Novobiocin and the differentiation of peptococci and peptostreptococci

Paper discs containing 5 microng of novobiocin were used as a presumptive test to differentiate peptococci and peptostreptococci. Zone diameters were measured and minimum inhibitory concentrations (MIC) of the antibiotic for each group were performed to ascertain the activity of the antibiotic against these genera. All strains of peptococci showed no zone of inhibition in the disc test together with an MIC of 25 microng/ml or greater. All strains of peptostreptococci showed zones of inhibition of at least 15 mm diameter together with an MIC of 1-6 microng/ml or less.