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A control strategy can maintain a low level of particulates, and thereby a low bioburden, in cleanrooms
Ingram Publishing/Getty ImagesThis article presents a control strategy for maintaining a low level of particulates, thereby a low bioburden in cleanrooms, and for conducting environmental monitoring to demonstrate the ongoing state of control. Consideration will be given to current and proposed regulatory guidance and other cleanroom standards and monographs. In particular, the revised United States Pharmacopeia (USP) general chapter <1116> on microbiological control of cleanrooms and other controlled environments will be discussed. Changes to the ISO standard 14644 for cleanroom commissioning and qualification are also underway and will be addressed. Finally, some pointers for good practices in contamination control will be presented.
In 2012, mold contamination was found in supposedly sterile vials recalled from the marketplace after hundreds of people were infected with fungal meningitis; the compounding pharmacy responsible for manufacture of the product had clear warning signals. According to one newspaper report, their environmental monitoring program showed extensive contamination by mold and bacteria throughout the production area but they failed to implement effective corrective actions (1).
In environmental control, it is essential to keep microbes out of a cleanroom environment. Escherichia coli (E. coli) has a doubling time of 20 minutes and one E. coli in a facility at 08:00 in the morning, means 8 by 09:00, and 16 million by 16:00 under ideal conditions. Therefore, to keep the environment clean, microbes must be excluded from the environment.
To exclude microbes from the cleanroom, a control strategy is needed. A control strategy is defined as “a planned set of controls, derived from … process understanding, that assures process performance and product quality” (2), or in other words, risk mitigation. Having identified the risk as one of contamination, the source being microbes that are carried on particulates, a whole host of measures is implemented to avoid contamination, starting with facility and equipment and primarily designed, wherever feasible, to separate the operator from exposed product.
Where complete separation is not possible, another set of measures is implemented with the intent of containing as much as possible of the particulate contamination that is shed by humans. Low levels of particulates (i.e., viable and total counts—the latter includes viable and non-viable but we cannot distinguish) are designed into the facility by having a sealed building shell with flush fittings and no gaps or cracks. High efficiency particulate air (HEPA) filters remove not less than 99.97% of particles greater than or equal to 0.3-micron diameter, which in the absence of humans in the area, gives a sterile environment with respect to microbes. Very high volumes of air are pushed through the clean area every hour ensuring many (usually more than 100) air changes per hour in the aseptic core. Cleaning and disinfection procedures are carefully designed and applied to remove any contamination that does find its way into the area, before it can multiply or settle. Operators undergo scrupulous gowning procedures to contain their bodies such that any particles shed are caught inside the cleanroom apparel and only removed outside the aseptic core. Operators are trained and qualified to perform operations in a cleanroom in a manner that does not disturb air currents and that minimizes shedding. Each of the individual measures that are part of the microbial control strategy is potentially crucial to the sterility of finished product especially where such product is aseptically filled (i.e., undergoes no terminal sterilization process in its final container).
Breach of any measure can potentially result in contaminated product, although this is not by any means a one-to-one relationship. Nevertheless, it is a risk that needs to be monitored, which is where environmental monitoring enters the picture. Environmental monitoring is like an intelligence service. It is a risk-monitoring tool that allows us to collect useful data, analyze the data, and feedback the information into our environmental monitoring program. The Central Intelligence Agency (CIA) defines their mission as:
Shouldn’t every pharmaceutical company have a director of environmental monitoring responsible for assuring the existence of an appropriate cleanroom environment by collecting and evaluating data related to the state of control of the environment and providing overall direction (based on analysis of the data collected) regarding the continued collection (e.g., when special sampling and/or corrective actions might be needed)? Most importantly, such a director could create special, multidisciplinary task forces that can get into action fast when high priority issues are identified.
The revised United States Pharmacopeia (USP) chapter <1116> (3) states that when operators are present in the aseptic processing operation, an expectation of zero contamination at all locations during every operation is not technically possible and is, therefore, unrealistic. This statement is problematic because, while scientifically correct, regulatory guidance (such as FDA’s 2004 Aseptic Processing Guide and Annex 1 of the EU GMPs) give “less than one colony forming unit (CFU)/m3 or per plate as the limit for an ISO 5 (Grade A/class 100) area, and FDA goes further, stating that ISO 5 should routinely yield zero counts. Indeed, it is true that in today’s aseptic processing environment it should be possible to routinely yield zero counts, which does not contradict the USP statement that zero at all locations during every operation is impossible. However, in order not to mislead newcomers to a highly regulated environment, it is important to emphasize the regulatory limits as stated. This means that any count at all in an ISO 5 area would require a product impact assessment of some kind if there were production activity when the count was retrieved.
The breakthrough in the USP chapter is the statement that “assessment of risk associated with aseptic operation must be assessed over a significant period of time and the contamination recovery metric based on actual data collected in the facility. The contamination rate can then be used to track the state of control of the facility/the ongoing performance and to allow early identification of trends and corrective actions and refinements to the overall control strategy” (3).
The USP chapter states that once optimal conditions are established (not necessarily immediately after performance qualification [PQ] is finished—optimal conditions may come later when operators are more experienced and therefore more competent), the contamination recovery rate should become stable within a known range of variability. This concept is a basic tenet of quality assurance, and at that point, even small excursions from the range should be treated as alarm signals requiring close scrutiny and possible aggressive corrective actions to return to the previous state of control. The point being made is that when there is a change in the recovery rate, this is generally indicative of breach of one or more of the risk mitigation measures described above and, therefore, signals a potential breakdown of the control strategy. It is a serious matter and must be addressed.
The revised USP chapter requires a carefully documented investigation when recovery rates increase, description of corrective actions, and monitoring of effectiveness. A change in the contamination recovery rate might be a reason to convene a multidisciplinary task force that would be disbanded only after confirmation that the previous levels of recovery have been achieved once again. The focus should be on containment measures to ensure uniformly low recovery rates and a company should be vigilant in trying to reduce the recovery rates over time.
Cautions when reading the revised chapter
The number 15 cfu is mentioned in a manner which, in the absence of an understanding of the issue, might be misinterpreted as suggesting product could be released if a single recovery of 15 cfu were found in an ISO 5 area, provided there was a uniformly low recovery rate for all preceding days in the same month. This author does not believe that is the USP’s intent—certainly not without exceedingly robust safeguards—and it will be interesting to hear regulators respond to the revised chapter. In any case, the ultimate and sole responsibility for the safety of product released to the marketplace is that of the company producing it; therefore, there must be a documented impact assessment for any excursion outside the predetermined acceptance criteria.
ISO 14644-1 and 2 guidelines address the design and operation of cleanrooms and are currently under revision. These guides only address particulate contamination of clean environments and do not discuss microbial contamination. They are often mistakenly quoted as addressing air velocities, changes, airflows, and pressures, which is not the case. The current revisions are intended to simplify testing to remove the need for evaluating the 95% upper confidence limit (UCL) at 2–9 locations, which is common practice. The target date for publication of the ISO documents is December 2013–January 2014. There is a proposal to delete the requirement for testing greater than or equal to 5 micron particles, which will take the EU Grades A and B out of the scope of the guide for classification purposes if the proposal passes into the final standard. Current issues still under discussion include:
Maintaining the quality of the environment in a cleanroom requires continual and relentless investment of energy in the facility and equipment maintenance and cleaning; in personnel competence (not just check the box “training and qualification”); in a garmenting program; in cleaning and disinfection; and in environmental control. Maintaining quality is about continual improvement. The environmental monitoring program provides the data to assess how well a risk management program is working. Response to risk must be rapid, and aggressive, and one must monitor the effectiveness when contamination recovery rates change.
1. Sun L., “Compounding Pharmacy Linked to Meningitis Outbreak Knew of Mold, Bacteria Contamination,” Washington Post (Oct. 26, 2012).
2. ICH Q10, Pharmaceutical Quality System (ICH, June 2008).
3. USP, General Chapter <1116> Microbiological Control of Cleanrooms and Other Controlled Environments, USP-NF, 35, May 2012.