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Physical Agents of Sterilization

Steam Under Pressure, Dry Heat, Radiation

Chemical Agents of Sterilization

Ethylene Oxide, Gas Plasma (Sterrad), Peracetic Acid (Steris)

Gravity Displacement Autoclave

Most common heat sterilization
Steam on top displaces air to bottom, Temp increases as pressure increases
Kills all known microbes by coagulation and denaturation of proteins

Routine Instruments - 13 min @ 121
Large Linen Packs - 30 min @ 121
Emergency Flash - 3 min @ 131

How long should you Autoclave?

Dry Heat

Kills by oxidation
good for powders, oils, needles
Uses greater time and temp than autoclave


Most common is intense gamma radiation
Industrial/Commercial use, pharmaceuticals, plastic disposables, needles
Very expensive

Ethylene Oxide

Flammable gas, contact burns, cannot be used with irradiation
NOT affected by organic matter, penetrates plastic
Kills by altering DNA through alkylation
Minimum 33% humidity and 50-55 degrees C
Endoscopes, cables, cameras, certain plastics

H2O2 Sterrad

Chemical alternative to EtO
Destroys cellular components of bacteria, spores, fungi, viruses, mycobacterium
Safe, very effective
NOT for endoscopes, liquids, or plant
1 year shelf life


Rapidly bactericidal, but NO residual
Not for spores, fungi, virus
Presurgical skin prep, can reduce residual of chlorhexidine,


Free iodine is active component, Free iodine increases with decreased concentration
Kills by cell metabolic interference of protein synthesis
Bactericidal, fungicidal, virucidal, NOT for spores
Minimal residual
NOT for joint or peritoneal lavage


Kills by cell membrane disruption and protein precipitation
Bactericial including Pseudomonas, variable against fungi and virus, only sporicidal at 1%
Residual, NOT cytotoxic, but NOT for joint or peritoneal lavage

Alcohol vs Iodine vs Chlorhexidine

Immediate Effect
Activity reduced by organic matter
Residual Effect
NONE are effective against spores

Quaternary Ammonium Compounds

Dissolve lipids in cell wall/membrane
Good for gram pos, some gram neg
Fungicidal, virucidal*, NOT spore
Inactivated by organic matter and soap*


BacT, virus, fungus
Inactivated by organic material, high pH, low or high temp
Dakin's solution (dilute for use on tissues)

Aldehydes (Cidex)

Disinfectant (previously a sterilant)
Protein and nucleic acid alkylation
BacT, fungus, spore, virus
NOT affected by organic matter
Activity higher at lower pH, but less stable


Complete destruction of all microorganisms; applies to NONliving objects


The destruction of most pathogenic microorganisms on NONliving objects


The destruction of most pathogenic microorganisms on LIVING objects


The removal of visible debris or contamination from surfaces


An agent that inhibits or arrests the growth of bacteria


An agent that kills bacteria

Single wrap muslin - 2-7 days
Double wrap muslin - 3-7 weeks
Single crepe paper - 3-8 weeks
Double crepe paper - 8 weeks - 6 months
Pouches - 1 year

Autoclave Storage Times


An agent lethal to vegetative organisms but suitable for use in LIVING tissue
The agent may be ________ at low concentrations and disinfectant at high concentrations

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