Moxifloxacin superior to vancomycin for treatment of bone infections—a study in rats

Abstract

Background Increasing resistance rates towards conventional antibiotics necessitate investigations of the efficacy of newly developed antibiotics. Thus, in a rat study, we compared the efficacy of moxifloxacin and vancomycin in the treatment of a local Staphylococcus aureus bone infection. Method The femoral medullary cavities of 36 Wistar rats were contaminated with 100 μL of an oxacillin-sensitive Staphylococcus aureus strain (ATCC 29213) at 108cfu/mL. On the seventh day, antibiotic treatment with moxifloxacin (10 mg/kg twice daily i.p.) or vancomycin (15 mg/kg twice daily i.p.) was commenced in 12 animals each. 12 control animals were left untreated. After 21 days, the infected femurs were explanted and the bacterial counts (cfu/g) were determined. Results In the control group, a median of 3.42 × 106cfu/g (LQ/UQ 1.09 × 106/ 1.55 × 107) was cultured, with a median of 2.53 × 106cfu/g (LQ/UQ 1.95 × 106/ 4.25 × 106) in the vancomycin group and a median of 2.49 × 105cfu/g (LQ/UQ 2.84 × 104/ 3.75 × 105) in the moxifloxacin group.The bacterial count was reduced by treatment with moxifloxacin both in comparison with the control group (p < 0.001), and in comparison with treatment with vancomycin (p < 0.001). There was no statistically significant difference between the vancomycin group and the control group (p = 0.53). Interpretation In contrast to vancomycin, moxifloxacin proved to be an effective antibiotic for the treatment of bone infections due to Staphylococcus aureus in our animal model.