Bioburden refers to the number of viable microorganisms (such as bacteria, yeasts, and molds) present on or within a surface, device, or substrate. In pharmaceutical or medical device manufacturing, bioburden testing is a quality control test used to assess microorganisms that can be present on or in medical devices, final products, water systems, raw materials, intermediates, active pharmaceutical ingredients (APIs), etc. In these manufacturing environments, bioburden can be introduced through people, processes (lack of environmental control or inadequate cleaning processes), and materials – including water used for production. 

Bioburden testing, also referred to as microbial limit testing, is a critical aspect of pharmaceutical and medical device quality control to ensure safety of the end user. It is essential for monitoring the manufacturing process, raw materials, and components. Applicable regulatory and guidance documents include but are not limited to: USP <61> Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests; USP <71> Sterility Tests; USP <1231> Water for Pharmaceutical Purposes; 21 CFR 211; ANSI/AAMI/ISO 11737-1:2018 Sterilization of health care products – Microbiological methods – Part 1.  

Rapid microbiology methods – also referred to as rapid microbiological methods, rapid micro methods, or RMMs – offer faster results than traditional culture-based methods for bioburden testing. With near real-time information about microbial contamination, organizations can make faster decisions to ensure quality control and manage processes. The use of viability-based flow cytometry as an RMM eliminates or reduced the need to wait on the compendial method for bioburden enumeration (agar plates). By adopting a RMM for bioburden enumeration, pharmaceutical companies benefit from improved process efficiencies.