Sterilization One Shot Notes and MCQs

Sterilization

1. Sterilization:

Sterilization is the process of eliminating or destroying all forms of microbial life, including bacteria, fungi, viruses, and spores, from surfaces, equipment, or pharmaceutical products. It ensures that the products are free from contamination, critical for pharmaceutical, surgical, and food industries.

2. Methods of Sterilization

a. Physical Methods

Heat Sterilization:
- Moist Heat Sterilization (Autoclaving):
  Uses: Sterilizing surgical instruments, culture media, pharmaceutical solutions.
  Conditions: 121°C, 15 psi for 15-30 minutes.
  Mechanism: Coagulates proteins by penetrating moist heat into cells.
- Dry Heat Sterilization:
  Uses: Glassware, metal instruments, oils, and powders.
  Conditions: 160°C for 2 hours or 180°C for 30 minutes.
  Mechanism: Oxidation of cellular components and denaturation of proteins.
Filtration:
- Membrane Filtration: Used for heat-sensitive liquids and air filtration.
- Pore size: 0.22 µm for removing bacteria.
- Applications: Sterilization of injectables, ophthalmic solutions, and culture media.
Radiation Sterilization:
- UV Radiation: Limited to surface sterilization.
- Gamma Radiation: Used for sterilizing disposable medical devices (e.g., syringes, catheters).
Gas Sterilization:
- Ethylene Oxide (ETO): Sterilizes heat-sensitive equipment (e.g., catheters, surgical instruments).
- Mechanism: Alkylation of DNA and proteins.

b. Chemical Methods

Aldehydes:
- Examples: Formaldehyde, glutaraldehyde.
- Used for sterilizing surgical instruments and endoscopes.
- Mechanism: Cross-linking proteins and nucleic acids.
Oxidizing Agents:
- Examples: Hydrogen peroxide, peracetic acid.
- Used for sterilizing medical instruments and surfaces.
Halogens:
- Examples: Chlorine, iodine.
- Used for water treatment and disinfection of surfaces.

3. Validation of Sterilization Methods & Equipment

Validation ensures that sterilization methods are consistently effective. It involves testing the reliability and reproducibility of the process.

Steps in Sterilization Validation:

Installation Qualification (IQ):
- Ensures the sterilization equipment is installed properly according to manufacturer guidelines.
Operational Qualification (OQ):
- Verifies that the sterilizer performs as expected under operational conditions.
Performance Qualification (PQ):
- Confirms that the equipment provides consistent sterilization over time with various loads.
- Uses biological indicators (BIs): spores of Geobacillus stearothermophilus are commonly used to test autoclaves.
Chemical Indicators (CIs):
- These indicators change color when exposed to sterilization conditions (e.g., steam, heat).

4. Sterility Testing of Pharmaceutical Products

Sterility testing ensures that pharmaceutical products are free from viable microorganisms.

Methods of Sterility Testing:

Membrane Filtration Method:
- Used for filterable products like injectables and ophthalmic solutions.
- Product is passed through a 0.45 µm membrane filter.
- Filter is incubated in Thioglycolate broth (for anaerobes) and Soybean Casein Digest Medium (for aerobes).
Direct Inoculation Method:
- Used for non-filterable products (e.g., ointments).
- Product is directly inoculated into sterility testing media.
Incubation Conditions:
- 35-37°C for aerobic organisms.
- 20-25°C for fungi and molds.
- Incubation period: 14 days.

5. Microbial Assays of Antibiotics, Vitamins, and Amino Acids

Microbial assays are used to determine the potency of antibiotics, vitamins, and amino acids based on their ability to inhibit or promote microbial growth.

A. Antibiotic Assays:

Method: Agar diffusion method (zone of inhibition) or turbidimetric method.
Principle: The growth of a sensitive microorganism is inhibited by the antibiotic.
Example:
- Microorganism used: Bacillus subtilis for penicillin assays.
- Agar Diffusion: Antibiotic discs are placed on inoculated agar plates. Zones of inhibition are measured to determine potency.

B. Vitamin Assays:

Vitamins Tested: Vitamin B12, riboflavin, thiamine.
Principle: The growth of a microorganism is stimulated in the presence of the specific vitamin.
Example: Lactobacillus leichmannii is used for Vitamin B12 assay.

C. Amino Acid Assays:

Amino Acids Tested: Lysine, tryptophan.
Principle: Microorganisms grow in proportion to the availability of amino acids.
Example: Escherichia coli can be used for lysine assays.

6. Dynamics of Disinfection and Sterilization

Bactericidal: Kills bacteria.
Bacteriostatic: Inhibits bacterial growth.
Factors Affecting Sterilization:
1. Type of microorganisms (e.g., spores are resistant).
2. Concentration of sterilant.
3. Exposure time.
4. Temperature and pH.

MCQs on Sterilization, Sterility Testing, and Microbial Assays

Which method uses steam under pressure for sterilization?
a) Dry heat sterilization
b) Autoclaving
c) Radiation sterilization
d) Ethylene oxide sterilization
Answer: b) Autoclaving
What is the typical condition for autoclaving?
a) 160°C for 2 hours
b) 121°C at 15 psi for 15-30 minutes
c) 100°C for 10 minutes
d) 180°C for 1 hour
Answer: b) 121°C at 15 psi for 15-30 minutes
Which sterilization method is suitable for heat-sensitive materials?
a) Autoclaving
b) Dry heat
c) Membrane filtration
d) Incineration
Answer: c) Membrane filtration
What is the pore size of filters used for sterilizing solutions?
a) 0.8 µm
b) 1.2 µm
c) 0.22 µm
d) 5.0 µm
Answer: c) 0.22 µm
Gamma radiation is primarily used for sterilizing:
a) Injectable solutions
b) Powders
c) Disposable medical equipment
d) Glassware
Answer: c) Disposable medical equipment
Ethylene oxide sterilization is suitable for:
a) Heat-stable equipment
b) Water solutions
c) Heat-sensitive instruments
d) Biological media
Answer: c) Heat-sensitive instruments
Which microorganism is commonly used as a biological indicator for autoclaves?
a) Escherichia coli
b) Staphylococcus aureus
c) Geobacillus stearothermophilus
d) Pseudomonas aeruginosa
Answer: c) Geobacillus stearothermophilus
Chemical indicators in sterilization change color to indicate:
a) Absence of contamination
b) Exposure to sterilization conditions
c) Sterility of the product
d) Biological contamination
Answer: b) Exposure to sterilization conditions
Which medium is used for sterility testing of anaerobic organisms?
a) Sabouraud’s dextrose agar
b) Thioglycolate broth
c) Nutrient agar
d) MacConkey agar
Answer: b) Thioglycolate broth
The incubation period for sterility testing is:
a) 7 days
b) 14 days
c) 21 days
d) 28 days
Answer: b) 14 days
Which method is used to test non-filterable products for sterility?
a) Membrane filtration
b) Direct inoculation
c) UV radiation
d) Ethylene oxide exposure
Answer: b) Direct inoculation
What type of test evaluates the effectiveness of disinfectants?
a) Turbidimetric test
b) Zone of inhibition assay
c) Chick-Martin test
d) Coagulation test
Answer: c) Chick-Martin test
Which technique is used to measure antibiotic potency?
a) Agar diffusion method
b) Flame photometry
c) UV spectroscopy
d) Polarography
Answer: a) Agar diffusion method
What microorganism is used in Vitamin B12 assay?
a) Saccharomyces cerevisiae
b) Lactobacillus leichmannii
c) Escherichia coli
d) Bacillus subtilis
Answer: b) Lactobacillus leichmannii
Sterilization by dry heat is typically carried out at:
a) 121°C for 15 minutes
b) 160°C for 2 hours
c) 100°C for 10 minutes
d) 200°C for 1 hour
Answer: b) 160°C for 2 hours
Which gas is used for cold sterilization?
a) Nitrogen
b) Ethylene oxide
c) Oxygen
d) Carbon dioxide
Answer: b) Ethylene oxide
The principle behind autoclaving is:
a) Oxidation
b) Protein denaturation
c) Adsorption
d) Alkylation
Answer: b) Protein denaturation
Turbidimetric assays are used to measure the concentration of:
a) Antibiotics
b) Polysaccharides
c) Steroids
d) Vitamins
Answer: a) Antibiotics
Which radiation is used in sterilizing pharmaceuticals?
a) Microwave
b) Infrared
c) Gamma
d) Visible light
Answer: c) Gamma
Which factor influences the activity of disinfectants?
a) pH of the solution
b) Shape of the bacteria
c) Molecular weight
d) Color of the disinfectant
Answer: a) pH of the solution
Sterility testing of injectable products is performed using:
a) Incineration
b) Membrane filtration
c) Centrifugation
d) Lyophilization
Answer: b) Membrane filtration
Biological indicators contain:
a) Inert gases
b) Spores of bacteria
c) Organic solvents
d) Activated charcoal
Answer: b) Spores of bacteria
Which sterilization method uses hot air?
a) Autoclaving
b) Dry heat sterilization
c) Filtration
d) Gas sterilization
Answer: b) Dry heat sterilization
Which organism is used for penicillin microbial assay?
a) Aspergillus niger
b) Bacillus subtilis
c) Staphylococcus aureus
d) Escherichia coli
Answer: b) Bacillus subtilis
UV radiation sterilizes by:
a) Protein coagulation
b) DNA damage
c) RNA polymerization
d) Oxidation
Answer: b) DNA damage
What type of media is used to cultivate fungi in sterility testing?
a) MacConkey agar
b) Sabouraud’s dextrose agar
c) Blood agar
d) Nutrient agar
Answer: b) Sabouraud’s dextrose agar
Which sterilization method uses high-frequency sound waves?
a) Gamma radiation
b) Ultrasonic sterilization
c) UV radiation
d) Microwave sterilization
Answer: b) Ultrasonic sterilization
Microbial assays are used to determine the potency of:
a) Hormones
b) Antibiotics
c) Proteins
d) Lipids
Answer: b) Antibiotics
Permeability tests are used to determine the:
a) Effectiveness of disinfectants
b) Density of powders
c) Resistance of packaging material
d) Adsorption of gases
Answer: c) Resistance of packaging material
What is thixotropy?
a) A change from solid to liquid
b) Reversible gel-sol transformation
c) Irreversible phase change
d) Formation of complex ions
Answer: b) Reversible gel-sol transformation