Merits and demerits of sterilization methods MCQs With Answer

Merits and demerits of sterilization methods MCQs With Answer provide B. Pharm students a focused review of sterilization techniques used in pharmaceutical manufacturing and laboratory practice. This concise, keyword-rich introduction highlights key sterilization methods — autoclave, dry heat, filtration, radiation, chemical sterilants, plasma — and examines their merits and demerits such as effectiveness against spores, material compatibility, validation challenges, and safety concerns. Understanding parameters like temperature, time, pressure, SAL, and indicators is essential for sterile product quality. These MCQs deepen comprehension of theory and practical selection of sterilization techniques for various pharmaceutical applications. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which sterilization method is most effective for inactivating bacterial spores and is commonly used for heat-stable laboratory glassware?

• Filtration through 0.22 μm membrane
• Autoclaving (moist heat under pressure)
• UV irradiation
• Ethylene oxide gas

Correct Answer: Autoclaving (moist heat under pressure)

Q2. What is a major disadvantage of dry heat sterilization compared to moist heat?

• Produces corrosive by-products
• Requires longer exposure time and higher temperature
• Leaves toxic residues
• Cannot sterilize glassware

Correct Answer: Requires longer exposure time and higher temperature

Q3. Which sterilization method is preferred for heat-sensitive pharmaceutical solutions?

• Steam autoclave
• Dry heat oven
• Membrane filtration (0.22 μm)
• Moist heat bath

Correct Answer: Membrane filtration (0.22 μm)

Q4. What is a primary demerit of ethylene oxide (EO) sterilization?

• Inability to penetrate packaging
• High temperatures required
• Toxic and potentially carcinogenic residues requiring aeration
• Poor efficacy against vegetative bacteria

Correct Answer: Toxic and potentially carcinogenic residues requiring aeration

Q5. Which indicator organism is commonly used as a biological indicator for validation of steam sterilization?

• Escherichia coli
• Bacillus stearothermophilus (Geobacillus stearothermophilus)
• Staphylococcus aureus
• Pseudomonas aeruginosa

Correct Answer: Bacillus stearothermophilus (Geobacillus stearothermophilus)

Q6. What advantage does gamma radiation sterilization offer for single-use medical devices?

• Leaves no residual radioactivity and penetrates packaging well
• Requires very high temperatures
• Produces toxic residues in polymers
• Is ineffective against spores

Correct Answer: Leaves no residual radioactivity and penetrates packaging well

Q7. Which sterilization method can denature proteins and is therefore unsuitable for many vaccines and biologics?

• Filtration
• Gamma irradiation
• Dry heat and moist heat at high temperature
• Low-temperature hydrogen peroxide plasma

Correct Answer: Dry heat and moist heat at high temperature

Q8. What is the main limitation of UV irradiation for sterilization in pharmaceutical settings?

• High penetration through opaque materials
• Limited surface penetration and shadowing effects
• Leaves toxic chemical residues
• Extremely long exposure times for spores

Correct Answer: Limited surface penetration and shadowing effects

Q9. Which sterilization method is most suitable for sterilizing air and aseptic processing environments?

• Autoclaving
• HEPA filtration and gaseous sterilants like hydrogen peroxide vapor
• Dry heat ovens
• Ethylene oxide for continuous air streams

Correct Answer: HEPA filtration and gaseous sterilants like hydrogen peroxide vapor

Q10. What is a key merit of membrane filtration sterilization?

• Excellent for sterilizing particulate suspensions
• Removes microorganisms without thermal damage to product
• Highly effective against endotoxins
• Can sterilize viscous, particle-laden fluids easily

Correct Answer: Removes microorganisms without thermal damage to product

Q11. Which parameter describes the time required at a given temperature to reduce a microbial population by one logarithmic cycle (90%)?

• Z-value
• D-value
• F0 value
• SAL

Correct Answer: D-value

Q12. What does SAL stand for and why is it important in sterilization?

• Standard Anthrax Level; to control spore-formers
• Sterility Assurance Level; indicates probability of a non-sterile unit after sterilization
• Steam Application Limit; limits on autoclave use
• Safety At Low-temperature; for cold sterilization

Correct Answer: Sterility Assurance Level; indicates probability of a non-sterile unit after sterilization

Q13. Which sterilization method is most appropriate for sterilizing surgical stainless-steel instruments?

• Ethylene oxide gas
• Autoclaving (steam sterilization)
• Membrane filtration
• Gamma radiation

Correct Answer: Autoclaving (steam sterilization)

Q14. What is a primary benefit of low-temperature hydrogen peroxide plasma sterilization?

• High-temperature operation
• Rapid cycle times and low residue levels for heat-sensitive materials
• Excellent penetration of dense loads
• Leaves long-lasting antimicrobial coating

Correct Answer: Rapid cycle times and low residue levels for heat-sensitive materials

Q15. Why is ethylene oxide often chosen for complex medical devices with lumens?

• It requires no aeration time
• It has excellent material compatibility with all polymers
• It penetrates packaging and long narrow lumens effectively
• It is non-toxic and leaves no residues

Correct Answer: It penetrates packaging and long narrow lumens effectively

Q16. What is a disadvantage of filtration sterilization for parenteral products?

• Can remove endotoxins effectively
• Not effective for cell-free solutions
• Membrane fouling and retention of product may occur
• Requires very high temperatures

Correct Answer: Membrane fouling and retention of product may occur

Q17. Which sterilization validation parameter represents the temperature increase needed to change the D-value by a factor of ten?

• D-value
• Z-value
• F0
• Q10

Correct Answer: Z-value

Q18. Which sterilization technique is commonly used for terminal sterilization of filled pharmaceutical vials when product stability allows?

• Membrane filtration
• Autoclaving or moist heat sterilization
• Ethylene oxide sterilization
• Ultraviolet irradiation of sealed vials

Correct Answer: Autoclaving or moist heat sterilization

Q19. What is F0 value used to express in sterilization processing?

• The number of filtration cycles needed
• Equivalent time in minutes at 121.1°C for moist heat sterilization lethality
• The salt concentration effect on sterilization
• The frequency of gamma irradiation cycles

Correct Answer: Equivalent time in minutes at 121.1°C for moist heat sterilization lethality

Q20. Which sterilant is effective at low temperatures and commonly used for heat-sensitive endoscopes but requires thorough aeration?

• Dry heat
• Hydrogen peroxide gas plasma
• Ethylene oxide
• Gamma radiation

Correct Answer: Ethylene oxide

Q21. Which sterilization method can degrade polymers and cause material embrittlement if improperly applied?

• Low-temperature plasma
• Gamma irradiation and high-dose electron beam
• Filtration
• Autoclaving at 121°C for 15 minutes

Correct Answer: Gamma irradiation and high-dose electron beam

Q22. What is a major advantage of radiation sterilization (gamma or e-beam) over ethylene oxide for single-use disposables?

• No need for long aeration to remove toxic residues
• Lower capital cost of equipment
• Requires high processing temperatures
• Unsuitable for packaged products

Correct Answer: No need for long aeration to remove toxic residues

Q23. Which sterilization indicator provides an immediate visual confirmation of exposure to sterilization conditions but not full proof of sterility?

• Biological indicator (spore test)
• Chemical indicator (color change tape)
• Endotoxin test
• Sterility test by culture

Correct Answer: Chemical indicator (color change tape)

Q24. What is a common chemical sterilant used for high-level disinfection of heat-sensitive medical instruments that must be rinsed off before use?

• Peracetic acid
• Dry heat
• Autoclaving
• Gamma radiation

Correct Answer: Peracetic acid

Q25. Which sterilization approach is most likely to inactivate prions effectively?

• Standard autoclave at 121°C for 15 minutes
• Routine chemical disinfectants
• Extended moist heat cycles at higher temperature and alkaline treatment
• Membrane filtration

Correct Answer: Extended moist heat cycles at higher temperature and alkaline treatment

Q26. What is a disadvantage of using peracetic acid for sterilization of medical devices?

• Poor antimicrobial activity
• Corrosive to certain metals and may require rinsing
• Leaves long-term toxic residues
• Requires temperatures above 200°C

Correct Answer: Corrosive to certain metals and may require rinsing

Q27. In sterile filtration, which pore size membrane is typically used to ensure removal of bacteria for pharmaceutical parenterals?

• 5 μm
• 0.45 μm
• 0.22 μm
• 1 μm

Correct Answer: 0.22 μm

Q28. Which sterilization method is least effective against bacterial spores?

• Autoclaving
• Dry heat at high temperature
• UV radiation at surface level
• Ethylene oxide gas

Correct Answer: UV radiation at surface level

Q29. What is a primary environmental concern with large-scale ethylene oxide sterilization facilities?

• Generation of greenhouse gases only
• Emission of toxic EO and ethylene chlorohydrin residues if not controlled
• Excessive use of water
• Noise pollution from autoclaves

Correct Answer: Emission of toxic EO and ethylene chlorohydrin residues if not controlled

Q30. Which sterilization validation test confirms actual microbial kill and is considered the gold standard?

• Chemical indicator color change
• Biological indicator with resistant spores
• Visual inspection of load
• pH indicator strip

Correct Answer: Biological indicator with resistant spores

Q31. Which sterilization parameter is commonly adjusted to achieve desired lethality when load mass or density varies?

• Membrane pore size
• Exposure time and temperature (or dose for radiation)
• pH of sterilant
• Type of packaging color

Correct Answer: Exposure time and temperature (or dose for radiation)

Q32. What is a key merit of autoclaving over dry heat for most biological waste?

• Autoclaving is slower but cheaper
• Autoclaving achieves sterilization at lower temperatures and shorter times due to moist heat lethality
• Autoclaving leaves toxic residues
• Dry heat sterilization is more penetrating

Correct Answer: Autoclaving achieves sterilization at lower temperatures and shorter times due to moist heat lethality

Q33. Why is terminal sterilization preferred over aseptic processing when feasible for a pharmaceutical product?

• Terminal sterilization is always cheaper
• Terminal sterilization provides higher assurance of sterility after product filling
• Aseptic processing uses no sterilization at all
• Terminal sterilization eliminates need for validation

Correct Answer: Terminal sterilization provides higher assurance of sterility after product filling

Q34. Which sterilization technique is commonly used to sterilize heat-labile ophthalmic solutions packaged in prefilled syringes?

• Autoclaving filled syringes
• Sterile filtration followed by aseptic filling
• Gamma irradiation of filled syringes
• Dry heat sterilization of filled syringes

Correct Answer: Sterile filtration followed by aseptic filling

Q35. Which sterilization method can be effective for decontaminating pharmaceutical cleanrooms and HVAC systems when used as vapor?

• Ethylene oxide vaporization
• Hydrogen peroxide vapor (vaporized hydrogen peroxide)
• Dry heat distribution
• Gamma irradiation of room air

Correct Answer: Hydrogen peroxide vapor (vaporized hydrogen peroxide)

Q36. What is a significant drawback of using high-dose gamma irradiation for some polymeric drug containers?

• Enhances clarity of polymers
• Causes polymer cross-linking or degradation affecting mechanical properties
• Generates heat damage similar to autoclave
• Leaves EO residues

Correct Answer: Causes polymer cross-linking or degradation affecting mechanical properties

Q37. Which sterilization approach is best for removing pyrogens (endotoxins) from water for injection systems?

• Standard 0.22 μm filtration
• Distillation and specific depyrogenation methods such as dry heat depyrogenation of glassware
• Autoclaving water for injection
• UV light exposure of bulk water

Correct Answer: Distillation and specific depyrogenation methods such as dry heat depyrogenation of glassware

Q38. What is one advantage of plasma sterilization over ethylene oxide for reusable medical devices?

• Long aeration times are required
• Plasma sterilization operates at low temperature and leaves minimal toxic residues
• It requires temperatures above 150°C
• Less effective against viruses

Correct Answer: Plasma sterilization operates at low temperature and leaves minimal toxic residues

Q39. Which sterilization method requires monitoring of chamber pressure, temperature, and steam quality to ensure efficacy?

• Gamma irradiation
• Autoclave (steam sterilization)
• Ethylene oxide sterilization
• Membrane filtration

Correct Answer: Autoclave (steam sterilization)

Q40. What is an important consideration when selecting a sterilization method for protein therapeutics?

• Proteins are unaffected by any sterilization method
• Choose non-thermal methods like filtration or aseptic processing to avoid denaturation
• Use dry heat to preserve activity
• Use high-dose gamma irradiation to ensure sterility

Correct Answer: Choose non-thermal methods like filtration or aseptic processing to avoid denaturation

Q41. Which of the following best describes a chemical indicator used in sterilization?

• A biological spore strip
• A color-change tape or strip that indicates exposure to a parameter like temperature or steam
• A sterility test by culture
• A measure of endotoxin levels

Correct Answer: A color-change tape or strip that indicates exposure to a parameter like temperature or steam

Q42. Why is validation of sterilization cycles critical in pharmaceutical production?

• Only to satisfy paperwork requirements
• To demonstrate consistent microbial lethality and product safety under defined conditions
• To reduce manufacturing speed
• Because sterilization rarely fails

Correct Answer: To demonstrate consistent microbial lethality and product safety under defined conditions

Q43. Which sterilization method is most suitable for sterilizing disposable plastic items that are sensitive to heat but compatible with radiation?

• Autoclave
• Dry heat
• Gamma irradiation
• Steam immersion

Correct Answer: Gamma irradiation

Q44. Which method is used to assess the efficacy of terminal sterilization processes by using a defined biological challenge?

• Use of chemical tape indicators only
• Use of biological indicators containing known spores and performing BI incubation
• Visual inspection of package integrity
• Measuring humidity in the sterilizer

Correct Answer: Use of biological indicators containing known spores and performing BI incubation

Q45. What is a common drawback of using peracetic acid sterilization for some implants and devices?

• Inability to inactivate bacteria
• Potential for corrosive effects and material compatibility issues
• Requires extremely high temperatures
• Generates radioactive waste

Correct Answer: Potential for corrosive effects and material compatibility issues

Q46. Which sterilization parameter is critical when sterilizing powders in a laboratory using dry heat?

• Membrane pore size
• Exposure time and temperature to ensure penetration and lethality without product alteration
• Gas concentration
• UV lamp wattage

Correct Answer: Exposure time and temperature to ensure penetration and lethality without product alteration

Q47. Which sterilization technique is favored for decontaminating culture media in large batches when the media is heat-stable?

• Filtration through 0.22 μm for large viscous batches
• Autoclaving media in bulk (moist heat sterilization)
• Gamma irradiation of liquid media
• Dry heat sterilization at 200°C

Correct Answer: Autoclaving media in bulk (moist heat sterilization)

Q48. What is the principal reason UV sterilization is used primarily for surface and air disinfection rather than sterilizing packaged products?

• UV penetrates deeply through plastics
• UV has limited penetration and is blocked by opaque or packaged items
• UV creates long-lived residues
• UV is effective against spores deep in materials

Correct Answer: UV has limited penetration and is blocked by opaque or packaged items

Q49. When a sterilization process yields a Sterility Assurance Level (SAL) of 10^-6, what does that imply?

• One in a thousand items may be non-sterile
• One in a million probability that an item is non-sterile after the process
• The load is completely free of prions
• The process is only effective against vegetative bacteria

Correct Answer: One in a million probability that an item is non-sterile after the process

Q50. Which combination best describes an ideal sterilization method for a heat-sensitive, protein-containing injectable product?

• High-temperature dry heat; long exposure
• Membrane filtration with aseptic filling and validated sterile environment
• Autoclave filled product at 134°C
• Gamma irradiation of filled vials

Correct Answer: Membrane filtration with aseptic filling and validated sterile environment

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