For more than 30 years, the field of alternative and rapid microbiological methods (RMMs) has influenced the application of novel technologies across a number of industry sectors. In fact, much of the development of new instrumentation, software and analytical methods for the detection, enumeration and identification of microorganisms has been driven by consumer and patient needs within the food, beverage, environmental and clinical or health care industries. For the past 15 years, advances in rapid technologies have also encouraged the pharmaceutical, biopharmaceutical, medical device and personal care industries to validate and implement RMMs in place of their traditional microbiology methods within QC/QA labs and on the manufacturing floor.
Rapid methods are now being used for a wide range of applications. For example, a number of companies within the pharmaceutical industry have obtained regulatory approval to implement RMMs as alternative methods for finished product release testing (e.g., sterility), in-process and raw material bioburden analyses, environmental monitoring, Purified and Water for Injection (WFI) testing, endotoxin analysis, microbial identification and the detection of Mycoplasma.
Many currently available technologies provide more accurate, precise, and sensitive test results when compared with classical growth-based methods. Additionally, they may be fully automated, offer increased sample throughput, operate in a continuous datacollecting mode, provide significantly reduced time-to-result (e.g., from days or weeks to hours or minutes), and for some RMM platforms, results in real-time may be achieved. These methods have also been shown to detect slow-growers, dormant and viable but non-cultural (VBNC) microorganisms as compared with standard methods used today. Most importantly, a firm that implements an RMM in support of sterile or non-sterile manufacturing processes may realize significant operational efficiencies during the monitoring and controlling of critical process parameters, reducing or eliminating process variability, improving product knowledge and reducing risk to patients and consumers. Additional benefits may include the elimination of off-line assays and a reduction in laboratory overhead and headcount, lower inventories (raw material, in-process material, and finished product), a reduction in warehousing space, and a decrease in repeat testing, deviations, out-of-specification investigations, reprocessing or lot rejection.
Because many RMM technologies consist of a combination of instrumentation, software, consumables and reagents, in addition to specific detection, quantitative or identification analytical methodologies, it is important to develop a comprehensive and holistic approach to the validation process to ensure that the entire RMM system is suitable for its intended use. This is where PDA Technical Report No. 33 (TR33) comes into play.
The original version of TR33, Evaluation, Validation and Implementation of New Microbiological Testing Methods, was published in 2000. This best practice document provided the pharmaceutical industry with the very first guidance on how to select and validate novel and rapid microbiology systems. Since that time, many new technologies were introduced, validation strategies were improved and, most importantly, acceptance and encouragement for implementing rapid and alternative methods by worldwide regulatory agencies increased significantly. For these reasons, there was a need to update the original technical report.
In the beginning of 2008, a task force team comprising subject matter experts in rapid and alternative microbiology technologies, validation, regulatory affairs, quality control, manufacturing and statistics was assembled for the purpose of revising TR33. Committee members represented industry, technology suppliers, consultants and regulators (see Table 1).
Table 1. TR33 Committee Members
When the committee was closing in on a final draft, additional reviews and input were provided by end-users who had successfully validated and implemented RMMs in their own facilities as well as key global regulators and pharmacopoeia experts. As a last step, PDA’s Science Advisory Board, Biotech Advisory Board, and Board of Directors provided their approval. The new TR33, Evaluation, Validation and Implementation of Alternative and Rapid Microbiological Methods, was published in October 2013.
TR33’s front matter is composed of an introduction, scope, purpose and a glossary of terms. The first section provides an overview of the challenges associated with classical microbiological methods including long times for obtaining a quantitative or qualitative result, the potential inability to recover microorganisms (e.g., when they are stressed, dormant or VBNC) and an unmet need for linking microbiology to Quality by Design and quality risk management principles. This is followed by an introduction to alternative and rapid methods including a discussion of their advantages over traditional growth-based methods in terms of time to result, sensitivity, accuracy and precision.
Because regulatory expectations for the validation and implementation of rapid and alternative methods have appreciably evolved over the last 10 years, TR33 addresses the current positions and opinions of authorities such as the U.S. Food and Drug Administration (FDA), European Medicines Agency (EMA), the Australian Therapeutic Goods Administration (TGA) and the Japanese Pharmaceuticals and Medicinal Devices Agency (PMDA). The section discusses industry guidance documents, changes in policy and regulations, validation expectations and instances when a formal regulatory submission may or may not be necessary. Additional considerations when working with other regulatory agencies and countries (i.e., Rest of World) are also provided.
Next, a discussion on enhancing the technical, quality and business aspects of manufacturing and quality assurance is provided. Here, TR33 describes increases in process and product knowledge, continuous improvement, automation, and return on investment when implementing rapid and alternative methods.
An evaluation of risk when using an alternative or rapid method, as well as the risk to product quality when implementing such methods, is the topic of the next section. Guidance on the identification of potential risks or hazards, severity, occurrence and the ability to detect these risks are discussed. Risk analysis tools and other resources are also provided.
The next section focuses on technology suppliers. TR33 provides recommendations for what end-users should consider prior to purchasing instrumentation and after a method is put in place. This includes a supplier’s quality systems, field support, assistance with validation and financial stability. Guidance on conducting supplier audits and assessments is also afforded.
A brief review of automated systems is then discussed. Methods that are considered an extension of compendial or classical methods (e.g., a growth-based system that produces colony forming units) may realize reduced validation requirements.
Table 2. Examples of scientifi c methods (this list is not inclusive of what TR33 describes).
The next series of sections provide an overview of the scientific principles for alternative and rapid systems that are currently available or are in development, and these are identified in Table 2. Technologies that detect, enumerate and identify microorganisms are described; however, supplier and technology names are excluded to avoid bias. Fortunately, TR33 provides references both in print and online (such as the RMM educational website, http://rapidmicromethods.com) that describe commercially available systems.
The second half of TR33 concentrates on validation and implementation. The validation section first describes the use of feasibility or proof-ofconcept testing when initially identifying systems/methods that may be compatible with a firm’s intended test samples or products. TR33 then provides recommended responsibilities for both the end-user and the technology supplier. Overviews of the User Requirements Specification, Design Qualification, Functional Design Specification, Requirements Traceability Matrix, SOPs and technology training, system integration, and Installation (IQ), Operational (OQ) and Performance (PQ) Qualification strategies follow. Approaches for on-going maintenance and periodic reviews (e.g., preventive maintenance, calibration and software updates) are also examined. It is of interest to note that TR33 now describes a two-phased approach to validating the entire system that includes verification of the equipment and software, followed by validation of the analytical method. The majority of the computer system validation will usually occur during the OQ, with the PQ covering both method validation and method suitability (see below).
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 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 welldefined validation and implementation plan.
Author biography
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).