Application of Flow Cytometry for Rapid Bioburden Screening in Vaccine Virus Production

Abstract

Sensitive and timely detection of bioburden in presterile filtration product in aseptic processing of biologics is a critical parameter for microbial control and assurance of final product sterility. An application of automated flow cytometry system was developed for rapid microbial assessment and in-process control in vaccine virus production. In order to minimize the background signal caused by the components of the chicken egg substrate sample matrix, a sample processing method to clear somatic cell debris was included. The sample processing and the automated analysis take approximately 5 to 7 min per test sample and the method provides objective results in real time, enabling uninterrupted processing. The flow cytometry method was compared with the standard aerobic plate count method using tryptic soy agar in a parallel study of 1566 independent production-scale samples. The method was further characterized by spike recovery of five model bacterial organisms in representative sample matrix. In comparison to the culture method, the flow cytometry method was shown to be 96.2% sensitive and 98.2% specific for the detection of bioburden at a level of sensitivity suitable for the process stage requirement with the advantage of a nearly instantaneous time to result. In-process bioburden control in the manufacturing of biopharmaceuticals is essential for final product sterility and integrity. In manufacturing contexts where an in-process hold time is infeasible or in cases where uninterrupted processing is desired, conventional culture-based bioburden detection methods cannot be used, as they require significant time to results that may not fit within the time constraints. In this case study we demonstrate the use of flow cytometry as an alternative rapid method that provides real-time results to enable uninterrupted processing.