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Science Driving New State-of-the-Art Practices for Microbial Control

Aug 27, 2015

While microbial contamination control in pharmaceutical manufacturing is at a level needed to ensure safe products, most would not characterize it as "state-of-the-art." An outsider taking a stroll through most pharmaceutical operations might question why 21st century products produced primarily with 21st century technologies are monitored using 19th and 20th century microbial tests. It is fair to say that this is one area where the science and its practical applications have left the industry far behind.

Nowhere is this contrast more stark than in the control of biofilms and bioburden and in sterility testing. Those who have been involved in pharmaceutical microbiology over the past two decades understand that the sterility test has its limitations—in fact, many consider it useless—yet it is still the most widely used control test within the industry. With respect to bioburden control, current approaches are based on a 30-year-old scientific understanding of bioburden, at least until very recently.

Microbiologists can now expect to access an increasing number of new tools for contamination control. To ensure successful control, however, these approaches will need to be utilized within a framework that accounts for knowledge passed down between generations of microbiologists. Current, mainstay technologies need to be fully understood even as new technology gradually becomes available.

Edward Tidswell, PhD, Director, Quality, Baxter Healthcare; Mark Pasmore, PhD, Manager, Sterility Assurance Research Center, Baxter HealthCare; and Cheryl Platco, Principal Scientist, Merck Research Laboratories, spoke to the PDA Letter about where the pharmaceutical industry stands on state-of-the-art microbial control. All three will present at the upcoming PDA 10th Annual Global Conference on Pharmaceutical Microbiology in October (1–3).

Logic-Driven System for Global Control

Baxter Healthcare is a large global firm with approximately 40,000 employees spread across 71 facilities in over 25 countries. The company found that an extensive global supply chain, differing regulatory standards and a growing portfolio of diverse, innovative products presented challenges to ensure the microbial control needed to manufacture product at its highest quality. This led to the development of a systems-based microbial control strategy.

Tidswell described this approach as a "self-detecting and self-correcting system." He characterized it as a systematic, logic-driven process that controls microbial risks during the product lifecycle, and relies on understanding the individual components of the system through each other rather than in isolation.

Baxter’s system is holistic. Real-time risk assessments and data trigger certain specifications that result in review and evaluation of risk (pFMEA, traffic flow, etc.) (Figure 1). Baxter’s real-time risk assessments occur on a frequent, periodic basis and involve subject matter experts (usually microbiologists) interacting directly with those on the manufacturing floor. Traditionally, risk assessments are performed only on an ad hoc basis with little to no direct involvement with those on the manufacturing floor.


Real-time risk assessments then lead to a control scheme that documents the controls, monitoring and logic, and then generates a Quality Plan that specifies the schedule of required improvements.

"We’ve got all these well-evolved elements that contribute," he said. "We’ve got these parts that are really, really good. We’ve got some well-established tools and very sophisticated parts to it...each part of these elements in this system have to work and keep together almost like pieces of a jigsaw, so you don’t have to keep going back and reinventing the wheel."

Tidswell’s team designed the system in such a way that it could be viewed, in a sense, as an "automated" system.

"It certainly has the aspect of running independently," he explained. "If you put these parts together, then the reliance upon human beings or subject matter experts remembering or relying upon trigger systems to do something is removed. It almost becomes an automated process and it drives continuous improvement."

Still, one could argue that these individual elements are characteristics of a company with an overall good quality system. But Tidswell said that he has not seen many firms that take a true systematic approach to it.

"Systems-based takes a sort of different perspective because systems-based microbial control instills automatically," he said. "Continuous improvement is not a singular project or program. It’s not a business venture or a business ideal. It is ingrained in what you do and how you behave as an organization. And that’s part of your system. I don’t think many organizations build that into true genuine systems that are self-identifying and self-correcting."

Further, he emphasized that it’s "far better to have a system that you plug in everywhere that automatically self-detects and automatically self-corrects. I think companies with strong quality cultures do have elements of this, but I don’t believe it’s put into a true system. It’s a slow process as well. When you implement a system, the scientists and engineers want things to be perfect like a well-oiled engine from the start. Systems-based allows you to turn that motor over and start it without having it perfect."

New Tool for Bioburden, Biofilm Control

The management of bioburden and biofilm within a facility is key to ensuring effective microbial control. Recalls and plant shutdowns have resulted from failure to control persistent bioburden and biofilm contamination. Until recently, however, pharmaceutical microbiologists and engineers lacked an authoritative document outlining control considerations for bioburden and biofilms.

PDA Technical Report No. 69: Bioburden and Biofilm Management in Pharmaceutical Operations is a groundbreaking document that not only provides an overview of the science of bioburden and biofilm management but also offers steps for remediation and approaches for microbial control in this area. This includes a guideline for an overall microbial control strategy and recommendations for a sound, scientifically based program to detect and characterize bioburden and biofilms.

Mark Pasmore, who participated on the technical report team, feels that TR-69 is overdue. In his opinion, there has been a lack of communication in the industry regarding how to effectively handle bioburden and biofilms—particularly the latter which present challenges due to being surface-adhered and notoriously difficult to inactivate with disinfectants and sanitizers.

"Part of it is that education piece—letting the community know about biofilms, getting not just the microbiologists, but the entire pharmaceutical community, up to speed on what they are has been a slow time coming," he said. "I think the other part of it is...some groups feel that if they haven’t noticed a problem, there isn’t a problem."

Pasmore added: "I think there has been, unintentionally, a little bit of a denial that this is truly an issue, and I think there is a little bit of that aspect of companies not wanting to air their dirty laundry when they’ve had an issue."

But now companies are looking more extensively into biofilm and bioburden. Some are even exploring automation of sampling. The ideal would be to remove human involvement in isolators and solution lines entirely as human contact increases contamination risk. Pasmore pointed out that cleanrooms in the silicon wafer industry are completely automated. These cleanrooms have "taken the human component out of there because the cost of having a single microbial contamination in those systems can cause millions of dollars of material to be scrapped. Those systems have become highly automated, highly functional and because of that, have very minimal bioburden issues."

At this time, both industry and regulatory agencies have been slow in embracing automation. At the same time, there is a critical need for enhanced solutions to detect biofilm instead of just measuring biobuden.

"Enhancing our detection of biofilms certainly will benefit down the road," Pasmore said. "That said, right now, there is no ideal system for biofilm detection. There is no great means to be able to readily detect biofilms."

He hopes that TR-69 leads industry to encourage academia and vendors to research new methods for biofilm detection. Pasmore sees rapid methods becoming an important technology, especially as these methods become more sensitive.

Awareness of LAL Intricacies Needed

Microbiologists now have expanded tools and methods to ensure microbial control along with greater knowledge of the variable nature of microorganisms. But while new technologies and processes offer innovative solutions for the future of control, some microbiologists worry that newer generations of microbiologists fail to understand the intricacies of standard tests used at present—even old standbys like the LAL assay.

Microbiologist Cheryl Platco views the latter as a factor in the controversy surrounding Low Endotoxin Recovery (LER), also referred to as Low Lipopolysaccharide Recovery (LLR).

She said, "the LLR phenomenon is observed when purified lipopolysaccharide (LPS) is added to undiluted biologics that contain chelating citrate or phosphate buffers with polysorbates. Purified LPS could not be recovered from these buffered products with the standard LAL assay because the lipid A molecule fails to activate the clotting cascade due to a masking effect."

Not surprisingly, this has generated controversy within the industry. Platco’s own observations suggest that the original LER study, which utilized purified LPS as an artificial endotoxin surrogate, brought to light the effect of chelating buffers and polysorbates on the LPS molecule in selected product matrices.

"What we’re trying to measure with the compendial LAL test methods is the activity of any naturally occurring contaminant endotoxin," she said. "The endotoxin test is an assay meant to detect clinically relevant endotoxin. Natural endotoxins which are the true contaminants in products are easily recovered. There are also certain matrices that may actually destroy or inactivate both LPS and natural endotoxin. Efforts to reactivate LPS molecules to active states are simply academic exercises if they cannot be demonstrated to be clinically relevant."

Platco is concerned that this confusion may be the result of a new generation of microbiologists who may not be fully aware of the complex nature of the compendial LAL test. Also, when dealing with biological molecules such as monoclonal antibodies and therapeutic proteins, it is important to discern between pyrogenicity from endotoxin versus pyrogenicity as side effect of the active ingredient protein molecule itself.

"I do think some of the confusion is due to a lack of understanding of the assay," she said. "Some do not understand how the rabbit pyrogen test and endotoxin standards were developed and what the LPS standard represents."

Although considerable background information on the LAL test is available from general USP chapters, older U.S. FDA guidances, as well as PDA books such as The Bacterial Endotoxins Test: A Practical Guide, Platco wonders if "there is a real need for us to pass down this information that’s in all these books about how the reference standard was originally defined, how the test was qualified against the rabbit pyrogen that there’s a better understanding that this was very variable."

One way, she suggested, might be for USP to develop a general chapter that not just instructs on how to run the test but also explains its variability and offers a comprehensive view of the exact nature of the LAL assay. Platco concedes that hers is just one opinion regarding the LER controversy. But the concern about newer microbiologists having a complete understanding of standard testing methods and protocols is valid.

While there are considerable developments under way to innovate microbial control, microbiologists still must have a complete understanding of existing methods. After all, building on the past is the epitome of good science. Without this holistic understanding, the future of microbial testing could become murky, especially as new control methods become available. Reviewing the latest research and existing literature will be the key to successful control programs. Still, these programs will need to use sound science and logic, or as Tidswell put it: "We’ve got to aspire to be more like Spock!"


Tidswell, E. "Implementation of Global System-Based Microbial Control – A Case Study." Presentation at the PDA 10th Annual Global Conference on Pharmaceutical Microbiology, Tuesday, Oct. 20, 2015, 2 p.m.

Pasmore, M. "An Overview of the New PDA Bioburden Biofilm TR." Presentation at the PDA 10th Annual Global Conference on Pharmaceutical Microbiology, Tuesday, Oct. 20, 2015, 10 a.m.

Platco, C. "LER Follow-up." Presentation at the PDA 10th Annual Global Conference on Pharmaceutical Microbiology, Tuesday, Oct. 20, 2015, 10:30 a.m.

About the Experts

Edward C. Tidswell, PhD, is Quality Director for Baxter Healthcare. This global role covers the entire breadth of microbiological control, sterilization and sterility assurance across a diversified healthcare company.

Mark Pasmore, PhD, currently works for Baxter Healthcare Corporation as a Sr. Principal Engineer in the Technology Resources Sterility Assurance department.

Cheryl Platco currently oversees the Research Microbiology laboratory, performing microbiological testing for both pharmaceutical and vaccine development products.


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