Susceptibility of Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis to 10 Kampo formulations

We examined the in vitro sensitivities of three bacteria: Propionibacterium acnes, and Staphylococcus epidermidis, commonly detected in acne lesions, and Staphylococcus aureus, a common cause of skin infections, to 10 Kampo formulations (Chinese herbal medicines; combinations of powdered extracts of crude drugs). Both Staphylococcus species showed similar sensitivities to all 10 formulations, with minimum inhibitory concentrations (MICs) ranging from 25 to 400 mg/ml. P. acnes, however, was particularly sensitive to one formulation, keigai-rengyo-to (MIC, 0.78 -25 mg/ml), prompting speculation that it might contain components with strong antibacterial activity to P. acnes. P. acnes showed similar sensitivities to all the other formulations (MIG 6.25 - 200 mg/ml). The ranges of MICs and the MIC(50)s (concentrations that inhibit 50% of isolates) were very similar to those previously recorded in 1990 for the two Staphylococcus species.