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RMM »
Table 2. Examples of scientifi c methods (this list is not inclusive of what TR33 describes).
Growth-based • Detection of carbon dioxide (CO2
)
• Utilization of biochemical and carbohydrate substrates • Digital imaging and auto-fl uorescence of micro-colonies • Fluorescent staining and laser excitation of micro-colonies • Use of selective media for the detection of specifi c microorganisms • Measurement of change in head space pressure
Viability-based • Flow cytometry
• Laser scanning solid phase cytometry • Direct epifl uorescence fi lter microscopy
Optical Spectroscopy • Light scattering/intrinsic fl uorescence • Raman spectroscopy
Cellular Component-based • ATP bioluminescence • Fatty acid profi ling • Matrix Assisted Laser Desorption Ionization Time of Flight (MALDI-TOF) mass spectrometry • Fourier Transform-Infrared (FT-IR) spectrometry • Endotoxin detection using LAL, recombinant factor C and ELISA
Nucleic Acid Amplifi cation Techniques • Polymerase Chain Reaction (PCR) • Reverse Transcriptase (RT) PCR • Ribotyping • Gene sequencing • PCR and MALDI-TOF mass spectrometry
Micro-Electro-Mechanical Systems (MEMS) • Lab-On-A-Chip and microfl uidics • Microarrays • Biosensors • Nanotechnology
added. These include the variability associated with the preparation of test samples, sample distribution error, cellular arrangement and metabolic activity.
To round out the discussions on validation, TR33 provides additional guidance on endotoxin testing methods, unique methods in which the use of standardized suspensions of microorganisms may not be applicable for use, changing existing specifications or acceptance criteria, Mycoplasma testing, and a new section focusing on microbial identification systems. Here, recommendations for demonstrating accuracy and precision are offered.
Following the sections on validation, TR33 provides greater consideration and guidance for implementation and transferring a validated alternative or rapid method to a secondary laboratory or manufacturing facility. The technical report concludes with a comprehensive reference section.
The revised PDA TR33 is a culmination of industry best practices that have been successfully used by multinational firms and accepted by global regulatory agencies when validating and implementing alternative and rapid microbiological methods. The document provides a blueprint for a practical, sensible and well- defined validation and implementation plan.
Author Biography
A familiar section describing method validation criteria for both quantitative and qualitative methods returns in the revised TR33. Standardized cultures in a suitable diluent are initially used to challenge the alternative or rapid system to demonstrate accuracy, precision (i.e., repeatability), specificity (e.g., using stressed organisms or mixed cultures, and to ascertain inclusivity and exclusivity), limit of detection and quantification, linearity, range, ruggedness (i.e., intermediate precision and reproducibility) and robustness. Actual product or test samples are subsequently used to demonstrate that the alternative or rapid system is at least equivalent or comparable to the existing method intending to be replaced. In each validation criteria section, guidance on actual testing procedures, acceptance criteria and the use of statistical models are specified.
The new section on method suitability provides enhanced guidance on false positive and false negative testing. The purpose of suitability testing is to demonstrate that the new method will be compatible with specific product or sample matrices that will be routinely assayed. A similar discussion used to be described under the Specificity section in the original TR33; however, the current revision includes enhanced guidance and recommended acceptance criteria.
A number of complementary sections that address further considerations while performing validation studies have also been
38 | | November/December 2013
Dr. Michael J. Miller is an internationally recognized microbiologist and subject matter expert in pharmaceutical microbiology and the design, validation and implementation of rapid microbiological methods. He is currently the President of Microbiology Consultants, LLC (
http://microbiologyconsultants.com). Over the course of 25 years, he has held numerous R&D, manufacturing, quality, and consulting and business development leadership roles. Currently, Dr. Miller consults with multinational companies in providing technical, quality and regulatory solutions in support of RMMs, sterile and non-sterile pharmaceutical manufacturing, contamination control, isolator technology, validation and microbiological PAT. He also provides comprehensive training for his clients in the areas of rapid method validation and implementation.
Dr. Miller has authored more than 100 technical publications and presentations in the areas of rapid microbiological methods, PAT, ophthalmics, disinfection and sterilization, is the editor of PDA’s Encyclopedia of Rapid Microbiological Methods, and is the owner of
http://rapidmicromethods.com, an educational website dedicated to the advancement of rapid methods. He was the Chairperson for the revision of PDA Technical Report #33: Evaluation, Validation and Implementation of New Microbiological Testing Methods.
Dr. Miller holds a Ph.D. in Microbiology and Biochemistry. He was appointed the John Henry Hobart Fellow in Residence for Ethics and Social Justice, awarded PDA’s Distinguished Service Award and was named Microbiologist of the Year by the Institute of Validation Technology (IVT).
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