6. Introduction … cont.
The sterilization processes are commonly used for parenteral
products,
except gas and ionizing radiation, which are widely used for
devices
and surgical materials.
To assist in the selection of the appropriate sterilization method,
certain
basic information must be considered:
1- The nature and amount of product
2- Whether the product and container-closure system will have a
predominately moist or dry environment during sterilization.
6
7. Introduction … cont.
For sterilization purposes, microorganisms can be categorized into
three
general categories:
1- Easy to kill with either dry or moist heat
2- Susceptible to moist heat, but resistant to dry heat (Bacillussubtilis)
3- Resistant to moist heat, but susceptible to dry heat
(Colstridium sporogenes)
Sterilization tests are performed to verify that an adequate sterilization
process has been carried out. Validation of sterilization cycle also gives
assurance of process (including the performance of the equipment
and
personnel)
7
8. General Facts
The procedure to be used for sterilizing a drug, a pharmaceutical
product, or a medical device is determined to a large extent by the
nature of the product. It is important to remember that the same
sterilization technique cannot be applied universally because the
unique properties of some materials may result in their destruction
or modification.
Methods of inactivating microorganisms may be classified as
either physical or chemical. Physical methods include: moist heat,
dry heat and irradiation. Sterile filtration is another process, but it
only removes, not inactivates, microorganisms, chemical methods
include the use of either gaseous or liquid sterilants
8
9. General Facts… (cont.)
Heat stable reusable medical devices that enter the blood stream or enter
normally sterile tissue should always be reprocessed using heat-based methods
of sterilization (e.g., steam autoclave or dry heat oven).
Laparoscopic or arthroscopic telescopes (optic portions of the endoscopic
set) should be subjected to a sterilization procedure before each use; if this is
not feasible, they should receive high-level disinfection. Heat stable
accessories to the endoscopic set (e.g., operative instruments) should
be sterilized by heat-based methods (e.g., steam autoclave or dry heat oven).
9
10. General Facts … (cont.)
Reusable devices or items that touch mucous membranes should, at
a minimum, receive high-level disinfection between patients. These
devices include reusable flexible endoscopes, anesthesia breathing
circuits, and respiratory therapy equipment.
Medical devices that require sterilization or disinfection must be
thoroughly cleaned to reduce organic material or bioburden before
being exposed to the germicide, and the germicide and the device
manufacturer's instructions should be closely followed.
10
11. General Facts … (cont.)
Except on rare and special instances (as mentioned previously), items
that do not ordinarily touch the patient or touch only intact skin are not
involved in disease transmission, and generally do not necessitate
disinfection between uses on different patients. These items include
crutches, bed boards, blood pressure cuffs, and a variety of other
medical accessories. Consequently, depending on the particular
piece of equipment or item, washing with a detergent or using a low-
level disinfectant may be sufficient when decontamination is needed.
11
13. Terminology
◦ Bioburden- The degree of contamination with microorganisms
and organic parameters
◦ Bioresistance- Factors such as heat and/or moisture sensitivities
and product stability
◦ Biostate- The nutritional, physical, and reproductive phase of
microorganisms
◦ Bioshielding- Characteristics of the packaging materials
◦ Bowie Dick test (DART)- A test run daily that validates the
vacuum function of the sterilizer. The test should be run in an
empty load at the same time every day
◦ Contaminate- To render unfit for use through introduction of a
substance which is harmful or injurious
13
14. Terminology … cont.
◦ Contamination- A state of being soiled or infected by contact
with infectious materials
◦ Culture- A growth of microorganisms on a medium
◦ Culture Medium- Any substance or preparation used for the
growth and cultivation of microorganisms
◦ Incubate- To maintain under optimum environmental conditions
that are favorable for growth
◦ Incubation period- The period between the time infection occurs
and the appearance of the first symptoms
◦ Incubator- an Apparatus for maintaining a constant and suitable
temperatures for the growth and cultivation of microorganisms
◦ Nonpathogenic- Not capable of producing disease
◦ Pathogenic- Capable of producing disease
14
15. Terminology … cont.
TDT is the time required to kill a known population of microorganism
in a specific suspension at a particular temperature
Increasing temperature decreases TDT
Lowering the temperature increases TDT
Acidic or basic pHs decrease TDT
Fats and oils slow penetration and increase TDT
15
16. Terminology … cont.
◦ Spore- Certain microorganisms which are capable of forming a
thick wall around themselves enabling them to survive in adverse
conditions. It is highly resistant to heat
◦ Sterile- Completely devoid of all living microorganisms
◦ Thermal equilibrium- A condition where all parts of a system have
reached the same temperature; in a steam autoclave, when the
temperature throughout the entire load is the same
16
17. Action (mechanism) of Steam
Steam contacts a cooler surface, condenses, causing a huge
decrease in volume and setting up a negative pressure that draws
more steam
Condensation occurs as long as there is a temperature differential
Action of steam ensures: Surface heating, penetration, and protein
coagulation
17
18. Advantages of Steam Sterilization
◦ Stainless steel instruments withstand repeated processing without
damage and no residue
◦ Steam kills at lower temperatures than dry heat
◦ Easiest, safest, and surest method of on-site sterilization
◦ Fastest method, total cycle time is shortest
◦ Least expensive and most easily supplied agent-piped in from the
facility’s boiler room
◦ Most sterilizers have automatic controls and recording devices to
eliminate human error from the process
18
19. Disadvantages of Steam Sterilization
◦ Preparing, packaging, loading and operating the sterilizer. Also,
drying time
◦ Instruments need to be free from grease and oil and not be
sensitive with heat
◦ All items must have direct contact with steam and must be able to
penetrate packaging material
◦ Timing is adjusted for the differences in load and material and
subject to human error
◦ The steam may not be pure. Refers to the amount of solid, vapor,
or liquid contamination in the steam
19
21. Principles
Two important factors should be controlled:
1- Application of pressure:
Because it is not possible to raise the temperature of the steam
above
100 °C under atmospheric conditions, pressure is employed to
achieve
higher temperature (it should be recognized that the temperature,
not the
pressure is destructive to the microorganism and that the
application of
pressure solely for the purpose of increasing the temperature of the
system.
21
22. Principles … cont.
2- Application of time:
Time is another important factor in the destruction of
microorganisms by
heat. Most modern autoclaves have gauges to indicate to the
operator
the internal conditions of temperature and pressure and timing
device to
permit the desired exposure time for the load. The usual conditions
(pressure/temperature/time), are as follows:
22
Pressure Temperature Time
10 pounds 115.5 °C 30 minutes
15 pounds 121.5 °C 20 minutes
20 Pounds 126.5 °C 15 minutes
24. How Long to Autoclave
Dry goods @ 121 °C Time (min)
Glassware, empty, inverted 15
Instruments, wrapped 30
Utensils, wrapped 30
24
25. Biohazardous waste bags, @ 121 °C, loosely
tied
Time (min)
◦2 or more bags 100 +
◦1 bag, full 90
◦1 bag, half full 60
Testing available for individual situations
25
How Long to Autoclave … cont.
26. Liquids, in bottles with vented caps
Size (ml) Time (minutes)
75 25
250 30
500 40
1000 45
1500 50
2000 55
26
How Long to Autoclave … cont.
27. Autoclave applicable:
A. Applicable for pharmaceuticals preparations and materials that
can
withstand the required temperature and are penetrated but not
adversely
affected by, moisture.
B. In sterilizingaqueous solutions, the moisture is already present,
and all
that is required is the elevation of the temperature of the solution
for the
prescribed period of time. Thus solutions packaged in sealed
container as
ampoules, are readily sterilized by this method.
C. Also applicable to bulk solutions, glassware, surgical dressings,
and
instruments.
27
28. Autoclave not applicable:
A. The sterilization of oils, fats, or any oleaginous
preparations.
B. Other preparations not penetrated by the moisture.
C. Sterilization of exposed powders that may be
damaged by condensed moisture.
28
29. Types of steam sterilizers
1. Gravity displacement
Definition: Gravity pushes air through the packages and down
through the drain. Sterilization begins when steam passes the
thermometer and reaches the desired temperature.
29
31. 2. Pre-vacuum (high temperature)
Sterilizer
Definition: Air is completely evacuated from the chamber by a
vacuum. The steam-injector helps eliminate the air out of
packages. Steam then penetrates the packages on all
surfaces.
31
Types of steam sterilizers … cont.
33. 3. High Pressure (flash) Sterilizer
Definition: Another sterilizer that can be used in either gravity
displacement or pre-vacuum. Gravity displacement is the most
common used. Steam in the jacket should be maintained at all
times.
33
Types of steam sterilizers … cont.
34. High Pressure Flash Uses
Urgent items: (dropped items for which no method of
sterilization exists) Items that are dropped, or forgotten
34
35. 4. Washer-sterilizer
Definition: Wash and sterilizeinstruments. The water floods the
chamber with cold water to prevent proteins from setting on the
instrument. The water is then heated with steam to agitate and
clean the instruments.
35
Types of steam sterilizers … cont.
36. Washer-sterilizer Uses:
to wash and terminallysterilizeitems which are non-heat
sensitive, immediatelyafter operative procedures.
NO GLASS, SHARPS OR DELICATE INSTRUMENTS GO THROUGH
THIS STERILIZER. BREAKAGE COULD OCCUR!!!
36
37. Biological Indicator
Controls/Spore Tests
Bacillus stearothermophilus: is used strictly as biological
indicator of effective heat sterilization (steam and dry
heat
sterilizers) by including filter paper strips carrying
a saturated number of spores into the autoclave cycle.
The strips are then incubated to attempt to recover
viable
organism. The usual autoclave cycle of 121 °C for
15 minutes is adequate to kill Bacillus stearothermophilus
with a high margin of safety.
37
39. Biological Indicator
Controls/Spore Tests
◦ Record results:
◦ Negative- no color change from original.
◦ Positive- color changed is usually amber in color.
◦ Take sterilizer out of service
◦ Report to supervisor
◦ Recall all items sterilized in sterilizer for
last 24 hour period
39
41. 41
- It depends upon the physical removal of
microorganisms by adsorption on the
filter medium or by sieving mechanisms.
- It is used for sterilization of heat-
sensitive solutions.
- Medicinal preparations sterilized by this
method are required to undergosevere
validation and monitoring since the
effectivenessof the filtered productcan
be greatly influenced by the microbial
load in the solution being filtered.
- It removes,but does not destroy
M.O.
- Commercially available filters are
produced with a variety of pore-size
specifications (e.g. Millipore filters).
Filtration
42. 42
Most filters consist of:
1- diatomaceousearth
2- cellulose acetateor
3- nitrocellulose
0.45 µm filters removes most
bacteria
0.20 µm more inclusive,
viruses need 0.01 µm
Useful for sterilizingliquids
(enzymes, vaccines) that are
destroyed by heat
Filtration …cont.
43. 43
Factors affectingremovalof M.O.:
1- Pore size of filter
2- Electricalcharge of the filter
and that of the M.O.
3- pH of the solution
4- T, P, and Vacuum applied
Advantages:
1- Speed
2- Good for thermolabile
materials
3- Inexpensive
4- The completeremoval of living
and dead M.O. as well as
other particulatematterfrom
the solution
Filtration …cont.
44. 44
Disadvantages:
1- The membrane is fragile and because
of that, it is essential to determine that
the assembly was properly made and the
membrane was not ruptured
2- Filtrationof large volumes of liquids
would require more time (particularlyif
the liquids were viscous)
3- Useful when heat cannot be used and
small volumes of liquids.
Filtration …cont.
46. Ultrasonic vibrations
46
– High frequency sound waves
– Know as Sonicator, untrasonic machines
– Killing by –shock waves that disintegrates cell wall
and membranes.
48. PYROGEN
48
- A pyrogen is a material which when injected into
a patient will cause a rise in body temperature
(pyrexia).
- The lipopolysacchride that comprise a a major
part of the cell wall of gram-negative bacteria are
called endotoxins, and it is these that are the
most commonly encountered pyrogens.
- Bacterial cells may be pyrogenic even when they
are dead and when they are fragmented, and so
a solution or material that passes a test for
sterility will not necessarily pass a pyrogen test.
49. PYROGEN… cont.
49
Two main procedures are used for the detection of pyrogens.
A. The traditional method:
It requires the administration of the sample to laboratory rabbits whose
body temperature is monitored for a period of time thereafter.
50. PYROGEN… cont.
50
Steps:
1- Render the syringes, needles, and glasswares free form pyrogens by
heating at 250 °C for not less than 30 minutes.
2- Warm the product to be tested to 37 °C ± 2 °C
3- Inject into an ear vein of each of three rabbits 10 ml of the product per
kg of body weight.
4- Record the temperature at 30-minute intervals between 1 and 3 hours
subsequent to the injection
51. PYROGEN… cont.
51
Steps:
5- If no rabbit shows an individual rise in temperature of 0.5 °C or more
above its respective control temperature, the product meets the
requirements for the absence of pyrogens.
6- If any rabbit shows an individual temperature rise of 0.5 °C or more,
continue the test using five other rabbits.
52. PYROGEN… cont.
52
Steps:
7- If no more than three of the eight rabbits show individual rise in
temperature of 0.5 °C or more and if the sum of the eight individual
maximum temperatures rises does not exceed 3.3°, the material under
examination meets the requirements for the absence of pyrogens.
53. PYROGEN… cont.
53
B. LimulusAmoebicyte Lyste Test (LAL)
In recent years, it has been shown that an extract from the blood cells of
the horseshoe crab (Limulus polyphemus) contains an enzyme and
protein system that coagulates in the presence of low levels of
lipopolysaccharides.
The discovery has led to the development of the LimulusAmoebicyte
Lyste Test (LAL) for the presence of bacterial endotoxins.
54. PYROGEN… cont.
54
B. LimulusAmoebicyte Lyste Test (LAL) … cont.
Proclotting enzyme
Activated clotting enzyme
Endotoxin
Coagulation Clottable protein GEL
The Lysate Clotting Mechanism
55. PYROGEN… cont.
55
B. LimulusAmoebicyte Lyste Test (LAL) … cont.
In the test procedure, the lysate is mixed with equal volume of the test
solution in a depyrogenated container, such as a glass tube. The tube is
then incubated undisturbed at 37 °C for a period of about 60 minutes.
The test is a pass or fail test. The end point is identified by gently inverting
the glass tube. A positive result is indicated by the formation of a solid
clot. The clot doesn’t disintegrate when the tube is inverted. A negative
result is indicated if no gel clot has been formed.
