This document provides an overview of disinfection and disinfectants. It begins by defining key terms like disinfection, sterilization, and antiseptics. It then discusses the types of disinfection like concurrent, terminal, and precurrent disinfection. Factors that impact disinfectant effectiveness and the ideal properties of a disinfectant are reviewed. Various chemical and physical disinfecting agents are described along with their mechanisms of action. The document concludes by emphasizing the importance of proper hand hygiene and other infection control procedures.

1. Dr. Khem R. Sharma
Assistant Professor
School of Public Health & Community
Medicine
DISINFECTION & DISINFECTANTS

2. Objectives
 After this SIS every one of you will be expected to
be able to:
 Define the term, “disinfection,” and explain how
disinfection differs from sterilization
 Understand the types of disinfection
 Review factors that impact the effectiveness of a
disinfectant
 Distinguish between high-level, intermediate-level
& low-level disinfection.
 Identify the properties of an ideal disinfectant
 Gain knowledge on the Disinfection agents
(Disinfectants)

3. Introduction
 Disinfection is the process of killing infectious
agents except spores outside the body by direct
exposure to chemical or physical agents.
 It can refer to the action of antiseptics as well as
disinfectants.
 Sterilisation - process by which an article, surface
or medium is made free of all living
microorganisms including spores.

4.  A disinfectant is a substance which destroys
harmful microbes (except spores) with the object
of preventing transmission of infection.
 Disinfectants are only suitable for application on
inanimate objects.
 Antiseptics - Chemicals used on living tissue such
as skin, to kill or slow the growth of
microorganisms.
Introduction

5. A brief History
 Early civilization practiced methods like salting, smoking,
pickling and exposure to sunlight to prolong shelf life of foods.
 Semmelweis (1818-1865) – demonstrated the value of hand-
washing with antiseptic solutions to reduce the death rate from
puerperal fever.
 Lister (1927-1972) was successful in reducing the number of
wound infections by prophylactic application of carbolic acid.

6. Types of Disinfection
1) Concurrent disinfection : It is the application of
disinfective measures as soon as possible after the
discharge of infectious material from the body of an
infected person.

7. 2) Terminal disinfection: Application of dis-infective
measures after the patient has been removed by death
or to a hospital or has ceased to be a source of
infection or after other hospital isolation practices
have been discontinued. Rarely practiced today.
3) Precurrent (prophylactic) disinfection: Disinfection of
water by chlorine, pasteurization of milk and
handwashing may be cited as examples of precurrent
disinfection.
Types of Disinfection

8. Chemical Disinfection
Cidal - chemical agents capable of killing
bacteria.
Agents that are bactericidal, virucidal,
fungicidal or sporicidal are capable of killing
these organisms.
Static - Chemical agents that inhibit the growth
of bacteria but do not necessarily kill them.

9. Properties of an Ideal Disinfectant
 Broad spectrum
 Fast acting
 Not affected by environmental facters
 Nontoxic
 Surface compatibility
 Residual effect on treated surfaces
 Easy to use with clear lebel directions
 Odourless
 Ecological
 Solubility
 Cleaner , Environmentally friendly.

10. Factors Impacting the
Effectiveness of Disinfectants
 Excessive Moisture
 Excessive moisture can
cause disinfectant solutions
to become diluted.
 Lowering the concentration
of the chemical disinfectant
can reduce its ability to kill
microorganisms
 Type and number of
microorganisms present

11. Factors Impacting the
Effectiveness of Disinfectants:
 Direct Contact with the Item
 In order to be effective, disinfectants must
make direct contact with all surfaces
being disinfected
 Time
 Disinfectants must be allowed some time
to work
 Check manufacturer’s instructions for the
correct exposure time required to achieve
the desired biocidal effect

12.  Temperature of the Disinfectant
 pH
 Hardness of the Water
 Material Compatibility
 Positioning of the Device(s) being disinfected
Other Factors Impacting the
Effectiveness of Disinfectants

13. Selecting a
Disinfectant
 Should be based on:
◦ The intended use of the device
◦ The degree of disinfection
required for the device
◦ Risk levels

14. Critical Items
 Items introduced directly
into the bloodstream or
other normally sterile
areas of the body
 Surgical Instruments,
Implants, etc.

15. Semi-Critical Items
 Items which come in
contact with intact
mucous membranes
 Fiberoptic Endoscopes,
Cystoscopes, etc.

16. Non-Critical Items
 Come in direct contact
with the patient’s
unbroken skin
 Crutches, Blood Pressure
Cuffs, equipment, etc.

17. Classification of
Patient Care Items
Body Contact Activity Level Item Class
Intact skin Low level Non-critical
Mucous membranes Intermediate level Semi-critical
Sterile body cavity High level Critical

18. Disinfectant Activity Levels
 High-level
 Intermediate-level
 Low-level

19. High level disinfection
 This processes destroy vegetative bacteria,
mycobacteria, fungi and enveloped (lipid) and
non-enveloped (non lipid) viruses, but not
necessarily bacterial spores.
 High level disinfectant chemicals (also called
chemical sterilants) must be capable of
sterilization when contact time is extended.
 Items must be thoroughly cleaned prior to high
level disinfection.

20. Intermediate level disinfection
Intermediate level disinfectants kill
vegetative bacteria, most viruses
and most fungi but not resistant
bacterial spores.

21. Low level disinfection
 Low level disinfectants kill most vegetative
bacteria and some fungi as well as
enveloped (lipid) viruses (e.g., hepatitis B,
C, hantavirus, and HIV).
 Low level disinfectants do not kill
mycobacteria or bacterial spores.
 Low level disinfectants are typically used to
clean environmental surfaces.

22.  Wear PPE
 Use an exhaust hood when necessary
 Develop a spill plan
 Provide an eyewash/shower and other first aid
supplies
 Provide easy access to a phone and phone
numbers for emergencies
 Provide yearly staff training
 Monitor disinfectants (including air quality)
Chemical Disinfectant
Safety

23. Disinfectants
1) Natural Agents
 Sunlight, Air
2) Physical Agents
 Burning
 Hot Air
 Boiling
 Autoclaving
 Radiation
Many disinfectants are used alone or in
combinations in the health-care setting.
 Chemical Agents
 Alcohols
 Chlorine and Chlorine compounds
 Formaldehyde
 Glutaraldehyde
 Ortho-phthalaldehyde,
 Hydrogen peroxide
 Iodophors
 Peracetic acid
 Phenolics
 Quaternary ammonium compounds.

24. Natural Agents
 Sunlight: Direct and continuous exposure to
sunlight is destructive to many disease producing
organisms.
 Air: Exposure to open air (airing) acts by drying or
evaporation of moisture which is lethal to most
microorganism.

25. Physical Agents
 Burning/incineration is an excellent method of
disinfection.
 Hot air sterilization is usually done in a hot air
oven & is very useful for sterilizing articles such
as glassware, syringes, swabs & dressings.
 Boiling is an effective method of disinfection
which provides an atmosphere of boiling and
steam.
 The drawbacks of boiling are that it is a slow
process, unsuitable for thick beddings and
woolen materials as they shrink.

26.  Autoclaving: It generates steam under pressure
(saturated steam) which is the most effective
sterilizing agent.
 Basically, the autoclave works on the same
principle as the domestic pressure cooker
 Ionizing radiation has great penetrating powers
with little or no heating effect making it one of the
most viable, safe and economic methods used
today..
Physical Agents

27. Alcohol
denaturation of proteins
 Alcohols are commonly used topical antiseptics. Rapid
bactericidal, tuberculocidal, fungicidal, and virucidal but
do not destroy bacterial spores.
 optimum bactericidal concentration is 60%–90%
solutions in water.
 Alcohols are not effective against bacterial spores and
have limited effectiveness against nonenveloped
viruses.
 They are also used to disinfect the surface of medical
equipment. Alcohols require time to work and they may
not penetrate organic material.

28. • They have a broad spectrum of
antimicrobial activity, do not leave
toxic residues, are unaffected by
water hardness.
• Hypochlorite, the most widely used
of the chlorine disinfectants, are
available as liquid or solid.
• The most common chlorine
products in are aqueous solutions
of 4 to 6% sodium hypochlorite,
which are readily available as
“household bleach”.
Chlorine and Chlorine Compounds
(Hypochlorite)

29.  Hypochlorite Most recommended in They are
included in most recommendation for
decontamination of hepatitis and AIDS viruses .
 Hypochlorite are also the agent of choice in
disinfecting surfaces used for food preparation or
in bathrooms.
 Organic material such as feces or blood
inactivate chlorine based disinfectants, therefore,
surfaces must be clean before their use.
Chlorine and Chlorine Compounds
(Hypochlorite)

30.  Formaldehyde is used as a disinfectant and
sterilants in both its liquid and gaseous states.
 The aqueous solution is a bactericide,
tuberculocide, fungicide, virucidal and sporicidal.
Formaldehyde
formalin

31. Formaldehyde
 Mode of Action. Formaldehyde inactivates
microorganisms by alkalizing the amino and
sulfhydral groups of proteins and ring nitrogen
atoms of purine bases.
 Be careful in handling Formaldehyde, wear
mask (irritant and potential carcinogenic )

32. Glutaraldehyde
high-level disinfectant and chemical sterilant
 Aldehydes have a wide germicidal spectrum.
 Gluteraldehydes are bactericidal, virucidal,
fungicidal, sporicidal and parasiticidal.

33. Glutaraldehyde
 They are used as a disinfectant or sterilant in
both liquid and gaseous forms.
 Glutaraldehyde is used most commonly as a
high-level disinfectant for medical equipment
such as endoscopes.
 Glutaraldehyde should not be used for cleaning
Noncritical surfaces because it is too toxic and
expensive.

34. Hydrogen Peroxide
3% hydrogen peroxide is a stable and effective
disinfectant when used on inanimate surfaces.
 Peroxides such as hydrogen peroxide
are often used as antiseptics to clean
wounds.
 The activity of peroxides is greatest
against anaerobic bacteria.

35. Hydrogen Peroxide
 Hydrogen peroxide at high concentrations is in
some cases is damaging to tissues, resulting in a
prolonged healing time.
 It is useful for cleaning surgical sites after closure,
but use sparingly to avoid penetrating suture
lines, which would inhibit healing.

36. Iodine
 The best-known and most widely used iodophor is
povidone-iodine.
 Mode of Action. Iodine can penetrate the cell wall of
microorganisms quickly, and the lethal effects are
believed to result from disruption of protein and nucleic
acid structure and synthesis.

37. Ortho-phthalaldehyde (OPA)
 Ortho-phthalaldehyde is a high-level disinfectant
 OPA solution is a clear, pale-blue liquid with a pH of 7.5.
 advantages: excellent stability over a wide pH range (pH 3–9)
 not a known irritant to the eyes and nasal passages, does not
require exposure monitoring, has a barely perceptible odor

38. Peracetic Acid
 rapid action against all microorganisms.
 Special advantages of peracetic acid are that it
lacks harmful decomposition products
 It remains effective in the presence of organic
matter and is sporicidal even at low
temperatures Uses. An automated machine
using peracetic acid to chemically sterilize
medical (e.g., endoscopes, arthroscopes),
surgical, and dental instruments.

39. Peracetic Acid and Hydrogen
Peroxide
 combination of peracetic acid and hydrogen
peroxide inactivated all microorganisms
except bacterial spores within 20 minutes.
 The 0.08% peracetic acid plus 1.0% hydrogen
peroxide product effectively inactivated
glutaraldehyde-resistant mycobacteria.
Peracetic Acid

40. Phenolics
 In high concentrations, phenol acts as a gross
protoplasmic poison, penetrating and disrupting the
cell wall and precipitating the cell proteins.
 Pure phenol is not an elfective disinfectant & is
used as a standard to compare the germicidal
activity of disinfectants
 Phenolics are bactericidal, fungicidal, virucidal, and
tuberculocidal (low level disinfectant).

41. Quaternary Ammonium Compounds
 The quaternary ammonium compounds are widely used
as disinfectants and good cleaning agents.
 Mode of Action. The bactericidal action of the
quaternaries has been attributed to the inactivation of
energy-producing enzymes, denaturation of essential cell
proteins, and disruption of the cell membrane.
 Uses. The quaternaries commonly are used in ordinary
environmental sanitation of Noncritical surfaces, such as
floors, furniture, and walls.

42. Chlorhexidine
Chlorhexidine products are often used as
disinfectants for inanimate objects or
antiseptics for cleaning skin wounds.
 Skin Antisepsis: 0.5% Chlorhexidine Skin
Preparation with Alcohol.
 Low toxicity
 Used in disinfection of the skin and hands
& mucous membranes

43. No disinfectant is substitute for
the following procedures
 Hand washing (hand hygiene)
 The use of personal protective equipment (e.g.
gloves) when handling blood, body substances
excretions and secretions.
 Appropriate handling of patient care equipment
and soiled linen.
 The prevention of needle stick/sharp injuries.
 Environmental cleaning.
 Appropriate handling of medical waste.
 Taking care of yourself (e.g. immunization)

44. Hands Spread Disease