Preparation and evaluation of bacterial stocks for filter validation

Bacterial cell stock paste of Brevundimonas diminuta (American Type Culture Collection # 19146) used for filter validation was evaluated by standard microbiological procedures to determine culture purity, monodispersion, cell size, and strain identity. Tests performed included direct microscopic count, standard plate count, gram stain, streak plate, sizing by microfiltration, scanning electron microscopy, and biochemical identification. Results indicated the bacterial stocks were of consistent quality in terms of bacteriological purity, cell size, viability, and concentration. Sizing by microfiltration confirmed consistent monodispersion and cell retention characteristics for each lot tested. Use of the commercially available RapID NF Plus system confirmed each lot to be B. diminuta as indicated by biochemical profile and identification database. These tests represent parameters necessary for qualification of bacterial stocks to be used for filter validation.