REVIEW OF PRECLINICAL STUDIES WITH OFLOXACIN

Most Enterobacteriaceae, enteropathogens, and fastidious gram-negative bacteria are highly susceptible to ofloxacin, a new tricyclic fluoroquinolone. Aerobic gram-negative bacilli and gram-positive bacteria are generally not as susceptible to ofloxacin. Obligate anaerobes are generally resistant to ofloxacin, while many mycobacteria, chlamydiae, legionellae, and mycoplasmas are susceptible. Ofloxacin is generally less active than ciprofloxacin against gram-negative bacteria, is similarly active against gram-positive bacteria, mycobacteria, legionellae, and mycoplasmas, and is more active against chlamydiae. However, numerous animal studies have shown these two fluoroquinolones to be similar. Ofloxacin inhibits DNA synthesis, is rapidly bactericidal, and is 1,000-2,400 times more potent against prokaryotic gyrase than against eukaryotic gyrase. The bactericidal effect of ofloxacin is not completely neutralized by inhibitors of protein or RNA synthesis. Resistance to ofloxacin arises from mutations within chromosomal genes involved with DNA gyrase and drug permeation. Selection of resistant mutants by ofloxacin is not as frequent as that seen with nalidixic acid. However, due to the cross-resistance between ofloxacin and other fluoroquinolones, all of these drugs should be used judiciously to preserve their clinical utility.