The document discusses chemical disinfection, defining it as the process of eliminating pathogenic organisms on inert surfaces, contrasting it with sterilization. It details various chemical disinfectants, their modes of action, ideal characteristics, potency levels, and specific agents including alcohols, aldehydes, and halogens. The text also outlines the uses, limitations, and effectiveness of these disinfectants in medical and healthcare settings.

1. CHEMICAL
DISINFECTION
By- SYED MAJDI MOHAMMADI
3rd BDS

2. CONTENTS
 DEFINITIONS
 DIFFERENCES FROM STERILIZATION
 CHEMICAL DISINFECTANTS
-MODE OF ACTION
-IDEAL REQUIREMENTS
-POTENCY
-AGENTS
 REFERENCES

3. DEFINITIONS
● DISINFECTION: It is the process of destruction or
removal of all pathogenic organism or organism capable
of giving rise to infection.
● DISINFECTANT: Disinfectants are chemical agents
designed to inactivate or destroy microorganisms on
inert surfaces.

4. DIFFERENCES
STERILIZATION DISINFECTION
A) Total destruction of all
microorganisms (whether or not
pathogenic) and their spores,
usually through the use of drastic
methods.
A) Minimizes the number of
microorganisms but doesn’t
eliminate them completely.
B) Uses more robust methods
such as high heat and radiation.
B) Uses moderately effective
methods.
C) It gives extreme cleanliness. C) It gives an adequate
cleanliness.

5. STERILIZATION DISINFECTION
D) Destroys both living
organisms and their resistant
structures.
D) Destroys only the living
organisms.
E) Use: decontamination of food,
medicine and surgical
instruments.
E) Use: mostly used to
decontaminate surfaces and air.
CONTD…

6. CHEMICAL DISINFECTANTS
• These are the chemical substances which are used to kill or
deactivate pathogenic microorganisms.
• The efficiency of chemical disinfection depends on-
i. Reactivity with biomolecules
ii. Disinfection concentration throughout the treatment
iii. Duration of the disinfection treatment(exposure time)

7. The chemicals used as disinfectants generally behave as
‘protoplasmic poisons’ in three different ways-
I. Damaging the bacterial cell membrane- agents: chlorhexidine,
quaternary ammonium compounds, alcohols and phenols.
II. Fixation of the cell membrane and blockage of egress of cellular
components- agents: formaldehyde and glutaraldehyde.
III. Oxidizing cellular constituents- agents: halide disinfectants such
as hypochlorite and bromides.
MODE OF ACTION

8. IDEAL REQUIREMENTS
• To be applicable in the context of sanitation, chemical disinfections
must have several basic characteristics-
1. Must be active against a wide range of pathogens
2. Be sufficiently cost-effective
3. Be reasonably safe to produce, store and apply
4. Act in the presence of organic matter
5. Have high penetration power and quick action

9. POTENCY OF CHEMICAL DISINFECTANTS
Depending on their ability to kill various groups of organisms,
disinfectants can be classified as-
■ High-level disinfectants: they are active against Gram-positive and
Gram-negative bacteria, spores and M. tuberculosis
■ Intermediate-level disinfectants: destroy M. tuberculosis,
vegetative bacteria, most viruses and fungi, but few, if any, spores.
■ Low-level disinfectants: kill most bacteria and most fungi, but not
M. tuberculosis or spores.

10. AGENTS OF CHEMICAL DISINFECTION
i. Alcohols
ii. Aldehydes
iii. Phenols
iv. Halogens
v. Hydrogen peroxide
vi. Peracetic acid
vii. Dyes
viii. Ethylene oxide(ETO)

11. i. ALCOHOLS
TYPES:
1. Ethyl alcohol
2. Isopropyl alcohol
3. Methyl alcohol (rarely used in healthcare)
MODE OF ACTION:
They act by denaturation of proteins.
(used in 60-70% water to be effective)

12. SPECTRUM OF ACTION:
They are Bactericidal, tuberculicidal and fungicidal.
USE:
• They are used mainly as skin antiseptics.
• To disinfect clinical thermometer, scissors,
stethoscopes, ultrasound instruments and hoods

13. LIMITATIONS:
• Alcohols lacks sporicidal action
• They cannot penetrate protein rich material
• They tend to swell and harden rubber and certain plastic tubing
after prolonged and repeated use

14. ii. ALDEHYDES
TYPES:
1. Formaldehyde
2. Glutaraldehyde
3. Ortho Phthalaldehyde(OPA)
MODE OF ACTION:
Inactivates bacterial proteins by forming covalent cross links with
several functional groups.

15. 1. FORMALDEHYDE
• It is markedly Bactericidal, sporicidal and virucidal.
• It is used both as an aqueous solution and in gaseous form.
• A 10% aqueous solution of Formalin is routinely used.
USES:
• Preservation of tissue for histological examination.
• To inactivate viruses and bacteria in vaccine
• Dilution containing 5% formaldehyde is used as a disinfectant
directly to a contaminated surface.

16. LIMITATIONS:
It has pungent strong smell, irritant to eyes and mucous membrane.
2. GLUTARALDEHYDE:
• It is effective against bacteria(including M. tuberculosis), fungi and
viruses(including HIV, Hepatitis B and enteroviruses).
• It is less toxic and irritant than formaldehyde.
• It is used as 2% buffered solution.
• It is available commercially as ‘Cidex’.

17. USES:
Disinfection of Hospital Equipments: Endoscope,
Cytoscope, anaesthetic equipment, Plastic material and
Thermometer.
LIMITATIONS:
• Respiratory irritation from glutaraldehyde vapour.
• Pungent and irritating odour.
• Allergic contact dermatitis.

18. 3. ORTHO-PHTHALALDEHYDE(OPA):
• OPA is a high level disinfectant.
• It is more stable during storage and more rapidly mycobactericidal
than glutaraldehyde.
• 0.5% OPA is sporicidal.
USES:
• It is used for endoscopes, cystoscope, thermometers, etc.
• Useful for glutaraldehyde resistant Mycobacteria.

19. LIMITATIONS:
• Irritant to respiratory tract and eyes.
• Has to be dealt with extreme
precaution.

20. iii. PHENOLS
• They are produced by distillation of coal tar between temperatures
of 170°C and 270°C.
• They are active against gram positive, gram negative bacteria and
mycobacteria.
MODE OF ACTION:
• Cell membrane damage
• Releases cell contents and causes lysis.

21. USES:
• Decontamination of infective discharges, bathrooms, and hospital
floors.
• In diluted form it is used as an antiseptic.
LIMITATIONS:
• Not active against endospores and viruses.
• Activity reduced in alkaline pH and hard water.

22. DISINFECTANTS OF PHENOLIC GROUP:
1. Phenol
2. Cresols
3. Chlorhexidine
4. Chloroxylenol
5. Hexachlorophane
1. PHENOL
• It has a powerful bactericidal action at a concentration of 1%.
• It’s activity is reduced drastically upon dilution.

23. Commercial preparations of Phenol:
A) SUDOL: Contains Xylenols and Phenols.
B) JEYES FLUID: Used to treat faeces and sputum before disposal.
2. CRESOLS:
• “Lysol” is a solution of Cresols in soap.
Uses:
To sterilize infected glass wares, cleaning floors and disinfection of
excreta.

24. Advantages:
• They are not readily inactivated by the presence of organic matter.
• They are active against a wide range of organisms.
3. CHLORHEXIDINE:
• It is bactericidal at a high dilution.
• It is more active against Gram positive than Gram negative
bacteria with no action against Tubercle bacilli or spores.
• Has very little activity against viruses.
• Has a good fungicidal activity.

25. • “Savlon” is a solution of chlorhexidine and cetrimide.
• It is widely used in wounds, preoperative disinfection of skin, as a
bladder irrigant, etc.

26. 4. CHLOROXYLENOL:
• It is an active ingredient of “Dettol”
(used in 4.8% concentration)
• It is less toxic and less irritant.
5. HEXACHLOROPHANE:
• Active against Gram positive bacteria.
• Applied on skin as prophylaxis against Staphylococcal infections.
• It is bacteriostatic at very high dilutions.
• It is potentially toxic and hence should be used with care.

27. iv. HALOGENS
• Chlorine and Iodine are two commonly used
disinfectants.
1. CHLORINE
• It is bactericidal and has a wide spectrum of
activity against viruses.
• It is used in water supplies, swimming pools, food
and dairy industries.

28. • 3 main chlorine compounds used as disinfectants are:
A) BLEACHING POWDER or CHLORINATED LIME
-used as a disinfectant for HIV infected material.
B) SODIUM HYPOCHLORITE
-has a bactericidal, fungicidal, virucidal and a rapid
sporicidal activity.
C) CHLORAMINE
-it retains chlorine longer and has a prolonged bactericidal
effect.
CONTD…

29. 2. IODINE:
• It is active against bacteria, viruses and fungi.
MODE OF ACTION:
By disruption of protein and nucleic acid structure and synthesis,
USES:
• Bactericidal antiseptic for intact skin
• For disinfection of wound.
• For disinfecting blood culture bottles and medical equipments.

30. • Preparations of Iodine:
A) Tincture of iodine: It is a weak solution of iodine
containing 2.5% iodine, 2.5% potassium iodide in
90% alcohol.
B) Iodine: 2% in 70% Isopropyl Alcohol.
-Tincture iodine and iodine are rapid
disinfectants and are used as antiseptics before
surgery.
C) Iodophores: they are iodine complexes with
anionic detergent.
-“Betadine” is a commonly used iodophore.

31. v. HYDROGEN PEROXIDE
• Hydrogen peroxide(H2O2) is effective against most organisms at
concentration of 3-6%.
• It kills all organisms including spores at higher concentrations of
10-25%.
MODE OF ACTION:
It works by producing free hydroxyl radicals that can attack
membrane lipids, DNA and other cell components.

32. USES:
• For fumigation of hospitals, operation theaters, ICUs,
dental clinics, OPD, blood banks, laboratories. (in conc. of
20% )
• For disinfection of surfaces, benches etc. (in conc. of 10%)
LIMITATIONS:
• The concentrated product may cause skin
irritation.

33. vi. PERACETIC ACID
• Peracetic acid is an oxidising agent.
• It is one of the high level disinfectants.
• It is also effective in the presence of organic matter.
• It is a more potent germicidal agent than H2O2.
MODE OF ACTION:
It denatures the proteins, disrupts the cell wall permeability, oxidizes
sulphur bonds in proteins.

34. USES:
• Used to prevent biofilm formation.
• Water purification
• Used to sterilize automated machine e.g. hemodialyzers.
LIMITATIONS:
• Can corrode metallic surfaces.
• Considered unstable, particularly when diluted.

35. vii. DYES
• Dyes can be divided into 2 groups-
A) ANILINE DYES:
i. Crystal Violet
ii. Brilliant green
iii. Malachite green
B) ACRIDINE DYES:
i. Proflavin
ii. Acriflavin
iii. Euflavin
iv. Aminacrine

36. MODE OF ACTION:
They impair the DNA complexes of the organism.
USE:
Dyes are used as skin and wound antiseptic.
LIMITATION:
• Not active in presence of organic matter as pus.
• Not active against Mycobacteria.

37. viii. ETHYLENE OXIDE(ETO)
• It is a colourless liquid with a boiling point of 10.7°C.
• It is effective against all types of microorganisms including viruses
and spores.
• It is highly penetrating and readily penetrates some plastics.
MODE OF ACTION:
• Acts by alkylating the amino, carboxyl, hydroxyl and sulphydryl
groups in protein molecule.
• It also reacts with DNA and RNA of microbes.

38. USES:
• Sterilization of heat labile delicate instruments.
• In hospitals to sterilize heart valves, respirators, lung machines,
syringes, sutures, dental equipment and clothing.
LIMITATIONS:
• ETO is toxic, inflammable, mutagenic and carcinogenic.
• Requires aeration time to remove ETO residue.

39. REFERENCES
• pediaa.com
• cdc.gov
• lentech.com
• waterpathogens.org/book/chemical-disinfectants
• CP Baveja Textbook of Microbiology
• Essential Microbiology Textbook by Lakshman Samaranayake

40. THANK YOU