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 pat hogen recovered from osteomyelitis patients. The current standard therapeut ic method for acute phase osteomyelitis is parenteral antibiotic therapy. H owever, parenteral administration has negative aspects, such as secondary i nfection, patient inconvenience and high cost. The use of single oral antib iotic therapy may alleviate these problems. Therefore, the purpose of this study was to compare the effectiveness of standard once per day dosing of o ral levofloxacin with a standard parenteral antibiotic regimen (nafcillin f our times daily) for the treatment of experimental MSSA osteomyelitis in ra bbits. Nearly all tibias from untreated infected controls (n = 27) revealed positive cultures (93%) for S. aureus, while the levofloxacin-treated grou p (n = 20) demonstrated significantly lower percentages of S. aureus infect ion (50%). The infected tibias of the nafcillin-treated group (n = 20) demo nstrated significantly lower percentages (10%) of infected tibias than eith er 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 sin gle dose administration, levofloxacin was almost undetectable after 12 h. S tudies in which levofloxacin is dosed every 12 h or given at increased dose s in order to obtain bactericidal concentrations throughout the treatment r egimen are needed.