Sterility indicators MCQs With Answer is an essential study resource for B.Pharm students preparing for practical exams and pharmaceutical quality assurance. This concise guide covers chemical indicators, biological indicators (spore strips), integrators, Bowie-Dick tests, and physical monitoring parameters used in autoclave, dry heat, ethylene oxide and radiation sterilization. Emphasis is on sterilization validation, sterility assurance level (SAL), D-value/Z-value concepts, indicator placement, incubation protocols and interpretation of results. Practicing these targeted MCQs will strengthen your conceptual understanding and exam readiness in sterility monitoring and regulatory compliance. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary purpose of a biological indicator in sterilization?
- To measure temperature directly inside the chamber
- To indicate presence of moisture
- To verify the lethality of the sterilization cycle using resistant spores
- To calibrate pressure gauges
Correct Answer: To verify the lethality of the sterilization cycle using resistant spores
Q2. Which organism is most commonly used as a biological indicator for steam sterilization (autoclave)?
- Bacillus subtilis
- Geobacillus stearothermophilus
- Bacillus atrophaeus
- Escherichia coli
Correct Answer: Geobacillus stearothermophilus
Q3. What does a chemical indicator typically respond to in sterilization processes?
- Microbial contamination
- Change in pH of the product
- Specific process parameters like temperature, steam, or time
- Radiation dose in greys
Correct Answer: Specific process parameters like temperature, steam, or time
Q4. The Bowie-Dick test is designed to detect which critical issue in a steam sterilizer?
- Insufficient temperature
- Air removal and steam penetration
- Low radiation dose
- Ethylene oxide concentration
Correct Answer: Air removal and steam penetration
Q5. What does SAL 10^-6 represent in sterilization terminology?
- The sterilization temperature in kelvin
- A probability of one viable microorganism in one million sterilized items
- The cycle duration in minutes
- The dose of radiation in megarads
Correct Answer: A probability of one viable microorganism in one million sterilized items
Q6. Which indicator gives a clear visual color change on exposure to the sterilization process but does not prove sterility?
- Biological indicator
- Chemical indicator
- Radiation dosimeter
- Microbial culture plate
Correct Answer: Chemical indicator
Q7. For ethylene oxide sterilization, which biological indicator organism is commonly used?
- Geobacillus stearothermophilus
- Pseudomonas aeruginosa
- Bacillus atrophaeus
- Staphylococcus aureus
Correct Answer: Bacillus atrophaeus
Q8. What is an integrator in sterilization monitoring?
- A device that integrates electrical load of a sterilizer
- A chemical indicator that responds to multiple parameters to approximate microbial inactivation
- A microbiology incubator
- A pressure relief valve
Correct Answer: A chemical indicator that responds to multiple parameters to approximate microbial inactivation
Q9. Which physical parameter is NOT directly monitored during steam sterilization?
- Temperature
- Pressure
- Time
- Microbial growth
Correct Answer: Microbial growth
Q10. What does the D-value represent in sterilization kinetics?
- The decimal dilution required for sterility testing
- The time required at a specific temperature to reduce the microbial population by 90%
- The dose of radiation needed to sterilize a product
- The density of spores in a biological indicator
Correct Answer: The time required at a specific temperature to reduce the microbial population by 90%
Q11. Which test is recommended daily for steam sterilizers to ensure proper vacuum and air removal?
- Biological indicator incubation
- Bowie-Dick test
- Radiation dosimetry
- Endotoxin test
Correct Answer: Bowie-Dick test
Q12. After placing a biological indicator in a sterilization load, what is the standard next step?
- Immediate visual inspection only
- Incubation of the BI to check for growth following manufacturer’s instructions
- Throwing away the BI
- Measuring chamber pressure
Correct Answer: Incubation of the BI to check for growth following manufacturer’s instructions
Q13. Which sterilization method requires monitoring of humidity as a critical parameter?
- Dry heat sterilization
- Steam sterilization
- Gamma irradiation
- Filtration
Correct Answer: Steam sterilization
Q14. What is the function of a process challenge device (PCD)?
- To challenge the compressor of the sterilizer
- To act as a surrogate load designed to be the most difficult to sterilize in a given load
- To serve as a chemical integrator
- To measure radiation dose
Correct Answer: To act as a surrogate load designed to be the most difficult to sterilize in a given load
Q15. Which indicator type is used to monitor radiation sterilization dose?
- Chemical steam tape
- Radiation dosimeters (e.g., radiochromic film)
- Biological spore strips for heat
- Bowie-Dick sheets
Correct Answer: Radiation dosimeters (e.g., radiochromic film)
Q16. In a sterility assurance program, what is the significance of the Z-value?
- The number of spores on a BI
- The temperature change needed to change the D-value by a factor of ten
- The incubation period for BIs
- The sterilizer cycle identification number
Correct Answer: The temperature change needed to change the D-value by a factor of ten
Q17. Which of the following is TRUE about biological indicators?
- They provide immediate results after sterilization
- They directly measure surviving microorganisms after the cycle by incubation
- They are only used for radiation sterilization
- They cannot be used in ethylene oxide cycles
Correct Answer: They directly measure surviving microorganisms after the cycle by incubation
Q18. What is the recommended placement of biological indicators within a sterilizer load?
- Only at the door of the chamber
- At the most challenging locations to sterilize, such as the center of the load or within hollow instruments
- Only on the top rack
- Always outside the load for convenience
Correct Answer: At the most challenging locations to sterilize, such as the center of the load or within hollow instruments
Q19. How does a Type 1 chemical indicator differ from a Type 5 integrator?
- Type 1 detects biological growth; Type 5 measures pressure
- Type 1 is an emulating indicator for all parameters; Type 5 responds only to one parameter
- Type 1 is a process indicator that shows exposure to one parameter; Type 5 is an integrating indicator responding to multiple parameters approximating BI performance
- They are the same and interchangeable
Correct Answer: Type 1 is a process indicator that shows exposure to one parameter; Type 5 is an integrating indicator responding to multiple parameters approximating BI performance
Q20. Which spore strip incubation result indicates a successful sterilization when using a BI?
- Color change indicating microbial growth
- Turbidity in media showing growth
- No growth/turbidity after the specified incubation period
- Immediate fluorescence under UV light
Correct Answer: No growth/turbidity after the specified incubation period
Q21. For validating an autoclave, what is the purpose of performing a biological indicator test on an empty chamber (overkill test)?
- To reduce steam usage
- To confirm sterilizer mechanics without load effect
- To save biological indicators
- To test packaging integrity
Correct Answer: To confirm sterilizer mechanics without load effect
Q22. Which indicator is most appropriate to detect real-time failure during a sterilization cycle?
- Biological indicator after incubation
- Chemical process indicator (e.g., autoclave tape)
- Radiation dosimeter read post-process
- Endotoxin assay
Correct Answer: Chemical process indicator (e.g., autoclave tape)
Q23. What does a Type 4 chemical indicator respond to?
- Only time
- Combination of parameters such as time and temperature but not steam presence
- Radiation dose only
- Microbial viability
Correct Answer: Combination of parameters such as time and temperature but not steam presence
Q24. During EO (ethylene oxide) sterilization, residual EO levels are monitored because:
- EO increases sterility assurance if residuals are high
- EO is toxic and residues must be within safe limits for patient use
- EO residues indicate bacterial contamination
- EO residues accelerate packaging degradation
Correct Answer: EO is toxic and residues must be within safe limits for patient use
Q25. Which of the following is a limitation of chemical indicators compared to biological indicators?
- CIs are more expensive than BIs
- CIs cannot detect actual microbial survival; they only indicate exposure to process conditions
- CIs require incubation time to show results
- CIs measure sterility assurance level directly
Correct Answer: CIs cannot detect actual microbial survival; they only indicate exposure to process conditions
Q26. What is the typical incubation temperature for Geobacillus stearothermophilus biological indicators used in steam sterilization?
- 37°C
- 55–60°C
- 22–25°C
- 4°C
Correct Answer: 55–60°C
Q27. Which practice improves the reliability of sterility monitoring in routine production?
- Using only chemical indicators
- Random placement of BIs without documentation
- Regular use of both biological indicators and chemical integrators with documented placement and results
- Ignoring expired BIs
Correct Answer: Regular use of both biological indicators and chemical integrators with documented placement and results
Q28. What is a false negative when interpreting a biological indicator result?
- Indicator shows growth when sterilization was successful
- Indicator shows no growth despite sterilization failure
- Indicator tape color changes correctly
- BI incubates at the wrong temperature
Correct Answer: Indicator shows no growth despite sterilization failure
Q29. Which statement best describes a process indicator (Type 2)?
- It confirms sterility by killing spores
- It indicates whether the package has been exposed to a sterilization process
- It measures exact temperature inside product packaging
- It is used to measure endotoxin levels
Correct Answer: It indicates whether the package has been exposed to a sterilization process
Q30. In radiation sterilization, what is the common target SAL for single-use medical devices?
- SAL 10^0
- SAL 10^-3
- SAL 10^-6
- SAL 10^6
Correct Answer: SAL 10^-6
Q31. Which control is essential before relying on biological indicator results for batch release?
- Calibration of incubator and temperature verification during incubation
- Measuring humidity in the laboratory
- Checking color of autoclave tape only
- Running the sterilizer empty
Correct Answer: Calibration of incubator and temperature verification during incubation
Q32. Which type of sterilization is most affected by product packaging permeability?
- Gamma irradiation
- Autoclave steam sterilization and ethylene oxide sterilization
- Dry heat sterilization only
- Filtration sterilization
Correct Answer: Autoclave steam sterilization and ethylene oxide sterilization
Q33. What does a biological indicator negative control check for?
- That the sterilizer reached temperature
- That the BI and incubation system are capable of supporting growth when not sterilized
- That chemical indicators are functioning
- That sterile product is free of endotoxins
Correct Answer: That the BI and incubation system are capable of supporting growth when not sterilized
Q34. Which factor does NOT affect the D-value of a microorganism?
- Type of microorganism
- Sterilization temperature
- Matrix or environment surrounding the organism
- Color of the biological indicator label
Correct Answer: Color of the biological indicator label
Q35. What is the role of a steam probe or thermocouple in sterilization validation?
- To add steam to the chamber
- To measure internal product/core temperature for cycle mapping and validation
- To incubate biological indicators
- To sterilize small tools
Correct Answer: To measure internal product/core temperature for cycle mapping and validation
Q36. Why are biological indicators incubated for a defined time after sterilization?
- To allow color tapes to dry
- To permit any surviving spores to germinate and grow so survival can be detected
- To cool down the indicator
- To sterilize the BI further
Correct Answer: To permit any surviving spores to germinate and grow so survival can be detected
Q37. Which statement is correct about dry heat sterilization indicators?
- Geobacillus stearothermophilus is ideal for dry heat
- Bacillus atrophaeus is commonly used as a BI for dry heat sterilization
- Chemical integrators are never used for dry heat
- Dry heat is unaffected by packaging
Correct Answer: Bacillus atrophaeus is commonly used as a BI for dry heat sterilization
Q38. What is the most important reason to document sterility indicator results in a quality system?
- For aesthetic record keeping
- To provide traceability, evidence of compliance and ability to investigate failures
- To increase the cost of production
- To train new operators only
Correct Answer: To provide traceability, evidence of compliance and ability to investigate failures
Q39. Which combination best describes a Type 5 indicator’s intended use?
- Single-parameter, non-integrating, for EO only
- Integrator designed to react to a full range of sterilization variables and approximate the response of BIs across many cycles
- Used only for packaging integrity tests
- Biological spore-based indicator for radiation
Correct Answer: Integrator designed to react to a full range of sterilization variables and approximate the response of BIs across many cycles
Q40. Which parameter is critical to monitor specifically in an ethylene oxide sterilization cycle?
- Sterilizer door color
- Vacuum level, humidity, EO concentration, temperature and exposure time
- Gamma dose only
- Drying oven speed
Correct Answer: Vacuum level, humidity, EO concentration, temperature and exposure time
Q41. What is a common cause of false positive growth when incubating biological indicators?
- Proper operator technique
- Contamination during handling or incubation
- Using an expired autoclave cycle
- Sterilizer achieving higher than required temperature
Correct Answer: Contamination during handling or incubation
Q42. How often should biological indicators be used for routine sterilization monitoring in a pharmaceutical production setting? (General expectation)
- Never, they are optional
- At least weekly or with each critical load depending on SOPs and regulations
- Only once during equipment installation
- Only in case of visible failure
Correct Answer: At least weekly or with each critical load depending on SOPs and regulations
Q43. What is the main advantage of using rapid biological indicators (RBIs)?
- They require no incubation
- They offer faster detection of surviving spores compared to conventional BIs, reducing turnaround time
- They replace chemical indicators completely
- They measure pressure
Correct Answer: They offer faster detection of surviving spores compared to conventional BIs, reducing turnaround time
Q44. Which of the following would invalidate a biological indicator result?
- Following manufacturer’s incubation time precisely
- Using a BI past its expiration date
- Recording results in the logbook
- Placing BI in the most challenging location
Correct Answer: Using a BI past its expiration date
Q45. In process validation, what does the term ‘overkill method’ imply?
- Using fewer spores to save costs
- Applying a sterilization cycle significantly harsher than needed to ensure inactivation of all microorganisms
- Avoiding the use of biological indicators
- Sterilizing only the outer packaging
Correct Answer: Applying a sterilization cycle significantly harsher than needed to ensure inactivation of all microorganisms
Q46. What is the correct action if a biological indicator shows growth after a production sterilization cycle?
- Release the batch immediately
- Quarantine the affected lot, investigate the cause, and perform a root-cause analysis before any release
- Change the BI brand and ignore results
- Only re-run a chemical indicator
Correct Answer: Quarantine the affected lot, investigate the cause, and perform a root-cause analysis before any release
Q47. Which statement best explains why spore-forming bacteria are used in biological indicators?
- Spores are less resistant than vegetative cells
- Spores are highly resistant and provide a conservative challenge to the sterilization process
- Spores change color faster for reading
- Spores are easier to grow at room temperature
Correct Answer: Spores are highly resistant and provide a conservative challenge to the sterilization process
Q48. Which monitoring device would you choose to validate steam penetration into lumen devices?
- Radiation dosimeter
- BI placed inside the lumen or a PCD designed for lumens
- Only autoclave tape on the outside
- Endotoxin strip test
Correct Answer: BI placed inside the lumen or a PCD designed for lumens
Q49. What is the purpose of a growth promotion test for biological indicators?
- To sterilize the BI before use
- To confirm that the incubation media and BI can support microbial growth if spores survive
- To calibrate the autoclave
- To measure chemical residue
Correct Answer: To confirm that the incubation media and BI can support microbial growth if spores survive
Q50. Which regulatory concept requires documentation of sterility monitoring, validation data, and corrective actions in pharmaceutical manufacturing?
- Good Distribution Practice (GDP)
- Good Manufacturing Practice (GMP)
- Patent law
- Trademark regulation
Correct Answer: Good Manufacturing Practice (GMP)
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