Sterilization
4-H Veterinary Science
Extension Veterinary Medicine
Texas AgriLife Extension Service
College of Veterinary Medicine and Biomedical Science
Texas A&M System
http://aevm.tamu.edu
Objectives
 Understand and utilize correct sterilization
and disinfection techniques
 Distinguish between sterilization and
disinfection
 List the characteristics of an ideal antiseptic
 Describe sterilizing agents and rank their
effectiveness
 Discuss the time/temperature relationship in
destroying microorganisms
 Microorganisms


Invisible
Cause infections
 Sterilization

Destruction of all microorganisms
 Disinfectant

Destruction of harmful organisms, or
pathogens on nonliving objects
 Disinfectants

Types of disinfectants





Bactericides
Fungicides
Germicides
Virucides
All prevent transfer of infection
 Sterilization
 Antiseptics
 Prevent growth of microorganisms without destroying
them
 Not harmful to patients

Characteristics
 Active against pathogens
 Non-irritating
 Cleansing
 Cost-effective
 Long shelf life
 Safe for patient and handler
 Stable in the presence of organic matter
Sterilizing Agents
 Type of agents


Chemical
Physical


Moist heat
Dry heat
 Most clinics use physical agents
Steps for Chemical Sterilization
Step 1
Decontaminate, clean, and thoroughly dry all instruments and other items to be sterilized. Water from wet
items will dilute the chemical solution, thereby reducing its effectiveness.
Step 2
Prepare the glutaraldehyde-containing solution (or other chemical solution) by following the manufacturer's
instructions--or use a solution that was prepared previously, as long as it is clear (not cloudy) and has not
expired. After preparing the solution, put it in a clean container with a lid. Always mark the container with the
date the solution was prepared and the date it expires.
Step 3
Open all hinged instruments and other items and disassemble those with sliding or multiple parts. The
solution must contact all surfaces in order for sterilization to be achieved. Completely submerge all
instruments and other items in the solution. All parts of the items should be under the surface of the
solution. Place any bowls and containers upright, not upside-down, and fill with the solution.
Step 4
Follow the manufacturer's instructions regarding the time necessary for sterilization to be achieved. In
general, if the solution contains glutaraldehyde, cover the container and allow the instruments and other
items to soak for at least 10-12 hours. (Times vary for different products. Follow the manufacturer's
instructions.) Do not add or remove any items to the solution once timing has begun.
Step 5
Remove the items from the solution using large, sterile pickups.
Step 6
Rinse thoroughly with sterile water to remove the residue that chemical sterilants leave on items. This
residue is toxic to the skin and tissues.
Step 7
Store items properly. Proper storage is as important as the sterilization process itself. Place the items on a
sterile tray or in a sterile container and allow to air-dry before use or storage. Use the items immediately or
keep them in a covered, dry, sterile container and use within one week.
From www.engenderhealth.org/IP/instrum/inm12.html
 Moist heat
 Steam and boiling water
 Alone not effective
 Captured steam effective
 Autoclave
 Sealed chamber that furnished both hear and
pressurized steam for sterilization
 Inexpensive
 Sterilizes




Instruments
Syringes
Needles
Other materials
 Dry heat



Slow sterilizer
Higher temperatures
Penetrates


Oil-based materials
Closed containers
Steps of Dry-Heat Sterilization
Step 1
Decontaminate, clean, and dry all instruments and other items to be sterilized.
Step 2
Either 1) wrap the instruments and other items using foil, double-layered cotton, or muslin fabric; 2) put unwrapped
instruments and other items on a tray or shelf; or 3) place instruments and other items in a metal, lidded
container.
Note: Because dry-heat sterilization works by raising the temperature of the entire item to the designated temperature, it is
not necessary to open or unlock hinged instruments or other items or to disassemble those with sliding or multiple
parts. In addition, instruments and other items can be placed in closed containers.
Step 3
Place instruments and other items in the oven, and heat to the designated temperature. The oven must have a
thermometer or temperature gauge to make sure the designated temperature is reached.
Use the list here to determine the appropriate amount of time to sterilize instruments and other items for different
temperatures. (do not begin timing until the oven reaches the desired temperature, and do not open the oven
door or add or remove any items). The times shown here represent the amount of time that items must be kept
at the desired temperature to ensure that sterilization is achieved. Keep in mind that the total cycle time-including heating the oven to the correct temperature, sterilization, and cooling--is usually twice as long as the
time noted here.
Temperature
170 degrees C (340 degrees F) - 1 hour
160 degrees C (320 degrees F) - 2 hours
150 degrees C (300 degrees F) - 2.5 hours
140 degrees C (285 degrees F) - 3 hours
Note: Because dry heat can dull sharp instruments and needles, these items should not be sterilized at
temperatures higher than 160 degrees C.
Step 4
Leave items in the oven to cool before removing. When they are cool, remove items using sterile pickups and use
or store immediately.
Step 5


Store items properly. Proper storage is as important as the sterilization process itself:
Wrapped items. Under optimal storage conditions and with minimal handling, properly wrapped items can be
considered sterile as long as they remain intact and dry. For optimal storage, place sterile packs in closed cabinets in
areas that are not heavily trafficked, have moderate temperature, and are dry or of low humidity. When in doubt about
the sterility of a pack, consider it contaminated and re-sterilize it.
Unwrapped items. Use unwrapped items immediately after removal from the autoclave or keep them in a covered,
sterile container for up to one week.
 Direct flame

Can damage the exposed object
Time/Temperature Relationship
 Most important factor in destroying
microorganisms is length of exposure to heat
 Varies with microorganisms
 The higher the temp the faster it will kill
microorganisms exposed
 Temps lower than boiling point can sterilize
some medications and milk
Other Sterilization Technology
 Filtration
 Ultraviolet irradiation
 Cold sterilization
 Ethylene oxide
 Filtration


Complete removal of microorganisms and
particles of a certain size from liquid or gas
Used by vet personnel in producing sterile and
particle-free fluids, such as intravenous fluids
 Ultraviolet irradiation



Destroys microorganisms in air, liquid, and
surface
Germicidal UV radiation is generated by
passing electricity through mercury vapor in
special glass tubes
UV lamps sterilize most effectively in still air at
room temperature
 Cold sterilization



Gamma radiation
Kill microorganisms without a rise in
temperature
Highly successful in sterilizing



Syringes
Stitching (sutures) materials
Containers
 Ethylene oxide



Makes possible the use of low cost, plastic
materials for sterile, disposable medical
instruments
Primary gas used in hospitals and clinics to
sterilize items that cannot withstand steam
sterilization
Vapors are hazardous to people