[Improved method of using antibiotics in the nutrient media for isolating Shigella (the 3-band method)]

A modified procedure for the use of antibiotics in nutrient media for isolation of Shigella is described. The procedure is designated as the method of 3 strips. It implies introduction of 3 different antibiotics, i. e. levomycetin, streptomycin and one of tetracyclines to definite areas of the nutrient medium in a petri dish. The antibiotics diffuse into the medium from 3 strips of filter paper. The greatest part of the medium contains minor amounts of the antibiotics and is used for isolation of the antibiotics sensitive Shigella strains. The procedure is simple and economic. It excludes the most frequent mistakes due to incorrect selection of antibiotics. The preliminary trials showed that the procedure may be used in the routine studies.