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Sterility Testing
Question | Answer |
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What is the purpose of sterility testing? | Reveal the presence/absece of vianle MO's in a sample of containers from a batch. Based on the results from testing the sample, a decision is made is the batch is sterile or not. |
What are the limitations of the test for sterility? | Can only test for some micro-organisms that will grow in the test media in selected conditions and can only test samples of the product, not the entire batch. |
What are the two methods of sterility testing? | Direct Inoculation and Membrane filtration |
Outline the membrane filtration method | Used for filterable aqeuous products, pore size of membrane not greater than 0.45 micrometers Filtration system and membrane are first sterilised Design process must be carried out under aseptic conditions. |
Membrane filtration method cont'd: | After filtration: whole membrane transferred to culture medium, or membrane cut inhalf and one half placed in 2 of suitable media, or media transferred to membrane Incubate for not less than 14 days. |
How is a membrane selected for membrane filtration method? | Cellulose nitrate filters: oily, weakly alcoholic solutions Cellulose acetate esters: strongly alcoholic solutions Specially adapted filters: solutions containing antibiotics (wash membrane 3 x, by filtering through it the chosen diluent) |
Outline the direct inoculation method | Transfer the quantity of the preparation directly into culture medium. Volume of product is not more than 10% of the volume of the medium. Incubate for not less than 14 days. |
Direct incoulation cont'd | Shake cultures with oily products gently each day Neutralise/dilute products with antimicrobial activity For large volume of product, use concentrated culture medium If appropriate, CM can be directly added to product in container. |
What decisions need to be made for the sterility test? | Sample size (refer to table in BP) Sample volume (refer to table in BP) Culture medium (FTM or SCDM) Incubation temperature |
For parenteral preparations, what is the minimum number of items to test for < 100 containers? | 10% or 4, whichever is greatest |
For parenteral preparations, what is the minimum number of items to test for >100 but < 500 containers? | 10 containers |
For parenteral preparations, what is the minimum number of items to test for >500 containers? | 2% or 20, whichever is less |
For ophthalmic and other non-injectable preps, what is the minimum number of items to be tested for <200 containers? | 5% or 2 containers, whichever is greater |
For ophthalmic and other non-injectable preps, what is the minimum number of items to be tested for >200 containers? | 10 containers |
How is the minimum number of single use ophthalmic or other non-injectable preparations decided? | As per table for parenteral preparations |
What is the minimum number tested for catgut and other surgical sutures for vet use? | 2% or 5 packagees, whichever is greater, up to a max of 20 packages |
What is the minimum number tested for bulk solid products up to 4 containers? | Each container is tested |
What is the minimum number tested for bulk solid products totally more than 4 but less than 50 containers? | 20% or 4 containers, whichever is greater |
What is the minimum number tested for bulk solid product totalling more than 50 containers | 2% or 10 containers, whichever is greater |
What is the minimum sample volume for liquids less than 1mL? | The whole contents of each container |
What is the minimum sample volume for liquids between 1-40mL in volume? | half the contents of each container but not less than 1 mL |
What is the minimum sample volume for liquids container more than 40mL but less than 100mL? | 20mL |
What is the sample volume for liquids greater than 100mL? | 10% of the container but not less than 20mL |
What is the sample volume for antibiotic liquids? | 1mL |
What is the sample volume for solids less than 50mg? | The whole contents of each container |
What is the sample volume for solids 50mg or more but less than 300mg? | Half the contents of each container but not less than 50mg |
What is the minimum sample volume for solids 300mg to 5g? | 150 mg |
What is the minimum sample volume for solids greater than 5g? | 500mg |
What are the two test culture mediums used for sterility testing? | Fluid thioglycollate medium (FTM) Soya-bean Casin Digest medium (SCDM) |
What is FTM used for? | Aerobic (staph aureus, bacillus subtilis, pseudomonas aeruginosa) and Anaerobic (clostridium sporogenes) MO's at an incubation temp of 30-35C |
What is SCDM used for? | Aerobic (staph aureus, bacillus subtilis, pseudomonas aeruginosa) and fungi (candida albicans, aspergillus niger) Incubation temps: Aerobic (30-35C) Fungi: 20-25C |
What are the control tests for sterility testing? | Negative Control (sterility): want no growth, eliminates flase positives, incubate for 14 days. Parallel to product sterility test Growth promotion test: confirms media can grow MO Validation test: confirms no inhibition of MO growth |
Which two control tests should be performed parallell with the product sterility test? | Validation test and sterility test (negative test) |
How long should the growth promotion tests be incubated for? | Bacteria: not more than 3 days Fungi: Not more than 5 days Use a separate portion of media for each MO |
How is the validation test performed? | Same methods as test for sterility but adding MO after transferring to membrane filter, or transferring to culture media. In both methods use same MO's as growth promotion test |
What does it mean for the validation test if there is no growth within the product? | If not growth observed in product and compared to controls without product, then the product is inhibiting the growth of any MO's. Modify conditions to eliminate the antimicrobial effect. Repeat test |
How are the results of sterility testing and control interpreted? | If no microbial grwoth, the product complies with test for sterility If MO grwoth found, product doesn't comply with test for sterility. Determine if test invalid or not. |
What is done if the material being tested turns the medium turbid? | If the presence of MO growth cannot be determined visually, 14 days after incubation started, transfer portions 1mL> to fresh vessels of the same medium. Incubate original and transfer for not less than 4 days. |
How can a sterility test be considered invalid? | If one ore more of the below is met: 1. data for microbiological monitoring shows a fault 2. review of testing procedure used during test shows a fault 3. MO growth found in neg controls 4. growth of MO is due to faults with material/technique used |
What happens if the test is invalid? | Declared invalid = test is repeated with the same number of units as original test No growth in repeat test = product complies with test for sterility If MO growth found in repeat test=product doesn't comply with test for sterility |