[Use of paper indicator discs for determining the minimal inhibitory concentration of antibiotics]

Sensitivity of clinical strains of Staphylococcus and some Enterobacteriaceae to a number of widely used antibiotics was compared simultaneously with the use of two methods, i. e. the agar diffusion method and the method of serial dilutions. Regularities in distribution of the staphylococcal strains according to their sensitivity to antibiotics, such as erythromycin, benzylpenicillin, levomycetin and others were also studied with respect to every year using indicator paper discs. Interrelation observed during the comparison of the microbial sensitivity with the use of the two assay methods provided elaboration of the criteria for classification of the strains as "resistant" or "sensitive". The differentiation boarder for these two groups was determined according to the principle of the assay error minimization. A necessity of using standard dry media for specification of individual characteristics of various drugs in estimation of the microbial sensitivity to them by the agar diffusion method is emphasized.