Microbiological Control Tests

Microbiology testing in pharmaceutical industry | Microbiological Testing |

Microbiological Testing

Objectives

• To review microbiological environmental and quality control testing
  • Microbiological Environmental Monitoring
  • Container integrity testing
  • Pre-sterilization bioburden testing
  • Media fill medium growth promotion testing
  • Sterility Testing
  • Other microbiological laboratory issues

Environmental Monitoring

Limits for Viable Particles

• Values are for guidance only – not intended to represent specifications
• Levels (limits) of detection of microbiological contamination should be established for alert and action purposes and for monitoring trends of air quality in the facility

Methods

• Surface monitoring
  • Product contact surfaces, floors, walls, and equipment should be tested on a regular basis
  • Touch plates – used for flat surfaces
    • sample area of 25cm²
    • medium protrudes above sides
    • medium contains neutralisers

• –Surface Swabs – used for irregular surfaces
  • area approx 25cm² is swabbed
  • qualitative or quantitative

• Surface monitoring should be performed at conclusion of aseptic processing (to minimise risk of contaminating critical surfaces during production

• Active Air Monitoring
  • impaction, centrifugal and membrane (or gelatin) samplers
  • a certain volume of air is sampled (volume and location should be meaningful)
  • instruments should be calibrated

• Passive Air Monitoring
  • Settle plates exposed for 30-60 minutes (longer may result in agar drying out) and replaced for duration of filling
  • Media should be capable of growing a range of bacteria and moulds (e.g. Soybean Casein Digest Agar (SCDA)/Trypticase Soy Agar (TSA)
  • Should consider use of medium specific for moulds if shown to be a problem in the environment
  • Only give qualitative or semi-quantitative results
  • Data generated considered in combination with active air sampling results

• Sampling Locations
  • Should be based on risk of microbiological contamination
  • Should be clustered around areas where product or components are exposed e.g.
    • at filling heads on filling lines
    • loading of product into lyophilizers
    • stopper bowls
    • where aseptic connections are made
    • where there are high levels of operator activity (but without impacting on production)
  • Lower grade areas are monitored less frequently and trends monitored

• Personnel
  • For each session – gloves should be monitored (but not immediately after sanitizing)
  • Periodic sampling for other locations on gown
  • Clean room operators should be regularly validated to demonstrate that they do not contaminate gowns during gowning up (gowning qualification)

• Levels and Trends
  • Limits in Code of GMP are for guidance only
  • Manufacturers should set alert and action limits appropriate to the location
  • Individual results should be considered – averaging can mask unacceptable localized conditions
  • There should be written procedures (SOPs) for data review and action to be taken if limits are exceeded
  • Trend Reports
    • Short and long term reports on environmental and personnel monitoring
    • Results of EM should be included in Batch Records
    • Significant changes in microbial flora should be considered

• Disinfectants
  • Suitability, efficacy, limitations of disinfectants and procedures should be assessed
    • minimum contact time established
  • Disinfectants in Grade A/B areas should be sterile, supplied in sterile containers and used for a defined period
  • Should be shown to be effective against facility microbial flora
  • Should be sporicidal (if spores found in the environment) and for “spraying in” of components and equipment
  • Disinfection SOPs should include sufficient detail to enable reproducibility
    • preparation, work sequence, contact time
  • Organisms identified from adverse trends should be tested for their sensitivity to the disinfectants used

• Water
  • microbiological quality of water very important
  • Should be an extensive, comprehensive water testing programmed
  • Feed water, pre-treatment, reverse osmosis (RO), deionized (DI), purified/highly purified and water for injection (WFI) should be tested
  • Alert and Action limits set by manufacturer (with action to be taken if limits are exceeded)
  • For purified/highly purified water and WFI, limits defined in pharmacopoeia
    • purified <100CFU/mL
    • Highly purified and WFI 10CFU/100mL (but is usually kept at high temperatures)

Suggested Microbial Limits (CFU/mL) for facility water

• Water should also be tested for presence of coliforms and/or pseudomonads if appropriate (may cause biofilm)
• Water used for parenteral should be tested for pyrogens
  • limit is not more than 0.25 EU/mL
• Water should be tested using R₂A agar (low nutrient for the recovery of water borne organisms) incubated for at least 5 days at 30-35°C
• Sampling procedures should follow those used in production

Compressed Air/Nitrogen/CO₂

• Should be tested for non-viables and viables
• Pressure reduction orifices should be used to provide a steady stream of air, validation of media should be ensured with consideration of validation

Container Integrity Testing

• Integrity of container/closure system
  • is initially validated by filling container with sterile growth medium then inserting container in broth containing 10⁶ CFU/mL of suitable microorganism
  • containers sealed under a vacuum should be periodically tested to demonstrate that vacuum is maintained over shelf life
  • procedures in place to detect faulty containers during manufacture
  • operators involved in visual inspection should have frequent breaks and regular eye-sight tests

Bioburden/IPC Testing

• Should be written procedures for pre-sterilization bioburden, in-process control and raw material  testing
• method should be validated for the recovery of low numbers of organisms
• use of anaerobic medium should be considered if shown to be present in environment
• target, alert and action limits should be documented and include action taken if limits exceeded

Growth Promotion Testing

Media used for microbiological testing should be tested for its ability to support microbial growth.

• media used for media fills should be able to support the growth of a wide range of microorganisms (bacteria and moulds)
• Soybean Casein Digest Medium is usually used. An anaerobic medium may also be substituted occasionally if environmental monitoring indicates presence
• After the media fill has been completed, it is important to demonstrate that the media would have been able to support the growth of organisms if they had been present
• containers with media should be inoculated with 10-100 CFU of organism such as Bacillus subtilis, Staphylococcus aureus, Candida albicans, Aspergillus niger. Environmental isolates should also be included

• Media
  • The inoculated media should be capable of showing growth within 3 days of incubation
  • Media used in environmental monitoring should also be tested for its growth promoting properties. Validation of recovery of organisms under test conditions should be carried out to demonstrate neutralization of disinfectant residuals (media should contain neutralisers).
  • Media purchased externally should also be tested
  • Media used for media fills and environmental monitoring should be pre-incubated to demonstrate “sterility” prior to use
  • Media should have a validated shelf life

Sterility Testing

• Sterility test is a quality control test used as part of product release for product required to be sterile.
  • Has significant statistical limitations – will really only detect gross contamination

• Sampling
  • No of containers and volume to be tested defined in Pharmacopoeia
  • Samples from aseptically manufactured product should be taken from beginning, middle and end of batch fill and also after interventions and stoppages
  • Samples from terminally sterilized product should be taken from previously identified cool spots within load
  • Sampling should be sufficient to allow for retests if needed

• Facilities
  • Sterility testing should be carried out under the same conditions as aseptic manufacture
    • In a Grade A laminar air flow cabinet in a Grade B background (may also be carried out in an isolator)
    • Air supply through HEPA filters, pressures should be monitored and alarmed
    • Access to area should be through airlocks
    • Operators should be appropriately gowned is sterile garments
    • Operators should be appropriately trained and validated
    • Appropriate cleaning, sanitisation and disinfection procedures should be in place
    • Environmental monitoring should be conducted

• Methods are defined in Pharmacopoeia
  • membrane filtration is the preferred method if product is filterable
  • direction innoculation is alternative

• Media types
  • Soybean Casein Digest medium (SCD), (also knows as Trypticase Soy Broth(TSB)) and Fluid Thioglycollate medium (FTM) is usually used (to detect aerobic and anaerobic organisms)
  • validation studies should demonstrate that the media are capable of supporting growth of a range of  low numbers of organisms in the presence of product. May need to incorporate inactivators
  • growth should be evident after 3 days (bacteria), 5 days (moulds)
  • media may be purchased or made in-house using validated sterilization procedures

• Negative Contols
  • media should be incubated for 14 days prior to use, either a portion or 100% of batch (may be done concurrently with test)
  • negative product controls – items similar in type and packaging to actual product under test should be included in each test session
    • facilitate interpretation of test results
    • negative control contamination rate should be calculated and recorded

• Positive Test Controls
  • bactiostasis/fungistasis test
    • should demonstrate that media are capable of supporting growth of a range of  low numbers of organisms in the presence of product. May need to incorporate inactivators
      • growth should be evident after 3 days (bacteria), 5 days (moulds)
    • should be performed on all new products and when any changes are made.
    • Should be repeated annually
  • Stasis test recommended particularly for product with antibiotics or preservatives or slow release tested by direct innoculation
    • demonstrates that media can support growth at the end of the incubation period and has not been affected by product

• Results
  • Any growth should be identified (genotypic)
  • Automated/Semi-automated systems used for identification should be periodically verified using reference strains

• Interpretation and Repeat Tests
  • No contaminated units should be found
  • A test may only be repeated when it can be demonstrated that the test was invalid for causes unrelated to the product being examined
  • European Pharmacopoeia criteria
    • •(a) the data of the micro monitoring of the sterility test facility show a fault
    • •(b) a review of the testing procedure used during the test in question reveals a fault
    • •(c) microbial growth is found in negative controls
    • •(d) after determination of the identity of the microorganisms isolated from the test, the growth of this species or these species may be ascribed unequivocally to faults with respect to the material and/or technique used in conducting the sterility test procedure
    • When conditions (a), (b) or (c) apply the test should be aborted
    • If a stasis test performed at the end of the test shows no growth of challenge organisms, this also invalidates the test
    • For conditions (d) to apply must demonstrate that the orgamisms isolated from the sterility test is identical to an isolate from materials (e.g. media) and/or the environment
    • must use genotypic identification methods
  • Repeat test is carried out with same number of samples as first test
  • Any contamination detected in repeat test, product does not comply

Other Microbiological Laboratory Issues

Reference Culture Collections

• Reference cultures may be used for
  • Quality control of media
  • Test method validation
  • Control of test reagents
• Must remain genetically stable to retain characteristics for which they have been selected.
• Cultures of microorganisms tend to undergo variation/genetic change that can affect characteristics of a culture – unsuitable for further use.
• Probability of variation/genetic change increases with frequency of repeated subculture of reference culture – working culture must be no more than 5 generations removed from original source culture.
• Laboratory must have a system for preserving and maintaining reference cultures with their original characteristics.
• Laboratory should:
  • maintain suitable reference cultures for QC of culture media and test reagents and for test method validation;
  • ensure reference cultures are traceable to a recognised culture collection eg. ATCC, NCTC;
  • ensure reference cultures are uniquely identified within laboratory, with traceability to recognised culture collection.
• Lab should have documented procedures:
  • that maintain hierarchical control of reference cultures (ie. master, stock & working cultures);
  • for purchase, preservation, maintenance, identification and frequency of subculturing of reference cultures;
  • that prevent use of working cultures as replacements for depleted stock and/or master cultures.

• Maintain records for each reference culture:
  • identity, source and history and date of receipt of master culture;
  • resuscitation, preservation, maintenance and storage conditions for master, stock and working cultures;
  • results of purity and identification tests for master and/or stock cultures; and
  • dates of preparation of stock and working cultures.

• QC of Culture Media
  • Media other than sterility testing media and media fill media must be subject to quality control
  • quantitative or semi-quantitative method/s to assess growth promotion/fertility
  • use of positive and negative controls for selective and/or dirrerential culture media
  • different levels of QC required dependent on whether culture is
    • manufactured in house (every batch should be tested)
    • purchased ready to use (supplier tests media with testing periodically verified in house)
  • Laboratory should:
    • have documented procedures for preparation, QC, release and storage of culture media;
    • have validated shelf life of culture media under normal storage conditions;
    • maintain records of preparation and QC of individual batches of culture media;
    • ensure that records of microbiological QC performance testing are traceable to batch preparation records; and
    • that microbiological QC performance test results are assessed against acceptance/rejection criteria.

• Sterilization processes for Culture Media
  • sterilzation process for culture media should be validated and monitored using same procedures as for sterilization of product.

• Equipment Calibration and Checks
  • Laboratory equipment (e.g. pipettes, balances, incubators, refrigerators, thermometers, autoclaves, laminar flow workstations etc) should be calibrated and recalibrated and routinely monitored (where appropriate)

• Personnel
  • Should be appropriately trained and authorized to perform testing

• Testing of Biological Indicators
  • if tested in-house the method should include a heat-shock step (this verifies that the indicators do actually contain spores and not vegetative organisms)
  • BIs should occasionally be tested in house to verify the suppliers count

• Endotoxin Testing
  • Parenteral products should be free from endotoxin
  • Endotoxin is a lipopolysaccharide present in the cell wall of gram negative bacteria which can cause fever if introduced into the body
  • Raw materials, WFI used in manufacture and some finished product must be tested for endotoxin
  • LAL (Limulus Amebocyte Lysate) test is used for detecting endotoxin (previously a rabbit test)
    • based on clotting reaction of horseshoe crab blood to endotoxin
  • Types of LAL test
    • Gel Clot
    • Turbidimetric
    • Colorimetric
  • Equipment used in test must be endotoxin free
  • Validation of accuracy and reliability of the method for each product is essential

• Gel Clot Method
  • Original method
  • The official “referee test”
  • The specimen is incubated with LAL of a known sensitivity. Formation of a gel clot is positive for endotoxin.

• Turbidimetric Method
  • A kinetic method
  • The specimen is incubated with LAL and either the rate of increase in turbidity or the time taken to reach a particular turbidity is measured spectrophotometrically and compared to a standard curve.

• Colorimetric Method
  • Endotoxin catalyzes the activation of a proenzyme in LAL which will cleave a colorless substrate to produce a colored
  • endproduct which can be measured spectrophotmetrically and compared to a standard curve.
  • Can be kinetic or endpoint

• Reference : WHO – Manufacture of sterile medicines – Advanced workshop for SFDA GMP inspectors 

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