Comparison of the in vitro activities of various parenteral and oral antimicrobial agents against endemic Haemophilus ducreyi.

The in vitro susceptibilities to various antimicrobial agents of 100 strains of beta-lactamase-producing Haemophilus ducreyi recently isolated from patients in New Orleans, La., were determined by an agar dilution method. All strains were highly susceptible to ceftizoxime, ceftriaxone, ceftazidime, azithromycin, erythromycin, ciprofloxacin, and sparfloxacin. beta-Lactam-beta-lactamase inhibitor combinations were less active, but all strains were susceptible to them. Doxycycline exhibited the poorest activity, and the rate of resistance to doxycycline varied depending on the time after inoculation that the MIC was determined.