PCR detects pathogen-specific DNA or RNA sequences with very high analytical sensitivity. It often reaches one to ten genome copies per reaction. Unlike culture, PCR does not need viable organisms and gives results within hours rather than days.
However, PCR detects nucleic acid from both live and dead cells. Combining PCR with a short enrichment step or propidium monoazide pre-treatment can help you distinguish viable from non-viable cells in food or environmental applications.