Efficacy of intramuscular moxifloxacin in the treatment of experimental osteomyelitis caused by methicillin-resistant Staphylococcus aureus.

Fluoroquinolones have been well studied in the treatment of chronic osteomyelitis due to their beneficial pharmacokinetic (PK) and pharmacodynamic profiles. The purpose of this study was to determine the efficacy of intramuscular (IM) moxifloxacin administration in the treatment of experimental osteomyelitis by methicillin-resistant Staphylococcus aureus. Following an experimental osteomyelitis animal model described previously, three groups of rabbits (A = control; B = IM moxifloxacin administration; C = PK study of moxifloxacin penetration into bone) were evaluated. Three weeks after bacterial inoculation, surgical debridement was performed in all animals and IM treatment commenced for Groups B and C. Sacrifice was performed in an A:B group animal ratio of 1:2 at weekly intervals from 7th to 42nd day post debridement and from 21st to 56th day post debridement for Groups A and B, respectively (including 2-week interval without antibiotics for Group B). Cancellous bone was harvested for microbiological and histopathological analyses at re-operation and sacrifice for Groups A and B. Cortical bone moxifloxacin levels were measured in Group C following 7, 14, 35 and 42 days of treatment. In Group A, bacterial growth after surgical debridement was significant, whereas high eradication rates were observed in Group B. Radiological abnormalities and histopathological findings were evaluated. Moxifloxacin bone levels, observed in Group C, were approximately 43 times higher than the minimum inhibitory concentration, with no difference found between infected and healthy tibial bone. The therapeutic protocol was very effective in this model of experimental osteomyelitis. However, further evaluation of these results in clinical studies is crucial.