Achieving Annex 1 Compliance In Sterile Manufacturing, Part 1: Common Compliance Failures

By Bikash Chatterjee, president and CSO of Pharmatech Associates, a USP Company and USP Microbiology

The 2022 revision of EU GMP Annex 1 represents the most comprehensive update to sterile manufacturing guidance in decades. The intent behind the update was to drive harmonization across health authorities while incorporating advances in manufacturing technology and approaches in an effort to remove ambiguity for manufacturers as to both the strategy and elements required to ensure the safe manufacture of sterile products. The need for a change in thinking was also partially driven by high-profile contamination events and a regulatory determination that historical, checklist-based approaches were no longer adequate. The revision mandates a fundamental shift: away from prescriptive compliance and toward risk-based, science-driven contamination control that manufacturers must design, justify, and continuously demonstrate.¹

Central to the revised framework is the requirement for a comprehensive, facility-wide contamination control strategy (CCS), which constitutes a single coherent narrative connecting facility design, engineering controls, personnel practices, and environmental monitoring (EM) data. Doing this requires microbiological sampling and testing methods that are reproducible and capable. For example, Annex 1 Section 9.29 requires that the recovery efficiency of each sampling method be empirically determined, documented, and available to support data interpretation. The FDA and regulatory agencies in Europe and PIC/S member states are applying these expectations with heightened scrutiny in inspections.

In practice, a persistent gap remains between what Annex 1 requires and what facilities can demonstrate. Manual surface sampling remains largely subjective and technique-dependent. Growth promotion testing (GPT) introduces inoculum variability. Endotoxin testing often lacks the inter-laboratory standardization regulators expect. This three-part series examines these gaps and the tools available to address them. Part 1 focuses on the real-world compliance failures that make the case for change, examining four areas in turn: false negatives in surface sampling, subjectivity in personnel qualification, variability in growth promotion testing, and inconsistency in endotoxin testing. Part 2 covers objective measurement tools and part 3 addresses building a compliant program across the CCS life cycle.

Understanding why programs fail is as important as knowing what the regulations require. The following challenges represent the most common and consequential compliance gaps observed across sterile manufacturing facilities.

The “False Negative” Fallacy

A fundamental requirement of any measurement system is that it can distinguish a true negative from a failure to detect. In EM, this distinction is rarely tested. Facilities frequently report near-zero EM counts without demonstrating that that their sampling system is capable of recovering contamination when it is present. When recovery efficiency is unknown and potentially very low, the resulting data reflects the limitations of the method as much as the state of the environment, and regulators are increasingly asking facilities to demonstrate, through challenge studies, recovery validation, and data trending, that a negative result represents a truly clean environment rather than an insensitive sampling process.

A landmark 2025 multi-site study conducted across more than 300 facilities and encompassing 1,155 individual participant sampling events revealed the scale of this problem. The objective of the study was to evaluate whether adding a surface sampling reference material to qualify sampling methods and operators could circumvent the bias observed in EM program designs and applications. The study utilized a viable surface sampling reference material that provided standardized surfaces precoated with a known quantity of Escherichia coli ATCC 25922. By adding the reference material as part of the sampling method design and qualification, researchers were able to objectively measure what operators actually recovered versus what was present on the surface.

The implications are significant. A facility where 22% of sampling events produce underestimated counts is not generating reliable EM data. Trend analyses built on that data cannot distinguish an improving environment from a worsening one or a true excursion from a technique-induced false positive. When EM data cannot be meaningfully interpreted, the risks to drug sponsors and manufacturers can compound quickly, from inconclusive investigations and unresolved excursions and inspection observations that challenge the validity of the entire EM program to the operational and financial consequences of batch rejections, import alerts, and remediation programs that could have been avoided with a more rigorous measurement foundation.⁵

The Subjectivity Problem In Personnel Qualification

Traditional approaches to surface sampling qualification rely on observation and demonstration. A trainer watches a new analyst perform sampling and evaluates their technique subjectively. The problem is fundamental: In a cleanroom environment designed to be low-bioburden, there are no microbes to recover during a typical training exercise. An analyst can demonstrate perfect visual technique and still have limited ability to recover contamination from a surface, because the training method has no mechanism to measure that capability.

USP General Chapter <1116> Microbiological Control and Monitoring of Aseptic Processing Environments recognizes this, noting that “a formal training program is required to minimize” the risk of sampling-related contamination and that monitoring activities should be conducted using aseptic technique that “approaches perfection as closely as possible.”¹ FDA’s Aseptic Processing Guidance, titled Sterile Drug Products Produced by Aseptic Processing-Current Good Manufacturing Practice, calls for “routine oversight of near-term and long-term trends in environmental and personnel monitoring data.” Neither of these expectations can be fully met without objective data on recovery performance. An observational pass is not the same as a quantitative demonstration of sampling competency.^6,7

In Practice: Preparing for an EU GMP Inspection

A sterile fill/finish facility is preparing for an EU GMP inspection following a Warning Letter issued to a competitor site for deficiencies in EM qualification. Their EM documentation is thorough, and their historical counts are consistently low. But when asked during a pre-inspection readiness review to demonstrate that surface sampling personnel can reliably recover contamination from a surface, they have no quantitative data to present, only training records showing analysts observed sampling demonstrations and signed off on SOPs.

By utilizing a standardized reference material as part of the EM program, across three shifts and two cleanroom suites, that same facility can present trendable, blinded recovery data by analyst, room, and shift, with documented pass/fail outcomes against a defined acceptance criterion. The inspector’s question is answered before it is asked, and the data provide a clear, scientifically defensible evidence trail: personnel are qualified, technique is consistent, and the EM data generated reflect environmental reality rather than sampling artifact.

Aseptic Process Simulation Risks From Variable GPT Methods

Media fills are among the most consequential qualification activities in sterile manufacturing. Any failure forces a complete investigation, potential batch rejections, and possibly additional regulatory scrutiny. The validity of a media fill depends, in part, on the quality of the GPT performed on each lot of culture media used. But traditional GPT methods introduce several critical variables:

• Culturing microorganisms from stock and preparing suspensions to the correct concentration is time-consuming and introduces risk of stock culture contamination.
• Manual dilution and plating methods make consistent CFU delivery inherently difficult, even for experienced analysts.
• Variability in inoculum preparation translates directly into variability in GPT outcomes, and a failed GPT on media fill medium triggers an investigation that may delay or invalidate the entire simulation.

A media fill that cannot be supported by well-documented, reproducible GPT data is a compliance vulnerability that adherence to Annex 1 does not permit.

Endotoxin Testing Inconsistencies

Endotoxin testing presents a different but equally significant challenge. Variability in reagents, test protocols, and equipment across different laboratories and shifts can produce inconsistent results for the same product. Without a harmonized reference material anchored to an internationally recognized authority, the calculation of route-specific endotoxin limits (K values), maximum valid dilutions (MVD), and method suitability data becomes a source of regulatory risk. The transition from animal-derived limulus amebocyte lysate (LAL) to recombinant Factor C (rFC) reagents adds another layer of complexity. The reference material provides the required comparator, enabling manufacturers to build an equivalence data package that can support regulatory submissions and method change notifications.⁸

References

1. European Commission. EU GMP Annex 1: Manufacture of Sterile Medicinal Products. Brussels, 22 August 2022. C(2022) 5938.
2. Erickson, J. Ensuring Repeatable, Viable Surface Sampling in Aseptic Settings. BioProcess Online, February 14, 2025.
3. Eaton, et al. Evaluation of Three Different Contact Plate Methods for Microbial Surface Sampling of Naturally Occurring Human Borne Microbial Contamination. European Journal of Parenteral and Pharmaceutical Sciences, vol. 27, no. 3, 2022.
4. Eaton, et al. To Determine the Microbial Recovery from Different Surfaces Using a Standard Contact Plate Sampling Method. European Journal of Parenteral and Pharmaceutical Sciences, vol. 27, no. 4, 2022.
5. Parenteral Drug Association. Technical Report No. 13 (Revised): Fundamentals of an Environmental Monitoring Program. 2022.
6. U.S. FDA. Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing — Current Good Manufacturing Practice. September 2004.
7. United States Pharmacopeia. General Chapter <1116> Microbiological Control and Monitoring of Aseptic Processing Environments. USP-NF, 2024.
8. United States Pharmacopeia. General Chapter <85> Bacterial Endotoxins Test. USP-NF, 2024.

About The Author:

Bikash Chatterjee, chief executive officer at Pharmatech Associates, has 30 years' experience in the design and development of pharmaceutical, biotech, medical device, and in vitro diagnostic products. His work has guided the approval and commercialization of over a dozen new products in the U.S. and Europe. Chatterjee is a member of the USP National Advisory Board and a past chairman of the Golden Gate Chapter of the American Society of Quality. He is the author of Applying Lean Six Sigma in the Pharmaceutical Industry (ISBN-13: 978-0566092046) and a keynote speaker at international conferences. Chatterjee holds a BA in biochemistry and a BS in chemical engineering from the University of California, San Diego.