Dr. T.V. Rao discusses disinfection in hospitals. An ideal disinfectant would sterilize without harming other life, be inexpensive, and non-corrosive, but such disinfectants do not exist. Most are potentially toxic to humans. Common disinfectants discussed include phenols, alcohols, halogens like iodine and chlorine, aldehydes, hydrogen peroxide, and glutaraldehydes. Proper concentration, contact time, and temperature are important for effectiveness. The mode of action and appropriate uses of various disinfectants are outlined.

1. Dr.T.V.Rao MD
DISINFECTION IN HOSPITALS
DR.T.V.RAO MD 1

2. 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.
DR.T.V.RAO MD 2

3. THE IDEAL DISINFECTANT
 Resistant to inactivation
 Broadly active (killing pathogens)
 Not poisonous (or otherwise harmful)
 Penetrating (to pathogens)
 Not damaging to non-living materials
 Stable
 Easy to work with
 Otherwise not unpleasant
DR.T.V.RAO MD 3

4. WHY DISINFECTION AND STERILIZATION?
• Contagious diseases
• Hospital infection (e.g., OR, ID ward) or other opportunistic
infection
• Lab contamination
• Etc.
• Microbes:
- usually easy to grow in environment;
- but also can be inhibited or killed by certain environmental (physical or
chemical) factors/conditions.
DR.T.V.RAO MD 4

5. 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
DR.T.V.RAO MD 5

6. TERMINOLOGY
• Biocide or germicide: kills
microorganisms
• Fungicide: kills fungi
• Virocide: inactivates viruses
• Bacteriostatic agent: stops growth of
bacteria
DR.T.V.RAO MD 6

7. 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
DR.T.V.RAO MD 7

8. BEGINNING OF SCIENTIFIC ERA OF
STERILIZATION AND DISINFECTION
DR.T.V.RAO MD 8

9. • Process of reducing or
eliminating living
pathogenic
microorganisms in or
on materials, so they
are no longer a health
hazard.
For example: use of
alcohol before drug
injection.
DISINFECTION
DR.T.V.RAO MD 9

10. • Process of
destroying all
microbial forms. A
sterile object is one
free of all microbial
forms, including
bacterial spores.
• More thorough
than disinfection
STERILIZATION
DR.T.V.RAO MD 10

11.  Soaps are sodium or
potassium salts of fatty
acids, a natural product
 Detergents, instead, are
artificial surfactants
 While soaps are always
negatively charged, some
detergents are negatively
charged while others are
positively charged
 One example of a
positively charged
detergent are quaternary
ammonium compounds
(a.k.a., quats)
SOAP AND DETERGENTS
DR.T.V.RAO MD 11

12. HALOGENS
 Halogens are the seventh (VII) column of the periodic table of elements
 Two halogens are regularly employed as antimicrobials: Iodine and
Chloride
 Iodine: commonly used as an antiseptic against all microbes, fungi, and
viruses
 Iodine: It inhibits protein synthesis and oxidizes –SH groups of amino
acids
 Chlorine: Used as a disinfectant (10% bleach)
 Chlorine: Hypochlorous acid (HOCl) is a product, formed in water, that is
the active form of the disinfectant
 Chlorine: Applied in treatment of drinking water, swimming pool, and
sewage
DR.T.V.RAO MD 12

13. ANTIMICROBIAL MODES OF ACTION OF
DISINFECTANTS AND ANTISEPTICS
• Denaturation of bacterial proteins by disrupting
hydrogen and disulfide bonds
—— phenol (high conc.), alcohol, heavy-metal (high conc.),
acids, alkalis, aldehydes)
• Damage to bacterial membrane (lipids and/or proteins),
causing leakage of intracellular molecules
—— phenol (low conc.), surfactants, dyes
• Interference of bacterial enzyme and metabolism
—— oxidants, heavy-metals (low conc.), alkylating agents
DR.T.V.RAO MD 13

14. • Alkylating agent（烷化剂）
—— alkylating
proteins and nucleic
acids
• formalin (formaldehyde) ——
surface disinfection, air,
surgical instruments
• glutaric dialdehyde— high-
precision instruments,
endoscopes
• 50mg/L epoxy ethane ——
surgical instruments and
dressing
ALKYLATING PROTEINS AND NUCLEIC ACIDS
DR.T.V.RAO MD 14

15. • Phenol and phenol
derivatives
—— altering membrane
permeability and
denaturing proteins
• 0.01% - 0.05%
Chlorhexidine）——
vaginal wash, OR hand-
wash
• 3% - 5% carbonic acid or
2% Lysol —— floor or
surface disinfection
PHENOL AND PHENOL DERIVATIVES
DR.T.V.RAO MD 15

16. • Alcohols
—— denaturing bacterial proteins and
membranes
• 70% - 75% ethyl or isopropyl
alcohol—— skin and
thermometer disinfection
–ineffective
against
endospores
and non-
enveloped
viruses
ALCOHOLS
DR.T.V.RAO MD 16

17. • Oxidants
—— oxidation, protein precipitation
• 3% peroxide—— small trauma wound, skin, mucosa
• 0.2% - 1% peroxyacetic acid—— plastics, glassware
• 0.2 – 0.5 ppm chlorines —— water and swimming pool
• 0.1% potassium permanganate—— skin,
fruits/vegetables
DR.T.V.RAO MD 17

18. 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.
• • What about Cost ?
• 5
DR.T.V.RAO MD 18

19. • 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.
PHENOLICS
DR.T.V.RAO MD 19

20. 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. DR.T.V.RAO MD 20

21. 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
DR.T.V.RAO MD 21

22. 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.
DR.T.V.RAO MD 22

23. 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.
DR.T.V.RAO MD 23

24. IODINE AND IODOPHOR
DISINFECTANTS
• Besides their use as
an antiseptic, Iodophor
have been used for the
disinfection of blood
culture bottles and
medical equipment
such as hydrotherapy
tanks, thermometers,
and endoscopes
DR.T.V.RAO MD 24

25. 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.
DR.T.V.RAO MD 25

26. 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
DR.T.V.RAO MD 26

27. 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. DR.T.V.RAO MD 27

28. ALCOHOLS
• Higher
concentrations are
less effective as the
action of denaturing
proteins is inhibited
without the
presence of water
DR.T.V.RAO MD 28

29. 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.
DR.T.V.RAO MD 29

30. 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
DR.T.V.RAO MD 30

31. 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
DR.T.V.RAO MD 31

32. 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
DR.T.V.RAO MD 32

33. DR.T.V.RAO MD 33

34. HYPOCHLORITE'S
• Other disadvantages of
hypochlorite's 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.
DR.T.V.RAO MD 34

35. HYPOCHLORITE'S
• Hypochlorite's 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.
DR.T.V.RAO MD 35

36. HYPOCHLORITE'S MOST RECOMMENDED
IN
• They are included
in most
recommendation
for
decontamination
of hepatitis and
AIDS viruses
DR.T.V.RAO MD 36

37. HYPOCHLORITE'S
• Hypochlorite's 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.
DR.T.V.RAO MD 37

38. 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.
DR.T.V.RAO MD 38

39. HIGH LEVEL DISINFECTANTS
DR.T.V.RAO MD 39

40. 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.
DR.T.V.RAO MD 40

41. 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
DR.T.V.RAO MD 41

42. FORMALDEHYDE
• Gluteraldehydes 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.
DR.T.V.RAO MD 42

43. 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
DR.T.V.RAO MD 43

44. 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
DR.T.V.RAO MD 44

45. GLUTARALDEHYDE
• 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
DR.T.V.RAO MD 45

46. ETHYLENE OXIDE
DR.T.V.RAO MD 46
• Ethylene oxide, also called oxirane, is the
organic compound with the formula C2H4O. It is
a cyclic ether. This means that it is composed of
two alkyl groups attached to an oxygen atom in
a cyclic shape (circular). This colorless
flammable gas with a faintly sweet odor is the
simplest epoxide, a three-membered ring
consisting of two carbon and one oxygen atom.

47. • Highly effective
against most
microbes
• Highly diffusive
• Compatible with a
wide variety of
materials in devices
and packaging
ETHYLENE OXIDE ADVANTAGES

48. • Complex process
• Longer turn-around times
• BI Testing
• Residual dissipation
• Safety concerns
• Flammable
• Explosive
• OSHA concerns
• Carcinogen
• EPA concerns
• Emissions
ETHYLENE OXIDE DISADVANTAGES

49. 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
DR.T.V.RAO MD 49

50. • 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).
ORTHO-PHTHALALDEHYDE
DR.T.V.RAO MD 50

51. • Per acetic, or peroxyacetic,
acid is characterized by a
very rapid action against all
microorganisms. A special
advantage of per acetic
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
PER ACETIC ACID
DR.T.V.RAO MD 51

52. PER ACETIC ACID
• It is used in
automated
machines to
chemically sterilize
medical, surgical,
and dental
instruments (e.g.,
endoscopes,
arthroscopies).
DR.T.V.RAO MD 52

53. PER ACETIC ACID AND HYDROGEN
PEROXIDE
• Two chemical sterilants are available that
contain per acetic acid plus hydrogen
peroxide (0.08 per acetic acid plus 1.0%
hydrogen peroxide [no longer marketed],
0.23% per acetic acid plus 7.35% hydrogen
peroxide). The bactericidal properties of
per acetic acid and hydrogen peroxide
have been established.
DR.T.V.RAO MD 53

54. PER ACETIC ACID AND HYDROGEN PEROXIDE
USEFUL IN HEM DIALYZERS
• 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.
DR.T.V.RAO MD 54

55. 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 microbicidal
because these materials absorb the active
ingredients. As with several other disinfectants
(e.g., phenolic, Iodophor) gram-negative bacteria
have been found to survive or grow in these
preparations
DR.T.V.RAO MD 55

56. 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
DR.T.V.RAO MD 56

57. GAS PLASMA
STERILIZATION
DR.T.V.RAO MD 57

58. • 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
• Can be used for hand
sterilization
WHAT IS GAS PLASMA
DR.T.V.RAO MD 58

59. 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.
DR.T.V.RAO MD 59

60. 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
DR.T.V.RAO MD 60

61. • 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
BASIC MECHANISMS OF PLASMA
STERILIZATION
DR.T.V.RAO MD 61

62. 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
cannot be subjected to autoclaves and ovens
Furthermore, plasma sterilization is safe,
both for the operator and the patient, in
contrast to EtO.
DR.T.V.RAO MD 62

63. 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,
DR.T.V.RAO MD 63

64. 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.
DR.T.V.RAO MD 64

65. 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
DR.T.V.RAO MD 65

66. 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
DR.T.V.RAO MD 66

67. 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
DR.T.V.RAO MD 67

68. 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.
DR.T.V.RAO MD 68

69. 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)
DR.T.V.RAO MD 69

70. HAN
YET – NO SUBSTITUTE FOR HAND WASHING
:
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
DR.T.V.RAO MD 70

71. • Programme Created by Dr.T.V.Rao MD for
Medical and Paramedical professionals in the
Developing World
• Email
• doctortvrao@gmail.com
DR.T.V.RAO MD 71