An effective cleaning program for equipment used in pharmaceutical and biopharmaceutical manufacturing is critical(1, 2). Consequences from insufficient equipment cleaning can be severe, including risk to patient health and product quality, and can result in product recalls. Given the criticality of such programs, equipment cleaning validation is often an area of rigorous scrutiny by regulators during inspections. In the following article we will discuss bioburden control in equipment cleaning validation.
1. Microbial Contamination of Equipment
Microbial contamination of equipment surfaces can occur via process materials, and from equipment use during manufacturing. Further proliferation of microorganisms can occur during equipment holding (clean and dirty hold times). Therefore, the prevention and control of microbial contamination of processing equipment should be assessed and validated throughout the equipment usage cycle(1, 2) – cleaning, clean hold time, and dirty hold time. Acceptable levels of bioburden must be determined by the manufacturer based on process, product type, and safety and quality requirements. A risk-based approach should be used to identify opportunities for microbial contamination of equipment. When assessing these risks, in line with the product type and patient group(s), consideration must be afforded not only to bioburden but also other forms of microbial contamination (for example endotoxins and enterotoxins) (1, 2).
2. Methods for Equipment Cleaning
The cleaning of manufacturing equipment is typically achieved via:
- Clean in Place (CIP)
- Clean out of Place (COP)
CIP is an automated process via hard piping or mobile systems where the equipment (e.g. production vessels) may be cleaned without disassembly. A combination of purified water (PW) or water for injection (WFI) rinsing, heat, chemical action (detergents, basic and acidic agents), and high velocity flow are typically used within CIP cycles to achieve the required cleaning. CIP facilitates efficient, repeatable, and consistent cleaning processes and reduces labour.
COP involves removing and transferring equipment to a dedicated cleaning area for cleaning and disinfection. COP is used when it is not possible to clean equipment sufficiently using CIP processes — typically small, complex or difficult to clean equipment. COP requires equipment to be disassembled prior to cleaning and cleaned via manual methods or via use of automated systems such as parts washers. COP is generally more labor- and time-intensive compared with CIP, but offers more flexibility.
Chemical agents used during cleaning and sanitisation processes depend on a number of factors which must be evaluated. For example:
- Product physical attributes
- Chemical reactivity
- Equipment material compatibility
- Toxicity and residues
- Safety and handling requirements
- Contact times
- Temperature requirements
- Environmental and disposal requirements
3. Validation of Cleaning Methods
Validation of equipment cleaning methods is a requirement (1, 2), with the objective being to ensure that the methods used can provide an acceptable level of cleaning and sanitization in a repeatable and consistent manner. Equipment cleaning validation should be implemented under a cleaning validation master plan (CVMP) (2, 3), within which sampling, detection methods, and acceptance criteria are defined. Based on the requirements identified within the CVMP and on the outcomes of a risk-based assessment, suitable cleaning validation protocols are drafted, approved, and executed.
Robust equipment cleaning protocols should be developed to control bioburden and prevent proliferation to maintain the quality and safety of the product. This is important since certain manufacturing processes create conditions that are conducive to microbial growth (for example aqueous processes). This can increase microbial load on manufacturing equipment surfaces and is a significant risk to product quality and safety. Insufficient removal could adulterate subsequent batches, resulting in patient safety issues and regulatory non-compliance. Cleaning validation protocols should describe the equipment to be cleaned, procedures, materials, acceptable cleaning levels, control parameters, and analytical methods (1, 2, 3). The validation protocol should consider microbial contamination for process steps where it has been identified that there is a requirement to reduce this or where it has been identified as a risk.
Cleaning validation protocols should be developed based on “worst case” conditions to ensure cleaning effectiveness (1, 2, 3). Worst case conditions should be determined under risk assessment and based on several factors associated with product characteristics, manufacturing processes and equipment used. For microbial concerns, worst case is considered to be processes that increase microbial load. Determination of worst-case conditions requires consideration of the opportunity for microbial introduction or conditions conducive to microbial proliferation, for example:
- Aqueous processes
- Type and nature of soil
- Processing temperatures and pH
- Equipment design and surface material
- Non-uniform contamination sites
- Time (dirty and clean hold times, process run time)
Cleaning validation process should reflect equipment usage patterns. Sampling methods usually include swabbing and rinse samples, and these should be tested using validated analytical test methods where the limit of detection has been established and is of suitable sensitivity to detect contamination within established acceptable levels. Post initial cleaning validation, the effectiveness of cleaning procedures should be monitored at suitable intervals to ensure ongoing effectiveness during routine operation.
4. Sampling Methods
Methods used for the recovery of microorganisms from cleaning validation samples is dependent on the identified risks and whether a specific species or group is of particular concern. Generally, the predominant type of microorganisms of concern are mesophilic aerobic organisms. In this case, the use of TSA with incubation at 30-35ºC would be a suitable approach.
Typically swab and rinse samples are used for bioburden testing. One or both methods can be used within a cleaning validation protocol. How they are used depends on the equipment being cleaned. For instance, swabs can be used for difficult to clean surfaces (e.g. valves, pipework, narrow areas, edges, curves, corners, angles etc.). Rinse samples can be used to sample large surface areas (e.g. tank interiors) and are collected using purified water or water for injection. Regardless of the sampling method, the associated test method must be qualified (1, 2, 3). It must be demonstrated that the method can recover microorganisms and can overcome any inhibitory effects from residual product or cleaning agents.
Conclusion
Robust cleaning validation activities are a critical element of product quality and safety and should be developed based on risk assessment. Product type and target patient groups are an important consideration when determining microbial risk. Variables that may facilitate the introduction, survival, and proliferation of microorganisms need to be considered, alongside removal or inactivation methods. Microbial detection methods in cleaning validation samples must demonstrate the capability of recovering bioburden and overcoming inhibition.
References
- FDA Inspection Guide – Validation of Cleaning Processes (7/93), Guide to Inspections of Cleaning Processes (2014).
- Eudralex Volume 4 – EU Guidelines for Good Manufacturing Practice for Medicinal Products for Human and Veterinary Use, Annex 15: Qualification and Validation (2015).
- Pharmaceutical Inspection Co-operation Scheme (PIC/S) – Recommendations on Validation Master Plan, Installation & Operation Qualification, Non-Sterile Process Validation, Cleaning Validation (2007).
About the author:
Noelle Clifford is a qualified and experienced Microbiologist with a BSc (Hons) in Industrial Microbiology from University College Dublin. She has worked within the pharmaceutical industry for approximately 16 years in QC Microbiology roles from ground level through to management. Noelle has worked for a number of multinational companies gaining experience with solid oral dosage products, sterile products, dry powder inhalation products, and topical products. She has worked on green field and startup operations, through to established and older facilities.
