Ozenoxacin, a novel non-fluorinated topical
quinolone, was assessed for in vitro antimicrobial activity against clinical isolates of propionibacteria and staphylococci according to the broth microdilution method recommended by the Clinical and Laboratory Standards Institute. The isolates used in this study were collected from Japanese patients with
acne vulgaris during a period from 2012 to 2013. The MIC90s of
ozenoxacin against Propionibacterium acnes (n=266), Propionibacterium granulosum (n=10), Staphylococcus aureus (n=23), Staphylococcus epidermidis (n=229) and other
coagulase-negative staphylococci (n=82) were ≤0.06, ≤0.06, ≤0.06, 0.125 and ≤0.06 µg ml-1, respectively. The antimicrobial activity of
ozenoxacin against the clinical isolates of propionibacteria and staphylococci was greater than that of five reference
antimicrobial agents which have been used for the treatment of
acne vulgaris. The MICs of
ozenoxacin were correlated with those of
nadifloxacin in P. acnes and S. epidermidis isolates. However, the MICs of
ozenoxacin were 0.25-0.5 µg ml-1 and 0.5-8 µg ml-1 against
nadifloxacin-resistant P. acnes (MIC: ≥8 µg ml-1; n=8) and S. epidermidis (MIC: ≥64 µg ml-1; n=10), respectively. These results indicated the potent antimicrobial activity against P. acnes and S. epidermidis isolates resistant to
nadifloxacin. Topical
ozenoxacin could represent an alternative therapeutic
drug for
acne vulgaris based on its potent antimicrobial activity against the isolates of propionibacteria and staphylococci from
acne patients.