Comparison of the antibacterial in vitro and in vivo activity of ofloxacin (HOE 280 DL 8280) and nalidixic acid analogues.

The in vitro and in vivo activity of ofloxacin (DL 8280, HOE 280) was compared with that of other antibacterial compounds. Ofloxacin was found to have a broad antibacterial spectrum which includes both gram-positive and gram-negative aerobic and anaerobic species. Its activity is generally higher than that of pipemidic acid and nalidixic acid. Against staphylococci and streptococci, ofloxacin proved to be more active than norfloxacin. In the case of Enterobacteriaceae and Pseudomonadaceae, ofloxacin and norfloxacin possess comparable activities. Ofloxacin was the most active compound against a number of aerobic isolates which are resistant to cefotaxime and ceftriaxone. Of the compounds compared, ofloxacin was the only one which exhibited reasonable activity against anaerobes. It inhibited all strains of Bacteroides fragilis at a concentration of 3.125 mg/l and the gram-positive anaerobes at 0.5 mg/l. In mice experimentally infected with various gram-positive and gram-negative bacteria, ofloxacin was more active than norfloxacin and pipemidic acid. With the gram-negative pathogens, orally administered ofloxacin was as active as gentamicin used parenterally. We conclude from our studies that ofloxacin could be a valuable therapeutic agent with a variety of indications.