Emergence of resistance to ciprofloxacin in Neisseria meningitidis in Brazil

We report on three cases of meningococcal disease caused by ciprofloxacin-resistant Neisseria meningitidis, one in North Dakota and two in Minnesota. The cases were caused by the same serogroup B strain. To assess local carriage of resistant N. meningitidis, we conducted a pharyngeal-carriage survey and isolated the resistant strain from one asymptomatic carrier. Sequencing of the gene encoding subunit A of DNA gyrase (gyrA) revealed a mutation associated with fluoroquinolone resistance and suggests that the resistance was acquired by means of horizontal gene transfer with the commensal N. lactamica. In susceptibility testing of invasive N. meningitidis isolates from the Active Bacterial Core surveillance system between January 2007 and January 2008, an additional ciprofloxacin-resistant isolate was found, in this case from California. Ciprofloxacin-resistant N. meningitidis has emerged in North America. 2009 Massachusetts Medical Society

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 μg/ml but not among isolates with MICs of ≤ 0.032 μg/ml. Experimental infection of ciprofloxacin-treated mice showed slower bacterial clearance when GyrA was altered. These data suggest a MIC of ≥ 0.064 μg/ml as the ciprofloxacin breakpoint for meningococci and argue for the molecular detection of ciprofloxacin resistance.