Sterilization

Question 1

Sterilization

Answer 1

Complete killing of all living organisms

Question 2

Pasteurization

Answer 2

Heating milk at a temp of 74 C for 3-5 seconds

*Spores are Resistant!!

Question 3

Disinfection

Answer 3

Use of liquid chemical agents, which usually have some degree of selectivity.

**Spores, Viruses, and Mycobacteria may be Resistant!!

Question 4

Asepsis

Answer 4

Prevent microbes from reaching a protected environment (e.g. operating room)

Question 5

Dry Heat

Answer 5

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.

Question 6

Moist Heat

Answer 6

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

Question 7

Gas

Answer 7

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.

Question 8

Ultraviolet Light

Answer 8

Limited by its poor ability to penetrate.

Unsafe for humans; cross-links DNA, damaging it and causing skin cancer.

Question 9

Ionizing Radiation

Answer 9

Irradiation of air in the vicinity of critical hospital sites.

Question 10

Filtration

Answer 10

Physical method

Microbes can be removed from liquids by filtration.

*Ineffective for removing Viruses!

Question 11

Microwaves

Answer 11

Physical method

Kill by generating heat.

**Heat-Resistant Spores may survive!! Use Autoclave instead!

Question 12

Alcohol

Answer 12

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).

Question 13

Iodophors (Povidone)

Answer 13

Gradually release small amounts of Iodine.

Preparation of Skin before Surgery

Not used on patients with history of Iodine Sensitivity.

Question 14

Chlorine

Answer 14

Ineffective on Body surfaces

• -inactivated by organic substances
• -painful to skin

Decontaminates Surfaces and Glassware.

**Legionella may be Resistant!

Question 15

Hydrogen Peroxide

Answer 15

Useful in disinfecting items such as Contact lenses, etc.

Question 16

Surface-Active Compounds

Answer 16

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!!

Question 17

Chlorhexidine

Answer 17

Hand and Skin Disinfectant.

Bactericidal activity.

Binds to the Skin to produce a Persistent Effect.

Neutralized by Soaps.

Question 18

Bactericidal

Answer 18

Bactericidal = kills bacterial cells by cell lysis.

Question 19

Glutaraldehyde

Answer 19

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.

Question 20

Medical Devices

Answer 20

Risk of infection After 24 - 48 hours

And is Cumulative

Question 21

Urinary Catheters

Answer 21

Risk of Infection of Urinary Catheterization: 1 %

Risk for Indwelling Catheters:
10%

Preventive measure is maintenance of a completely closed system.

Question 22

Vascular Catheters

Answer 22

Needles and Plastic catheters are a leading cause of Nosocomial Bacteremia.

Preventive measures:

• -Aseptic insertion technique
• -Appropriate care of the lines.