Top-down evaluation of the matrix effects in microbial enumeration test uncertainty.

Microbial contamination may compromise the efficacy and safety of pharmaceutical products. Microbial enumeration tests are required by most of the pharmacopeial compendia and consist in conventional pour-plate inoculation of a sample aliquot followed by incubation under appropriate conditions. Despite of this, the measurement uncertainty evaluation for microbial enumeration tests is rarely considered.