Chemotherapeutic efficacy of ofloxacin on renal and subcutaneous infection models with Staphylococcus aureus in mice.

Ofloxacin, a new pyridone-carboxylic acid derivative, was evaluated in descending nephritis and subcutaneous abscess models with Staphylococcus aureus in mice in comparison with norfloxacin. Descending nephritis was produced by intravenous injection of S. aureus 39 (MIC 0.78 microgram/ml for ofloxacin and 3.13 micrograms/ml for norfloxacin). Subcutaneous abscess was established by subcutaneous injection of soft agar containing S. aureus 56230 (MIC 0.39 microgram/ml for ofloxacin and 1.56 micrograms/ml for norfloxacin). Three days after infection, the lesions of both models were characterized by purulent inflammation accompanied with massive infiltration of neutrophils and bacterial multiplication. The animals were treated twice a day orally with each compound for 4 consecutive days, and subjected to bacteriological examination 18 h later. In the renal model, the 50% effective doses calculated on the basis of clearance of bacteria from kidneys were 38.4 mg/kg for ofloxacin and greater than 100 mg/kg for norfloxacin. In the subcutaneous model, the 50% effective doses based upon 90% reduction of viable bacteria as compared with untreated controls were 25.2 mg/kg for ofloxacin and greater than 100 mg/kg for norfloxacin. The excellent efficacies of ofloxacin in both infection models are attributed to its high oral absorbability and tissue distribution.