Antimicrobial susceptibility of Propionibacterium acnes isolated from acne vulgaris.

Systemic and topical antimicrobial treatment for acne vulgaris remains the mainstay method of therapy in Japan. Strains of Propionibacterium acnes (P. acnes) resistant to erythromycin (EM), clindamycin (CLDM), tetracycline (TC), doxycycline (DOXY) and minocycline (MINO) have been reported. The aim of the present study was to examine the antimicrobial susceptibility to 10 currently used antimicrobial agents of 50 strains of P. acnes isolated from acne lesions and identified using a Rap ID ANA II panel. Minimum inhibitory concentrations (MIC) were determined by the agar dilution method according to the criteria of the Japan Society of Chemotherapy. EM, ampicillin (ABPC), and CLDM were the most potent drugs, followed by MINO, nadifloxacin (NDFX), cephalexin (CEX), DOXY, ofloxacin (OFLX), and TC. In terms of the MIC80, EM and ABPC were the most potent, followed by CLDM, NDFX, MINO, CEX, DOXY, OFLX, TC and gentamycin (GM). Although most of the strains used were susceptible to the antimicrobial agents tested, strains of P. acnes resistant (MIC 12.5 mug/ml) to EM (4%), CLDM (4%), DOXY (2%) and TC (2%) were observed. In this study, no strains of P. acnes resistant to MINO were seen, suggesting that oral MINO is the most useful treatment for acne vulgaris with minimal risk of bacterial resistance.