Induced resistance in Staphylococcus aureus for assay of antibiotic mixtures in pharmaceutical preparations

A new microbiological method was developed for the assay of neomycin and spiramycin. These antibiotics usually cannot be quantitated individually when they are combined in a pharmaceutical preparation since both act on the same test organism. By inducing resistance to each antibiotic in Staphylococcus aureus, two new strains were obtained. Quantitation can be accomplished easily with these strains.