Sterility testing of ophthalmic products MCQs With Answer

Sterility testing of ophthalmic products MCQs With Answer

Sterility testing of ophthalmic products is a critical area in pharmaceutical microbiology and quality control for B.Pharm students. This introduction covers key concepts: USP <71>, membrane filtration and direct inoculation methods, incubation conditions, media selection (Fluid Thioglycollate Medium and Soybean-Casein Digest Medium), preservation effects, and validation of aseptic processes. Understanding sterility testing ensures patient safety for sterile ophthalmic preparations, guides contamination investigations, and supports regulatory compliance. These MCQs emphasize practical test setup, neutralization of preservatives, interpretation of results, and common microbial contaminants specific to eye drops and ocular devices. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which USP reference specifically describes sterility testing procedures commonly applied to ophthalmic products?

• USP <71>
• USP <85>
• USP <61>
• USP <797>

Correct Answer: USP <71>

Q2. Which two media are recommended in the USP sterility test to detect a broad range of microorganisms?

• Fluid Thioglycollate Medium and Soybean-Casein Digest Medium
• Blood Agar and MacConkey Agar
• Sabouraud Dextrose Agar and Mannitol Salt Agar
• Nutrient Broth and Cetrimide Agar

Correct Answer: Fluid Thioglycollate Medium and Soybean-Casein Digest Medium

Q3. For USP sterility testing, at what temperature is Fluid Thioglycollate Medium (FTM) incubated?

• 20–25°C
• 30–35°C
• 37–40°C
• 4–8°C

Correct Answer: 30–35°C

Q4. At what temperature is Soybean-Casein Digest Medium (SCDM) typically incubated in sterility testing?

• 30–35°C
• 20–25°C
• 37°C
• 15–20°C

Correct Answer: 20–25°C

Q5. What is the standard incubation period for sterility testing according to USP?

• 3 days
• 7 days
• 14 days
• 28 days

Correct Answer: 14 days

Q6. Which sterility testing method is preferred for ophthalmic products that contain preservatives?

• Direct inoculation without modification
• Membrane filtration with neutralization
• Surface plating on agar
• Visual turbidity check only

Correct Answer: Membrane filtration with neutralization

Q7. What is the main advantage of membrane filtration over direct inoculation for sterile ophthalmic products?

• Faster incubation time
• Ability to remove preservatives and concentrate microorganisms
• Less equipment required
• No need for trained personnel

Correct Answer: Ability to remove preservatives and concentrate microorganisms

Q8. Which pore size is commonly used for membrane filters in sterility testing to retain microorganisms?

• 0.8 μm
• 0.45 μm
• 0.1 μm
• 1.2 μm

Correct Answer: 0.45 μm

Q9. What is the primary reason for neutralizing preservatives during sterility testing?

• To enhance nutrient content of media
• To prevent preservatives from killing microorganisms during the test
• To change the pH of the sample
• To increase sample viscosity for filtration

Correct Answer: To prevent preservatives from killing microorganisms during the test

Q10. Which of the following is a common neutralizer used when testing ophthalmic formulations containing benzalkonium chloride?

• Sodium lauryl sulfate
• Polysorbate 80 (Tween 80)
• Calcium chloride
• Potassium sorbate

Correct Answer: Polysorbate 80 (Tween 80)

Q11. Which control is essential to verify culture media are capable of supporting microbial growth?

• Sterility control
• Growth promotion test (positive control)
• Temperature control
• pH control

Correct Answer: Growth promotion test (positive control)

Q12. What does a sterility control (negative control) in sterility testing demonstrate?

• Media supports microbial growth
• Test incubators are operating correctly
• Media and handling are sterile and not contaminated
• Neutralizers are effective

Correct Answer: Media and handling are sterile and not contaminated

Q13. When performing membrane filtration sterility testing, what should be done if the filter clogs?

• Discard the sample and repeat test
• Use additional filters or dilute the sample and re-filter
• Incubate the clogged filter as is
• Increase vacuum pressure to force filtration

Correct Answer: Use additional filters or dilute the sample and re-filter

Q14. Which microorganism is most concerning as a contaminant in ophthalmic solutions due to corneal infections?

• Pseudomonas aeruginosa
• Escherichia coli
• Bacillus subtilis
• Lactobacillus acidophilus

Correct Answer: Pseudomonas aeruginosa

Q15. What is the purpose of the disinfection and aseptic technique during sample collection for sterility testing?

• To alter sample pH
• To prevent introduction of extrinsic contaminants that would give false positives
• To sterilize the tested product
• To preserve the product for storage

Correct Answer: To prevent introduction of extrinsic contaminants that would give false positives

Q16. Which regulatory guideline besides USP <71> is most relevant for sterile manufacturing and sterility assurance?

• ICH Q9
• EU GMP Annex 1
• ICH Q8
• WHO TRS 1000

Correct Answer: EU GMP Annex 1

Q17. For ophthalmic products, what property of container-closure systems is critical for sterility maintenance?

• Color of the container
• Integrity and absence of leaks
• Shape of the cap
• Manufacturing date printed

Correct Answer: Integrity and absence of leaks

Q18. Which test assesses whether culture media can support growth after being stored or processed?

• Sterility test
• Growth promotion test
• Preservative efficacy test
• Endotoxin test

Correct Answer: Growth promotion test

Q19. Which test is specifically used to evaluate the effectiveness of preservatives in multi-dose ophthalmic formulations?

• Sterility test
• Preservative Efficacy Test (PET) / Antimicrobial Effectiveness Test (AET)
• Endotoxin test
• Particulate matter test

Correct Answer: Preservative Efficacy Test (PET) / Antimicrobial Effectiveness Test (AET)

Q20. During sterility testing, what is the role of a method suitability test?

• To determine shelf life
• To confirm that the test method can detect microorganisms in the presence of product components
• To evaluate container color impact
• To measure endotoxin levels

Correct Answer: To confirm that the test method can detect microorganisms in the presence of product components

Q21. Which of the following is NOT typically a step in membrane filtration sterility testing?

• Filtering the sample through a sterile membrane
• Rinsing the membrane to remove residual product
• Placing the membrane in culture media and incubating
• Heating the membrane to 121°C to sterilize it before incubation

Correct Answer: Heating the membrane to 121°C to sterilize it before incubation

Q22. What is the minimum sample size often recommended for sterility testing of ophthalmic solutions when using membrane filtration?

• 0.1 mL
• 1–10 mL depending on product and method suitability
• 100 mL only
• Any volume is acceptable without validation

Correct Answer: 1–10 mL depending on product and method suitability

Q23. Which statement about the direct inoculation method is true?

• It concentrates microorganisms prior to incubation
• It involves inoculating portions of the product directly into culture media
• It always requires filtration
• It is immune to preservative effects

Correct Answer: It involves inoculating portions of the product directly into culture media

Q24. If turbidity appears in the test medium during sterility testing, what is the correct immediate action?

• Discard the sample and ignore
• Record result as a positive growth and proceed with identification
• Assume contamination of incubator and restart test
• Heat the medium to clarify it

Correct Answer: Record result as a positive growth and proceed with identification

Q25. Which microorganism is routinely used as a challenge organism in growth promotion tests for FTM?

• Aspergillus brasiliensis
• Bacillus subtilis
• Staphylococcus aureus
• Pseudomonas aeruginosa

Correct Answer: Bacillus subtilis

Q26. Which organism is commonly used to challenge SCDM (or soybean-casein digest medium) in growth promotion tests for the aerobic/fungal incubation?

• Clostridium sporogenes
• Candida albicans
• Escherichia coli
• Bacillus subtilis

Correct Answer: Candida albicans

Q27. What does bioburden testing measure prior to terminal sterilization of ophthalmic products?

• Pyrogen levels
• Number of viable microorganisms present on or in the product before sterilization
• Endotoxin concentration
• Particulate count

Correct Answer: Number of viable microorganisms present on or in the product before sterilization

Q28. Which sterilization process is commonly used for terminal sterilization of some ophthalmic instruments but not always suitable for heat-sensitive eye drops?

• Sterile filtration at 0.22 μm
• Autoclaving (moist heat at 121°C)
• Gamma irradiation
• Dry nitrogen sparging

Correct Answer: Autoclaving (moist heat at 121°C)

Q29. Why might terminal sterilization not be feasible for many ophthalmic drug solutions?

• They are too viscous
• Active ingredients may be heat-sensitive or degrade
• Regulators prohibit terminal sterilization
• It always causes precipitation

Correct Answer: Active ingredients may be heat-sensitive or degrade

Q30. Which of the following is an indicator of microbial contamination specific to ophthalmic products that could cause patient harm?

• Endotoxin presence only
• Presence of Pseudomonas and other opportunistic gram-negative organisms
• Low pH alone
• High viscosity only

Correct Answer: Presence of Pseudomonas and other opportunistic gram-negative organisms

Q31. What is the purpose of incubating sterility test media at two different temperatures?

• To save incubator space
• To detect both mesophilic bacteria and fungi/psychrotolerant organisms
• To rapidly speed up the test to 7 days
• To sterilize the media

Correct Answer: To detect both mesophilic bacteria and fungi/psychrotolerant organisms

Q32. Which practice is essential during transfer of samples for sterility testing to avoid contamination?

• Open the container completely in the open air
• Perform transfers in an ISO-classified laminar flow hood using aseptic technique
• Use hands only after washing without gloves
• Shake the container vigorously before sampling

Correct Answer: Perform transfers in an ISO-classified laminar flow hood using aseptic technique

Q33. Which statement about environmental monitoring in sterile production areas is correct?

• It is optional for ophthalmic production
• It includes air and surface sampling to control contamination risks
• It only monitors temperature and humidity
• It replaces product sterility testing

Correct Answer: It includes air and surface sampling to control contamination risks

Q34. What is the minimum number of membrane filter rinses recommended to remove traces of product before placing the filter on media?

• No rinse is required
• Usually two or more rinses with sterile diluent as validated
• One rinse with sterile water is always sufficient
• Rinse with alcohol only

Correct Answer: Usually two or more rinses with sterile diluent as validated

Q35. Which is a common false-negative cause in sterility testing of ophthalmic products?

• Excessive neutralization of preservatives
• Residual antimicrobial activity killing contaminants during test
• Using two media types
• Incubating for 14 days

Correct Answer: Residual antimicrobial activity killing contaminants during test

Q36. When interpreting sterility test results, what must be done if growth is observed?

• Ignore and release the batch
• Record positive, identify the organism, and investigate root cause
• Re-run the test and assume second run is correct
• Change the media and test again without investigation

Correct Answer: Record positive, identify the organism, and investigate root cause

Q37. Which statement correctly distinguishes pyrogen (endotoxin) testing from sterility testing?

• Both tests are identical in purpose
• Endotoxin testing detects bacterial endotoxins whereas sterility testing detects viable microorganisms
• Sterility testing measures endotoxin concentrations
• Pyrogen testing is unnecessary for ophthalmics

Correct Answer: Endotoxin testing detects bacterial endotoxins whereas sterility testing detects viable microorganisms

Q38. In method suitability for membrane filtration, what is the purpose of a recovery check using a known inoculum?

• To standardize incubation temperatures
• To confirm that the filtration and rinsing process does not prevent recovery of microorganisms
• To validate preservative strength
• To ensure membranes are sterile prior to test

Correct Answer: To confirm that the filtration and rinsing process does not prevent recovery of microorganisms

Q39. Which of the following organisms is often included in preservative efficacy test challenge panels?

• Clostridium difficile
• Staphylococcus aureus
• Helicobacter pylori
• Lactobacillus casei

Correct Answer: Staphylococcus aureus

Q40. What would be an appropriate initial step if sterility test media fail the growth promotion test?

• Use media anyway for production testing
• Reject the media lot and investigate media quality and storage
• Shorten incubation time to improve results
• Change incubation temperatures arbitrarily

Correct Answer: Reject the media lot and investigate media quality and storage

Q41. How is sample handling time important for sterility testing of ophthalmic samples?

• Delays can allow any contaminants to multiply or die affecting results; timely processing is critical
• Delays always sterilize the sample
• Time has no effect on sterility results
• Longer storage improves test accuracy

Correct Answer: Delays can allow any contaminants to multiply or die affecting results; timely processing is critical

Q42. For a multi-dose ophthalmic product, which testing or control is critical in addition to sterility?

• Preservative efficacy testing
• Color matching test
• Weight variation test
• Tablet hardness test

Correct Answer: Preservative efficacy testing

Q43. What is the expected outcome of a valid sterility test for a sterile ophthalmic batch?

• Growth in one of the media only
• No growth in either medium throughout incubation
• Immediate turbidity within 24 hours
• Positive endotoxin reaction

Correct Answer: No growth in either medium throughout incubation

Q44. Which laboratory practice reduces the risk of false positives in sterility testing?

• Poor aseptic technique
• Strict aseptic technique and environmental controls during sampling and testing
• Using non-sterile disposables
• Opening incubators frequently to inspect samples

Correct Answer: Strict aseptic technique and environmental controls during sampling and testing

Q45. What documentation is essential when a sterility test yields a positive growth?

• No documentation is needed
• Complete investigation report including identification, source assessment, and corrective actions
• Only record the organism name without investigation
• Destroy all records to avoid regulatory issues

Correct Answer: Complete investigation report including identification, source assessment, and corrective actions

Q46. Which approach helps ensure representative sampling of ophthalmic product batches for sterility testing?

• Sampling only from finished packaged units at random and following approved sampling plans
• Sampling only the first unit produced
• Sampling only after retail distribution
• Sampling arbitrarily without documentation

Correct Answer: Sampling only from finished packaged units at random and following approved sampling plans

Q47. What is the most appropriate action if method suitability shows inadequate neutralization of a preservative?

• Ignore and perform the test anyway
• Optimize or change neutralizer and revalidate the method
• Reduce incubation time to compensate
• Increase preservative concentration

Correct Answer: Optimize or change neutralizer and revalidate the method

Q48. Which microbial type is most resistant to many preservatives and sterilization, requiring careful consideration in ophthalmic product testing?

• Vegetative gram-positive bacteria
• Fungi and spores (e.g., molds, Bacillus spores)
• Enveloped viruses
• Gram-negative nonfastidious bacteria only

Correct Answer: Fungi and spores (e.g., molds, Bacillus spores)

Q49. Why is filter integrity testing important following sterile filtration of ophthalmic solutions?

• To verify the filter is colored correctly
• To ensure filter integrity was maintained and sterilizing capability was achieved
• To measure product concentration
• To ensure membranes are reusable

Correct Answer: To ensure filter integrity was maintained and sterilizing capability was achieved

Q50. Which best practice improves reliability of sterility testing results for ophthalmic products?

• Using a single-person testing workflow without cross-checks
• Robust validation, regular training, environmental control, and method suitability testing
• Skipping growth promotion tests to save time
• Relying solely on historical data without current testing

Correct Answer: Robust validation, regular training, environmental control, and method suitability testing

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