The comparative in-vitro activity of ofloxacin

The antibacterial activity of ofloxacin, a new fluoroquinolone, was evaluated against a wide range of clinical bacterial isolates and compared with that of nalidixic acid, norfloxacin, enoxacin, pefloxacin and ciprofloxacin by determination of minimum inhibitory concentrations (MICs). Ofloxacin was very active against nalidixic acid-susceptible isolates of the Enterobacteriaceae (MIC⩽0·12 mg/1) and was also active against strains resistant to nalidixic acid (MIC ⩽ 2 mg/1). The activity was similar to norfloxacin, enoxacin and pefloxacin but some four-fold less than that of ciprofloxacin. All of the fluoroquinolones were highly active against Vibrio cholerae (MIC ⩽0·015 mg/1), V. parahaemolyticus (MIC ⩽0·12 mg/1) Aeromonas hydrophila (MIC ⩽0·03 mg/1), Plesiomonas shigelloides (MIC ⩽0·015 mg/1), Campylobacter jejuni (MIC ⩽0·5 mg/1), Neisseria spp., Haemophilus influenzae, H. ducreyi, Bordetella pertussis and Legionella pneumophila (MIC ⩽0·06 mg/1 for all species). Ofloxacin, ciprofloxacin and pefloxacin (MIC ⩽1,2 and 2 mg/1, respectively) showed similar activity against Staphylococcus spp. and were somewhat more active than enoxacin (MIC ⩽4 mg/1) and norfloxacin (MIC ⩽8 mg/1). Ofloxacin was moderately active against β-hacmolytic Streptococcus spp. (MIC ⩽2 mg/1), Corynebacterium diphtheriae (MIC ⩽1 mg/1) and Cory. jeikeium (MIC ⩽2mg/1) and somewhat less active against α- and non-haemolytic Streptococcus spp., Str. pneumoniae and Listeria monocytogenes (MIC ⩽mg/4 for all species) and Str. faecalis (MIC ⩽8 mg/1). The activity of ofloxacin, against these species, was similar to ciprofloxacin and four to eight times greater than norfloxacin, enoxacin and pefloxacin. Ofloxacin, and all of the fluoroquinolones, were less active against anaerobic than aerobic bacteria. Clostridium perfringens (MIC ⩽1 mg/1) was more susceptible to ofloxacin than were other anaerobic species and Cl. difficile (MIC ⩽16 mg/1) was more resistant. Ofloxacin was the most active compound tested against Chlamydia trachomatis SA2f (MIC ⩽0·5 mg/1) with only ciprofloxacin (MIC ⩽1 mg/1) approaching similar activity. Ofloxacin was moderately active against Mycoplasma hominis (MIC ⩽2 mg/1) and Ureaplasma urealyticum (MIC ⩽4 mg/1).