Development of a method for the quantitative assessment of the microorganism sensitivity to antibiotics by using discs. A study of the patterns of doxycycline diffusion from discs into the nutrient agar]

Doxycycline concentrations provided by the antibiotic diffusion from paper discs into sterile agarized medium and the medium plated with staphylococci and Coli bacteria were studied at different distances from the disc center. Infection of the nutrient medium with the test cultures had no effect on the antibiotic diffusion rate. A linear relation between the logarithm of the antibiotic concentration in the agar and distance from the disc centre were found. Probably it is possible to determine the MIC of the antibiotic with respect to various microorganisms by the value of the radius of the growth inhibition zone around the disc using diagrams expressing such a relation.