Sterilization

Question 1

Sources of contaminations

Answer 1

• Airborne
• Breath
• Skin
• Hair
• Clothing
• Surfaces

Question 2

Methods to minimize contamination

Answer 2

• Airborne: use laminar airflow
• Breath: use masks
• Skin: nails must be scrubbed and hands and forearms washed with detergents
• Hair and clothing: wear sterile down over normal clothing, wear a cotton cap
• Working surfaces: clean with a bactericidal solution/ethyl alcohol

Question 3

Definition of sterility

Answer 3

Absence of life; absolute freedom from biological contamination

Question 4

Definition of sterilization

Answer 4

Inactivation/elimination of all viable organism and their spores

Question 5

Definition of disinfectant

Answer 5

Substance used on non-living objects to render them non-infectious; kills vegetative bacteria, fungi, viruses but not spores e.g. formaldehyde

Question 6

Definition of antiseptic

Answer 6

Substance used to prevent multiplication of microorganism when applied to living systems
Bacteriostatic in action but not necessarily bacteriocidal

Question 7

Definition of bacteriostat

Answer 7

Substance which stops growth and multiplication of bacteria but does not necessarily kill them

Question 8

Definition of bactericide

Answer 8

Substance that kills vegetative bacteria and some spores

Question 9

Thermal death time

Answer 9

Time required to kill a particular organism under a given condition

Question 10

What are the techniques for sterilization

Answer 10

1. Steam sterilization
2. Dry heat sterilization
3. Filtration
4. Gaseous
5. Ionizing Radiation/Irradiation

Question 11

Describe Steam sterilization

Answer 11

• Use steam under pressure in autoclaves
• Time, temp. 240C, pressure 20-30 lb
• Killing due to denaturation and coagulation of the microorganism’s proteins
• Highly effective, less time, inexpensive and large volumes
• therapeutic agent must be stable to water, heat
• Not for oily and moisture sensitive preparations

Question 12

Applications for steam sterilization

Answer 12

• Solutions in ampoules
• vials
• instruments
• glassware
• surgical dressing

Question 13

Describe dry heat sterilization

Answer 13

• No water used
• 160 - 170C for 2-4h in an oven
• Killing is due to dehydration of the microbial cells followed by slow oxidation
• Not for therapeutic agents that are thermolabile

Question 14

Applications for dry heat sterilization

Answer 14

• Glassware
• Heat stable powders
• Paraffin
• Petrolatum
• Fixed oils

Question 15

Describe filtration

Answer 15

• Physical removal of microorganisms by adsorption on the filter medium - filtration membrane
• Highly impt for sterilization of therapeutic agents especially heat sensitive materials
• Slow for large volumes and saturable (difficult to push a saturated material through the membrane)
• Membranes may absorb drug

Question 16

Advantages of bacterial filtration

Answer 16

• Speed - in case of small volumes
• Ability to sterilize thermolabile materials
• Inexpensive
• Complete removal of living and dead microorganism and particulate matters

Question 17

Describe gaseous sterilization

Answer 17

• Used mainly for heat and moisture sensitive materials

- Propylene oxide/ethylene oxide-carbon dioxide mixture at pressure 30 psi, temp 20-60C, 4-16h

Question 18

Application of gaseous sterilization

Answer 18

• Thermolabile powder
• Polymers
• Ophthalmics
• Subcutaneous, vaginal inserts
• Plastic syringes
• Tubing sets

Question 19

Disadvantages of gaseous sterilization

Answer 19

• Toxic
• gases are highly flammable
• explosive hazard
• not appropriate for solutions

Question 20

Describe ionizing radiation/irradiation for sterilization

Answer 20

• Limited in use -> effect of radiation on containers and products
• Need highly specialized equipment: UV Lamp, ionization
• Mechanism: altering the chemicals within/supporting the microorganism to form deleterious new chemicals capable of destroying the cell
• Good for thermolabile material

Question 21

How is sterility tests done?

Answer 21

• Organisms resistant to the method is used as the marker organism
• Choice of test method depends on the types of microorganisms involved

Question 22

Marker organism for steam and ethylene oxide

Answer 22

Bacillus stearothermophilus

Question 23

Marker organism for dry heat

Answer 23

Bacillus subtilis

Question 24

What are pyrogens

Answer 24

Fever producing organic substances arising from contamination by bacteria, molds, viruses, and yeasts.
Causative material thought to be a lipopolysaccharide from the outer cell wall of the bacteria and endotoxins.

Question 25

Removal of pyrogens

Answer 25

- Heating at high temp. (e.g. 250C for 45 mins) | - Reverse osmosis and ultrafiltration are excellent ways of removing pyrogen contamination from water

Question 26

Testing for pyrogens

Answer 26

- Rabbit tests | - Limulus Amebocyte Lysate (LAL) Tests

Question 27

Describe rabbit tests

Answer 27

1. Render the syringes, needles and glassware free from pyrogens by heating at 250C for not less than 30 mins 2. Warm the product to be tested to 37C plus/minus 2C 3. Take 3 healthy rabbits and weigh and record temp 4. Inject into an ear vein of each of 3 rabbits 10 ml of the product per kg body weight 5. Record the temp at 1,2 and 3 hrs - Material only meets the USP requirements for the absence of pyrogen if no rabbit shows an individual rise in temp at 0.6C or more above its respective control temp and sum of the temp. rises is less than 1.4C - IF NOT, repeat tests using 5 other rabbits - Material meets the USP requirements for the absence of pyrogens if not more than 3 of the 8 rabbits show individual rises in temp of more than or equal to 0.6C and sum of 8 individual temp. rises < 3.7C

Question 28

Describe Limulus Amebocyte Lysate (LAL) Tests

Answer 28

- Extract from the blood cells of the Horse Shoe Crab (Limulus Polyphemus) contains an enzyme and protein that coagulates in the presence of low levels of lipopolysaccharides - Considered more sensitive to endotoxin compared to the rabbit test - Some products cannot be tested by LAL cos of API

Question 29

Types of sterile products

Answer 29

- Systems and administration devices: Dispersed systems - lipid microspheres, liposomes, microparticulates Implants - bone growth, fertility controls, sustained delivery - Parenterals - Ophthalmics - Topicals