Fluoroquinolone resistance in Neisseria meningitidis in Spain

Objectives: To assess the ciprofloxacin resistance of Neisseria meningitidis isolated from 1999 through 2006 in Spain, susceptibility testing was conducted on 5300 isolates. Methods: Ten isolates showed MICs of ciprofloxacin ranging between 0.06 and 0.25 mg/L, and they were characterized by analysis for mutations within the quinolone resistance determining regions (QRDRs) in the gyrA, gyrB, parC and parE genes. Mutations in the mtrR gene were also analysed. Results and conclusions: Single mutations in gyrA appeared to be the main mechanism involved, Thr-91!Ile being the most frequent substitution seen. Two meningococci had four different gyrA substitutions. No mutations in the QRDRs of the parC and gyrB genes were detected, and three strains showed a His-495!Asn substitution in the parE gene. In addition, two different alterations in the mtrR gene affecting the expression of the MtrCDE efflux system were identified which may also contribute to the reduced susceptibility to quinolones seen in three strains.