In vitro activity of ofloxacin against Chlamydia trachomatis

The activity of ofloxacin against Chlamydia trachomatis isolates obtained from eight metropolitan areas in the United States has been evaluated. Growth of C. trachomatis in first passage was completely inhibited by less than 1 microgram/ml of ofloxacin (all 27 isolates tested). The bactericidal effect (inability to pass in the absence of antibiotics) was less than or equal to 1 microgram for 26 of the 27 isolates. Other studies have shown that less than 0.1 microgram/ml of ofloxacin is the minimal inhibitory concentration for 90 percent of strains tested (MIC90) for Neisseria gonorrhoeae and less than 2 micrograms/ml is the MIC90 for Haemophilus ducreyi. Ofloxacin is less active (MIC90, 8 to 25 micrograms/ml) against Ureaplasma urealyticum. These in vitro results suggest that ofloxacin may be useful in the treatment of bacterial sexually transmitted diseases. Because there is a need for a single antibiotic active against both chlamydiae and gonococci, this quinolone could play an important role in the management of these infections.