Neisseria meningitidis with reduced susceptibility to quinolones in Singapore

Sir, Ciprofloxacin is commonly prescribed as a single-dose chemoprophylactic agent for close contacts of patients with meningococcal infection. Neisseria meningitidis with reduced susceptibility to fluoroquinolones has recently emerged, with sporadic cases reported in France, Australia,1 Argentina,2 Spain,3 Hong Kong4 and Israel.5 Recently an outbreak of serogroup A emerged in India,6 and a cluster of three cases of serogroup B in the USA.7 To our knowledge, failure of ciprofloxacin prophylaxis due to quinolone resistance has not been reported To date, reduced susceptibility to fluoroquinolones in meningococci has remained rare, with 10 unrelated strains found in an analysis of 5300 isolates in Spain,3 and only 3 from >5000 isolates in France.8 Most mutations have arisen in GyrA.3 However, mutations have also been detected in GyrB5 and ParE, although their significance remains uncertain.3,5 In addition, in vitro changes have been induced in ParC9 and resistance to quinolones has also been reported through an efflux mechanism.2–4