How To Record And Evaluate Data For Regulatory Microbiology Testing
What are regulatory microbiology tests, and why are microbiology tests important for your medical device or product?
Microbiology testing identifies the presence and the type of microbes in a manufacturing environment, medical product, or medical device. Microbiology testing is both a regulatory requirement and a risk mitigation strategy for aseptic manufacturing environments. Specific regulatory testing for microbiology may include microbial enumeration testing, particulate analysis, yeast analysis, antifungal activity assessment, growth promotion testing, microbial limits testing, zone of inhibition testing, water analysis, bacteriostasis/fungistasis testing, bacteria identification, yeast identification, fungi identification, gram-negative staining, product inoculations, biological indicator tests, and BI incubation time reduction studies.
As medical devices and products must be sterile to be used within a human body, microbial testing is imperative for preventing product-induced infections at the time of use.
There are two methods used to create a sterile medical product. Firstly, a final chemical or heat sterilization process is used on packaged medical products or devices to kill any live microorganisms picked up during the manufacturing process for terminal sterilization. The second method utilizes aseptic processing through the entire medical device or product manufacturing process. Aseptic processing requires the exclusion of microorganisms from the manufacturing methods. Thus, microorganisms must be prevented from entering open containers or product materials during processing for aseptic processing. As a result, microbial tests are used to monitor clean rooms and facilities that manufacture products using aseptic processing.
How are records for microbiology testing accurately collected?
Documentation
Microbiological documentation should record the four W’s for testing and record details of media, sample, and microbial test strain quality control. The four W’s for testing are who performed the test, when the test was performed, where the test was performed, and what samples, methods, test strains, etc., were used.
Suggested microbiology documentation:
- Microbiologist training and verification of proficiency
- Equipment validation, calibration, and maintenance
- Equipment performance during the test (e.g., 24-hour/7-day chart recorders)
- Media preparation, sterility checks, and growth-promotion and selectivity capabilities
- Media inventory and control testing
- Critical aspects of test conducted as specified by a procedure
- Data and calculations verification
- Reports reviewed by QAU or a qualified, responsible manager
- Investigation of data deviations (when required)
Resources
One measure of laboratory performance is the number of test investigations a laboratory performs. Two other performance metrics are measures of time, the period between sample submission and initiation of testing, and the period between the end of testing and report release. Significant delays in these measures are indications of under-resourced laboratory staff. Laboratory management is responsible for ensuring that the laboratory has sufficient human and material resources to meet the current testing needs.
How are records for microbiology testing maintained?
Proper recording of testing procedures and acquired data is a critical microbiology testing success. To this end, there is an established system of checks and balances with SOPs, laboratory notebooks, and the actual evaluation of microbial samples. In this system of checks and balances, the microbiological test is performed per the SOP’s instructions. The SOP itself is updated regularly to reflect how the test is currently performed. For each test, the laboratory notebook records enough information to reconstruct the details of the microbial test and confirm the integrity of the data.
A laboratory notebook write-up will include the following (at minimum):
- Date
- Material tested
- Microbiologist’s name
- Procedure number
- Document test results
- Deviations (if any)
- Documented parameters (equipment used, microbial stock cultures used, media lots)
- Management and secondary review signatures
In addition to noting the equipment used, equipment temperatures (water baths, incubators, autoclaves) should be recorded and trackable. Also, Write-ups should clearly note the governing SOP and revision. Changes in any laboratory notebook data should be crossed off with a single line and initialed. Original data should not be erased or covered over. Test results should include the original plate counts, allowing a reviewer to recreate the calculations used to derive the final test results. SOPs govern how data analysis is performed. If charts or graphs are included in laboratory write-ups, they should be secured with clear tape and signed by the person adding the document. Lab notebooks should include page numbers, a table of contents, and a timeline of use. All laboratory records should be archived and protected against catastrophic loss.
How are data from assay results accurately interpreted?
Due to the difficulties in microbial testing results (listed below), test results must be interpreted from a broad microbiological perspective. In other words, microorganisms identified in testing results get to be assessed for their likelihood of survival in a particular pharmaceutical ingredient, excipient, medical device, or environment under assessment. In addition, the growth characteristics of the microorganism should be considered. When results are observed that do not conform to established acceptance criteria, an investigation into the microbial data deviation (MDD) is needed.
Reasons why microbiological assay results can be difficult to interpret:
- Microorganisms are everywhere. Common environmental contaminants are organisms associated with humans
- The analyst has the potential to introduce contaminating organisms during sample handling or processing in the laboratory
- Microorganisms may not be homogeneously distributed within a sample or an environment
- Microbiological assays are subject to considerable variability of outcome
How are incongruent microbial testing results handled?
There are two reasons for incongruent microbial contamination. The first reason is a laboratory error producing an invalid result. The second reason is that the product contains contamination or specific types of contaminants outside established levels or limits. It is difficult to ascertain if a laboratory error resulted in an invalid result or if a sample contains an unexpected contaminant without a quality control evaluation of the laboratory situation. Thus, quality control should be alerted as soon as a questionable test result appears. An estimate of the variability of the assay may be required to determine whether the finding is significant. As part of a laboratory investigation, the laboratory environment, protective sampling conditions, historical data concerning the samples, the nature of the materials from which samples were taken, and the microbial survival or proliferation rate detected are all evaluated.
If laboratory operations cause a nonconforming test result, a corrective action plan should be developed and implemented. After action plan implementation, managers should carefully monitor the microbiological test or practice in question to determine if the correction action plan has the desired effect. Assay results invalidated due to laboratory operations are all documented, and retesting is performed.
Summary
Overall, appropriate recording and evaluation of data for regulatory testing are vital to accurate microbiology testing. The testing laboratory’s layout, equipment qualification, and regular laboratory technician training all ensure that microbiological testing is completed time and time accurately. Whether you choose to do microbiology testing in-house or outsource your regulatory testing, establish procedures that provide consistent recording and evaluation of data obtained from microbial assays. Should you decide to outsource your microbiological or aseptic environmental monitoring testing for your medical device or medical product, choose a contract testing organization that can support your needs.
Ethide Labs is a contract testing organization that specializes in Microbiology Testing and Environmental Monitoring. Ethide Labs provides in-vitro cytotoxicity tests in-house and outsources in-vivo cytotoxicity work for toxicity testing of medical devices, products, and drugs. Ethide Labs also offers Sterilization Validations, Bioburden Testing, Bacterial Endotoxin Testing, EO Residual Testing, Package Integrity Testing & Cytotoxicity Testing services for medical device companies and allied industries. Ethide is an ISO 13485 certified facility.
References
United States Pharmacopeial Convention. <1117> Microbiological Best Laboratory Practices. Rockville, MD, USA. 2021. (USPC <1117>)
