Applications of sterilization methods MCQs With Answer focuses on practical sterilization principles essential for B.Pharm students. This SEO-rich introduction covers applications of sterilization methods — autoclaving, dry heat, filtration, ethylene oxide, gamma irradiation and chemical sterilants — and their roles in aseptic processing, sterilization validation, sterility assurance level (SAL), bioburden control and pharmaceutical packaging. Understanding mechanisms, parameters, indicator selection and compatibility with drugs and equipment prepares students for quality control, regulatory compliance and industrial pharmacy tasks. Clear examples and targeted questions help reinforce decision-making for sterile product manufacturing and validation. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary application of autoclaving in pharmaceutical manufacturing?
- Sterilization of heat-sensitive injectable solutions
- Sterilization of heat-stable surgical instruments and glassware
- Sterilization of plastic disposable syringes using gas
- Terminal sterilization of finished proteins
Correct Answer: Sterilization of heat-stable surgical instruments and glassware
Q2. Which sterilization method is most suitable for heat-sensitive sterile injectables?
- Dry heat sterilization
- Saturated steam autoclaving
- Membrane filtration using 0.22 µm filters
- Moist heat at 121°C for 30 minutes
Correct Answer: Membrane filtration using 0.22 µm filters
Q3. What is the sterile filter pore size commonly accepted for sterilizing pharmaceutical solutions?
- 1.2 µm
- 0.45 µm
- 0.22 µm
- 0.05 µm
Correct Answer: 0.22 µm
Q4. Which biological indicator is most commonly used to validate steam sterilization cycles?
- Bacillus subtilis spores
- Geobacillus stearothermophilus spores
- Escherichia coli cells
- Pseudomonas aeruginosa cells
Correct Answer: Geobacillus stearothermophilus spores
Q5. Which sterilization method uses ethylene oxide gas and is chosen for heat- and moisture-sensitive medical devices?
- Gamma irradiation
- Autoclaving
- Ethylene oxide (EtO) sterilization
- Dry heat sterilization
Correct Answer: Ethylene oxide (EtO) sterilization
Q6. What does SAL (Sterility Assurance Level) 10^-6 indicate?
- One viable microorganism remains per batch
- Probability of one non-sterile unit in one million sterile units
- Sterilization achieved by double autoclaving
- Sterility achieved only by filtration
Correct Answer: Probability of one non-sterile unit in one million sterile units
Q7. Which sterilization method is most appropriate for polymer single-use devices sensitive to heat and moisture?
- Dry heat at 160°C
- Steam autoclaving
- Gamma irradiation at validated dose
- Boiling in water
Correct Answer: Gamma irradiation at validated dose
Q8. What is the main mechanism by which moist heat (steam) sterilizes?
- Oxidation of microbial membranes
- Hydrolysis of cell wall components
- Coagulation and denaturation of microbial proteins
- Removal of water from microbial cells
Correct Answer: Coagulation and denaturation of microbial proteins
Q9. Which parameter defines the time required at a given temperature to reduce a microbial population by 90%?
- Z-value
- D-value
- F0-value
- SAL
Correct Answer: D-value
Q10. The Z-value in thermal sterilization indicates:
- Time to reduce population by one log at a fixed temperature
- Temperature increase required to reduce D-value by a factor of ten
- Total heat delivered during a cycle
- Sterility assurance level achieved
Correct Answer: Temperature increase required to reduce D-value by a factor of ten
Q11. Which chemical sterilant is commonly used for low-temperature sterilization of heat-sensitive medical equipment by vapor?
- Ethylene oxide
- Hydrogen peroxide vapor
- Glutaraldehyde liquid immersion
- Saturated steam
Correct Answer: Hydrogen peroxide vapor
Q12. Which test is used to evaluate steam penetration in pre-vacuum autoclaves?
- Bowie-Dick test
- Geobacillus sterility test
- F0 test
- VHP validation strip
Correct Answer: Bowie-Dick test
Q13. For the sterilization of bulk heat-stable powders, which method is commonly applied?
- Filtration through 0.22 µm filter
- Ethylene oxide sterilization
- Dry heat sterilization
- Gamma irradiation at 5 kGy
Correct Answer: Dry heat sterilization
Q14. What is a common standardized dose for gamma irradiation sterilization of medical devices?
- 1 kGy
- 10 kGy
- 25 kGy
- 100 kGy
Correct Answer: 25 kGy
Q15. Which sterilization approach is best for removing endotoxins from parenteral solutions?
- Autoclaving at 121°C for 15 min
- Membrane filtration with depyrogenation by dry heat
- Ethylene oxide sterilization
- Gamma irradiation
Correct Answer: Membrane filtration with depyrogenation by dry heat
Q16. In sterilization validation, what does “overkill” approach mean?
- Using repeated low-level sterilization cycles
- Selecting a cycle that achieves at least a 12-log reduction of a resistant test organism
- Using chemical sterilants beyond expiration
- Applying sterilization to products that do not require it
Correct Answer: Selecting a cycle that achieves at least a 12-log reduction of a resistant test organism
Q17. Which indicator provides a direct measure of lethality by using highly resistant spores?
- Chemical indicator tape
- Biological indicator
- Integrating temperature probe
- Autoclave printout
Correct Answer: Biological indicator
Q18. What is the main limitation of using autoclaving for sterilizing certain pharmaceutical formulations?
- Insufficient kill of spores
- Chemical residues remain after autoclave
- Thermal degradation of heat-sensitive active ingredients
- Inability to sterilize glassware
Correct Answer: Thermal degradation of heat-sensitive active ingredients
Q19. Which method is preferred to sterilize oxygen-sensitive aqueous solutions?
- Steam autoclave
- Gamma irradiation
- Membrane filtration under aseptic conditions
- Dry heat oven
Correct Answer: Membrane filtration under aseptic conditions
Q20. Which indicator color change denotes exposure to steam sterilization conditions for a chemical indicator strip?
- No color change
- Random speckling
- Specific color change indicated by manufacturer (e.g., brown to black)
- Fluorescence under UV
Correct Answer: Specific color change indicated by manufacturer (e.g., brown to black)
Q21. Which sterilization method relies on alkylation of proteins and DNA and requires long aeration times to remove residues?
- Gamma irradiation
- Ethylene oxide sterilization
- Dry heat sterilization
- Hydrogen peroxide vapor
Correct Answer: Ethylene oxide sterilization
Q22. When sterilizing a biological safety cabinet HEPA filter, which method is commonly used?
- Autoclaving the filter in place
- Vaporized hydrogen peroxide decontamination
- Membrane filtration
- Immersion in glutaraldehyde
Correct Answer: Vaporized hydrogen peroxide decontamination
Q23. Which parameter is typically monitored continuously during a validated steam sterilization cycle?
- Relative humidity outside the chamber
- Chamber temperature, pressure and time
- Flow rate of autoclave vacuum pump
- Chemical residues on product
Correct Answer: Chamber temperature, pressure and time
Q24. Which sterilization technique is effective for endoscope flexible channels while avoiding heat damage?
- Dry heat sterilization
- High-level disinfection or low-temperature sterilization (e.g., EtO or peracetic acid)
- Autoclaving at 121°C
- Boiling
Correct Answer: High-level disinfection or low-temperature sterilization (e.g., EtO or peracetic acid)
Q25. What does a biological indicator showing growth after incubation indicate about the sterilization cycle?
- Cycle was successful and over-effective
- Sterilization failed or was insufficient
- Chemical indicator must be replaced
- Packaging integrity is perfect
Correct Answer: Sterilization failed or was insufficient
Q26. What is the main advantage of using vaporized hydrogen peroxide (VHP) for sterilization?
- High thermal penetration into dense loads
- Short cycle times, no toxic residues after aeration
- Leaves long-lasting antimicrobial residues
- Suitable for sterilizing liquids
Correct Answer: Short cycle times, no toxic residues after aeration
Q27. Which sterilization method is least likely to penetrate dense or multilayer packaging effectively?
- Gamma irradiation
- Ethylene oxide gas
- Saturated steam without proper penetration testing
- Vaporized hydrogen peroxide
Correct Answer: Saturated steam without proper penetration testing
Q28. Why is aeration required after ethylene oxide sterilization?
- To allow steam to condense
- To remove toxic ethylene oxide residues from materials
- To cool the sterilized load
- To sterilize packaging labels
Correct Answer: To remove toxic ethylene oxide residues from materials
Q29. Which sterilization process variable does the F0 value integrate for steam sterilization?
- Total microbial count before sterilization
- Time-equivalent at 121.1°C for a defined lethality
- Amount of chemical sterilant used
- Pore size of sterile filters
Correct Answer: Time-equivalent at 121.1°C for a defined lethality
Q30. In aseptic processing, what is the primary application of laminar flow hoods?
- Sterilizing products with dry heat
- Providing unidirectional clean air to protect the product from contamination
- Sterilizing instruments using steam
- Measuring microbial contamination in rooms
Correct Answer: Providing unidirectional clean air to protect the product from contamination
Q31. What is a common use of peracetic acid in pharmaceutical sterilization?
- Sterilizing large-volume parenteral solutions by filtration
- Automated endoscope reprocessor high-level disinfection
- Dry heat depyrogenation
- Gamma sterilization replacement for plastics
Correct Answer: Automated endoscope reprocessor high-level disinfection
Q32. Which of the following best describes a sterility test for a pharmaceutical product?
- Measurement of endotoxin concentration only
- Culturing a sample in suitable media to detect viable microorganisms
- Measuring residual sterilant levels
- Counting spores on filter membranes only
Correct Answer: Culturing a sample in suitable media to detect viable microorganisms
Q33. For dry heat sterilization, which temperature–time combination is commonly used for glassware depyrogenation?
- 121°C for 15 minutes
- 160°C for 2 hours
- 80°C for 30 minutes
- 37°C for 24 hours
Correct Answer: 160°C for 2 hours
Q34. Which microorganism is often used as a biological indicator for dry heat sterilization validation?
- Geobacillus stearothermophilus
- Bacillus pumilus or Bacillus subtilis spores
- Escherichia coli
- Staphylococcus aureus
Correct Answer: Bacillus pumilus or Bacillus subtilis spores
Q35. What is the purpose of prefiltration using a 0.45 µm filter before sterilizing by 0.22 µm filtration?
- To produce sterile air for laminar flow
- To remove large particulates and extend life of sterilizing filter
- To sterilize via chemical action
- To reduce endotoxin levels
Correct Answer: To remove large particulates and extend life of sterilizing filter
Q36. Which sterilization method is commonly used for final terminal sterilization of sealed, heat-stable parenteral preparations?
- Membrane filtration
- Steam sterilization (autoclave)
- Ethylene oxide
- Hydrogen peroxide vapor
Correct Answer: Steam sterilization (autoclave)
Q37. In sterilization validation, what is “bioburden”?
- Sterility Assurance Level target
- Initial population of viable microorganisms on product before sterilization
- Amount of residual sterilant on product
- Filter integrity value
Correct Answer: Initial population of viable microorganisms on product before sterilization
Q38. Which test assesses the integrity of sterilizing-grade membrane filters after filtration?
- Bubble point test
- F0 test
- Bowie-Dick test
- Biological indicator incubation
Correct Answer: Bubble point test
Q39. Which sterilization agent is used for cold sterilization of heat-sensitive biological materials and requires extended contact times in liquid form?
- Gamma irradiation
- Glutaraldehyde solution (high-level disinfectant/sterilant)
- Dry heat
- Autoclave steam
Correct Answer: Glutaraldehyde solution (high-level disinfectant/sterilant)
Q40. Which of the following is an advantage of radiation sterilization (gamma or electron beam)?
- No need for validation
- High temperature exposure increases potency
- Sterilizes in packaged state with good penetration for many materials
- Leaves safe chemical residues on products
Correct Answer: Sterilizes in packaged state with good penetration for many materials
Q41. Which cleaning/sterilization consideration is critical when choosing a sterilization method for a pharmaceutical container-closure system?
- Color of the label
- Compatibility of materials with chosen sterilant and packaging integrity
- Manufacturer’s logo placement
- Shipping route
Correct Answer: Compatibility of materials with chosen sterilant and packaging integrity
Q42. Which area classification relates to aseptic processing where sterile products are exposed and requires highest air quality?
- ISO Class 8
- ISO Class 7
- ISO Class 5 (Grade A)
- Non-classified area
Correct Answer: ISO Class 5 (Grade A)
Q43. What does a chemical indicator on a sterilization pack tell you?
- Definitive proof of sterility
- That specific physical conditions (e.g., temperature, steam) were met externally
- Microbial kill achieved
- Sterilant residual concentration
Correct Answer: That specific physical conditions (e.g., temperature, steam) were met externally
Q44. For aseptic filling of parenterals, which sterilization concept is essential for components entering the sterile zone?
- Use of contaminated seals to prevent leaks
- Sterilization and/or aseptic transfer (e.g., sterile filtration of liquids, terminal sterilization of closures or sterile barrier systems)
- Removal of all packaging before filling
- Using only dry heat for all components
Correct Answer: Sterilization and/or aseptic transfer (e.g., sterile filtration of liquids, terminal sterilization of closures or sterile barrier systems)
Q45. Which parameter is NOT directly part of steam sterilization cycle control?
- Temperature
- Pressure
- Time
- pH of sterilant
Correct Answer: pH of sterilant
Q46. What is the primary concern when using gamma irradiation on certain polymeric materials?
- Improved mechanical strength always
- Potential for polymer degradation or changes in material properties
- Unlimited shelf life extension
- Elimination of all chemical residues
Correct Answer: Potential for polymer degradation or changes in material properties
Q47. Which practice helps ensure sterility of final parenteral products during aseptic filling?
- Random door opening in cleanroom during filling
- Strict environmental monitoring and operator aseptic technique
- Minimizing cleaning cycles to save time
- Using unverified disinfectants
Correct Answer: Strict environmental monitoring and operator aseptic technique
Q48. Which sterilization method can inactivate prions least effectively and therefore is not recommended alone for prion decontamination?
- Autoclaving at 134°C for extended time is fully effective
- Standard autoclaving may be insufficient; specialized protocols needed
- Ethylene oxide is highly effective for prions
- Gamma irradiation reliably inactivates prions at low doses
Correct Answer: Standard autoclaving may be insufficient; specialized protocols needed
Q49. Which documentation is essential after each validated sterilization cycle in a pharmaceutical facility?
- Only a verbal confirmation
- Physical cycle printout, biological indicator results, and batch record entry
- Uncontrolled handwritten note
- No documentation required for terminal sterilization
Correct Answer: Physical cycle printout, biological indicator results, and batch record entry
Q50. Which factor most strongly affects the choice between filtration and terminal sterilization for a sterile drug product?
- Color preference of manufacturer
- Thermal and chemical stability of the drug and container-closure system
- Shipping cost
- Number of marketing approvals
Correct Answer: Thermal and chemical stability of the drug and container-closure system
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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