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The protocol summarizes the best practices to minimize microbial bioburden in a cleanroom environment and includes strategies such as environmental monitoring, process monitoring, and product sterility testing. It is relevant for manufacturing and testing facilities that are required to meet current good tissue practice standards and current good manufacturing practice standards.
A well-validated and holistic program that incorporates robust gowning, cleaning, environmental monitoring, and personnel monitoring measures is critical for minimizing the microbial bioburden in cellular therapy manufacturing suites and the corresponding testing laboratories to ensure that the facilities are operating in a state of control. Ensuring product safety via quality control measures, such as sterility testing, is a regulatory requirement for both minimally manipulated (section 361) and more than minimally manipulated (section 351) human cells, tissues, and cellular and tissue-based products (HCT/Ps). In this video, we provide a stepwise guide for how to develop and incorporate the best aseptic practices for operating in a cleanroom environment, including gowning, cleaning, staging of materials, environmental monitoring, process monitoring, and product sterility testing using direct inoculation, provided by the United States Pharmacopeia (USP<71>) and the National Institutes of Health (NIH) Alternative Sterility Testing Method. This protocol is intended as a reference guide for establishments expected to meet current good tissue practices (cGTP) and current good manufacturing practices (cGMP).
Implementing a strong microbial monitoring program through environmental monitoring (EM), process monitoring, and product sterility testing is a regulatory requirement for current good tissue practices (cGTP) and current good manufacturing practices (cGMP) in cellular therapy laboratories1. Additionally, the United States Food and Drug Administration (FDA) expects that the laboratory performing the quality control (QC) testing of the product should also employ facilities and controls comparable to those used for aseptic filling operations2.
This protocol has four main sections: 1) Aseptic practices, including personnel gowning, cleaning, and staging of materials; 2) EM, including viable air and surface cultures and non-viable particle air monitoring; 3) process monitoring, including settling plates and gloved fingertip sampling; and 4) product sterility testing via the compendial United States Pharmacopeia (USP) <71> method3 or the NIH Alternative Sterility Testing Method4. When used together, these measures can be an effective method for ensuring that a facility remains in a state of control.
The techniques described here are not novel; however, current standards from regulators and professional organizations lack detail, which has led to an absence of microbial monitoring or the implementation of non-standardized practices, particularly in academic centers where on-site manufacturing and product sterility testing are emerging at a rapid rate1,5,6. This protocol can be used as a guide to create a microbial monitoring and control program that meets regulatory requirements when used in conjunction with end-user validation and risk assessments.
1. Aseptic practices
Figure 1: Example of a BSC cleaning pattern. Working from back to front (or top to bottom), clean the BSC using overlapping wipes in the following order: the HEPA diffuser grill (the top of the BSC), the back wall of the BSC, both side walls of the BSC, the sash, and the work surface. Finally, wipe the sash of the BSC using 70% sIPA to remove any residual disinfectant. Please click here to view a larger version of this figure.
2. Environmental monitoring (EM)
Category | Media | Culture conditions | Culture observation | Results | ||||||
Environmental monitoring | TSA (viable air) | 30 Β°C-35 Β°C, air, for at least 3 days | End of incubation | The QA group of each facility should establish alert and action limits for each sampling type and location. Action limits for viable samples based on ISO classification can be guided using PIC/S 009-16 (Annexes) 18 and ISO-14644-1 7. Action limits for non-viable air samples are typically set to a percentage of the ISO limit (e.g., 99%). Alert limits for viable samples are typically set to a percentage of the Action limit or ISO limit (e.g., 95%). Refer to PDA TR-13 and USP<1116> for more details regarding establishment of alert and action levels and validating selected culture conditions 8,9.Β | ||||||
SAB (viable air) | 20 Β°C-25 Β°C, air, for at least 7 days | |||||||||
TSALT (viable surface) | 30 Β°C-35 Β°C, air, for at least 3 days | Representative images of EM plates are shown in Figure 2, Figure 3, Figure 4, and Figure 5.Β | ||||||||
SABLT (viable surface) | 20 Β°C-25 Β°C, air, for at least 7 days | |||||||||
Process monitoring | TSA (settling plate) | 30 Β°C-35 Β°C, air, for at least 3 days | For information only. Provides useful information in the event of an OOS investigation in response to a failed product sterility test. | |||||||
SAB (settling plate) | 20 Β°C-25 Β°C, air, for at least 7 days | See Figure 6 for an example of a positive settling plate. | ||||||||
Gloved fingertip sampling | TSALT | 30 Β°C-35 Β°C, air, for at least 48 hours days followed by 20 Β°C-25 Β°C for at least 5 days 19. | The acceptability criteria for GFS is <1 CFU/plate (i.e., no growth) as per PIC/S 009-16 (Annexes) 18. Acceptability criteria may be modified at the discretion of facility QA.Β | |||||||
Product sterility testing | TSB (USP<71>) | 20 Β°C-25 Β°C, air, for at least 14 days | Periodically throughout the incubation period (days 3, 5, 7, and 14) | No growth.Β | ||||||
FTM (USP<71>) | 30 Β°C-35 Β°C, air, for at least 14 days | |||||||||
iFA+ (NIH method) | 30 Β°C-35 Β°C, air, for at least 14 days | Monitoring automatically by the BacT/ALERT Dual-T instrument. Visual check of each bottle at the end of incubation for mold balls is strongly recommended. | See Figure 8 for an example of visible mold balls that failed to be automatically detected by the BacT/ALERT. | |||||||
iFN+ (NIH method) | ||||||||||
SAB (NIH method) | 20 Β°C-25 Β°C for at least 14 days | Periodically throughout the incubation period (days 3, 5, 7, and 14) |
Table 1: Summary of the recommended culture conditions and expected results. The culture conditions described here are recommendations based on a validated program used at the NIH. Each end-user is required to validate their own microbiology testing program. The microbial control and testing strategies may differ between institutes depending on variables including the facility design, facility flora, and product risk classification.
Figure 2: Growth on the TSALT plate. The TSALT surface sampling plate showing three CFUs of two distinct colony morphologies. Please click here to view a larger version of this figure.
Figure 3: Contamination of the TSALT plate during collection. The TSALT surface culture showing a single colony on the edge of the plate, indicative of poor aseptic handling during the sampling process. Please click here to view a larger version of this figure.
Figure 4: Culture obtained using a contaminated air sampling head. Example of a TSA active air sampling culture showing >100 colony forming units (CFU) of mixed morphologies. The pattern of growth indicates contamination of the sampling head. Please click here to view a larger version of this figure.
Figure 5:Β No growth on a TSA active viable air plate. TSA active viable air plate illustrating no growth following incubation. Indents from the active air sampler head can be seen in the image. Please click here to view a larger version of this figure.
3. Process monitoring
Figure 6: Growth on a TSA air settling plate. A TSA air settling plate illustrating a single colony of a contaminant cultured during passive air process monitoring in the BSC. Please click here to view a larger version of this figure.
Figure 7: Gloved fingertip sampling. The correct method for obtaining gloved fingertip samples using the largest surface area (or pad) of each finger/thumb is shown on the left. The incorrect process where only the fingertip is sampled is shown on the right. Please click here to view a larger version of this figure.
4. Sterility testing by direct product inoculation
Figure 8: Growth of mold that failed to be detected by the BacT/ALERT. Example of mold balls, visible to the naked eye, that failed to be automatically detected by the BacT/ALERT system. Based on these findings, we recommend terminal visual inspection of all BacT/ALERT bottles and the addition of the SAB plate for fungal culture using the NIH Alternative Sterility Testing Method. Please click here to view a larger version of this figure.
The expected results are described in Table 1. The EM data should be reviewed and followed up with an appropriate investigation and response to action, alert, or ISO limit excursions. If an excursion occurs for non-viable particles, one should proceed as per ISO 14644-Annex A, sec A.5.57. If the excursion can be attributed to an immediately identifiable abnormal occurrence, the original sampling results should be documented, a note should be added to disregard the original results...
There are several critical areas in this protocol, including the maintenance of aseptic technique and unidirectional airflow within cleanrooms and the BSCs. Best practices include moving slowly and deliberately to minimize turbulence. Aseptic manipulations should be performed from the side of the product, not from above. Closed system processing and the use of terminally sterilized raw materials are recommended. Speaking in critical areas and leaning against walls or equipment should be avoided. Similarly, unnecessary to...
The authors declare no conflicts of interest.
This work was supported by the Intramural Research Program of the National Institutes of Health Clinical Center. The content is solely the responsibility of the authors and does not represent the official views of the National Institutes of Health.
Name | Company | Catalog Number | Comments |
20-25Β°C Incubator | Lab preference | ||
30-35Β°C Incubator | Lab preference | ||
Alcohol-based hand sanitizer | Lab preference | ||
BacT/ALERT Dual-T instrument | BioMerieux Industry | ||
Beard cover | Lab preference | ||
Biosafety cabinet (BSC) | Lab preference | ||
Cleanroom shoes | Lab preference | ||
Fluidthioglycollate medium (FTM) | Hardy DiagnosticsΒ | U84 | USP |
Handheld cleaning mop | Contec | 2665LF | |
Hypodermic needle | Lab preference | ||
iFA+ BacT/ALERT bottle | Biomerieux | 412990 | |
iFN+ BacT/ALERT bottle | Biomerieux | 412991 | |
Isokinetic head | Lab preference | ||
Laser particle counter | TSI Incorporated | 9500-01 | |
LpH III | Steris | 1S16CX | |
Mirror | Lab preference | ||
Non-sterile bouffant | Lab preference | ||
Non-sterile gloves | Lab preference | ||
Non-sterile shoe covers | Lab preference | ||
Non-sterile sleeve covers | Lab preference | ||
Parafilm | Lab preference | ||
Peridox RTU | Contec | CR85335IR | |
Plastic bag | Lab preference | ||
Sabouraud Dextrose Agar with Lecithinase and Tween (SABLT) | Hardy DiagnosticsΒ | P595 | USP, irradiated |
Sabouraurd Dextrose Agar (SAB) | Hardy DiagnosticsΒ | W565 | USP, irradiated |
Safety glasses | Lab preference | ||
Scrubs (top and bottom) | Lab preference | ||
Spor-Klenx RTU | Steris | 6525M2 | |
Sterile 70% isopropyl alcohol (IPA) | Decon CiDehol | 8316 | |
Sterile alcohol wipe | Lab preference | ||
Sterile boot covers | Kimberly Clark | Cat# varies based on size | |
Sterile coveralls | Kimberly Clark | Cat# varies based on size | |
Sterile face mask | Lab preference | ||
Sterile gloves | Lab preference | ||
Sterile hood | Kimberly Clark | Cat# varies based on size | |
Sterile low-lint wipes | Texwipe | TX3210 | |
Sterile mop cleaning pads | Contec | MEQT0002SZ | |
Sterile sleeve covers | Kimberly Clark | 36077 | |
Sterile spreading rod | Fisher Scientific | 14665231 | |
Sterile syringe | Lab preference | ||
Tacky mats | Lab preference | ||
Tryptic Soy Agar (TSA) | Hardy DiagnosticsΒ | W570R | USP, irradiated |
Tryptic Soy Agar with Lecithinase and Tween (TSALT) | Hardy DiagnosticsΒ | P520R | USP, irradiated |
Tryptic Soy Broth (TSB) | Hardy DiagnosticsΒ | U46 | USP |
Tubing | Lab preference | ||
Vesphene III | Steris | 1S15CX | |
Viable air sampler | Hardy DiagnosticsΒ | BAS22K | |
Vortex | Lab preference |
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