If we take the titer of a virus preparation (in plaque forming-units per milliliter) and divide it by into the number of virus particles in the sample, we obtain a number known as the particle-to-PFU ratio. It is a measure of the fraction of virus particles in a given sample that can complete an infectious cycle.

How do you calculate PFU per ml?

Then use the formula: (total PFU needed) / (PFU/ml) = total ml of virus needed to reach your desired dose. For example: You have a virus with a titer of 1.3×1011 PFU/ml and a well that contains 1.8×106 cells.

What does a high PFU mean?

A high particle-to-pfu ratio is sometimes caused by the presence of noninfectious particles with genomes that harbor lethal mutations or that have been damaged during growth or purification.