The growth of the HPV was monitored as follows: 10 9 cells and 10 6 viruses in o

Question

The growth of the HPV was monitored as follows: 109 cells and 106 viruses in one milliliter were incubated under appropriate conditions. Following a first infectious cycle, a direct count and a plaque assay were performed. In the case of the direct count, the mixture was diluted by a factor of 1000X after which beads were added to obtain a final concentration of 1 X 104 beads/mL. A microscopic field of vision revealed 20 beads and 150 virions. In the case of the plaque assay, 67 plaques were observed on a plate on which 0.1 mL of a 10-5 dilution was assayed.

What was the initial multiplicity of infection?

Explanation / Answer

Direct count = 1 x 104 beads / mL in 1000x or 10-3 dilution

Microscopic field count = 20 beads and 150 virions

The total number of viruses after last infectious cycle= 1 x 104 x 10-3 x 20 x 150 = 1x 20 x 150 x 10 = 30000

or 3 x 104 virions.

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