lecture slides on Sterilization and disinfection of environment and instruments

1.  Dr Shireen Rafiq
 MBBS, M.Phil, Ph.D

2.  The physical removal of soil e.g., dust, mud,
organic material such as blood, secretions,
excretions and microorganisms
 It is accomplished with water, detergents and
mechanical action
 The terms “decontamination” and “sanitation” may
be used for this process

3.  Bed pans (Salmonella, Shigella, Vibrio cholerae
and Clostridia )
 Respiratory therapy eqpt
 Sputum -> Active TB
 Blood spills

4.  Medical eqpt
 Blood -> HBV, HCV and HIV
 Surgical / Medical Instruments
 Tissues / Fluids

5.  Soil protects microorganisms from the chemical
agent
 Physical cleaning eliminates large numbers of
microorganisms associated with soil
 Effective cleaning is important for aesthetic
reasons

6.  Follow the label instructions when mixing and
using a chemical
 Have specific cleaning schedules of the work or
care area
 Disassemble object to be cleaned

7. ◦ Equipment
◦ Instruments
◦ Environmental
surfaces

8.  Factors in cleaning action
◦ Chemical energy
◦ (detergent)
◦ Thermal energy (temperature)
◦ Mechanical energy (friction)

9.  Keep housekeeping surfaces visibly clean on regular
basis
 Clean up spills promptly
 Clean and disinfect high-touch surfaces, such as
doorknobs, bed rails, light switches, and surfaces in and
around toilets on a more frequent schedule
 Clean walls, blinds, and window curtains in patient-care
areas when visibly soiled or dusty

11.  CLEANING OF NURSERIES
 CLEANING OF FLOORS
1 % of the microbes present on the floors are
pathogenic.
On many occasion S. aureus. Isolated as a prominent
pathogen.
Keep the mops dry when not in use
 CLEANING OF SURGICAL PROCEDURES ROOMS
 CLEANING OF OT

14.  A simple detergent reduces
flora by 80 %
 Addition of disinfectant
reduces to 95 %
 In busy Hospitals counts raise
in 2 hours

15. Sodium hypochlorite blood and body
fluids
Bleaching powder Toilets
9grams/lit

16.  To sterilize the operation
theatre formaldehyde gas
(bactericidal &
sporicidal,viricidal) is widely
employed as it is cheaper
for sterilization of huge
areas like operation
theatres

18.  The destruction of harmful microorganisms,
usually other than bacterial spores, on inanimate
objects by the use of a chemical agent.
 chemical agents used are disinfectants.
 Two broad classes
ANTISEPTICS
DISINFECTANTS

19.  Antiseptics are non toxic for living tissues used for
skin disinfection e.g spirit, alcohol,
iodine.
 Basically the same chemicals as disinfectants
but their reduced conc .e.g 70% Alcohol or 2% Tincture
of iodine.
 Disinfectants Strong chemicals used to disinfect non
living objects these are generally toxic and corrosive.

20. The disinfectants are classified as high,
intermediate, or low level, based on the
effectiveness and contact time of the solution and
the biocidal activity of an agent against bacterial
spores, mycobacterium tuberculosis, lipid
and nonlipid viruses, and vegetative bacteria.

21.  Nature of the Material
The easiest surface to disinfect is a smooth
,nonporous, and cleanable one. If the materials
are incompatible with disinfectant, damage and
corrosion can occur

22.  Bioburden
Under a given set of circumstances ,the higher
the level of microbial contamination,
the longer,required exposure to the disinfectant
is needed.
Additionally, resistant micro-organisms require
longer exposure times.

23.  Organic Debris Present
Blood, saliva, and other organic material may
contribute to the failure of a germicidal process by
either direct inactivation of the disinfectant or the
actual layering of the micro-organisms on the
instrument or equipment, preventing penetration
of the germicide.

24.  Type and Concentration of the Germicide
Generally, the higher concentrations of a chemical
agent are more effective and require a shorter
time to disinfect.

25.  Can be expected to destroy all microorganisms,
with the exception of high numbers of bacterial
spores

26.  Inactivates Mycobacterium tuberculosis,
vegetative bacteria, most viruses, and most fungi,
but does not necessarily kill bacterial spores

27.  Kills most vegetative bacteria, most fungi, lipid
and non-lipid viruses, but cannot be relied on to
kill resistant microorganisms such as
mycobacteria or bacterial spores.

28.  Level of disinfection desired
 Biocidal properties
 Environmental factors
 Non-toxic, Non-irritating
 Soluble in water
 Pleasant odor
 Stability

29.  Disruption of cell membrane.
Alcohols
Detergents
Phenols
 Modification of proteins
chlorine
iodine
heavy metals
hydrogen per oxide

30. Formaldehyde and Gluteraldehyde
Ethylene oxide
Acids and alkalis
 MODIFICATION OF NUCLEIC ACIDS
Crystal violet used as skin antiseptic.
Malachite green dye inhibit the growth of
unwanted micro organism in sputum and grow M.

31.  Alcohol
 Chlorines
 Iodophors
 Phenolics
 Quaternary ammonium compounds

32.  They are classified as high-level disinfectants
or sterilants.
 Always wear impermeable gloves and protective ,
eyewear when handling these
solutions.
 It s more effective than formaldehyde use to
sterlize respiratory therapy equipment.

34.  These solutions may be used for high-level
disinfection of semicritical items that are not
subject to corrosion.
 It has a rapid action of 3 minutes for disinfection
or 6 hours for sterilization.
 It must be used with protective eyewear and
gloves because it is extremely irritating to the
eyes and skin

35.  Chlorine is used to disinfectant to purify the water
supply /swimming pools.
 Hypochlorite(bleach) used in the home and
hospitals.
 It is powerful oxidizing agent kills sulfhydryl
gp in enzymes to form inactive disulfide.

37.  Iodophors are classified as intermediate-level
disinfectants.
 Iodophor preparations are less irritating to
tissues and cause less allergies.
 Iodophor antiseptics are useful in the
preparation of oral mucosa for local anesthesia,
surgical procedures,and hand washing.

38.  Tincture of iodine (2% of iodine and potassium
iodide in ethanol) is used on skin before blood
culture.
 It is irritating to skin should be removed with
alcohol.

40.  Phenolics are also classified as an intermediate-
level disinfectant.
 They act as good surface spray cleaners and
are effective in the presence of detergents.
 Phenolics are useful on metal, glass, rubber, and
plastic, and are less toxic and corrosive than
glutaraldehyde solutions.

41.  Phenols was the first disinfectant used in 0.T
bt it is rarely used nw as it is too caustic.
 It not only damage membranes bt also denatures
proteins.

42.  Ethanol is widely used befor immunization and
venipuncture.
 It disrupts the cell membrane.
 It require presence of water much effective at
70% than at 100%.
 Used as antiseptic bt not as effective as iodine
containing compounds.

43.  Surface active agents long chain ,lipid soluble
hydrophobic and a polar hydrophilic .
 It disrupts the cell membrane.
 Quaternary ammonium compounds widely used
as antiseptics.

44.  It is available as 37% solution in water(formalin)
denatures proteins and nucleic acids.
 It is mostly used for preservative purpose.

45.  This gas is used for heat sensitive materials
sterlization of surgical instruments and plastics.

46.  It is used as antiseptic to clead wounds and to
disinfect contact lenses.
 Its use is limited by the organism s containing
catalase that degrades it.

47.  Mercury and silver have the antibacterial activity
widely used in medicines.
 Silver nitrate drops useful in gonococcal
opthalmia neonatorum.
 Silver sulfadiazine to prevent infection of burn
wounds.

48.  The process by which all forms of microbial life,
including bacteria, viruses, spores and fungi are
destroyed.
 It is usually carried out by autoclaving ,exposing
to steam at121c under pressure of 15lb/in, for 15
min.

49.  Instruments and materials used in penetration into
normally sterile body parts.
 Media, reagents and eqpt used in laboratory
practices

50.  Instruments and materials used in penetration into
normally sterile body parts
damaged by moist heat sterlized by exposure to
ethylene oxide gas.
 I.v solution are sterlized by filtration.

51. PHYSICAL AGENTS
 Heat
 Ionizing radiation
 Filtration
 Gases
 Liquids

52.  DRY HEAT
Dry heat kills by oxidation (slow, uneven penetration).
It kills by denaturing of proteins ,membrane damage and enzyme
cleavage of DNA may occurs.
It includes sterilization by:
Incineration
Flaming
Red heat
Hot air ovens
Microwave oven

53.  Incineration
1200-1500 C,
pathological waste,
surgical dressings,
sharps, needles, other
clinical wastes
 Flaming
Scalpels, neck of flasks
 Red heat
Inoculating loops, wires

54.  Hot air ovens
160-180 C for
one hour
Glassware, oily
fluids, powder
 Microwave
oven
Not reliable due
to variable
heat

55.  Kills by protein coagulation (denaturation of
enzymes) so requires lower temperatures and
shorter times, but the moisture must penetrate the
pathogens to be effective.
 Water disrupts non covalent bonds e.g hydrogen
bond which hold protein chain together.

56. It include
 Boiling
 Pasteurization
 Tyndallization
 Autoclave

57.  Boiling
At 100 C at sea level, kills many
vegetative cells and viruses
within 10 minutes.
 Pasteurization
Destroys pathogens esp for
milk( Mycobacterium bovis ,
Salmonella typhi , etc.) without
altering the flavor of the food
sterilize at 62 C for 30min by
rapid cooling.

58.  Higher temperature short time
pasteurization
It applies higher heat for a
much shorter time (72 0 C for
15 sec)
 UHT treatment
An ultra-high-temperature, very
short duration treatment (140 0
C for 3 sec) is used to sterilize
dairy products

59.  Tyndallization
Intermittent exposure at 100 C.
Principle : One exposure kills
vegetative organisms,
between heatings the spores
become vegetative forms
which get killed during
subsequent heating
Gelatin media, media
containing sugars.

60. It was invented by Charles Chamberland in 1879.
The name comes from Greek auto-, ultimately
meaning self, and Latin clavis meaning key — a
self-locking device.

61.  Autoclaving
Steam applied under
pressure 15 lb/in
square(121C for 15-20 min)
is the most effective method
of moist heat sterilization.
Kills highly resistant org(
Clostridium botulinum)
The steam must directly
contact the material to be
sterilized

62.  AN autoclave provides moist heat at 100c.
 At this temp vapour pressure equals the pressure
of the surrounding atmosphere i.e 760 mm Hg.
 Water is heated within a closed vessel,the
pressure inside inc.
 Steam thus formed is superheated,much more
than 100c.
 Superheated steam condenses on cooler loads
,releasing thermal energy and moisture.
 Combined effect denatures the microbial proteins.

63.  STEAM is first intoduced into the jacket, kept filled
through out the day at 121 c.
 jacket is hot, the load is placed in the chamber.
 door is closed, steam allow to enter the chamber.
 air and condensate start coming out of the discharge
channel,it reaches 121c temp steam trap is
automatically controlled.
 holding period starts as it endssupply of steam to the
chamber is stopped,steam left in
Chamber cool pressure falls.

64.  All part of the load must be permeated by steam ,the
load should be loosely arranged.
 Steam should be saturated and dry.
 Minimum holding time for various temp and pressures
necessary for complete sterlization.
 Air must be completely removed from chamber and
from the load so that load is subjected to pure steam.

65.  Because damp heat is used, heat-labile products
(such as some plastics) cannot be sterilized this
way or they will melt.
 Paper and other products that may be damaged
by steam must also be sterilized another way.
 Items should always be separat to allow the
steam to penetrate the load evenly

66.  Autoclaves are widely used in microbiology,
medicine, tattooing, body piercing,
veterinary science, mycology, dentistry, and
prosthetics fabrication. They vary in size and
function depending on the media to be sterilized.
 Typical loads include laboratory glassware,
surgical instruments, medical waste, and
bateriological culture media.

67.  It is very important to ensure that all of the trapped
air is removed from the autoclave before
activation as hot air is a very poor medium for
achieving sterility.
 Stat 134 °C can achieve in three minutes the
same sterility that hot air at 160 °C takes two
hours to achieve

68.  A medical autoclave is a device that uses steam
to sterilize equipment and other objects .This
means that all bacteria, viruses, fungi, and spores
are inactivated.
 Autoclaves are found in many medical settings,
laboratories, and other places that need to ensure
the sterility of an object

69.  Simple, NON Jacketed ;pressure cooker type.
vertical or horizontal cylinder of metal in a
supporting frame. Cylinder contains water and a
gas burner below cylinder heats it.Lid is fastened
by screw clamps and made air tight.
Method of discharging air is in efficient.
Lacks the mechanism of drying the load after
sterlization.

71. Autoclaves with automatic air discharge ;horizontal
or vertical metal cylinder to which a door is
fastened by a capstan head that operates by bolt.
Automatically remains locked while the chamber
pressure is raised.it has steam jacket which heats
the side walls.
Vaccum system is provided in drying the load.An air
intake channel with self-sterlizing
filter warm sterile air into the chamber.

73.  Equipped with electrically driven pumps, produce
vaccum in the chamber.
 This allow the steam to pentrate very rapidly.

74.  There are physical, chemical, and biological
indicators that can be used to ensure that an
autoclave reaches the correct temperature for the
correct amount of time.
 Chemical indicators on medical packaging and
autoclave tape change color once the correct
conditions have been met, indicating that the object
inside the package, or under the tape, has been
appropriately processed.

75.  Biological indicators contain spores of a heat-resistant
bacterium. If the autoclave does not reach the right
temperature, the spores will germinate when
incubated and their metabolism will change the color
of a pH-sensitive chemical.
 Physical indicators consist of an alloy designed after
being subjected to a given temp for the relevant
holding time. If the alloy melts, the change will be
visible

76.  Both ß and gama radiations are
employed industrially for
sterilization of large-scale pre-
packed single use disposable
items
 Needles, syringes, latex
catheters, surgical gloves
 In food industry to reduce
spoilage and remove pathogens

77. uv-light
 uv irridation inhibits DNA replication and
the organism could not grow.
 It occurs at 250-260nm.
X-rays
 X-rays have higher energy and penetrating
power than UV.
 It kills by production of free radical,this
break covalent bond in DNA.
 It kill vegetative cells bt spores are
resistant.
 Surgical gloves,sutures,syringes and
plastic items.

78.  Removal of bacteria and other
larger microorganisms from
‘liquids’ that are liable to be
spoiled by heating
 Blood serum, antibiotic
solutions, i.v solutions
 Removal of protozoal cysts from
drinking water, that are not
destroyed by chlorination
 Nitrocellulose filter(0.22um)

79.  Ethylene oxide
Highly penetrative,
microbicidal gas
Used in industry to
sterilize plastics and
other thermo-labile eqpt
 Catheters, syringes and
prosthetic heart valve

80.  Formaldehyde in combination with steam
Used in hospitals to reprocess thermo-labile eqpt.
 Both processes carry toxic hazards

81.  Categorizes how an object is disinfected by how
the object is used:
◦ Critical
◦ Semi-critical
◦ Non-critical

82.  Used on or in sterile areas of the body
 Require sterilization

83.  Cutting or dissecting devices
 Microsurgical instruments
 Cardiac catheters
 Implantables
 Dental Instruments
 IV Fluids
 IV catheters,needles,urinary catheters

84.  All “critical” and “semi-critical” instruments should
be sterilized by autoclave, dry heat or chemical
vapor.

85.  Used in or on mucous membranes or damaged
skin
 Require sterilization or high-level disinfection

86.  Flexible endoscopes
 Laryngoscopes
 Endotracheal tubes
 Vaginal speculums
 Dental x-ray jackets
 ENT exam instruments
 Thermometers

87.  May come into contact with patient’s intact skin
 Intermediate or low-level disinfection

88.  Room furniture
 Blood pressure cuffs and ambu bags
 Wheelchairs, stretchers
 Electronic thermometers
 Glucometers
 Stethescopes
 Bed pan
 ECG machine

89.  They usually require chemical disinfection at least
once daily
 Use disposable barriers since they reduce the
number of surfaces requiring disinfection.
 If a non critical item gets visibly soiled with blood
or other potentially infectious material,scrub it with
detergent and water,dry it with a disposable towel
and disinfect it with a low-level disinfectant like
phenol,iodophore,bleach or alcohol

90.  World Health Organization, 2000
◦ When instruments contact high infectivity tissue, single-use instruments
recommended.
◦ If single-use instruments not available, maximum safety attained by
destruction of reusable instruments.
◦ Where destruction is not practical, reusable instruments must be
decontaminated by immersing in NaOH and autoclaved (121°C/30m),
cleaned rinsed and steam sterilized.
◦ After decontamination by steam and NaOH, instruments can be cleaned
in automated mechanical reprocessor.