A detailed summary of all the possible chemical disinfectants used in hospital sterilization procedures. Innovative pictures and brief explanations of all important topics clearly illustrated.........

1. Dr. Jasmine Vinshia
Assistant Professor
Department Of Microbiology
Rajas Medical Institutions

2. • Classification Of Chemical Agents used for
Disinfection
• Mode of action of chemicals
• Classification of Instruments
• Levels of Disinfection & Disinfectants
• Brief Summary of Chemicals used for
Disinfections

3. CHEMICALAGENTS
LIQUIDS
3
GASES
• Alcohols
• Aldehydes
• Phenols
• Halogens
• Heavy Metals
• Surface ActiveAgents
• Dyes
• Formaldehyde
• Ethylene Oxide

4.  Protein coagulation
 Disruption of the cell membrane
 Removal of the free sulphydryl groups
 Substrate competition
4

5. CLASSIFICATION
OFINSTRUMENTS
Critical
instruments
Semi-critical
Instruments
Non-critical
Instruments
Penetrate the soft tissue
 Contact the bone
Enter into or contact the
blood stream
They must be sterilized
by autoclaving(if heat
stable) or with ethylene
oxide or H2O2gas(if heat
sensitive)
Eg: Surgical instruments,
Scalers, Scissors , Dental burs,
Scalpels blades,
Forceps,implants
, Bone grafts
 Contact the mucous
membrane but will not
penetrate the soft tissue
 Glutaraldehyde is most
commonly used(For
high level disinfection)
or alcohols(for
intermediate level
disinfection)
Eg : Mouth mirror,
impression trays,
handpieces, probe,
tweezers, amalgam
condensers
 Come into contact
with intact skin but not
mucous membrane
•No risk of transmitting
infections so they can be
treated with low level
disinfectants .
Eg : X-Ray tubes, Light
handles, Counter tops

6. 33

7. • High-level disinfectant: This is a chemical that kills all microbial
pathogens except large numbers of spores. It may have some activity
against a smaller number of spores if the contact time is increased.
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• For example, glutaraldehyde and hydrogen peroxide.
• Uses: They are active against Gram-positive and Gram-negative
bacteria, spores and M. tuberculosis
Levels Of Disinfectants

8. • Intermediate-level disinfectant: A chemical that kills all
microbial pathogens including mycobacteria and non-enveloped
viruses except spores.
• For example, alcohol, phenolic compounds and iodophores.
• Uses: Destroys M. tuberculosis, vegetative bacteria, most viruses and
fungi.

9. • Low-level disinfectant: A chemical that kills only vegetative
bacteria, fungi and lipid- enveloped viruses.
• For example, quaternary ammonium compound.
• Uses: Kill most bacteria and most fungi, but not M. tuberculosis or
spores
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10. ALCOHOL
 70% ethyl alcohol
 Ethyl alcohol is active against the fungal
spores and used to treat cabinets and
incubator
 Suitable for skin preparation before
venepuncture
Disadvantage : . Inflammable
. Mucous membrane irritant.
. Promotes rusting.
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Mechanism of Action : Denaturation ofProteins
 Isopropyl alcohol
Used as a skin
disinfectant

11. A)Formaldehyde (formalin)
In aqueous solution it acts as a bactericidal and sporicidal
Active against Gram -ve bacteria, spores, viruses (HB, HIV) & fungi
Aqueous soultion: Formalin(37% solution) - 10% formalin +
0.5% Na tetraborate used to clean metal instrument e.g.
Endoscope, dialysis equipment.
Gaseous form: Fumigation of wards/corridors/ICU’s
DISADVANTAGE: Have pungent odour & irritating effect on
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skin & mucous membrane.
ALDEHYDES

12.  High level disinfectant
 Especially active against tubercle bacilli,f ungi
and viruses
 Less toxic than formaldehyde
 Can be safely used to treat corrugated rubber
anaesthetic tubes, face masks, metal instruments.
 Exposure time: > 10hrs.
B.GLUTARALDEHYDE / CIDEX ( 2% alkaline NaHCO3)
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13. C. Orthophthalaldehyde
• Has bactericidal
activity.
• It is used to cleanse
endoscopes between
patients as it is quick,
effective and safe.
1
3

14. PHENOLS:
Acts by cell membrane damage thus releasing cell contents and
causing lysis
 Eg. Cresol ( LYSOL) ,chlorhexidine ( SAVLON),chloroxylenol
(DETTOL)
 Phenol is commonly found in mouthwashes, scrub soaps and
surface disinfectants
 Low efficiency disinfectant
 Used for decontamination of the hospital environment, including
laboratory surfaces, and noncritical medical items.
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15. HALOGENS :
A) Chlorine compounds:
 Bleaching powder or hypochloritesolution
mostly used disinfectant for HIV infected
material.
 in concentration of 0.05 or 0.5% used for
surface material and instruments disinfection
 Should be prepared daily because of
instability of sodium hypochlorite solution
 Active against bacteria, spores, fungi and
viruses (HB, HIV) 38

16. B) IODOPHORS & IODINE
 Active against bacteria, spores & some
viruses & fungi
 Suitable for skin preparation, mouthwash&
as a surgical scrub
(7.5% Povidone+iodine= Betadine)
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17. SALTS
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 Salts of heavy metals have toxic effect on bacteria.
 The salts of copper , silver and mercury are used as disinfectant.
SURFACE ACTIVEAGENTS
 substances which alter energy relationships at
interfaces,producing a reduction of surface tension, are known as
surface active agents. E.g. quaternary compounds

18. ETHYLENE OXIDE
• Effective against all types of micro-organism including
viruses and spores.
• Reacts with DNA and RNA (rendering them virucidal).
• Potentially toxic to human beings, causing mutagenicity and
carcinogenicity.
• It diffuses through many types of porous materials and readily
penetrates some plastics.
• It is especially used for sterilizing heat-sensitive equipment like heart-
lung machines, respirators, suture materials, dental equipment, books
and clothing.
• Highly inflammable and explosive in concentration more than 3%
and hence not used for fumigation of rooms. Thus mixed with carbon
dioxide or nitrogen to eliminate its explosive tendency 41

19. Formaldehyde gas:
• This is employed for fumigation of
operation theatres and other rooms.
• The sealed room is left unopened for
48 hours after fumigation;. The gas
is neutralized with ammonia(300 ml
for every liter of formaldehyde used)
.
• Fumigation of operation theatres
is no longer
preferred. 1
9

20. • Betapropiolactone: This is a
condensation product of ketane and
formaldehyde. It is no longer used for
fumigation as it is carcinogenic.
• Hydrogen peroxide fogging:
Bactericidal action is by oxidizing the
cell wall of the organism. This has
replaced fumigation. It has the
advantage of short cycle time and is
non- toxic.

21. Hypochlorous acid
• It is generated from the reverse reaction
of sodium hypochlorite and hydrogen
peroxide. It has bactericidal activity
against common pathogenic organisms.
Highly active against biofilms producing
microorganisms.
2
1
Peracetic Acid
•Highly active against common antibiotic
resistant bacterias such as Methicillin-resistant
S.aureus, Vancomycin resistant S.aureus and
Clostridium sps.
Acids

22. • The aniline dyes include brilliant
green, malachite green and crystal
violet.
• The are non-irritant and non-toxic
to the tissues.
• They are inhibited by organic
material.
• Their acidic content makes them
lethal to bacteria.
2
2

23. Acridine dyes
• They are not as selective as the aniline
dyes. They are minimally affected by
the presence of organic matter.
• They impair the DNA complexes of the
organisms and prevent replication.
• Examples: Proflavine, Acriflavine,
Euflavine and Aminacrine.
2
3

24. Halogens
• Iodine(aqueous and alcoholic
solution) is widely used as a skin
disinfectant.
• Bactericidal, with moderate action
against spores. Highly active against
the tubercle bacteria and viruses.
• Iodophores(Compounds of iodine
with non-ionic wetting or surface-
active agents) have better action
than aqueous or alcoholic solutions
of iodine.
2
4

25. • Chlorine and its compound
hypochlorite have been used as
disinfectants over time. They are
markedly bactericidal and
virucidal.
• Town water supplies, swimming
pools, food and dairy industries
use chlorine for disinfection. The
organic chloramines are used as
antiseptics for dressing wounds.
2
5

26. Phenols
• These compounds are obtained by distillation of coal tar
between temperatures of 170°C and 270°C.
• Causes cell membrane damage by inactivating
membrane-bound oxidases and dehydrogenases leading
to lysis and death of the microorganism.
• Widely used as disinfectants in hospital(Lysol and
cresol). They are not readily inactivated by the presence
of organic matter; hence, they are good general
disinfectants
2
6

27. • Chlorhexidine (Hibitane) is a
relatively non-toxic skin antiseptic and
wound dressing. They are active
against most Gram-positive organisms
and fairly effective against Gram-
negative bacteria.
2
7

28. • They are substances that
proves lethal by reducing the
surface tension.
• Widely used as wetting
agents, detergents and
emulsifiers.
2
8
Surface-active agents

29. Mechanism:
• These act on the phosphate groups of the cell membrane and also enter
the cell. The membrane loses its semi-permeability and the cell
proteins are denatured. They act on bacteria, but have no action on
spores, tubercle bacilli and most viruses.
2
9

30. Metallic salts
• They are protein coagulants and have the
capacity to combine with free sulfhydryl
groups of cell enzymes.
• Thimerosal, phenyl mercury nitrate and
mercurochrome are less toxic and are used
as mild antiseptics and have marked
bacteriostatic but weak bactericidal and
limited fungicidalaction.
3
0
•Though all salts have a certain degree of heavy metals,
they have a greater germicidal activity
•Silver, Copper and mercury salts are used as
disinfectants.

31. RECOMMENDED CONCENTRATIONS
DISINFECTANT CONCENTRATI
ON
Chlorhexidine 1 - 4%
EthylAlcohol 70%
Gluteraldehyde 2%
Lysol 2.5%
Savlon 2%
Dettol 4%
Bleaching powder (Calcium hypochlorite) 14 gm in 1 Lwater
Sodium hypocholorite 1%, 0.1%
Betadine (Iodophore) 2%
Poviodine iodine 10%
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