This document discusses the history and methods of disinfection. It begins with key figures in the development of disinfection practices like Louis Pasteur, Joseph Lister, and Ignaz Semmelweis. It then covers various classifications of items based on disinfection needs, factors affecting disinfection effectiveness, ideal properties of disinfectants, and common sites of action. The document concludes by describing several physical (e.g. cleaning, heat) and chemical (e.g. phenols, alcohols, halogens) methods used for disinfection.

1. By Dr. vikas saini
Disinfection

2. Discussion
 HISTORY
 DEFINITIONS
 SPAULDING CLASSIFICATION
 FACTORS AFFECTING DISINFECTION
 PROPERTIES OF IDEAL DISINFECTANT
 DISINFECTANTS – site of action
 METHODS OF DISINFECTION
 OTHER METHODS FOR DISINFECTION
 CHANGES IN STERLIZATION AND DISINFECTION SINCE 1981
 TESTING OF DISINFECTANTS
 SUMMARY
 DISINFECTANT POLICY

3. HISTORY OF DISINFECTION

4. LOUIS PASTEUR
 Louis pasteur (1822-95) was the first scientist to
show clearly that bacteria never generate
spontaneously and that no growth of any kind
occurs in the sterilized media.

5. JOSEPH LISTER
FATHER OF ANTISEPTIC
SURGERY

6. Joseph lister(1827-1912)
 Discovered the effectiveness of carbolic acid
which was used in controlling typhoid . using
carbolic acid , lister was able to keep his hospital
ward in glasgow free of in infection.
 Lister began washing his hands before operating
, and wearing clean clothes.
 Lister also sprayed the air with carbolic acid to kill
airborne germs.

7. IGNAZ SEMMELWEIS(1847)
 Advocated the value of
hand washing and
fingernail scrubbing
 Used antiseptic
chlorinated lime solution
 Proposed avoiding
decaying organic matter

8. STERILISATION
 The complete removal or destruction of all
forms of microbial life
 bacteria
 viruses
 fungi
 spores

9. MEASURE OF STERILITY
 Sterility assurance level (SAL) is used as a
measure of sterility
 SAL = probability of survival of a microorganism
after sterilization process
 SAL is normally expressed a 10-n (probability of
survival)
 SAL of 6 = < 1 in a million chance that a particular
item is contaminated
 SAL = 6 is acceptable

10. DISINFECTION
According to CDC , Disinfection describes a
process that eliminates many or all pathogenic
microorganisms, except bacterial spores, on
inanimate objects
Main difference with sterilization = the lack of
sporocidal activity

11. OTHER DEFINITIONS
 Cleaning : the removal of adherent visible soil
and other dirt thus reducing the microbial burden
,making sterilisation or disinfection more effective.
 Sanitizing : process that reduces microbial
population on object to a safe level

12.  Decontamination:
the removal of
disease-producing
microorganisms to
leave an item safe for
further handling

13. SPAULDING CLASSIFICATION

15. Critical items
 Enter normally sterile
tissues , vascular
system
 Sterilized by
autoclaving if heat
stable or by
Hydrogen Oxide Gas
Plasma or ETO if
heat sensitive.
 Eg. surgical
instruments ,
implants , cardiac
catheters , ultrasound
probes

16. SEMI CRITICAL
 Contact with mucous
membrane or non
intact skin.
 High level disinfection
by Glutaraldehyde.
 Eg: Endoscopes,
laryngoscopes ,
esophageal
manometry probes,
cystoscopies

17. NON CRITICAL
 contact with intact skin
but not mucous
membranes
 Eg. bedpans, blood
pressure cuffs, crutches,
stethoscopes
 Requires intermediate or
low level disinfection

18. TYPES OF DISINFECTANTS
High level
disinfectant
s
Intermediate
level
disinfectants
Low level
disinfectant
s

19. High-level disinfectants
 complete elimination of all microorganisms in or on
an instrument, except for small numbers of bacterial
spores.

20. Intermediate-level disinfectants
 agent that destroys all vegetative bacteria,
including tubercle bacilli, lipid and some nonlipid
viruses, and fungi, but not bacterial spores

21. Low-level disinfectants
 agent that destroys all vegetative bacteria (except
tubercle bacilli), lipid viruses, some nonlipid
viruses, and some fungi, but not bacterial spores.

22. Decreasing Order of Resistance of Microorganisms to
Disinfectants
 Prions
 Spores
 Mycobacteria
 Non-Enveloped Viruses
 Fungi
 Bacteria
 Enveloped Viruses

23. Factors Affecting Effectiveness of
Disinfection
 Prior cleaning of the object;
 organic and inorganic load present;
 level of microbial contamination;
 concentration and exposure time
 physical nature of the object (e.g., crevices,
hinges, and lumens);
 presence of biofilms; temperature and pH of
the disinfection process; and in some cases,
 relative humidity of the sterilization process
(e.g., ethylene oxide).

24. Properties of an ideal
disinfectant
 Has a broad spectrum of activity.
 Is bactericidal.
 Acts rapidly
 Does not deteriorate in storage.
 Is persistent and stable.
 Is not inactivated.
 Is cheap.
 Is non corrosive.

25.  Is non toxic and leaves no toxic residues.
 Is easily used.
 Deodorises.
 Is colourless and non-staining.
 Is non flammable.
 Is soluble.
 Is odourless

26. Disinfectants
Two basic mechanism of action :
 Dissolution of lipids from cell membrane by
detergents and lipid solvents.
 Irreversible alteration of proteins eg by
denaturants, oxidants, alkylating agents and
sulphydryl agents

27. Site of action

28. Disinfection
Can be achieved by:
•Choice of method depends on practical issues such as
ease of use or material compatibility
•Cleaning of objects needed before attempt at
sterilization
Or high level disinfection
 PHYSICAL
METHODS
 CHEMICAL
METHODS

29. PHYSICAL METHODS
 Cleaning
 Sunlight
 Desiccation
 Radiation
 Heat
 Boiling
 Pasteurization
 Vaccine bath
 Serum bath
 Bacteriological filters

30. CLEANIN
G

31. cleaning
 Widely used.
 Cheapest
 Removal of microbial
flora from surfaces
such as skin and
clothing- soaps-
mechanical removal.

32. Decrease in Surface tension
Alter permeability characteristics of cytoplasmic
membrane
Leakage of cellular substance
damage to cell

33. Hand washing
 “hand washing is considered to be one of the
most important procedures in prevention of
infections”.
 Mere mechanical action of rubbing the hands
together and rinsing them under running water is
an important aspect in removal of transient
organisms.

34.  HAND RUB

36.  HAND WASHING

37. Technique
 Wet your hands with clean, running water (warm
or cold), turn off the tap, and apply soap.
 Lather your hands by rubbing them together with
the soap. Be sure to lather the backs of your
hands, between your fingers, and under your
nails.
 Scrub your hands for at least 20 seconds. Need
a timer? Hum the "Happy Birthday" song from
beginning to end twice.
 Rinse your hands well under clean, running
water.
 Dry your hands using a clean towel or air dry

38. ULTRASONIC WASHER

39.  Five Chambers
 Pre-wash: water/enzymatic is circulated over the
load for 1 min
 Wash: detergent wash solution (150oF) is
sprayed over load for 4 min
 Ultrasonic cleaning: basket is lowered into
ultrasonic cleaning tank with detergent for 4 min
 Thermal and lubricant rinse: hot water (180oF) is
sprayed over load for 1 min; instrument milk
lubricant is added to the water and is sprayed
over the load
 Drying: blower starts for 4 min and temperature
in drying chamber 180F

40.  Ultrasonic Washer are very effective (>7 log10
reduction) in removing/inactivating
microorganisms from instruments

41. IMPORTANCE OF CLEANING
 Meticulous cleaning must precede any
sterilization or high-level disinfection of
instruments.
 Failure to perform good cleaning can result in
sterilization or disinfection failure, and outbreaks
of infection can occur.
 Several studies have demonstrated the
importance of cleaning in experimental studies
with the duck hepatitis B virus (HBV), HIV and
Helicobacter pylori

42.  Using human immunovirus (HIV)-contaminated
endoscopes, several investigators have shown that
cleaning completely eliminates the microbial
contamination on the scopes.
 Similarly, other studies found that EtO sterilization or
soaking in 2% glutaraldehyde for 20 minutes was
effective only when the device first was properly
cleaned

43. SUNLIGHT

44.  Active germicidal action , due to content of UV
rays.
 Natural method of sterilization in case of water in
tanks, river & lakes.

45. Desiccation
 Cessation of metabolic activity- decline in total
viable population
 Species of Gram negative cocci such as
gonococci and meningiococci are very sensitive
to dessication.
 Streptococci are more resistant.
 Dried spores remain viable, indefinitely.

46. Radiation
 Mode of transmission of energy through space.
 Less energetic, nonionizing- UV radiation
 UV radiation is absorbed specifically by different
compounds.

47. UV light
 150- 3900 A- UV spectrum
 2650 A , highest bactericidal action.
 UV light has limited penetration, even a thin layer
of glass, filters off large percentage of light.
 Microorganisms on the surface are susceptible.

48. Application

49. Heat
 Microbes can grow over a range of temperatures.
 Psychrophiles- very low temperature.
 Mesophiles- moderate temperature (body
temperature)
 Thermophiles- very high temperature.

50. BOILING

51. Boiling water
 90-100 degree, 10- 30 min
 All vegetative spores gets destroyed when
exposed to boiling water ,but some bacterial
spores can withstand this condition for hours.
 Dis adv: makes surgical instruments blunt.

52. pasteurization

53.  Milk, cream and certain alcoholic beverages (beer
and wine) are subjected to controlled heat treatment
called pasteurization.
 Milk heated at 63 degree for 30 mts.(holder method)
 72 degree for 15- 20 sec (flash process)
 Followed by cooling to less than 13 degree , all the
nonsporing pathogens – Mycobacterium, Brucellae,
Salmonella are destroyed

54. Vaccine bath
 Vaccines of nonsporing bacteria are inactivated in
special vaccine bath at 60 degree for 1 hour.

55. Serum bath
 Serum or body fluids contain coagulable proteins
can be disinfected by heating for 1 hour at 56
degree in water bath .

56. BACTERIOLOGI
CAL FILTERS

57.  HEPA filters.
 High Efficiency Particulate Air Filter has made it
possible to deliver clean air to an enclosure such
as cubicle or a room.

58. CHEMICAL METHODS
 Phenols
 Alcohols
 Halogens
 Oxidizing agents
 Surface active agents
 Heavy Metals
 Aldehydes
 Dyes
 Beta-propiolactone
(BPL)

59. PHENOL AND PHENOLICS
 Intermediate- to low-level
disinfectants
 Denature proteins and
disrupt cell membranes
 Effective in presence of
organic matter and remain
active for prolonged time

60.  Eg.
- 5% phenol,
- 1-5% Cresol,
- 5% Lysol (a saponified cresol)
- hexachlorophene
- chlorhexidine,
- chloroxylenol (Dettol)

61. PHENOLICS
 Examples: Benzyl-4-
chlorophenol, Amyl phenol,
Phenyl phenol

62. USES
PHENOLICS - disinfection of ward floors, in
discarding jars in laboratories and disinfection of
bedpans
CHLORHEXIDINE - skin disinfection
- as an aqueous solution for wound
irrigation
- antiseptic hand wash
- Chlorhexidine gluconate + QACs
(eg. Savlon)
CHLOROXYLENOLS - topical purposes
- more effective against gram
positive
bacteria than gram negative
bacteria

63. DISADVANTAGES
 Toxic,
 Corrosive
 Skin irritant

64. ALCOHOLS
 Intermediate-level disinfectants
 Denature proteins and disrupt
cytoplasmic membranes
Eg. Ethyl alcohol, isopropyl alcohol
and methyl alcohol

65. uses
70% ethyl alcohol (spirit) - antiseptic on skin
Isopropyl alcohol –disinfect surfaces.
- disinfect clinical thermometers.
Methyl alcohol kills fungal spores, hence is useful
in disinfecting cabinets and incubators affected
by them

66. DISADVANTAGES
 Skin irritant,
 volatile (evaporates rapidly),
 inflammable

67. HALOGENS
Halogens: iodine and chlorine
 Intermediate-level antimicrobial chemicals
 Believed that they damage enzymes via oxidation
or by denaturing them

68. 1. Iodine
 Two forms:
a) Tincture of iodine
 2% iodine solution +
potassium iodide in
ethanol
 Used to prepare skin
prior to blood culture
b) Iodophors
 Complexes of iodine
with detergents (e.g.
Betadine)
 Used to prepare skin
prior to surgery; less
irritating

69. Providone Iodine

71. 2. Chlorine
 Kills by cross-linking essential sulfhydryl groups in
enzymes  form inactive disulfide
 For water treatment
 Hypochlorite (HOCl) – sanitize dairy & food
processing equipment; household disinfectant

72. DISADVANTAGES
 rapidly inactivated in the presence of organic
matter
 Iodine is corrosive and staining
 Bleach solution is corrosive and will corrode
stainless steel surfaces.

73. OXIDIZING AGENTS
 Peroxides, ozone, and per
acetic acid kill by oxidation of
microbial enzymes
 High-level disinfectants and
antiseptics

74. USES
 3% peroxide—— small trauma wound, skin,
mucosa
 0.2% - 1% peroxyacetic acid—— plastics,
glassware
 0.1% potassium permanganate—— skin,
fruits/vegetable

75. DISADVANTAGES
 proteinaceous organic matter drastically reduces
its activity.

76. SURFACE ACTIVE AGENTS
 Surface active” chemicals that
reduce surface tension of
solvents to make them more
effective at dissolving solutes
 Soaps and detergents
 Low-level disinfectants

77. Anionic detergents Cationic detergents
( quaternary
ammonium
compounds or quat)
soaps and bile salts Cetrimide and
benzalkonium chloride
DETERGENTS

78. uses
 active against vegetative cells, Mycobacteria
and enveloped viruses.
 used as disinfectants at dilution of 1-2% for
domestic use and in hospitals

79. DISADVANTAGES
 Their activity is reduced by hard water and
organic matter.
 Pseudomonas can metabolise cetrimide, using
them as a carbon, nitrogen and energy source

80. HEAVY METALS
 Denature proteins
 silver nitrate (topical cream)
 mercuric chloride (paint)
 copper sulfate (algaecide)
 zinc (mouthwash, paints)

81. uses
 1% silver nitrate solution can be applied on eyes
as treatment for opthalmia neonatorum (Crede’s
method).
 Silver sulphadiazine - burn and wounds
 Mercurials are active against viruses at dilution of
1:500 to 1:1000.
 Merthiolate at a concentration of 1:10000 -
preservation of serum.
 Copper salts - fungicide.

82. DISADVANTAGES
 Mercuric chloride is highly toxic, are readily
inactivated by organic matter.

83. Burns and Wounds

85. ALDEHYDES
 alkylation of sulfhydryl,
hydroxyl, carboxyl, and amino
groups of microorganisms
 alters RNA, DNA, and protein
synthesis
 Formaldehyde (formalin) and
glutaraldehyde

86. USES
 40% Formaldehyde (formalin) -
surface disinfection and fumigation of
rooms, chambers, operation theatres,
biological safety cabinets, wards, sick
rooms etc.
 10% formalin with 0.5% tetraborate
sterilizes clean metal instruments.
 2% formaldehyde at 40oC for 20
minutes is used to disinfect wool .
 0.25% formaldehyde at 60oC for six
hours to disinfect animal hair and
bristles.
 2% gluteraldehyde is used to sterilize
thermometers, cystoscopes,
bronchoscopes, centrifuges,
anasethetic equipments etc.

87. DISADVANTAGES
 Vapors are irritating (must be
neutralized by ammonia),
 has poor penetration,
 leaves non-volatile residue,
 activity is reduced in the presence
of protein.
 Gluteraldehyde requires alkaline
pH and only those articles that are
wettable can be sterilized.

88. DYES
 ANILINE DYES
 Brilliant green, malachite green and crystal violet
 React with acid groups in cell
 More active against gram+ve than gram-ve bacteria, no
activity against tubercle bacilli
 Non irritant,non toxic
 ACRIDINE DYES
 Proflavine,acriflavine,euflavine,aminacrine
 Impair DNA complexes of organisms and destroy
reproductive capacity of the cell
 More active against gram+ve bacteria than gram-ve

89. uses
 They may be used topically as antiseptics to treat
mild burns.
 They are used as paint on the skin to treat
bacterial skin infections.
 selective agents in certain selective media.

90. DISADVANTAGES
• Inhibited by organic material

91. BETA-PROPIOLACTONE (BPL)
 alkylating agent
 acts through alkylation of carboxyl- and hydroxyl-
groups.
 colorless liquid with pungent to slightly sweetish
smell. It is a condensation product of ketane with
formaldehyde

92. USES
 effective sporicidal agent, and has broad-
spectrum activity.
 0.2% is used to sterilize biological products.
 more efficient in fumigation than formaldehyde.
 sterilize vaccines, tissue grafts, surgical
instruments and enzymes.

93. DISADVANTAGES
 It has poor penetrating power and is a
carcinogen

94. OTHER METHODS
1) ORTHO-PHTHALALDEHYDE
2)SURFACINE
3)SUPEROXIDIZED WATER

95. Ortho-phthalaldehyde (OPA)

96. Received FDA clearance in October 1999.
It contains 0.55% 1,2-benzenedicarboxaldehyde.
It is a clear, pale-blue liquid with a pH of 7.5.

97. MOA
 by the lipophilic aromatic nature of OPA that is
likely to assist its uptake through the outer layers
of mycobacteria and gram-negative bacteria.
 OPA appears to kill spores by blocking the spore
germination process

98. ADVANTAGES
 OPA has several potential advantages over
glutaraldehyde.
 is not a known irritant to the eyes and nasal
passages,
 does not require exposure monitoring,
 has a barely perceptible odor, and requires no
activation.
 OPA, like glutaraldehyde, has excellent material
compatibility.
 It has excellent stability over a wide pH range (pH
3–9).

99. DISADVANTAGES
 is a potential respiratory and dermal irritant and
there have been problems with prolonged or
repeated contact
 it stains proteins gray (including unprotected skin)
and thus must be handled with caution

100. SURFACINE
 Surfacine is a new, persistent antimicrobial agent
that may be used on animate or inanimate
surfaces.

101. MOA
silver iodide + polyhexamethylenebiguanide
chemical recognition and interaction with the lipid
bilayer of the bacterial outer cell membrane
accumulate silver on the micro organisms
Lysis of micro organisms

102. ADVANTAGES
Antimicrobial persistence ->13days,broad spectrum
Transfers active agent (silver) for use as an antiseptic to
microbes on demand without elution
Resistant to forming biofilm
No toxicity to mammalian cells

103. disadvantage
 expensive

104. SUPEROXIDIZED WATER
 basic materials, saline and electricity, are cheap
and the end product (water) is not damaging to
the environment.
 The mode of action is not clear but probably
relates to a mixture of oxidizing species

105. ADVANTAGES
Basic materials (saline and electricity) for production are
inexpensive
End product not damaging
to environment
Non toxic to biological tissues

106. DISADVANTAGE
Endoscope compatibility unknown
Decreased efficacy in presence of organic matter
Production equipment expensive

107. CHANGES IN CDC GUIDELINE FOR
DISINFECTION AND STERILIZATION SINCE 1981
1. Formaldehyde-alcohol has been deleted as
a recommended chemical sterilant or high-
level disinfectant.
2. Several new chemical sterilants have been
added,
 hydrogen peroxide,
 peracetic acid and
 peracetic acid and hydrogen peroxide

108. 3. 3% phenolics and iodophors have been deleted
as high-level disinfectants because of their
unproven efficacy against bacterial spores, M.
tuberculosis, and/or some fungi.
4. Isopropyl alcohol and ethyl alcohol were
excluded as high-level disinfectants because of
their inability to inactivate bacterial spores and
because of the inability of isopropyl alcohol to
inactivate hydrophilic viruses (i.e., poliovirus,
coxsackie virus).

109. 5. The exposure time required to achieve high-
level disinfection has been changed from 10-30
minutes to 12 minutes or more depending on the
FDA-cleared label claim and the scientific
literature.
6. New sterilization processes, such as hydrogen
peroxide gas plasma and liquid peracetic acid;
and disinfection of complex medical instruments
(e.g., endoscopes) were included.

110. TESTING OF DISINFECTANTS
 Suspension tests:
Determination of phenol coefficient:
- Rideal Walker method
- Chick Martin test
 Capacity tests:
-Kelsey-Sykes test
-Test for stability and long-term
effectiveness
 Practical tests :
- In-use test

111.  PHENOL COEFFICIENT
 RIDEAL WALKER TEST : suspensions with equal numbers of
typhoid bacilli are submitted to action of varying
concentrations of phenol and of disinfectant to be tested
 Dilution of disinfectant sterilizing the suspension = phenol
coefficient
corresponding dilution of phenol
-Interpretation
- Higher the phenol coefficient- more is the effectiveness
- If the value is greater than 1, test disinfectant is more
potent than phenol
 CHICK MARTIN TEST : the disinfectant acts in presence of
organic matter
Both these fall short of simulating natural conditions

112. The In-use Test – The only User’s test for
monitoring performance of an agent.
-Dilute disinfectant (1ml) in 9ml of diluent. Place ten
drops (0.02ml) on two NA plates
-One is incubated at 37 C for three days and the
other at room temperature for seven days
-Five or more colonies on either plate indicate
contamination.

114. SUMMARY

116. Disinfectant policy :
 Small Committee !
 Define uses
 Eliminate use of chemicals where
1. you aim to sterilise.
2. use of heat is possible
3 Where they are unnecessary

117. Disinfectant policy (cont’d)
 Distribute frequently and in correct dilutions (Preferably
by pharmacist)
 Instruction and supervision
 In-use testing on occasion.

118. Make your contributions for safe
Hospitals