Comparative evaluation of oral levofloxacin and parenteral nafcillin in the treatment of experimental methicillin-susceptible Staphylococcus aureus osteomyelitis in rabbits.

Methicillin-susceptible Staphylococcus aureus (MSSA) is the most common pathogen recovered from osteomyelitis patients. The current standard therapeutic method for acute phase osteomyelitis is parenteral antibiotic therapy. However, parenteral administration has negative aspects, such as secondary infection, patient inconvenience and high cost. The use of single oral antibiotic therapy may alleviate these problems. Therefore, the purpose of this study was to compare the effectiveness of standard once per day dosing of oral levofloxacin with a standard parenteral antibiotic regimen (nafcillin four times daily) for the treatment of experimental MSSA osteomyelitis in rabbits. Nearly all tibias from untreated infected controls (n = 27) revealed positive cultures (93%) for S. aureus, while the levofloxacin-treated group (n = 20) demonstrated significantly lower percentages of S. aureus infection (50%). The infected tibias of the nafcillin-treated group (n = 20) demonstrated significantly lower percentages (10%) of infected tibias than either the controls or the levofloxacin-treated groups (P < 0.05). The inferior efficacy of levofloxacin may have been due to the pharmacokinetic profile of this fluoroquinolone. The serum kinetics demonstrated that following single dose administration, levofloxacin was almost undetectable after 12 h. Studies in which levofloxacin is dosed every 12 h or given at increased doses in order to obtain bactericidal concentrations throughout the treatment regimen are needed.