Sterility testing of sterile pharmaceutical products (IP/BP/USP) MCQs With Answer is an essential review for B. Pharm students preparing for exams and quality control roles. This concise guide covers sterility test principles, IP/BP/USP requirements, membrane filtration and direct inoculation methods, incubation conditions, media selection, growth promotion, validation, handling bacteriostatic products, and environmental monitoring. Keywords included: sterility testing, sterile pharmaceutical products, IP, BP, USP, membrane filtration, direct inoculation, validation, and microbiological quality. These MCQs reinforce critical concepts used in aseptic processing, regulatory compliance, and batch release decisions. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary objective of sterility testing of sterile pharmaceutical products?
- To determine chemical purity
- To detect viable microorganisms in the product
- To measure endotoxin levels
- To assess physical stability
Correct Answer: To detect viable microorganisms in the product
Q2. Which two compendial methods are primarily used for sterility testing?
- Chromatography and ELISA
- Direct inoculation and membrane filtration
- PCR and flow cytometry
- Gravimetric and titration methods
Correct Answer: Direct inoculation and membrane filtration
Q3. What is the standard incubation period for compendial sterility tests (IP/BP/USP)?
- 7 days
- 10 days
- 14 days
- 30 days
Correct Answer: 14 days
Q4. Which medium is commonly used for detection of aerobic bacteria in sterility testing?
- Fluid Thioglycollate Medium (FTM)
- Sabouraud Dextrose Agar
- Luria-Bertani Broth
- Peptone Water
Correct Answer: Fluid Thioglycollate Medium (FTM)
Q5. Which incubation temperature is typically used for Fluid Thioglycollate Medium in sterility testing?
- 2–8°C
- 20–25°C
- 30–35°C
- 50–55°C
Correct Answer: 30–35°C
Q6. For the medium used to detect fungi and some bacteria (e.g., SCDM/TSB), what is the usual incubation temperature?
- 0–10°C
- 20–25°C
- 37–40°C
- 45–50°C
Correct Answer: 20–25°C
Q7. What pore size is standard for membrane filtration in sterility testing?
- 0.1 µm
- 0.22 µm
- 0.45 µm
- 1.2 µm
Correct Answer: 0.45 µm
Q8. Why is membrane filtration preferred over direct inoculation for some products?
- It is faster in all cases
- It reduces interference from bacteriostatic or fungistatic substances
- It requires no aseptic technique
- It is cheaper for all products
Correct Answer: It reduces interference from bacteriostatic or fungistatic substances
Q9. What is the purpose of a growth promotion test for sterility media?
- To sterilize the media
- To confirm the medium supports growth of specified microorganisms
- To check pH only
- To validate filter integrity
Correct Answer: To confirm the medium supports growth of specified microorganisms
Q10. Which of the following organisms is commonly used in growth promotion testing of FTM?
- Aspergillus niger
- Staphylococcus aureus
- Escherichia coli
- Geobacillus stearothermophilus
Correct Answer: Staphylococcus aureus
Q11. What control is used to ensure sterility test procedures do not introduce contamination?
- Positive control
- Negative control (uninoculated medium)
- pH control
- Temperature control
Correct Answer: Negative control (uninoculated medium)
Q12. What is a positive control in a sterility test intended to demonstrate?
- That the test can detect viable microorganisms when present
- That media are sterile
- That filters are intact
- That incubation temperature is low
Correct Answer: That the test can detect viable microorganisms when present
Q13. If a product contains residual antimicrobials, what must be done before sterility testing?
- Ignore antimicrobial effect
- Perform neutralization or remove antimicrobials (e.g., by filtration or dilution)
- Increase incubation temperature
- Shorten incubation time
Correct Answer: Perform neutralization or remove antimicrobials (e.g., by filtration or dilution)
Q14. Which compendial monograph provides general chapters for sterility testing in USP?
- USP General Chapter on Dissolution
- USP General Chapter Sterility (e.g., 71)
- USP General Chapter on Assay
- USP General Chapter on Appearance
Correct Answer: USP General Chapter Sterility (e.g., 71)
Q15. Which of the following is a common reason for false-positive sterility test results?
- Insufficient sample volume
- Contamination during test handling
- Proper neutralization of antimicrobials
- Using fresh media
Correct Answer: Contamination during test handling
Q16. What is the main risk addressed by environmental monitoring in aseptic manufacturing?
- Chemical degradation
- Microbial contamination of product and process areas
- Incorrect labeling
- Mechanical failure of equipment
Correct Answer: Microbial contamination of product and process areas
Q17. According to compendial guidance, how many media types are used simultaneously for each sample in a sterility test?
- One medium only
- Two media (FTM and SCDM/TSB)
- Three media
- No media required
Correct Answer: Two media (FTM and SCDM/TSB)
Q18. Which statement correctly describes membrane filtration sterility test steps?
- Filter sample, rinse filter, transfer filter to media for incubation
- Heat sample to 100°C then plate
- Directly inject sample into animals
- Shake sample with solvent and read OD
Correct Answer: Filter sample, rinse filter, transfer filter to media for incubation
Q19. What is the typical filter rinse volume used to remove inhibitory substances after membrane filtration? (Conceptual)
- No rinsing required
- A single small rinse of 0.1 mL
- Multiple rinses with sterile diluent sufficient to remove inhibitors
- Dry wiping the filter
Correct Answer: Multiple rinses with sterile diluent sufficient to remove inhibitors
Q20. Which organisms are commonly included in growth promotion testing for the SCDM/TSB medium?
- Bacillus subtilis and Pseudomonas aeruginosa
- Staphylococcus aureus and Candida albicans
- Salmonella typhi only
- Mycobacterium tuberculosis and Clostridium botulinum
Correct Answer: Staphylococcus aureus and Candida albicans
Q21. In sterility test interpretation, what does a single outgrowth in any medium indicate?
- Pass (product is sterile)
- Fail (presence of viable microorganisms)
- Test is inconclusive and should be discarded
- Only contamination of media
Correct Answer: Fail (presence of viable microorganisms)
Q22. How should sterility test samples be taken from a final product batch?
- Randomly according to sampling plan and compendial requirements
- Only from the first unit
- From expired units
- From open containers only
Correct Answer: Randomly according to sampling plan and compendial requirements
Q23. Which factor is critical when testing ophthalmic solutions for sterility?
- Viscosity only
- Use of appropriate sampling volume and aseptic technique to avoid contamination
- Color matching
- Packaging aesthetics
Correct Answer: Use of appropriate sampling volume and aseptic technique to avoid contamination
Q24. What is the significance of container-closure integrity in sterility assurance?
- No relation to sterility
- It helps prevent ingress of microorganisms and maintains sterility after sterilization
- Only affects product appearance
- Only relevant for chemical stability
Correct Answer: It helps prevent ingress of microorganisms and maintains sterility after sterilization
Q25. Which method is commonly used to test container-closure integrity?
- Membrane filtration
- Helium leak detection, dye ingress, or vacuum decay methods
- pH measurement
- Gram staining
Correct Answer: Helium leak detection, dye ingress, or vacuum decay methods
Q26. For parenteral products, what is the typical acceptance criterion for a compendial sterility test?
- No growth in any medium for the test period
- Growth allowed in one medium
- At least three positive tubes
- Growth in negative control only
Correct Answer: No growth in any medium for the test period
Q27. What is the effect of bacteriostatic preservatives on sterility testing if not neutralized?
- They enhance microbial growth
- They can mask contamination leading to false-negative results
- They have no effect
- They cause media to change color
Correct Answer: They can mask contamination leading to false-negative results
Q28. Which compendial guideline discusses sterility test validation and alternative methods?
- Guidelines on packaging only
- General chapters and monographs in IP/BP/USP addressing sterility testing and validation
- Guidelines on stability only
- Only pharmacopoeial appendices for dissolution
Correct Answer: General chapters and monographs in IP/BP/USP addressing sterility testing and validation
Q29. What is a major limitation of the traditional compendial sterility test?
- It detects non-viable particles only
- It is time-consuming and may lack sensitivity for low-level contamination
- It always gives immediate results
- It measures endotoxin levels directly
Correct Answer: It is time-consuming and may lack sensitivity for low-level contamination
Q30. Which of the following is considered during sterility test sample size selection?
- Batch size, risk assessment, and compendial recommendations
- Color of the product
- Company logo size
- Operator preference only
Correct Answer: Batch size, risk assessment, and compendial recommendations
Q31. What is the role of a filter integrity test after membrane filtration?
- To sterilize the filter
- To confirm the filter remained intact and functioned correctly during filtration
- To inoculate media
- To measure pH
Correct Answer: To confirm the filter remained intact and functioned correctly during filtration
Q32. Which organism is commonly used as a biological indicator for steam sterilization, not sterility testing media promotion?
- Geobacillus stearothermophilus
- Escherichia coli
- Staphylococcus epidermidis
- Candida albicans
Correct Answer: Geobacillus stearothermophilus
Q33. For sterile products produced by terminal sterilization, how does sterility assurance compare to aseptic processing?
- Terminal sterilization generally provides higher sterility assurance
- Aseptic processing is always better
- Both are identical in assurance
- Terminal sterilization is not used for sterile products
Correct Answer: Terminal sterilization generally provides higher sterility assurance
Q34. What is the main reason to perform a bioburden test before sterility testing?
- To assess the number of viable microorganisms on non-sterile product before terminal sterilization or production
- To determine color stability
- To check viscosity
- To measure endotoxin only
Correct Answer: To assess the number of viable microorganisms on non-sterile product before terminal sterilization or production
Q35. What is the acceptable outcome for growth promotion test results?
- No growth with test organisms
- Demonstrated growth with specified organisms within defined limits
- Only fungal growth is acceptable
- Media solidification
Correct Answer: Demonstrated growth with specified organisms within defined limits
Q36. When performing sterility testing on a product with a viscous matrix, which method is often preferred?
- Direct inoculation always
- Membrane filtration with appropriate pretreatment or dilution
- Heating to evaporate viscosity
- Using optical density only
Correct Answer: Membrane filtration with appropriate pretreatment or dilution
Q37. Which practice minimizes false positives during sterility testing?
- Poor aseptic technique
- Strict aseptic handling, validated cleaning, and use of controls
- Prolonging incubation beyond validated period
- Using expired media
Correct Answer: Strict aseptic handling, validated cleaning, and use of controls
Q38. What action is recommended if sterility test results are positive?
- Release the batch immediately
- Investigate root cause, quarantine batch, perform confirmatory testing and CAPA
- Ignore the result
- Label product as sterile
Correct Answer: Investigate root cause, quarantine batch, perform confirmatory testing and CAPA
Q39. Which of the following is true about alternative rapid sterility tests?
- They never require validation
- They may be acceptable if validated to demonstrate equivalence or superiority to compendial methods
- They are always prohibited by pharmacopeias
- They always replace environmental monitoring
Correct Answer: They may be acceptable if validated to demonstrate equivalence or superiority to compendial methods
Q40. What is the role of neutralizers in sterility testing?
- To enhance antimicrobial activity
- To inactivate residual antimicrobials that would otherwise inhibit test organisms
- To color the media
- To increase incubation temperature
Correct Answer: To inactivate residual antimicrobials that would otherwise inhibit test organisms
Q41. Which parameter is important for validation of sterility test membrane filtration for a specific product?
- Demonstrating recovery of low levels of microorganisms in the presence of product matrix
- Only verifying pH
- Only measuring viscosity
- Only checking color
Correct Answer: Demonstrating recovery of low levels of microorganisms in the presence of product matrix
Q42. What is the typical outcome if filters used in membrane filtration are clogged during the test?
- Continue without change
- Change the procedure—use smaller sample volumes, prefilters or dilution as validated
- Discard the product without investigation
- Heat the filter to unclog
Correct Answer: Change the procedure—use smaller sample volumes, prefilters or dilution as validated
Q43. In sterility testing, what is the importance of sample handling and transport?
- It does not matter how samples are handled
- Proper handling and transport prevent extrinsic contamination and maintain sample integrity
- Samples should be exposed to environment
- Samples must be frozen always
Correct Answer: Proper handling and transport prevent extrinsic contamination and maintain sample integrity
Q44. Which of the following is assessed during media quality control for sterility testing?
- Growth promotion, sterility, and physical properties such as clarity and pH
- Only label color
- Only the container shape
- Only the expiration date
Correct Answer: Growth promotion, sterility, and physical properties such as clarity and pH
Q45. What is a microbiological obstruction that could invalidate a sterility test?
- Appropriate controls
- Evidence of contamination during sample preparation or from the laboratory environment
- Using validated methods
- Proper incubation
Correct Answer: Evidence of contamination during sample preparation or from the laboratory environment
Q46. How does aseptic process simulation (media fill) relate to sterility assurance?
- It evaluates the aseptic manufacturing process to simulate worst-case contamination risk and operator performance
- It replaces sterility testing entirely
- It is used for chemical assay
- It measures endotoxin only
Correct Answer: It evaluates the aseptic manufacturing process to simulate worst-case contamination risk and operator performance
Q47. Which compendial requirement is critical when performing sterility tests on lyophilized products?
- Ignore reconstitution steps
- Reconstitute under validated aseptic conditions and consider neutralization of excipients if needed
- Use water without validation
- Only test the cake visually
Correct Answer: Reconstitute under validated aseptic conditions and consider neutralization of excipients if needed
Q48. Which practice improves detection of slow-growing organisms during sterility testing?
- Shortening incubation time
- Using appropriate media, correct incubation temperatures, and full 14-day incubation
- Ignoring fungus detection
- Using only one medium
Correct Answer: Using appropriate media, correct incubation temperatures, and full 14-day incubation
Q49. What documentation is essential after completing a sterility test?
- No documentation required
- Complete records including sample ID, methods, controls, observations, and conclusions
- Only the final pass/fail
- Only operator initials
Correct Answer: Complete records including sample ID, methods, controls, observations, and conclusions
Q50. How should changed or out-of-specification sterility test methods be handled?
- Apply changes without validation
- Perform method qualification/validation, document justification, and obtain regulatory approval if required
- Ignore changes
- Re-run tests indefinitely without investigation
Correct Answer: Perform method qualification/validation, document justification, and obtain regulatory approval if required
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