Common Sterilization Techniques

Question 1

Moist heat (autoclaving)

Answer 1

1. Mechanism: coagulates and denaturates proteins
2. Common use:
   - normal cycle: 121 C, 15-20 min, 15 lb/in2
   - fast cycle: 134 C, 3 min, 30 lb/in2
3. Most common, can corrode and dull instruments.

Question 2

Dry heat

Answer 2

1. Mechanism: denaturates protein
2. Common use:
   - 160 C, 2 h
   - 170 C, 1 h
3. Doesn’t corrode or dull instruments

Question 3

Chemical vapor (chemiclave)

Answer 3

1. Mechanism: denaturates and alkalyates nucleid acids and proteins
2. Common use: 132 C, 20-30 min, 25 lb/in2
3. Doesn’t corrode or dull instruments, uses a combination of alcohol and formaldehyde.

Question 4

Ethylene oxide gas

Answer 4

1. Mechanism: alkalyates nucleic acids and proteins
2. Sterilization is slow, 8-10h
3. Toxic to humans (chamber and ventilation system required), mostly in hospitals for heat/moisture-sensitive materials.

Question 5

Formaldehyde

Answer 5

1. Mechanism:
   - alkalyates nucleic acids and proteins
   - cross-links proteins
2. 37% solution in water (formalin)
3. Toxic fumes, less efficacious compared to other methods

Question 6

Glutaraldehyde (2%)

Answer 6

1. Broadest antimicrobial spectrum of activity.
2. Mechanism:
   - alkalyates nucleic acids and proteins
   - cross-links proteins
3. Sterilization is slow, 10h
4. Most potent chemical germicide, mostly for heat-sensitive materials, associated with hypersensitivity.

Question 7

Filtration

Answer 7

1. Mechanism: physically and electrostatically traps microorganisms larger than the pore size
2. Nitrocellulose filter (0.22 um pore size)
3. Preferred method of sterilizing liquid solutions