Evaluation of efficiency of sterilization methods MCQs With Answer

Evaluation of efficiency of sterilization methods MCQs With Answer

Understanding the evaluation of efficiency of sterilization methods is essential for B.Pharm students preparing for practical and regulatory roles. This introduction covers key concepts such as sterilization validation, sterilant types (autoclave, dry heat, filtration, radiation, ethylene oxide), sterilization indicators, D-value and Z-value, log reduction, sterility assurance level (SAL) and biological indicators. These sterilization methods MCQs focus on mechanism, parameters, monitoring, and pharmaceutical compatibility to strengthen learning for exams and quality control. Targeted practice improves decision-making in aseptic processing, terminal sterilization, and validation protocols. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which parameter directly indicates the time required to reduce a microbial population by 90% at a specified temperature?

• D-value (decimal reduction time)
• Z-value
• F0 value
• SAL (sterility assurance level)

Correct Answer: D-value (decimal reduction time)

Q2. The Z-value in sterilization denotes which of the following?

• The temperature increase required to reduce D-value by one log
• The exposure time at reference temperature for complete sterilization
• The initial microbial load of the sample
• The oxygen concentration in gas sterilization

Correct Answer: The temperature increase required to reduce D-value by one log

Q3. Which biological indicator organism is most commonly used to monitor moist heat (steam) sterilization?

• Geobacillus stearothermophilus
• Brevundimonas diminuta
• Bacillus subtilis var. niger (Bacillus atrophaeus)
• Staphylococcus aureus

Correct Answer: Geobacillus stearothermophilus

Q4. Which indicator is specifically designed to detect inadequate air removal in pre-vacuum steam sterilizers?

• Bowie-Dick test pack
• Biological indicator with Bacillus pumilus
• Chemical integrator for EO
• Helix test for filtration

Correct Answer: Bowie-Dick test pack

Q5. For sterilization validation, “overkill” approach typically refers to:

• Applying conditions that achieve a very high log reduction to ensure sterility
• Using a lower temperature for shorter time to preserve product quality
• Sterilizing only a subset of the load
• Relying solely on chemical indicators without biological indicators

Correct Answer: Applying conditions that achieve a very high log reduction to ensure sterility

Q6. Which sterilization method is most suitable for heat-sensitive parenteral solutions?

• Membrane filtration (0.22 µm)
• Autoclaving at 121°C
• Dry-heat sterilization at 160°C
• Gamma irradiation

Correct Answer: Membrane filtration (0.22 µm)

Q7. Which organism is commonly used as a biological indicator for ethylene oxide (EO) sterilization?

• Bacillus atrophaeus (formerly B. subtilis var. niger)
• Geobacillus stearothermophilus
• Brevundimonas diminuta
• Pseudomonas aeruginosa

Correct Answer: Bacillus atrophaeus (formerly B. subtilis var. niger)

Q8. What does SAL 10^-6 signify in sterilization assurance?

• Probability of one viable microorganism in a million sterilized items
• Six-log increase in microbial count
• Sterilization achieved at 10^6 seconds
• Residual EO concentration of 10^-6 mg/kg

Correct Answer: Probability of one viable microorganism in a million sterilized items

Q9. Which parameter summarizes cumulative lethal effect of moist heat sterilization normalized to 121.1°C?

• F0 value
• D121 value
• Z-value
• K-value

Correct Answer: F0 value

Q10. Which test microorganism is typically used to challenge 0.2 µm sterilizing filters?

• Brevundimonas diminuta
• Escherichia coli
• Staphylococcus epidermidis
• Geobacillus stearothermophilus

Correct Answer: Brevundimonas diminuta

Q11. What is the primary mechanism of microbial inactivation by moist heat?

• Protein denaturation and coagulation
• Oxidative DNA damage
• Membrane lipid peroxidation
• Desiccation of cellular contents

Correct Answer: Protein denaturation and coagulation

Q12. Which sterilization method requires validation of aeration phase to remove toxic residues?

• Ethylene oxide (EO) sterilization
• Steam autoclave sterilization
• Dry heat sterilization
• Membrane filtration

Correct Answer: Ethylene oxide (EO) sterilization

Q13. What does a chemical integrator indicate when used in sterilization cycles?

• That the process parameters (time/temperature/chemical) were potentially met
• Guaranteed sterility of the load
• Biological inactivation has been confirmed
• Filter integrity has passed

Correct Answer: That the process parameters (time/temperature/chemical) were potentially met

Q14. Which sterilization method is most appropriate for heat-stable, moisture-sensitive powders and glassware?

• Dry heat sterilization
• Steam sterilization
• Membrane filtration
• Ethylene oxide sterilization

Correct Answer: Dry heat sterilization

Q15. In assessing sterilization efficiency, “log reduction” refers to:

• The factor by which the microbial population is reduced on a log10 scale
• The increase of contaminant logs during sterilization
• The pressure change inside an autoclave
• The pH change of culture media

Correct Answer: The factor by which the microbial population is reduced on a log10 scale

Q16. Which parameter would you adjust to shorten the time required for moist heat sterilization while maintaining lethality?

• Increase temperature
• Decrease pressure
• Decrease humidity
• Reduce steam quality

Correct Answer: Increase temperature

Q17. Which method is most effective for sterilizing single-use syringes en masse while preserving integrity?

• Ethylene oxide (EO) sterilization
• Hot-air oven
• Autoclaving assembled syringes filled with liquid
• Membrane filtration

Correct Answer: Ethylene oxide (EO) sterilization

Q18. What is the main disadvantage of gamma irradiation for sterilizing pharmaceuticals?

• Potential radiolytic degradation of some drugs
• Inability to penetrate packaging
• Leaves toxic residues requiring aeration
• Requires high moisture content

Correct Answer: Potential radiolytic degradation of some drugs

Q19. During filter validation, which test confirms the filter’s integrity after use?

• Bubble point or diffusion test
• Bacterial endotoxin test
• Biological indicator incubation
• Color change chemical indicator

Correct Answer: Bubble point or diffusion test

Q20. Which factor most significantly affects penetration of steam into porous loads?

• Presence of trapped air and preconditioning vacuum cycles
• Chemical compatibility of load materials
• Relative humidity outside the sterilizer room
• Ambient light level during sterilization

Correct Answer: Presence of trapped air and preconditioning vacuum cycles

Q21. Which sterilization indicator provides the most definitive evidence of lethality?

• Biological indicator
• Class 1 process indicator (tape)
• Indicator label placed outside packaging
• Temperature chart recorder trace

Correct Answer: Biological indicator

Q22. What is the typical reference temperature used for calculating F0 in moist heat sterilization?

• 121.1°C
• 100°C
• 134°C
• 160°C

Correct Answer: 121.1°C

Q23. Which sterilant acts primarily by alkylation of nucleic acids and proteins?

• Ethylene oxide
• Steam
• Dry heat
• Gamma irradiation

Correct Answer: Ethylene oxide

Q24. Which is a critical limitation of using glutaraldehyde as a liquid sterilant in pharmaceutical settings?

• Long exposure times and potential toxicity/residue concerns
• Ineffectiveness against vegetative bacteria
• Requires high temperatures above 121°C
• Cannot sterilize metal instruments

Correct Answer: Long exposure times and potential toxicity/residue concerns

Q25. What is the primary test to confirm sterility of a batch after sterilization according to pharmacopeial methods?

• Sterility test using membrane filtration or direct inoculation
• Endotoxin test (LAL) alone
• Visual inspection for particulates
• Assay of active pharmaceutical ingredient (API)

Correct Answer: Sterility test using membrane filtration or direct inoculation

Q26. Which of the following best describes the “kill curve” used in sterilization evaluation?

• Graph of surviving organisms vs. time under defined conditions
• Temperature vs. pressure chart for autoclave
• Moisture uptake by packaging over time
• Concentration of residue vs. time post-EO

Correct Answer: Graph of surviving organisms vs. time under defined conditions

Q27. Which sterilization method requires monitoring of humidity as a critical parameter for efficacy?

• Moist heat (steam) sterilization
• Dry heat sterilization
• Gamma irradiation
• Membrane filtration

Correct Answer: Moist heat (steam) sterilization

Q28. Endotoxin (pyrogen) removal for glassware is best achieved by which process?

• Depyrogenation by dry heat at 250°C for 30 minutes (or validated conditions)
• Steam autoclaving at 121°C for 15 minutes
• Membrane filtration through 0.22 µm
• Ethylene oxide sterilization

Correct Answer: Depyrogenation by dry heat at 250°C for 30 minutes (or validated conditions)

Q29. Which chemical sterilant is commonly used for low-temperature sterilization of endoscopes but requires long contact times?

• Glutaraldehyde
• Hydrogen peroxide gas plasma
• Ozone
• Autoclave steam

Correct Answer: Glutaraldehyde

Q30. Which parameter is NOT directly used to evaluate sterilization efficiency?

• Color of packaging ink
• D-value
• Log reduction
• Biological indicator outcome

Correct Answer: Color of packaging ink

Q31. What is the main advantage of hydrogen peroxide vapor or plasma sterilization compared to ethylene oxide?

• No toxic residues and shorter cycle times
• Better penetration into deep-packed loads
• Higher compatibility with all plastics
• Lower equipment capital cost

Correct Answer: No toxic residues and shorter cycle times

Q32. When validating a sterilization cycle, “worst-case” load selection means:

• Choosing items/conditions most difficult to sterilize to demonstrate robustness
• Selecting the smallest, simplest load to ensure pass
• Using empty chamber validation only
• Running cycles without biological indicators

Correct Answer: Choosing items/conditions most difficult to sterilize to demonstrate robustness

Q33. Which measurement quantifies reduction in viable microorganisms per unit time under fixed conditions?

• Death rate constant or k-value (related to D-value)
• Z-value
• SAL
• Bowie-Dick value

Correct Answer: Death rate constant or k-value (related to D-value)

Q34. What is the recommended pore size for sterilizing-grade membrane filters used for parenteral solutions?

• 0.22 µm
• 0.45 µm
• 1.2 µm
• 5 µm

Correct Answer: 0.22 µm

Q35. Which test helps detect gross air leaks and steam penetration problems in a steam sterilizer chamber?

• Bowie-Dick test or equivalent
• Endotoxin test
• Bubble point test
• pH indicator strip

Correct Answer: Bowie-Dick test or equivalent

Q36. Which factor tends to decrease the D-value of a microorganism during moist heat sterilization?

• Increased temperature
• Lower steam quality
• Encapsulation in protective matrix
• Increased initial bioburden

Correct Answer: Increased temperature

Q37. For gamma irradiation validation, which parameter is critical for dose mapping?

• Absorbed dose distribution within product and packaging
• Autoclave cycle vacuum level
• Bubble point across filter membrane
• Concentration of EO gas

Correct Answer: Absorbed dose distribution within product and packaging

Q38. Which statement about membrane filtration sterilization is TRUE?

• It physically removes microorganisms but does not inactivate endotoxins
• It kills all microorganisms by heat generated across the filter
• It sterilizes by chemical reaction with filter material
• 0.45 µm filters are recommended for parenterals

Correct Answer: It physically removes microorganisms but does not inactivate endotoxins

Q39. What is a principal concern when sterilizing biological products (e.g., vaccines) by terminal methods?

• Loss of biological activity or denaturation of the product
• Insufficient removal of endotoxin by autoclave
• Excessive filtration pore size
• Difficulty in using Bowie-Dick test

Correct Answer: Loss of biological activity or denaturation of the product

Q40. Which monitoring device gives continuous record of temperature and pressure during autoclave cycles?

• Data logger or chart recorder
• Class 1 chemical indicator tape
• Bacterial endotoxin test device
• Bubble point tester

Correct Answer: Data logger or chart recorder

Q41. Which sterilization method is most appropriate for sterilizing heat-labile ophthalmic solutions?

• Filtration through 0.22 µm sterilizing-grade filters
• Dry heat sterilization at 180°C
• Steam autoclaving
• Gamma irradiation of filled vials

Correct Answer: Filtration through 0.22 µm sterilizing-grade filters

Q42. What is the role of a biological indicator strip after sterilization?

• To demonstrate whether a known resistant microorganism has been inactivated
• To act as a chemical time-temperature integrator only
• To measure residual sterilant concentration
• To test the filter integrity

Correct Answer: To demonstrate whether a known resistant microorganism has been inactivated

Q43. Which sterilization parameter is especially critical for effective EO sterilization besides EO concentration?

• Relative humidity and temperature during exposure
• Autoclave vacuum depth
• Bubble point pressure of filters
• Gamma dose rate

Correct Answer: Relative humidity and temperature during exposure

Q44. How does relative humidity affect steam sterilization efficiency?

• Condensation (moisture) facilitates heat transfer and microbial inactivation
• Higher humidity always prevents sterilization
• Humidity is irrelevant in steam sterilization
• Lower humidity increases protein denaturation efficiency

Correct Answer: Condensation (moisture) facilitates heat transfer and microbial inactivation

Q45. Which concept describes the resistance of microorganisms to a sterilization process quantified by the time or dose to reduce population by one log?

• D-value
• SAL
• Bowie-Dick index
• Bubble point

Correct Answer: D-value

Q46. Which sterilization method would be least suitable for sterility assurance of live cell therapy products?

• Terminal heat-based sterilization (autoclave or dry heat)
• Validated aseptic processing with filtration
• Low-temperature gas plasma for some components
• Controlled aseptic fill-finish with closed systems

Correct Answer: Terminal heat-based sterilization (autoclave or dry heat)

Q47. Which test is recommended to demonstrate removal of bacterial endotoxins from water for injection (WFI)?

• Limulus Amebocyte Lysate (LAL) endotoxin test
• Sterility test only
• Bowie-Dick test
• Filter bubble point test

Correct Answer: Limulus Amebocyte Lysate (LAL) endotoxin test

Q48. Which of the following best describes a biological indicator result after incubation showing growth?

• The sterilization cycle failed to achieve required lethality
• The sterilization cycle was successful and product is sterile
• Chemical indicators always override BI results
• The data logger must have malfunctioned

Correct Answer: The sterilization cycle failed to achieve required lethality

Q49. What is the purpose of a process challenge device (PCD) in sterilizer qualification?

• To simulate the most difficult-to-sterilize condition within a real load
• To measure EO residuals in product
• To record autoclave temperature only
• To filter parenteral solutions during sterilization

Correct Answer: To simulate the most difficult-to-sterilize condition within a real load

Q50. Which documentation element is essential after sterilization validation for regulatory compliance?

• Validation protocol, report, routine monitoring records, and change control documentation
• Only a single biological indicator pass report is sufficient
• Informal notes without signatures
• Only photographic evidence of equipment

Correct Answer: Validation protocol, report, routine monitoring records, and change control documentation

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com