Target Gene Sequencing To Define the Susceptibility of Neisseria meningitidis to Ciprofloxacin

Meningococcal gyrA gene sequence data, MICs, and mouse infection were used to define the ciprofloxacin breakpoint for Neisseria meningitidis. Residue T91 or D95 of GyrA was altered in all meningococcal isolates with MICs of >= 0.064 mu g/ml but not among isolates with MICs of <= 0.032 mu g/ml. Experimental infection of ciprofloxacin-treated mice showed slower bacterial clearance when GyrA was altered. These data suggest a MIC of >= 0.064 mu g/ml as the ciprofloxacin breakpoint for meningococci and argue for the molecular detection of ciprofloxacin resistance.