The bacteriology of acne vulgaris and antimicrobial susceptibility of Propionibacterium acnes and Staphylococcus epidermidis isolated from acne lesions.

We examined the species of bacteria aerobically and anaerobically isolated from 30 acne lesions and determined antimicrobial susceptibilities of Propionibacterium acnes (P. acnes) and Staphylococcus epidermidis (S. epidermidis) using nine antimicrobial agents. Among the bacteria isolated, S. epidermidis was most dominant. Both P. acnes and S. epidermidis were isolated from half of the acne lesions. The MIC of seven antimicrobials (ampicillin, erythromycin, roxithromycin, clindamycin, tetracycline, minocycline, nadifloxacin) against P. acnes was under 3.13 micrograms/ml. There were very few resistant strains of P. acnes, but many of S. epidermidis. More than 30% of the S. epidermidis isolates were resistant to erythromycin, roxithromycin, and clindamycin. After long-term systemic antibiotic therapy, the resistant strains of S. epidermidis increased, but P. acnes resistance was still limited. When we use antimicrobial agents for the treatment of acne, it should be noticed that not only P. acnes but also S. epidermidis in the acne lesions may acquire resistance to antimicrobials.