With a note by K. E. COOPER on the theory of inhibition zones

SUMMARY: The time taken for agar plates to reach incubator temperature under different conditions was determined by thermocouple measurements. From 1 to 5 hr. was taken to reach within 1 of the incubator temperature, according to their mass, position, stacking and original temperature. Delay in heating slowed the growth of organisms and produced larger inhibition zones due to diffusing antiseptics. This leads to errors in sensitivity and thus in assay work unless technique is standardized to overcome these differences. Deviations from the calculations resulting from the formula of Cooper & Woodman (1946) can be overcome by such standardization.

An appendix discusses the theory of inhibition zones and compares the formulae proposed by Cooper & Woodman (1946) , by Vesterdal (1947) and by Mitchison & Spicer (1949) .


Article metrics loading...

Loading full text...

Full text loading...



  1. Cooper K.E., Gillespie W. 1952; The influence of temperature on streptomycin inhibition zones in agar cultures. J. gen. Microbiol. 7:1
    [Google Scholar]
  2. Cooper K.E., Woodman D. 1946; The diffusion of antiseptics through agar gels, with special reference to the agar cup assay method of estimating the activity of penicillin. J. Path. Bact. 58:75
    [Google Scholar]
  3. Dubos R.J. 1945 The Bacterial Cell pp 137–43 Harvard University Press.:
    [Google Scholar]
  4. Mitchison D.A., Spicer C.G. 1949; A method of estimating streptomycin in serum and other body fluids by diffusion through agar enclosed in glass tubes. J. gen. Microbiol. 3:184
    [Google Scholar]
  5. Schmidt W.H., Moyer A.J. 1944; Penicillin. I. Method of assay. J. Bact. 47:199
    [Google Scholar]
  6. Vesterdal J. 1947; Studies on the inhibition zones observed in the agar cup method for penicillin assay. Acta path, microbiol. scand. 24:272
    [Google Scholar]

Data & Media loading...

Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error