What is microbiological filtration and when should you use it?

The core technique

A measured sample volume is passed through a membrane fine enough to retain the target organisms. The membrane is then transferred to a nutrient medium and incubated—what grows is counted or identified. See our full microbiology filtration workflow guide for the step-by-step process.

Who relies on it

Water and environmental testing labs (checking for coliforms and other indicator organisms), pharmaceutical and biotech quality control (bioburden and sterility testing), food and beverage testing, and academic/research microbiology all use this technique regularly, adapted to their specific organisms and methods.

Why filtration instead of direct plating

Filtration lets you concentrate organisms from a larger sample volume than you could practically plate directly—useful when the organism of interest is present at low concentration and direct plating wouldn't reliably detect it.

Key product decisions

Membrane material (MCE is common for general recovery; PCTE for a cleaner field), pore size (0.45 µm and 0.22 µm are common), gridded vs. non-gridded, and sterility all factor into the right product for your specific method.

This is method-driven, not generic

Compendial methods, regulatory methods, and internal SOPs typically specify exact membrane, media, and incubation parameters—treat this article as orientation to the technique, not a substitute for your actual validated method.