
denatures proteins.
 Stains skin and clothes
 bactericidal, virucidal and fairly active against
spores

17. Iodophors:
Iodine compounds with non ionic wetting or surface
active agents
It inhibits protein synthesis and oxidizes –SH groups
of amino acids
 Used as skin antiseptic in surgery.

18. CHLORINE
 When mixed in water forms hypochlorous acid:
 Cl
2
+ H
2
O ------> H+ + Cl- + HOCl
Sodium hypochlorite (NaOCl)- Is active ingredient of
bleach
 Chlorine is easily inactivated by organic materials.
The organic chloramines are used as antiseptics for
dressing wounds.

19. CONTD…….
Not much useful against spores
Used to disinfect drinking water, pools, and sewage
For household use (bleach) it is used in conc. of
0.2-1%.

20. SURFACE ACTIVE AGENTS
Alter energy relationship at interfaces producing a reduction of
interfacial tension
Effective against gram positive bacteria
 Also destroy fungi, amoebas, and enveloped viruses

21. Anionic compounds: Common soap and detergents
Cationic compounds: Cetrimide and bezalkonium
chloride- used as antiseptics.
Advantages: Strong antimicrobial action, colorless,
odorless, tasteless, stable, and nontoxic.
 Disadvantages: Form foam. Organic matter
interferes with effectiveness

22. OXIDIZING AGENTS
Hydrogen peroxide and peracetic acid.
H
2
O
2
kills most organisms at 3-6% conc.
At 10-25% kills even spores
Used to disinfect plastic implants, contact lenses
and surgical prosthesis

23. Peracetic Acid:
Has good sterilization effect on
bacteria,particulary common antibiotic
resistant bacteria such as methicilin
resistant Staphylococcus aureus,
vancomycin resistant Enterococcus and
Clostridium defficile

24. Ozone:
 Highly reactive form of oxygen
Used along with chlorine to disinfect water
 More effective killing agent than chlorine
 Less stable and more expensive

25. PHENOLS AND PHENOLICS
 Phenol (carbolic acid) was first used by Lister as a
disinfectant.
Obtained by distillation of coal tar between temp
170-270
0
C
Active against gram+ve and –ve bacteria,
mycobacteria
 Little activity against spores and viruses

26. Act by causing cell membrane damage, releasing
cell contents and causing lysis
Resistant to inactivation by organic matter
2% phenol is used to disinfect surfaces, floors,
tables etc

27. PHENOLICS
Are chemical derivatives of phenol
Cresols: Derived from coal tar (Lysol)
LYSOL is used to disinfect linen- 3% lysol
Advantages: Stable, persist for long times after
applied, and remain active in the presence of
organic compounds

28.  Related products chlorophenols and
chloroxyphenols are less toxic, less irritant but
inactive against pseudomonas
Chlorhexidine is a nontoxic skin antiseptic- most
active against gram+ve and fairly against gram-ve
ones

29. HEAVY METALS
A. Silver
 1% silver nitrate used to protect infants against
gonorrheal eye infections
B. Mercury
 Organic mercury compounds like merthiolate and
mercurochrome are used to disinfect skin wounds.
C. Copper
Bactericidal
Fungicidal

30. GASES
 ETHYLENE OXIDE :
Colourless liquid
Boiling point 10.7
0
C
At normal temp and pressure, it is a highly
penetrating gas with ethereal smell
Acts by alkylating the amino, carboxyl, hydroxyl
and sulphydryl groups in protein molecule and also
by damaging DNA and RNA

31. Highly inflammable
Highly explosive at a concentration of >3% in air
Carcinogenic and mutagenic
Explosive tendency eliminated by mixing with inert
gases like CO2 and N2 to a concentration of 10%
Sterilizing property

32. USES : heat and moisture sensitive articles like
plastic and rubber articles, blankets,
pharmaceutical products, sutures, heart lung
machines, ventilators, catheters

33. Objects to be sterilized are put in a cabinet from
which air has been removed using vacuum, and a
non explosive mixture containing ETO gas is
introduced to a pressure of 5-30 lb/in
2
above atm
pressure,temp to be maintained at 45-55
0
C and
relative humidity 20-40%

34. ETO GAS TEST ORGANISM : Bacillus subtilis
var.globigii
A long period of aeration (to remove all traces of the
gas) is required before the equipment can be
distributed.
The operating cycle ranges from 2-24 hours
 It is a relatively expensive

35. FORMALDEHYDE GASFORMALDEHYDE GAS
Used to fumigate sick rooms, OT etc
 FORMALDEHYDE FUMIGATION :
 1) Electric boiler fumigation method
 2) Addition of formalin to potassium
permanganate (150 gm of potassium permanganate
to 280ml of formalin per 1000 cu.ft. of the room)


36. PROCEDURE:
 Close all doors & windows air tight and switch off
fans and A.C.
 Heat formalin solution till boiling
 Leave the OT unentered over night
 Enter the OT next day morning with
ammonia( 250ml/litre of formaldehyde)
 Keep the ammonia solution for 2-3 hrs to neutralize
formalin vapours

37. Betapropriolactone (BPL):
More efficient than formaldehyde for fumigation
carcinogenic

39. CONTD………