[Culture medium for the isolation of group B Streptococcus]

Comparative studies were carried out on a new medium--a soybean agar of the Difco type with the addition of beta-staphylococcus toxin, washed sheep erythrocytes, esculin, and Congo red to isolate and differentiate the streptococci of the serologic B group. Congo red was used in dilution of 1:10000 to suppress the beta-hemolysis of the streptococci belonging to other serologic groups. The higher objectivity of the final results required the use of a blood agar and a medium with thallium sulfate and crystal violet--nutrient media for the bacteriologic diagnostics of mastitis. It was established with all three lines of research of selected cultures (control strains) through sampling milk of the four quarters of the udder and pooled milk by groups and farms that soybean agar proved superior to the remaining nutrient media, more specifically in the diagnosis of mastitis caused by streptococci of the serologic group.