Classification and Modes of action of Disinfectants.pdf

This presentation introduces the classification and modes of action of disinfectants, highlighting their role in infection control and public health. It covers different types of disinfectants, mechanisms of microbial action, and applications in healthcare and daily life. Designed for students and professionals in pharmacy, medicine, and life sciences, it serves as a concise learning resource.

1. MICROBIOLOGY
CLASSIFICATION AND
MODES OF ACTION OF DISINFECTANTS
DEPARTMENT OF PHARMACEUTICAL SCIENCES,
DR. HARI SINGH GOUR UNIVERSITY, SAGAR [MP] .
SUBMITTED BY :
ANANYA MOURYA
(Y19150008)
SUBMITTED TO :
DR. UDITA AGRAWALMA’AM
PRIYANKA JAIN MA’AM

2. INDEX
INTRODUCTION TO DISINFECTANTS
CLASSIFICATION OF DISINFECTANTS
•Based on consistency.
•Based on spectrum of activity .
•Based on modes of action.
Mode of actions of different disinfectants.

3. DISINFECTANTS
•Disinfection is the process of destruction or removal of
micro-organisms and reducing them to the level not
harmful to health.
•Disinfection generally kills the sensitive vegetative cells
but not heat resistant endospores.
•If the object is inanimate(lifeless), such as working area,
dishes, benches, etc. the chemical agent is known as
Disinfectants.
•However if the object is animate(living) such as human
body tissue, the chemical is known as Antiseptics.
•Disinfectants are usually bacteriocidal but occasionally
they may be bacteriostatic.

4. IDEAL DISINFECTANT’S PROPERTIES
•Broad spectrum.
•Non-toxic.
•Fast acting.
•Odourless.
•Surface compatibility.
•Economical.
•Stable on storage.
•Not affected by the physical factors.

5. CLASSIFICATION OF DISINFECTANTS
•Liquid
•Gases
Based on consistency.
•Low level
•Intermediate level
•High level
Based on spectrum of
activity .
•On cytoplasmic membrane
•Denaturation of cellular proteins
•Oxidation of cellular proteins
•Alkylation of cellular contents
•On nucleic acid
Based on mode of
action.

6. 1. Based on consistency:
In this classification the disinfectants are classified on
the basis of their physical forms .
•Alcohols, Phenols, Aldehydes,
Halogens, Quaternary ammonium
compounds, Biguanides, acids and
esters.
•Text
LIQUIDS
•Formaldehyde vapours, ethylene
oxide, propylene oxide, ẞ-
propiolactone.
GASES

7. •In this classification disinfectants are divided in several
categories according to their effectiveness over many types
of vegetative bacteria, viruses and spores .
1.High level : These chemical agents kills vegetative
microorganisms, fungi and also inactive virus, but not
effective against spores.
2.Intermediate level: These chemical kills vegetative cells, all
fungi and most viruses, no affect on spores .
3.Low level : These chemicals kills vegetative microbial cells,
some fungi and very few viruses, no effect on spores .
2. Based on spectrum of activity :

8. Based on spectrum of activity
Low level
Quat.Ammonium
compounds
Iodophores
Phenols
Intermediate level
Alcohols
Chlorine
hypochlorite
Phenols
High level
Hydrogen peroxide
Aldehydes
Glutaraldehydes

9. 3. Based on mode of action:
•The classification divides the disinfectants on their
mechanism of action and site of action to destroy the
microbial cells .
1.Act on cytoplasmic membrane [Quat. Ammonium
compounds, phenols and alcohols].
2.Denaturation of cellular proteins [Aldehydes and
Halogens].
3.Oxidation of cellular contents [Hydrogen peroxide and
ethylene dioxide] .
4.Alkylation of cellular contents [Formaldehyde, ẞ-
propiolactone and Glutaraldehyde] .
5.Act on nucleic acids

10. Different Disinfectants and their
mode of actions
1.Alcohol
2.Aldehyde
3.Ethyleneoxide
4.Halogens
5.Phenolanditsderivatives
6.Quaternaryammoniumcompounds
7.Hydrogenperoxide
8.Biguanidepolymer

11. 1. Alcohols
•It is observed that alcohols specifically exert a bactericidal
and fungicidal action [Not on endospores].
•Mechanism of action : protein denaturation of bacteria.
Besides, they may also cause denaturation based on the
following mechanisms, namely:
a)Disruption of tissue membranes, and
b)Dissolution of several lipids [fats].
•Examples :The most frequently employed alcohols are ,
namely :
1.Ethanol.
2.Isopropanol.

12. 1.Ethanol : The usual recommended concentration of
ethanol is 70%(v/v).However, varying conc. Between
60-95%(v/v) appear to cause bactericidal effect quite
rapidly. While pure alcohol is found less effective in
comparison to corresponding aqueous ethanolic
solutions since, the phenomenon of denaturation
essentially requires water .
2.Isopropanol [Rubbing alcohol] : It is observed to be
definitely superior to ethanol as an antiseptic as well as
disinfectant. Besides, it is available more conveniently,
less volatile in nature (than ethanol), and less
expensive.
[Both Ethanol and Isopropanol are remarkably and
distinctly employed to potentiate the overall
effectiveness of certain other chemical substances] .

13. •Mechanism of action:
Cross-linking, coagulating, clumping.
•Like many disinfectants, alcohols are generally considered
to be non-specific antimicrobials because of their many
toxic effects.
•Alcohols cause cell proteins to clump and lose their
function.
•Specifically, the cell membranes lose their structure and
collapse, thereby killing it.
•Alcohol is also effective in inhibiting spore germination by
affecting the enzymes necessary for germination.
•However, once it’s removed, spores can recover, so it’s
not considered a sporicidal.

14. 2. Aldehyde
•In general, the aldehydes are found to be the most effective
antimicrobial agents(disinfectants).
•Advantages :
These are given as :
1.In the sterilization of various hospital equipments,
instruments, including the respiratory therapy assembly.
2.Glutaraldehyde enjoys the wide spread recognition and
reputation of being the only liquid chemical disinfectant
which may be regarded as a possible sterilant(or sterilizing
agent) .

15. •There are two glaring examples, such as:
a)Formaldehyde : It invariably causes inactivation of the
proteins by forming the most critical covalent cross-
linkages together with a plethora of ‘organic functional
moieties’ on the proteins.
[formaldehyde gas is found
oto exert an excellent disinfectant action
oFormalin was previously employed to embalm dead
bodies, to preserve biological specimens, and also to
cause inactivation of microbes and viruses in vaccines.]
b)Glutaraldehyde[Cidex ; Glutarol ; Sonacide ; Verutal]:
It represents a chemical entity relative to formaldehyde
which being less irritating and definitely has an edge
over formaldehyde.

16. 3. Ethylene oxide
•Gaseous disinfectant.
•Mechanism of action solely depends upon its inherent
ability to cause ‘Denaturation of protein’. In fact, the
liable H-atoms strategically attached to the proteins, are
critically replaced by the available alkyl
moieties(Alkylation).
Advantages :
1.Ethylene oxide practically kills all microorganisms
besides the endospores; however, it may requires a
perceptionally lengthy exposure ranging between 4-18
hours .
2.High degree of penetrating power .

17. 4. Halogens
•The two most important halogens that are effectively
employed as the disinfectant are Iodine(I₂) and
Chlorine(Cl₂) frequently in solution; besides, being
used as the integral constituents of both organic or
inorganic compounds.
•We will discuss about :
A. Iodine
B. Chlorine :
oHypochlorous Acid
oLiquid chlorine gas

18. A. Iodine(I ₂) Or Iodophor
•The most commonly used iodine solution was the Iodine
Tincture, which has been duly replaced by Iodophor[-an
unique combination of iodine and an organic molecule,
from which iodine gets released gradually].
•Mechanism: iodine combines with Tyrosine-an amino acid
which essentially represents an integral common
constituent of several enzymes and many cellular proteins.
Advantages of an Iodophor :
1.Possesses the same activity as that of iodine as an
antimicrobial agent.
2.Doesn't stain either the skin surface or clothes, and
3.It is much less irritating in nature (compared to Iodine
Tincture)

19. B. Chlorine(Cl₂)
•This group comprises aqueous solution of chlorine,
hypochlorite, or Hypochlorous acid.
•Frequently, a concentration of < 1 ppm of
available chlorine is sufficient to kill bacteria and
viruses, spores and mycobacterium requiring higher
concentrations.
•Chlorine has been used for applications, such as
the deactivation of pathogens in drinking water,
swimming pool water and wastewater, for the
disinfection of household areas and for textile
bleaching.

20. •Chlorine works by oxidizing proteins, lipids and
carbohydrates.
•Hypochlorous acid, which is a weak acid that forms when
chlorine is dissolved in water, has the most effect on the
bacterial cell, targeting some key metabolic enzymes and
destroying the organism.
•Chlorine compounds have also been shown to affect
surface antigen in enveloped viruses and
deoxyribonucleic acid (DNA) as well as structural
alterations in non-enveloped viruses.
•However, chlorine compounds in higher concentrations
have been shown to kill bacterial spores such
asClostridium difficile(C. diff).

21. 5. Phenol and its derivatives
•Phenol is the chief products obtained by the distillation
of the coal tar. Phenol 1% has bactericidal action.
•Many derivatives of phenol are more effective and less
costly.
•Phenolics are active ingredients in some household
disinfectants. They are also found in some mouthwashes
and in disinfectant soap and handwashes.
•o-Phenylphenol is often used instead of phenol, since it
is somewhat less corrosive .
•These are however toxic for new borns or pets.

22. Derivatives
1.Hexachloropheneis a phenolic that was once used as
a germicidal additive to some household products but
was banned due to suspected harmful effects.
2.Chloroxylenolis the principal ingredient in Dettol, a
household disinfectant and antiseptic.
3.Thymol,derived from the herb thyme, is the active
ingredient in some "broad spectrum" disinfectants that
often bear ecological claims. It is used as a stabilizer in
pharmaceutics preparations. It has been used for its
antiseptic, antibacterial, and antifungal actions, and
was formerly used as a vermifuge.
4.Amylmetacresol is found in Strepsils, a throat
disinfectant.
• Although not a phenol, 2,4-dichlorobenzyl alcohol has
similar effects as phenols, but it cannot inactivate viruses.

23. •Mechanism of action:
Cross-linking, coagulating, clumping.
•Phenol and its derivatives exhibit several types of bactericidal
action.
•At higher concentrations, the compounds penetrate and
disrupt the cell wall and make the cell proteins fall out of
suspension.
1.One of the first things to occur is stopping essential enzymes.
2.The next level in the damage to the bacteria is the loss in the
membrane’s ability to act as a barrier to physical or
chemical attack.
•Though phenols can act at the germination —beginning of
growth —stage of bacterial spore development, this effect is
reversible, making them unsuitable as sporicides.

24. 6. Quaternary ammonium compound :
•("quats"), such as benzalkonium chloride, are widely
used for the control of microorganisms like non-
enveloped viruses such as norovirus, rotavirus, or polio
virus , bacteria and pathogenic fungi within (3–5
minutes) on floors, walls, nursing homes and other public
places.
•They are also used as skin antiseptics and as sanitizing
agents in dairy, egg and fishing industries.
•Quats are biocides that also kill algae and are used as
an additive in large-scale industrial water systems to
minimize undesired biological growth.

25. 7. Hydrogen peroxide
•It is used in hospitals to disinfect surfaces and it is used in
solution alone or in combination with other chemicals as a
high level disinfectant.
•Hydrogen peroxide is sometimes mixed with colloidal silver. It
is often preferred because it causes far fewer allergic
reactions than alternative disinfectants.
•Also used in the food packaging industry to disinfect foil
containers. A 3% solution is also used as an antiseptic.
•Hydrogen peroxide vapour is used as a medical sterilant and
as room disinfectant. Hydrogen peroxide has the advantage
that it decomposes to form oxygen and water thus leaving
no long term residues.

26. 8. Biguanide polymer
•It is specifically bactericidal at very low concentrations (10
mg/l).
•It has a unique method of action: The polymer strands are
incorporated into the bacterial cell wall, which disrupts the
membrane and reduces its permeability, which has a lethal
effect to bacteria.
•It is also known to bind to bacterial DNA, alter its
transcription, and cause lethal DNA damage.
•It has very low toxicity to higher organisms such as human
cells, which have more complex and protective
membranes.

27. Chlorhexidine: (Savlon)
•The general mechanisms of chlorhexidinecan be
summarized as follows:
■Damage to cell membrane by interaction with lipid
layer.
■Leakage of cellular constituents at low-level
exposure.
■Precipitation of nucleic acids and proteins at high-
level exposure.
■Coagulation of intracellular and disruption of
enzymatic pathways at high-level exposure.