Effects of antimicrobial substances (1 MIC) of P. elgii DS381 (A), P. elgii DS1515 (B), B. gladioli DS518 (C), and S. lienomycini DS620 (D) on survival of P. acnes GNUH-NCCP2875 (◇) and P. acnes GNUH-NCC 2876 (△).