Sterilization Flashcards
Sterilization
Complete killing of all living organisms
Pasteurization
Heating milk at a temp of 74 C for 3-5 seconds
*Spores are Resistant!!
Disinfection
Use of liquid chemical agents, which usually have some degree of selectivity.
**Spores, Viruses, and Mycobacteria may be Resistant!!
Asepsis
Prevent microbes from reaching a protected environment (e.g. operating room)
Dry Heat
Expose the Surface to be sterilized to a Naked Flame
Dry Heat requires 160 C for 2 Hours to kill.
Frequently used to sterilize glassware.
Moist Heat
Moist Heat (Steam)
Far more Rapid and Effective in sterilization than Dry Heat.
- Autoclave: a sophisticated Pressure Cooker
- 121 C with a pressure of 15 lbs/sq in.
**Autoclave kills Spores in 5 minutes
- Flash Autoclaves:
- -are widely used in Operating Rooms
- -134 C for 3 minutes
Gas
Certain Plastics and Lensed instruments that are damaged or destroyed by autoclaving (Heat-sensitive materials) can be sterilized with gases.
- *Ethylene Oxide:
- -an inflammable and potentially explosive gas
- -is a Mutagen
- -Artificial heart valves can be cleaned with it; they would be destroyed in autoclave.
- *Formaldehyde vapor:
- -another alkylating agent.
Ultraviolet Light
Limited by its poor ability to penetrate.
Unsafe for humans; cross-links DNA, damaging it and causing skin cancer.
Ionizing Radiation
Irradiation of air in the vicinity of critical hospital sites.
Filtration
Physical method
Microbes can be removed from liquids by filtration.
*Ineffective for removing Viruses!
Microwaves
Physical method
Kill by generating heat.
**Heat-Resistant Spores may survive!! Use Autoclave instead!
Alcohol
Ethanol (70-90%) and Isopropyl alcohol (90-95%)
Used as Skin Decontaminants for Venipuncture.
*Inactive against Spores and Viruses!!
Alcohols require water and time (for evaporation).
Iodophors (Povidone)
Gradually release small amounts of Iodine.
Preparation of Skin before Surgery
Not used on patients with history of Iodine Sensitivity.
Chlorine
Ineffective on Body surfaces
- -inactivated by organic substances
- -painful to skin
Decontaminates Surfaces and Glassware.
**Legionella may be Resistant!
Hydrogen Peroxide
Useful in disinfecting items such as Contact lenses, etc.
Surface-Active Compounds
Soaps:
- -Highly Effective cleaners
- -But have Little Antibacterial
- *Quaternary Ammonium Compounds (Quats)
- -e.g. Benzalkonium Chloride
–Highly Bactericidal
–Inactivated by Soap
**Spores and Most Viruses are Resistant!!
**Pseudomonas Aeruginosa can Grow in Quat solutions!!
Chlorhexidine
Hand and Skin Disinfectant.
Bactericidal activity.
Binds to the Skin to produce a Persistent Effect.
Neutralized by Soaps.
Bactericidal
Bactericidal = kills bacterial cells by cell lysis.
Glutaraldehyde
Disinfectant for Apparatus that cannot be heat treated, such as some Lensed instruments and equipment for Respiratory Therapy.
Mechanism:
- -Polymerizes, then interacts with amino acids in proteins to cross-link them, or with amino acids in bacterial Peptidoglycan.
- -Results in alkylation and inactivation of the amino acids.
Medical Devices
Risk of infection After 24 - 48 hours
And is Cumulative
Urinary Catheters
Risk of Infection of Urinary Catheterization: 1 %
Risk for Indwelling Catheters:
10%
Preventive measure is maintenance of a completely closed system.
Vascular Catheters
Needles and Plastic catheters are a leading cause of Nosocomial Bacteremia.
Preventive measures:
- -Aseptic insertion technique
- -Appropriate care of the lines.
