Expanding test panels for pharmaceutical microbiology: Making an informed decision

Expanding microbial test panels beyond pharmacopeial strains is increasingly important for ensuring the robustness and relevance of pharmaceutical microbiology methods. This paper presents a structured, data-driven approach to selecting representative organisms, drawing on environmental monitoring data from cleanrooms, aseptic processing, water systems, and in-process samples. While the use of environmental isolates can improve representativeness, their variability and lack of standardisation require careful consideration. The study demonstrates that selection should be based on frequency of recovery, morphological grouping, ecological relevance, and phylogenetic diversity, rather than simply origin. By comparing facility isolates with compendial organisms, the methodology ensures supplementary strains provide meaningful challenge without redundancy. The outcome is a rationalised panel of additional organisms that better reflects facility microbiota and supports applications such as growth promotion testing, disinfectant efficacy studies, and method validation. This structured approach enables scientifically justified, reproducible, and risk-based decisions when expanding microbiological test panels.