DISINFECTANTS are chemical agents that inhibit or kill microorganisms (surgical apparatus, periphery of the patient, and the objects used by the patient). Disinfection It is the application of chemicals to destroy most pathogenic organisms on inanimate surfaces Can be accomplished by application of chemical agents, use of physical agents (ionizing radiation) dry or moist heat, superheated steam(autoclave, 120̊ C) idela surfactant effective at room temperature, noncorrosive and nontoxic, inexpensive, capable of killing the vegetative form of all pathogenic organisms, require limited time of exposure

1. DISINFECTANTS BY- SANCHIT
DHANKHAR

2. DISINFECTION
DISINFECTANTS are chemical agents that
inhibit or kill microorganisms (surgical
apparatus, periphery of the patient, and the
objects used by the patient).
Disinfection It is the application of chemicals to
destroy most pathogenic organisms on
inanimate surfaces
Can be accomplished by application of chemical
agents, use of physical agents (ionizing
radiation) dry or moist heat, superheated
steam(autoclave, 120̊ C) 2

3. IDEAL DISINFECTANT
effective at room temperature,
noncorrosive and nontoxic,
inexpensive,
capable of killing the vegetative form of
all pathogenic organisms,
require limited time of exposure
3

4. PROCESS OF
DISINFECTION
Prevents infection by reducing the
number of potentially infective
organisms either by killing, removing or
diluting them.
Application of chemical agent
Use of ionizing irradiation, dry or moist
heat or superheated steam (autoclave,
120◦ C)
-PHYSICAL-
4

5. DISINFECTANTS WITH THEIR MECHANISM
Chemical MOA
ALCOHOLS (70%)
e,g,Ethyl alcohol, isopropyl alcohol
Alcohols dehydrate cells, disrupt membranes and cause
coagulation of protein
ALDEHYDES
Examples: 40% Formaldehyde, Gluteraldehyde
Acts through alkylation of amino-, carboxyl- or hydroxyl
group, and probably damages nucleic acids.
PHENOL:
Examples: 5% phenol, 1-5% Cresol, 5% Lysol
Act by disruption of membranes, precipitation of proteins and
inactivation of enzymes
HALOGENS They are oxidizing agents and cause damage by oxidation of
essential sulfydryl groups of enzymes.
HEAVY METALS
Examples: Mercuric chloride, silver nitrate
Act by precipitation of proteins and oxidation of sulfydryl
groups.
SURFACE ACTIVE AGENTS: They have the property of concentrating at interfaces between
lipid containing membrane of bacterial cell and surrounding
aqueous medium, disrupt membrane resulting in leakage of
cell constituents. Examples: These are soaps or detergents.
ETHYLENE OXIDE It is an alkylating agent. It acts by alkylating sulfydryl-,
amino-, carboxyl- and hydroxyl- groups.
BETA-PROPIOLACTONE (BPL) It is an alkylating agent and acts through alkylation of
carboxyl- and hydroxyl- groups.
HYDROGEN PEROXIDE: It acts on the microorganisms through its release of nascent
oxygen. Hydrogen peroxide produces hydroxyl-free radical
that damages proteins and DNA. 5

6. HALOGENS
The halogens and halogen – releasing
compounds include some of the most
effective antimicrobial compounds used
for disinfection and antisepsis.
Iodine and chlorine are the most
effective halogens with bromine and
fluorine being less active.
Because of the irritating nature of the
products of sodium hypochlorite, it is
currently used primarily as a
disinfectant. 6

7. IODINE
Tincture of iodine (2g I, 2.5 g NaI and 50% ethanol to 100
mL).
Powerful antiseptic for intact skin, should avoid contact
with mucosas. Can cause serious hypersensitivity
reactions, staining of skin and dressing can happen and
this limits its use.
7

8. IODOPHORES
less irritating less hypersensitivity compared to tincture
of iodine.
Povidon iodine (A complex of I with polivinyl
pyrrolidone-surface active agent-). Can be used as
antiseptics or disinfectants.
Kill vegetative bacteria, mycobacteria, fungi, lipid
containing viruses. They kill spores as well on
prolonged use
Iodine and other free halogens oxidize the –SH groups
of proteins and enzymes and produce -S-S- bonds
and disrupts the structure and function of these
8

9. CHLORINE
Chlorine is a strong oxidizing agent.
Hypochloric acid and sodium
hypochlorite (household bleach 5.25%)
are bactericidal and effective
disinfectants
1:10dilutions it provides 5000 ppm of
chlorine. This is the concentration
recommended for disinfection of blood
spills. Dilutions are made with tap water
and when the opaque bottle is tightly
closed it preserves its activity. 9

10. < 5 ppm kills vegetative bacteria
5000 ppm is needed to kill spores
1000-10,000 ppm is tuberculocidal
100 ppm kills vegetative fungal cells in 1 h
500 ppm kills fungal spores
200-500 ppm inactivate viruses
HOCl is the active form, pH↑ less active OCl-
is formed→blood serum feces protein
containing materials should be removed
from surfaces
10

11. ALCOHOLS
Ethyl alcohol (70% [60-90]) and isopropyl
alcohol are effective antiseptic and
disinfectant agents. They reduce the number
of bacteria 90% when applied to the skin.
They rapidly kill vegetative bacteria, M
tuberculosis, many fungi and inactivate
lipophilic viruses. They denature proteins and
disturb the membrane permeability of
bacteria.
They are not effective as sterilizing agents
because of their inefficient antibacterial
spectrum 11

12. They are flammable and must be stored
in cool and well ventilated places.
They can damage corneal tissue if
directly applied, therefore instruments
that will be used in the eye must be free
of alcohol before use.
12

13. ALDEHYDES
2-8% of formaldehyde can be used as a sterilizing
agent for surgical instruments. Not corrosive for
metal, plastic or rubber. Broad spectrum of activity
against microorganisms and viruses. Alkylate
chemical groups in proteins and nucleic acids. It is
especially useful for instruments that can not be
autoclaved. (hemodialyzers, dental handpieces,
respiratory therapy equipment). 3% solution is useful
topically on hands and feet in treatment of
hyperhidrosis. Presence of organic material, low conc,
and perfusion inefficiency can cause failure.
Formaldehyde is marketed as the 34-38% solution and
is called formol and contains methyl alcohol in order
to prevent polymerization and precipitation of
formaldehyde. 13

14. Formaldehyde has a pungent odor and is
highly irritating to repiratory mucous
membranes and eyes at conc 2-5 ppm is
rarely used because of its toxicity and
tendency to cause sensitization with
repeated contact. The relative risk of
formaldehyde as a human carcinogen
when used as a disinfectant is significant
(OSHA).
14

15. Glutaraldehyde 2% w/v pH7.4-8.5 is not
significantly affected by the presence of
organic material and is relatively nonirritating,
nonallergenic and noncorrosive when proper
safeguards are employed. Activated solutions
are bactericidal, sporicidal, fungicidal and
virucidal. Exposure of skin and mucus
membranes can cause sensitization, irritation
and damage. Protection of health care workers
from exposure to glutaraldehyde conc>0.2
ppm is advised It is important to use it only in
well – ventilated areas and never using it as a
surface disinfectant. 15

16. OXIDIZING AGENTS
Hydrogen peroxide is the most common of a
number of oxidizing compounds that have
been used as antiseptics. It is also effective in
injured skin due to its bubbling effect. 3%
solution is effective
Concentrations potentially useful for antisepsis
are effective against vegetative bacteria,
higher concentrations are sporicidal
Disinfection of respirators, acrylic resin
implants, plastic eating utensils, soft contact
lenses, cartons for milk or juice
10-25% conc is sporicidal 16

17. PHENOLS
Phenol is the oldest surgical antiseptic
but is no longer used even as a
disinfectant because of its corrosive
effect on tissues and its carcinogenic
effects.
Phenolic derivatives (o-phenylphenol-
coal tar distillates- etc) can be used.
Skin absorption and skin irritation still
occurs with these derivatives.
Detergents are added to formulations to
clean and remove organic material that
may decrease the activity of these
compounds.
17

18. They are bactericidal , fungicidal and
inactivate lipophilic viruses. Not
sporicidal. Used on floors, beds,
countertops and benchtops
Disrupt cell walls and membranes,
precipitate proteins and inactivate
enzymes
Hexachlorophen as skin disinfectant has
no longer been used because of its 18

19. CHLORHEXIDINE
Chlorhexidine was approved for use in
surgical scrubs
It is highly effective against gram-
positive organisms, vegetative bacteria,
mycobacteria, moderately active against
fungi and viruses, spore germination is
also inhibited. Strongly adsorbs to
bacterial membranes and causes leakage
of small molecules and precipitation of
cytoplasmic proteins.
19

20. Water soluble chlorhexidine digluconate is used
as an antiseptic. Most effective against gram-
positive cocci and less active against gram-
positive and gram-negative rods, spore
germination is also inhibited.It strongly
adsorbs to bacterial membranes and causes
leakage of small molecules and precipitation of
cytoplasmic proteins. It is resistant to inhibition
by blood or organic material. Anionic or
nonanionic agents in moisturizers,
soaps,surfactants neutralize its action. Used in
oral rinses, should not be used during surgery
of the middle ear, causes sensorineural
deafness.
20

21. SURFACE ACTIVE AGENTS
These are compounds that produce a detergent
effect. They are quaternary ammonium compounds.
Cationic agents were used as cold sterilization
solutions. But they are ineffective against bacterial
spores, tubercle bacilli, fungi, viruses and many
gram-negative bacteria. The bactericidal action of
these compounds is due to inactivation of energy-
producing enzymes, denaturation of proteins and
disruption of cell membrane.
Cetylpyridinium chloride, benzethonium chloride
and similar cationic agents are used in mouth rinses
and sore throat remedies.
21

22. They bind to the surface of colloidal
protein in blood, serum, milk and to
fibers in cotton, mops, cloths and paper
towels (inactivation). Anionic detergents
also inactivate them.
They are also used for sanitation of
floors and bench tops. Since their
toxicity is low they are used as sanitizers
in food production facilities.
Polyhexamethylene biguanide used in
drop form for acanthamoeba keratitis. 22

23. HEAVY METALS
Mercury and silver compounds were used
as antimicrobial agents. Silver nitrate
was commonly used in dentistry to treat
oral ulcers but is no longer used
because it delays healing and alters
cellular morphology. In medicine, silver
nitrate eyedrops remain useful in the
prophylaxis of gonococcal infection in
the newborn.
23

24. Mercury is an environmental hazard,
however, thiomersal (0.001-0.004%) is
still used as a preservative of vaccines,
antitoxins and immune sera
Benzoic acid and salts, parabens
-alkyl esters of p-hydroxybenzoic acid
Sorbic acid and salts, phenolic
compounds
Quaternary ammonium compounds,
alcohols also used
24

25. TESTS TO EVALUATE DISINFECTANTS/
BACTERICIDAL/VIRUCIDAL/FUNGICIDAL
AGENTS
Rideal walker test
Chick martin test
Kelsey sykes method
Use dilution method
25

26. 26

27. Phenol is diluted from 1:400 to 1:800 and the test disinfectant
is diluted from 1:95 to 1:115.
Their bactericidal activity is determined against Salmonella
typhi suspension.
Subcultures are performed from both the test and phenol at
intervals of 2.5, 5, 7.5 and 10 minutes.
The plates are incubated for 48-72 hours at 37°C.
That dilution of disinfectant which disinfects the suspension in
a given time is divided by that dilution of phenol which
disinfects the suspension in same time gives its phenol
coefficient.
27

28. 28

29. KELSEY-SYKES TEST
Kelsey-Sykes test is acapacity use dilution test , designed to determine concentrations of
disinfectant that will be effective in clean and dirty conditions.
The disinfectant is challenged by three successive additions of a bacterial suspension during the
course of the test. The duration of test takes over 30 minutes to perform.
The concentration of the disinfectant is reduced by half by the addition of organic matter
(autoclaved yeast cells), which builds up to a final concentration of 0.5%.
Depending on the type of disinfectant, a single test organism is selected from S. aureus, P.
aeruginosa, P. vulgaris and E. coli. The method can be carried out under 'clean' or 'dirty'
conditions.
The dilutions of the disinfectant are made in hard water for clean conditions and in yeast
suspension for dirty conditions. Test organism alone or with yeast is added at 0, 10 and 20
minutes interval.
The contact time of disinfectant and test organism is 8 min.
The three sets of five replicate cultures corresponding to each challenge are incubated at 32oC for
48 hours and growth is assessed by turbidity. The disinfectant is evaluated on its ability to kill
microorganisms or lack of it and the result is reported as a pass or a fail and not as a coefficient.
Sets that contain two or more negative cultures are recorded as a negative result. The disinfectant
passes at the dilution tested if negative results are obtained after the first and second challenges.
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30. 30

31. USE DILUTION TEST :-
•These test are the oldest test .
•AOAC used dilution test is a carrier based test.
•S.aureus, Pseudomonas aeruginosa, Salmonella
choleraesuis bacteria culture is used.
•Metal ring dipped into microbial culture .
•Dried at 37°C
•Dipped in solution of disinfectant for 10min.
•Ring is washed & placed into tube of medium for
48 hours.
1.Growth occur – less effective disinfectants .
2. No Growth occur – more effective disinfectants
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32. THANKYOU
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