Microbiology Testing Vs. Microbial Immersion Challenge Testing
What is microbiology?
Microbiology contains the Greek and Latin roots of “micro,” “bio,” and “ology.” The “micro” stands for small, the “bio” stands for biology, and the “ology” is the study of something. Microbiology can also be defined by “microbial,” which refers to microorganisms. Thus, microbiology is the study of microorganisms, where microorganisms are small living components of the broad field of biology. Microbe testing, Information about microbiology test labs for medical devices and products, microbe testing, microbial challenge testing, and GMP microbial broth for testing is covered in this article.
What is a microbial challenge?
The “microbial” in microbial challenge testing refers to microorganisms. The “challenge” component of microbial challenge testing refers to exposure. In a physical challenge, you are exposing your body to physical challenges. In a microbial challenge, a product is exposed to (challenged by) microbes.
What are the differences between microbial challenge and microbiology?
Microbiology involves microbial characterization, such as identifying the species and genus of different microbes in a sample. Where microbiology refers to identifying all types of microorganisms (fungi, bacteria, etc.), microbial challenge typically refers to selected microorganisms used for the microbial challenge.
What is microbiology testing?
Microbe testing identifies the presence and the type of microbes in a manufacturing environment, medical product, or medical device. Specific regulatory testing for microbiology may include assays such as 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. Microbe tests are governed by USP 61 and USP 62.
What is microbial immersion challenge testing?
In a microbial challenge, a product, agent, or process is exposed to (challenged by) microbes.
Microbial immersion challenge testing evaluates a finished product’s package integrity by exposing the sterile packaged product to liquid bacteria. The liquid bacteria are grown in a special GMP microbial broth for testing. After the package has been exposed to bacteria, the contents are assessed for bacterial contamination. Only the visual presence of the bacterium can be evaluated with microbial immersion testing.
What products require microbiology testing?
Microbe tests are imperative for preventing product-induced illness and mitigating contamination risk in manufacturing environments, especially aseptic manufacturing environments. Aseptic manufacturing environments rely heavily on microbiological testing because aseptic processing requires the exclusion of microorganisms from the manufacturing methods. Thus, microorganisms must be prevented from entering open containers or product materials during aseptic processing. As a result, microbial tests are used to monitor clean rooms and facilities that manufacture products using aseptic processing. All sterile products and medical non-sterile products will require one or more microbial tests before marketing.
What products require microbial immersion challenge testing?
Microbial challenge tests by immersion are used when a validated physicochemical leak test method does not exist or when there is a need for direct evidence of the prevention of microbial entry into a packaging system. Thus, the packaging used for the product determines whether a microbial immersion challenge is an appropriate or unnecessary regulatory assessment. Microbial immersion challenge testing is a qualitative measure that confirms leaks in nonporous rigid or nonporous flexible packages. For this test to be effective, the packages must tolerate liquid submersion. Microbial immersion challenge testing is often used during product–package development and validation studies.
How are microbiology tests performed?
Microbiology testing often requires sample collection from a product, a surface, a water source, or the air. Once samples are obtained, various microbiology testing can be performed. Below are links to articles related to multiple microbiology tests and testing methods. Firstly, you can find further details on USP 788 particulate matter testing here. Microbial characterization methods can be found here, whereas the top techniques for microbiology examination are here. Lastly, information on how to record and evaluate microbiology data is here.
How are microbial immersion challenge tests performed?
Microbial immersion challenge testing is performed in a microbiology test lab. Challenge testing begins by filling test samples with sterile, growth-supporting media (a GMP microbial broth for testing). The growth-supporting media undergoes incubation and visual sample inspection to ensure the sterility of the microbial growth broth before the microbial challenge. Soybean-casein digest medium is commonly used for microbial immersion challenge testing. Samples are then immersed in a concentrated bacterial suspension at temperatures that support microbial growth. Brevundimonas diminuta and Serratia marcescens are the most used microorganisms for immersion challenge testing and are used at a minimum concentration of 105 colony-forming units per milliliter.
After immersion within the bacterial suspension, samples are exposed to pressure cycles under a vacuum. Differential pressure helps eliminate trapped air and ensures that liquid media within the packages make it to any leak sites. Additionally, differential pressure simulates the pressure changes during air transport of the product. In some cases, differential pressure can simulate conditions experienced by the product during sterilization treatments.
After immersion, samples are incubated under growth-promoting conditions. Package contents are then examined for evidence of microbial growth by visual inspection. A positive visual inspection will find bacterial growth inside the tested packages. Microbial immersion challenge testing takes about 1-2 weeks for completion due to the time needed for pre-incubation, sample immersion, incubation following sample immersion, and microbial inspection.
What are the differences between microbiology testing and microbial immersion challenge testing?
Microbiology testing is used for environmental monitoring and sterility assurance. In contrast, microbial immersion challenge testing is a package leak test for nonporous packaging that applies differential pressure under a vacuum. The differential pressure supports leak testing and simulates pressure differentials if packages are shipped as air freight. Microbial immersion challenge testing is qualitative (pass/fail), whereas most microbiology testing is quantitative and expressed as colony-forming units (CFUs). Contract testing laboratories with microbiology test labs are typically capable of performing both microbe and microbial immersion challenge testing.
Summary
Overall, microbiology testing and microbial immersion challenge testing are imperative for the regulatory approval of pharmaceuticals, cosmetics, medical devices, and certain types of product packaging. These tests ensure that parenteral products, topicals, and medical devices have sufficient sterility and packaging integrity to keep patients safe during product use. All in all, ensure you choose a contract manufacturing organization with a microbiology test lab that can support you with appropriate microbiology and microbial challenge testing for your unique cosmetic, pharmaceutical, or medical device product needs.
MycoScience is a contract manufacturing organization specializing in Microbial Aerosol Challenge Testing and Microbiology Testing. MycoScience also offers Sterilization Validations, Preservative Efficacy Testing,Cleaning Validations, Accelerated Aging, Bioburden Testing, Cytotoxicity Testing, Bacterial Endotoxin Testing, EO Residual Testing, Package Integrity Testing & Environmental Monitoring services medical devices and allied industries. MycoScience is an ISO 13485 certified facility.
References
Michael J. Akers. Sterile Drug Products Formulation, Packaging, Manufacture, and Quality. Drugs and the Pharmaceutical Sciences. Informa Healthcare. 2010.
United States Pharmacopeial Convention. <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests. Rockville, MD, USA. 2021. (USPC <61>).
United States Pharmacopeial Convention. <62> Microbiological Examination Of Nonsterile Products: Tests For Specified Microorganisms. Rockville, MD, USA. 2021. (USP <62>).
United States Pharmacopeial Convention. <1207.2> Package Integrity Leak Test Technologies. Rockville, MD, USA. 2021. (USPC <1207.2>).
