[A method of diffusion in agar for determining streptococcal sensitivity to antibiotics].

An agar diffusion method for determination of antibiotic sensitivity to streptococci of different serological groups with semiquantitative estimation of the results was developed with the use of the dry nutrient medium of the I. I. Mechnikov Central Research Institute of Vaccines and Sera for isolation of hemocultures and cultivation of streptococci. The addition of blood or serum to this medium is not required. The standard inoculum (2 milliard microbial bodies) is added into the depth of the nutrient agar thus providing the optimal conditions for the growth of the facultative anaerobes. The MICs of the antibiotics and the diameters of the growth inhibition zones of 150 streptococcal strains were compared and an estimation table for interpretation of the data of the agar diffusion test was presented. This simple method provides a sufficient accuracy and satisfactory reproducibility in the clinical tests.