[Dry medium for determining the beta-galactosidase activity of enterobacteria]

Differential diagnosis of enterobacteria is based on the determination of beta-galactosidase enzyme, hydrolyzing lactose in the nutrient substrates; however, the tests suggested for its determination are time consuming and their use in practice is limited. Dry nutrient medium prepared by the authors containing o-nitrophenyl-betaD-pyranoside was tested on 1625 strains of enterobacteria in comparison with the Le Minor's ONPS test used at present. The results of beta-galactosidase determination by the, mentioned methods proved to coincide (significance level greater than 95%); this permits to recommend the method described--in dry nutrient medium--as a differential-diagnostic test for the identification of enterobacteria.