FIELD: medicinal and veterinary bacteriology. SUBSTANCE: method involves the following stages: preparing successive dilutions of antibiotic to be studied in nutrient medium with indicator in wells of plate; then analyzed material containing microorganisms is added into wells with antibiotic (experiment) and into wells with nutrient medium (control). Plate is incubated for 3-6 h and the presence of microorganisms growth is recorded by turbidity and/or alternation of medium color. In the case of growth in control and absence growth in experimental wells with small antibiotic dilution the concentration of antibiotic in latter is reduced and incubation continuous up to 11-14 h Then the presence of microorganism growth is recorded again by the same indices and in the case of its presence the bacteriostatic effect is determined and the case of its absence bactericidal effect of antibiotic. The concentration of antibiotic is reduced using bets-lactamase in the case of differentiation of beta-lactam antibiotic or by method of serial dilutions for antibiotics of other classes. Invention can be used for differentiation of antibiotics by their bactericidal and bacteriostatic effect. EFFECT: improved assay method. 3 cl, 3 tbl, 3 ex
