Bioburden

What it determines

Nucleic acid is extracted from a portion of the sample and combined with primers directed at regions of the bacterial ribosomal RNA gene that are conserved across a wide range of species. Thermal cycling copies any matching template present, doubling it with every cycle.

Fluorescence is read at each cycle. Template present at a higher starting amount crosses the detection threshold earlier, so the crossing point gives a relative sense of how much bacterial DNA was in the extract. Every run carries a no-template control so that background from reagents stays visible.

Practical notes

• The assay responds to DNA from viable and non-viable cells alike, so material contaminated before a kill step can still return a detection.
• Sampling technique matters. Opening a vial in ambient air introduces bacterial DNA, and clean handling at the sender's end keeps the result about the material.
• A dedicated, unopened vial gives the most interpretable result.