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I am a student, so I hope it is okay to put this question here. I've done the virus plaque assay in a practical recently and have a few questions regarding the plaque count for pfu calculation.

In the plates corresponding to times 0 and 10 mins, a few plaques formed (less than 5 plaques in every plate where plaques could be seen) Should I still calculate pfu with those results, or should I leave it as 0 pfu, and use only plaque counts that are at least more than 10?

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  • $\begingroup$ Wouldn't the actual number of plaque forming units be more precise? Would it make any if your following steps more difficult or why do you want to simplify it? $\endgroup$ – Arsak Nov 23 '18 at 19:23
  • $\begingroup$ microbiol.org/resources/monographswhite-papers/… $\endgroup$ – canadianer Nov 23 '18 at 20:01
  • $\begingroup$ Sorry, I don't understand what you mean by simplyging? We were told to count the plaques we could see in the petri dishes and calculate pfu from there. What I don't understand if I should calculate pfu even when there's only one plaque in the plate. The protocol says we should choose the plate that has 20 to 300 plaques for the calculation, but I cannot do that with the plates for time 0 and time 10, because all plates have less than 10 plaques in them. In plates of time 0 the maximum I have is 2 plaques. So I don't know whether it's okay to calculate pfu of 2 plaques or it is usually left out $\endgroup$ – Laura Nov 24 '18 at 1:26
  • $\begingroup$ What is the virus? If, for example, it is a bacteriophage, then you would not expect any virus particles to be produced at those early time points, right? $\endgroup$ – mdperry Nov 24 '18 at 3:23

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