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Microbiology Expert Committee Takes Closer Look at Contamination, Antibiotic Potency and Modern Methods
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For manufacturers, the extent of microbial contamination in a finished product must always be a consideration.
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USP's Microbiology Expert Committee looks at multiple issues related to microbial contamination, with the goal to ensure the quality of different types of drug products. Under the committee's guidance, several new or revised General Chapters are being advanced.
With regard to sterile as well as non-sterile pharmaceutical products, microbiological control is a key factor. Sterile products—which include parenteral drugs—cannot allow for any microbial presence, given that they are administered into the bloodstream. Non-sterile drugs—such as solid oral dosage forms or syrups—allow for the presence of small amounts of microorganisms in their makeup. Microbial contamination in sterile drugs can result in disease and—in some cases—even death. While all products purported to be sterile have to meet the requirements of USP General Chapter Sterility Tests <71>, sterility assurance is gained only through the use of robust and validated sterilization processes.
USP's General Information Chapter Sterilization and Sterility Assurance of Compendial Articles <1211> currently deals with general principles of sterility assurance as well as some information on various sterilization processes. Feedback from users and stakeholders indicates that greater detail is also needed to address specific sterilization processes. With future revisions, <1211> will focus exclusively on sterility assurance, and USP has initiated the development of several chapters—the <1229.x> series—dedicated to individual sterilization processes. Chapter <1229> will serve as the overarching chapter covering the general concepts of sterilization. Eleven chapters have been planned that will focus on distinct methods for sterilization, how they are to be conducted and what materials are most suitable for their use.
Another major consideration for manufacturers with regard to microbial presence is the issue of contamination control. General Chapter Microbiological Control and Monitoring of Aseptic Processing Environments <1116> has recently undergone a major revision and will become official in 2012. In the arena of bioburden control for non-sterile pharmaceutical products, very little information is available either in the pharmacopeias or regulatory guidance documents. The quality of raw materials, the surrounding environment during manufacture and personnel conducting quality control activities are just some of possible factors that can contribute to the bioburden of a product. In a draft proposed chapter that will be available for public comment in 2012, USP will recommend a risk-based approach to bioburden control of non-sterile drug products. By looking at factors that have the potential to affect product quality and patient safety and considering the best ways of dealing with those specific factors, the user can then identify the risk associated with a product and apply appropriate methods for bioburden control.
In the case of antibiotics, microbial assays are used to measure the potency of a drug by measuring its inhibitory effect on a target microorganism. Because of difficulties associated with conducting this type of assay and the time required for its completion (i.e., 3 to 4 weeks), USP is exploring the use of a more rapid assay (e.g., high-performance liquid chromatography, or HPLC) as a replacement. While not all antibiotics have an approved HPLC assay, USP will look for guidance from its newly established Expert Panel on the topic to recommend validation criteria for replacement of an antibiotic microbial assay by HPLC methods. USP will also look to manufacturers for information on validated HPLC methods that have been approved by the regulators, for inclusion in specific antibiotic monographs.
A major limitation of current pharmacopeial microbiology tests is their reliance on demonstration of growth of microorganisms and low sensitivity. Consequently they are slow and can take up to several weeks. Therefore, an important area of focus for USP in its 2010–2015 cycle is the development of new referee tests based on more sensitive, modern microbiological methods that can detect or enumerate microorganisms in a rapid and sensitive manner. The USP Microbiology EC is also working to update General Chapter Validation of Alternative Microbiological Methods <1223>, to enable the user to validate modern tests relative to compendial methods.
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Radhakrishna S. Tirumalai, Ph.D.
Principal Scientific Liaison-
General Chapters
Documentary Standards Division
United States Pharmacopeial Convention (USP)
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