plating efficiency

Dr. Wolfgang Schwarz schwarz at
Thu Nov 16 09:37:31 EST 2000

> Patrick Druggan wrote:
> It is used to compare a selective medium (zb. XLD) with a non-
> selective medium (zb. TSA).
> XLD should grow Salmonella well and there should be no-more than 0.5
> log10 difference in the plate counts compared to a non-selective
> medium like TSA.
> A selective medium must be selective, and should inhibit the growth of
> non-pathogens. A reduction of 2 log10 in plated count on the selective
> medium when compared to a nonselective medium has been suggested as a
> standard.
> This is covered in an ISO standard on microbiological methods. I think
> the number is ISO6358. Pd.

There is also a meaning in the number of colonies growing up by the
number of colonies you saw in the microscope, esp. if you are working
with fastidious bacteria or with very handling-sensitive bacteria (like
strict anaerobes) or after a threatning procedure. e.g. electroporation
or protoplasting and regeneration.
Wolfgang Schwarz
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