DISINFECTION in Health Care

1. DISINFECTION
in Health Care
Dr.T.V.Rao MD

2. What is Disinfection
•Disinfectants are substances that are
applied to non-living objects to destroy
microorganisms that are living on the
objects. Disinfection does not
necessarily kill all microorganisms,
especially resistant bacterial spores; it is
less effective than sterilization, which is
an extreme physical and/or chemical
process that kills all types of life

3. A tribute to Ignaz
Semmelweis

4. A Hygienic and Scientific Hand Washing
continues to be best prayer in the Hospital

5. Defining What is
Disinfection
•Disinfection may be defined as: Cleaning
an article of some or all of the pathogenic
organisms which may cause infection
• Perfect disinfectant would also offer
complete and full sterilization, without
harming other forms of life, be inexpensive,
and non-corrosive. Unfortunately ideal
disinfectants do not exist. Most disinfectants
are also, by their very nature, potentially
harmful (even toxic) to humans or animals.

6. Terminology
•Antisepsis: chemical destruction of
vegetative pathogens on living
tissue
•Degerming: mechanical removal of
microbes from limited area
•Sanitization: lowering microbial
counts on eating and drinking
utensils to safe levels

7. Terminology
•Biocide or germicide: kills
microorganisms
•Fungicide: kills fungi
•Viricide: inactivates viruses
•Bacteriostatic agent: stops
growth of bacteria

8. Terminology
• Sepsis: bacterial
contamination
• Asepsis: absence of
significant
contamination
• Aseptic technique
minimizes
contamination

9. Antiseptics versus
Disinfectants
Antiseptics:
Use on skin and mucous membranes to kill
microorganisms
Not for use on inanimate objects
Disinfectants:
Use to kill microorganisms on inanimate objects
Not for use on skin or mucous membranes
High-level versus low-level disinfectants

10. Chemical Methods
• Disinfectants and
antiseptics
• Surface-active agents
(surfactants)
• Chemical food
preservatives
• Aldehydes
• Gas sterilization
• Oxidizing agents
• [Antibiotics]

11. Chemicals – Disinfection
• Antiseptics - chemicals that kill
microorganisms on living skin or mucous
membranes.
• Bactericidal - chemical agents capable of
killing bacteria. Similarly agents that are
virucidal, fungicidal or sporicidal are agents
capable of killing these organisms.
• Bacteriostatic - Chemical agents that inhibit
the growth of bacteria but do not necessarily
kill them.

12. Disinfectants
• Kill/inhibit growth of
microbes on surfaces
• Phenols and phenolic:
damage lipid
membranes
• Active in
presence of
organic matter
• Stable
• Persist for long
periods after
application

13. Antiseptics
•Biguanides:
Chlorhexidine
•Low toxicity
•Used on
skin and
mucous
membranes

14. Cleaning
• Cleaning - the physical removal of foreign material,
e.g., dust, soil, organic material such as blood,
secretions, excretions and microorganisms.
Cleaning generally removes rather than kills
microorganisms. It is accomplished with water,
detergents and mechanical action. The terms
“decontamination” and “sanitation” may be used
for this process in certain settings, e.g., central
service or dietetics. Cleaning reduces or eliminates
the reservoirs of potential pathogenic organisms

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

16. Disinfection
• Disinfection: the inactivation of disease-
producing microorganisms. Disinfection does
not destroy bacterial spores. Disinfectants
are used on inanimate objects in contrast to
antiseptics, which are used on living tissue.
Disinfection usually involves chemicals, heat
or ultraviolet light. The nature of chemical
disinfection varies with the type of product

17. High level disinfection
•High level disinfection processes
destroy vegetative bacteria,
mycobacteria, fungi and enveloped
(lipid) and nonenveloped (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.

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

19. 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.

20. Antiseptics
•Biguanides:
Chlorhexidine
•Low toxicity
•Used on
skin and
mucous
membranes

21. Antiseptics
•Alcohol : protein
denaturation and
membrane damage
• evaporate quickly
• ethanol and
isopropanol
• [not effective if
taken internally]

22. Disinfectants
• Halogens: iodine and
chlorine
• Iodine used in
solution : Betadine®
and Isodine®
• Chlorine is a gas that
forms bleach
(hypochlorite) in
water
• Chloramines are
chlorine and
ammonia

23. Selection and Use of
Disinfectants

24. Sterilization – An absolute
Procedure
• The destruction of all
forms of microbial life
including bacteria,
viruses, spores and
fungi. Items should
be cleaned
thoroughly before
effective sterilization
can take place.

25. Noncritical items
• That either come in
contact with only
intact skin but not
mucous membranes
or do not directly
contact the patient.
Reprocessing of
noncritical items
involves cleaning
and/or low level
disinfection

26. Sanitation
• Process that
reduces
microorganisms on
an inanimate
object to a level
below that of
infectious hazard
(e.g., dishes and
eating utensils are
sanitized

27. Semi critical items
• Devices that come in
contact with no intact
skin or mucous
membranes but
ordinarily do not
penetrate them.
Reprocessing semi
critical items involves
meticulous cleaning
followed preferably by
high-level disinfection

28. Disinfectant effectiveness
depends on many factors.
• Type of contaminating microorganism. Each disinfectant
has unique antimicrobial attributes.
• • Degree of contamination. This determines the quality of
disinfectant required and time of exposure.
• • Amount of proteinaceous material present. High protein
based materials absorb and neutralize some chemical
disinfectants.
• • Presence of organic matter and other compounds such as
soaps may neutralize some disinfectants.
• • Chemical nature of disinfectant. It is important to
understand the mode of action in order to select the
appropriate disinfectant.

29. Disinfectant effectiveness
depends on many factors.
• Concentration and quantity of disinfectant. It is important to choose the
proper concentration and quantity of disinfectant that is best suited to
each situation.
• • Contact time and temperature. Sufficient time and appropriate
temperature must be allowed for action of the disinfectant and may
depend on the degree of contamination and organic matter load.
• • Residual activity and effects on fabric and metal should be considered
for specific situations.
• • Application temperature, pH and interactions with other compounds
must be considered.
• • Toxicity to the environment and relative safety to people that may be
exposed.
•• Cost. An important factor
• 5

30. Microbial Characteristics and Microbial Control
Figure 7.11

31. PHENOLICS
•Examples: Benzyl-4-chlorophenol, Amyl
phenol, Phenyl phenol
•Advantages and disadvantages: good
general purpose disinfectants, not
readily inactivated
•by organic matter, active against wide
range of organisms (including
mycobacterium), but not sporicidal.

32. Phenol as Disinfectant
• Phenolic disinfectants
are effective against
bacteria (especially gram
positive bacteria) and
enveloped viruses. They
are not effective against
nonenvelopedd viruses
and spores. These
disinfectants maintain
their activity in the
presence of organic
material.

33. Phenol as Disinfectant
• They are not effective
against nonenvelopedd
viruses and spores.
These disinfectants
maintain their activity in
the presence of organic
material. This class of
compounds is used for
decontamination of the
hospital environment,
including laboratory
surfaces, and noncritical
medical items

34. Phenol as Disinfectant
• Phenolics are not
recommended for semi
critical items because of
the lack of validated
efficacy data for many of
the available
formulations and
because the residual
disinfectant on porous
materials may cause
tissue irritation even
when thoroughly rinsed.

35. Alcohols
• “Alcohol" refers to two water-soluble
chemicals: ethyl alcohol and isopropyl
alcohol. These alcohols are rapidly
bactericidal rather than bacteriostatic
against vegetative forms of bacteria (Gram +
and Gram -); they also are tuberculocidal,
fungicidal, and virucidal against enveloped
viruses. Alcohols are not effective against
bacterial spores and have limited
effectiveness against nonenveloped viruses

36. Alcohols
• Their cidal activity drops
sharply when diluted
below 50%
concentration and the
optimum bactericidal
concentration is in the
range of 60-90%
solutions in water
(volume/volume). The
antimicrobial activity of
alcohols can be
attributed to their ability
to denature proteins.

37. Alcohols
•Higher
concentrations
are less effective
as the action of
denaturing
proteins is
inhibited without
the presence of
water

38. Alcohols
• Alcohols are
commonly used
topical antiseptics.
They are also used to
disinfect the surface
of medical
equipment. Alcohols
require time to work
and they may not
penetrate organic
material.

39. Alcohols
• They also evaporate
rapidly which makes
extended exposure
time difficult to
achieve unless the
items are immersed.
Alcohol irritates
tissues. They are
generally too
expensive for general
use as a surface
disinfectant

40. Soap, Water and common sense
are yet the best antiseptics
William Osler

41. Gaining importance in Hand
Washing with Alcohols
• The use of either ethyl
alcohol or isopropyl
alcohol in a 60-90%
solution has recently
gained wide acceptance
in health care settings as
hand antiseptics. They
can be used as a
reasonable substitute for
handwashing as long as
hands are not visibly
soiled

42. Hypochlorite's
•Hypochlorite's are the most widely used
of the chlorine disinfectants and are
available in a liquid (e.g. sodium
hypochlorite) or solid (e.g. calcium
hypochlorite, sodium
dichloroisocyanurate) form. The most
common chlorine products in are
aqueous solutions of 4 to 6% sodium
hypochlorite, which are readily available
as “household bleach”.

43. Hypochlorite's
• They have a broad
spectrum of
antimicrobial
activity, are
unaffected by water
hardness, are
inexpensive and fast
acting, and have a
low incidence of
serious toxicity

44. Hypochlorite's
• Other disadvantages of
hypochlorites include
corrosiveness to metals
in high concentrations
(>500 ppm), inactivation
by organic matter,
discoloring or
“bleaching” of fabrics,
and release of toxic
chlorine gas when mixed
with ammonia or acid.

45. Hypochlorite's
• Hypochlorites can eliminate both enveloped
and nonenveloped viruses if used in correct
dilution and contact time. They are also is
effective against fungi, bacteria, and algae
but not spores. Household bleach is typically
diluted using 1:50 with water (1000ppm) for
surface disinfection. Bleach solutions have
been recommended for use in both hospitals
and the community as disinfecting solutions.

46. Hypochlorite's Most
recommended in
•They are
included in most
recommendation
for
decontamination
of hepatitis and
AIDS viruses

47. Hypochlorite's
• Hypochlorites 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.

48. Hypochlorite's
•Chlorinated
drinking water
should not exceed
6 to 10 ppm of free
chlorine with the
lower value being
in continuous flow
or low volume
reservoir systems.

49. Iodine And Iodophor Disinfectants
• These compounds have
been incorporated in
time release
formulations and in
soaps (surgical scrubs).
Simple iodine tinctures
(dissolved in alcohol)
have limited cleaning
ability. These
compounds are
bactericidal, sporicidal,
virucidal and fungicidal
but require a prolonged
contact time.

50. Iodine And Iodophor Disinfectants
• Besides their use as an
antiseptic, iodophors
have been used for the
disinfection of blood
culture bottles and
medical equipment such
as hydrotherapy tanks,
thermometers, and
endoscopes

51. Iodine And Iodophor Disinfectants
• The disinfective ability of
iodine, like chlorine, is
neutralized in the
presence of organic
material and hence
frequent applications are
needed for thorough
disinfection. Iodine
tinctures can be very
irritating to tissues, can
stain fabric and be
corrosive.

52. HIGH LEVEL
DISINFECTANTS

53. Hydrogen Peroxide
• Peroxides such as hydrogen peroxide are
often used as antiseptics to clean wounds.
The activity of peroxides is greatest against
anaerobic bacteria. 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.

54. Hydrogen Peroxide
• Stabilized hydrogen
peroxides can be used to
disinfect environmental
surfaces. The literature
contains several
accounts of the
properties, germicidal
effectiveness, and
potential uses for
stabilized hydrogen
peroxide in the hospital
setting

55. Hydrogen Peroxide
• Stabilized peroxides
may also be blended
with iodophors or
quaternary ammonia.
Hydrogen peroxide is
also blended with
paracetic acid in high
concentrations for
use as a high-level
disinfectant

56. Gluteraldehyde
• Aldehydes have a wide
germicidal spectrum.
Gluteraldehydes are
bactericidal, virucidal,
fungicidal, sporicidal and
parasiticidal. They are
used as a disinfectant or
sterilant in both liquid
and gaseous forms. They
have moderate residual
activity and are effective
in the presence of
limited amounts of
organic material

57. Formaldehyde
• Formaldehyde is used as a
disinfectant and sterilant
both in the liquid and
gaseous states.
Formaldehyde is sold and
used principally as a water-
based solution called
formalin, which is 37%
formaldehyde by weight. The
aqueous solution is
bactericidal, tuberculocidal,
fungicidal, virucidal and
sporicidal

58. Formaldehyde
• Formaldehydes are very
potent disinfectants,
which can be highly
toxic. Use them only as a
last resort and then
under trained
supervision in a well-
ventilated setting and
with appropriate
personal protective
equipment.

59. Formaldehyde
• Formaldehyde should be
handled in the workplace as
a potential carcinogen with
an employee exposure
standard that limits an 8
hour time-weighted average
exposure to a concentration
of 0.75 ppm. For this reason,
employees should have
limited direct contact with
formaldehyde and these
considerations limit its role
in sterilization and
disinfection processes

60. Ortho-phthalaldehyde
• Ortho-phthalaldehyde (OPA) is a chemical sterilant
similar to Gluteraldehydes with similar
antimicrobial activity. OPA has several potential
advantages compared to Gluteraldehydes. It has
excellent stability over a wide pH range (pH 3-9), 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 Gluteraldehydes, has excellent material
compatibility

61. Ortho-phthalaldehyde
• A potential disadvantage of OPA is that it
stains proteins gray (including unprotected
skin) and thus must be handled with caution.
However, skin staining would indicate
improper handling that requires additional
training and/or personal protective
equipment (PPE) (gloves, eye and mouth
protection, fluid-resistant gowns).

62. Per acetic Acid
•Peracetic, or peroxyacetic, acid is
characterized by a very rapid action
against all microorganisms. A special
advantage of peracetic acid is it has no
harmful decomposition products (i.e.,
acetic acid, water, oxygen, hydrogen
peroxide) and leaves no residue. It
remains effective in the presence of
organic matter and is sporicidal even at
low temperatures

63. Per acetic Acid
•It is used in
automated
machines to
chemically sterilize
medical, surgical,
and dental
instruments (e.g.,
endoscopes,
arthroscopes).

64. Per acetic Acid and Hydrogen
Peroxide
•Two chemical sterilants are available
that contain peracetic acid plus
hydrogen peroxide (0.08 peracetic acid
plus 1.0% hydrogen peroxide [no longer
marketed], 0.23% peracetic acid plus
7.35% hydrogen peroxide). The
bactericidal properties of peracetic acid
and hydrogen peroxide have been
established.

65. Per acetic acid and hydrogen
peroxide useful in Hemodialysis
• Findings demonstrated
that this product
inactivated all
microorganisms with the
exception of bacterial
spores within 20
minutes. The
combination of per
acetic acid and hydrogen
peroxide has been used
for disinfecting hem
dialyzers.

66. Quaternary Ammonium
Compounds
• The quaternaries are good cleaning agents
but high water hardness and materials such
as cotton and gauze pads may make them
less microbiocidal because these materials
absorb the active ingredients. As with several
other disinfectants (e.g., phenolics,
iodophors) gram-negative bacteria have
been found to survive or grow in these
preparations

67. Quaternary Ammonium
Compounds
• They are not effective against non-enveloped
viruses, fungi and bacterial spores. QA disinfectants
carry a very strong positive charge that makes good
contact with negatively charged surfaces. This
characteristic makes most very good cleaning
agents. QA compounds are generally low in toxicity,
but prolonged contact can be irritating. The
quaternaries are commonly used in ordinary
environmental sanitation of noncritical surfaces
such as floors, furniture, and walls

68. Work with Caution
•A wide range of microorganisms is
destroyed by varying concentrations of
aqueous formaldehyde solutions.
Although formaldehyde-alcohol is a
chemical sterilant and formaldehyde is a
high-level disinfectant, the hospital uses
of formaldehyde are limited by its
irritating fumes and the pungent odor
that is apparent at very low levels (<1
ppm).

69. Gas plasma
Sterilization

70. What is Gas Plasma
•Plasma is a fourth state of matter which
is distinguishable from liquid, solid, or
gas. In nature, plasma is widespread in
outer space.
•Gas plasma generated in an enclosed
chamber under deep vacuum using
Radio frequency or Microwave emery to
excite gas molecules are produced
charged particles

71. How Gas Plasma works.
• Many particles are in the form of free
radicals
• A free radical is an Atom with an unpaired
electron and is a highly reactive species
• The mechanism of action of this device is the
production of free radicals within a plasma
field that are capable of interacting with
essential cell components, ie is enzymes and
nucleic acids. And thereby disrupt the
metabolism of microorganisms.

72. Gas Plasma - Sterilization
• Plasma sterilization
operates differently
because of its specific
active agents, which are
ultraviolet (UV) photons
and radicals (atoms or
assembly of atoms with
unpaired electrons,
therefore chemically
reactive, e.g., O and OH,
respectively

73. BASIC MECHANISMS OF
PLASMA STERILIZATION• Destruction by UV
irradiation of the
genetic material of the
microorganism; this is a
statistical process
requiring a sufficient
number of lesions of
the DNA strands.
• Erosion of the
microorganism, atom
by atom, through
intrinsic photo
desorption

74. Advantage of the plasma method
• An advantage of the plasma method is the
possibility, under appropriate conditions, of
achieving such a process at relatively low
temperatures (≤50 °C), preserving the
integrity of polymer-based instruments,
which cannotbe subjected to autoclaves and
ovens
Furthermore, plasma sterilization is safe,
both for the operatorand the patient, in
contrast to EtO.

75. Hydrogen Peroxide Sterilization
Offers Fast Cycle Times
• Benefits of gas
plasma (vaporized
hydrogen peroxide)
sterilization are fast
cycle times, the
absence of toxic
residuals, and a low-
moisture
environment not
exceeding 50ºC, a

76. New CDC guidelines
Factors Related To Infection Risk
• Endoscope
contamination
accounts for more
health care related
infections than any
other medical
instrument and is
responsible for
consequences
ranging from
bacterial colonization
to death.

77. Disinfection and sterilization are
affected by
• Initial cleaning of the
device
• Physical complexity of
the device
Biofilms and microbial
load
• Microbe type and
quantity
• HLD exposure time and
concentration

78. When things go wrong
•Inadequate
cleaning
Using the
wrong
disinfectant
• Failure to
follow
procedures

79. Guideline Excerpts
Infection Risks
• “Multiple studies in
many countries have
documented lack of
compliance with
established guidelines
for disinfection and
sterilization.
• Failure to comply with
scientifically-based
guidelines has led to
numerous outbreaks.

80. Biofilms interfere in effective
antimicrobial action
• “Biofilms are microbial
communities that are
tightly attached to
surfaces and cannot be
easily
removed...Bacteria
within biofilms are up to
1,000 times more
resistant to
antimicrobials than are
the same bacteria in
suspension

81. Biofilms interfere in effective
antimicrobial action
• “One multistate
investigation found that
23.9% of the bacterial
cultures from the
internal channels of 71
gastrointestinal
endoscopes grew
≥100,000 colonies of
bacteria after
completion of all
disinfection and
sterilization procedures

82. 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 waste and
• 􀂾 Taking care of yourself (e.g. immunization)

83. Hand Washing
Yet no substitute for washing hands
Do not forget to Wash Your Hands:
Immediately on arrival at work
Before and after examining each client
After touching anything that might be
contaminated
After handling specimens
Before putting on gloves for clinical
procedures
After removing gloves
After using the toilet or latrine
Before leaving work

84. Hand Washing is the Best Solution
to Prevent the Spread of Infections

85. Make your contributions for
safe Hospitals

86. Programme Created by
Dr.T.V.Rao MD for Health
Professionals in Global Health
Care
Email
doctortvrao@gmail.com