ANTIBACTERIAL ACTIVITY OF NADIFLOXACIN AGAINST Staphylococcus AND Propionibacterium ISOLATED FROM PATIENTS WITH DERMATOLOGICAL INFECTIONS

Nadifloxacin (NDFX) is a fluoroquinolone antibiotic developed by Otsuka Pharmaceutical Co., Ltd. and is used as a topical drug for the treatment of infections in the field of dermatology. We investigated the susceptibility of a total of 575 strains (two kinds of Staphylococcus species and Propionibacterium species which were isolated from patients with dermatological infections for 3 periods, i.e., 1996, 2000 and 2005) to NDFX and other reference antibiotics. The minimum inhibitory concentration of the four antibiotics, NDFX, levofloxacin (LVFX), clindamycin (CLDM) and gentamicin (GM), against the test strains were determined by the agar dilution methods, in according with the Japan Society of Chemotherapy. The antibacterial activity of NDFX against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis and P. acnes was the most potent of all the antibiotics tested, and there were no test organisms which became resistant to NDFX with period. The MIC 90 values of NDFX for the four test organisms isolated in 2005 were 0.05 μg/mL; MSSA, 1.56 μg/mL; MRSA, 0.78 μg/mL; S. epidermidis and 0.20 μg/mL; P. acnes, respectively. On the other hand, there were LVFX-, CLDM- and GM-resistant MRSA. The MIC 50 values of CLDM and GM for MRSA were >100 and 25 pg/mL, respectively. The MIC 50 value of GM for P. acnes was 12.5 μg/mL, but NDFX was potently active against these organisms as compared with these two antibiotics and the MIC 50 values of NDFX were 0.05 μg/mL for MRSA and 0.20 μg/mL for P. acnes. These results suggest that NDFX is even at present useful as an antibiotic for the treatment of infections in the field of dermatology though it is more than 12 years since the approval to manufacture and sell the drug was obtained in 1993.