Besides plaque assay infectious virus titers can be measured...

Besides plaque assay, infectious virus titers can be measured by 50% end points. This measurement may be written in terms of tissue culture 50% infectious doses, or TCID50. If virus A has a TCID50 of 10,000 and 1,000 for virus B, then there is more infectious virus in stocks of [virus A/virus B].

The titer of a virus stock can be calculated in plaque-forming units (PFU) per milliliter. To determine the virus titer, the plaques are counted. To minimize error, only plates containing between 10 and 100 plaques are counted, depending on the size of the cell culture plate that is used. Statistical principles dictate that when 100 plaques are counted, the sample titer will vary by plus or minus 10%. Each dilution is plated in duplicate to enhance accuracy. In the example shown below, there are 17 plaques on the plate made from the 10-6 dilution. The titer of the virus stock is therefore 1.7 x 107 PFU/ml. What is a viral plaque? An assay that gives an estimate at the number of viruses in a sample. A collection of living cells in a viral assay. A circular zone of infected cells. A biofilm of microorganisms.

Katlin K.

Question

Besides plaque assay, infectious virus titers can be measured by 50% end points. This measurement may be written in terms of tissue culture 50% infectious doses, or TCID50. If virus A has a TCID50 of 10,000 and 1,000 for virus B, then there is more infectious virus in stocks of [virus A/virus B].

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