Neisseria meningitidis showing decreased susceptibility to ciprofloxacin: first report in Spain.

Abstract

Sir, In February 2002, a serogroup B meningococcal strain was isolated in Girona, Catalonia, Spain, from cerebrospinal fluid in a 2-year-old male with meningitis. The isolate was sent to the Reference Laboratory for characterization and determination of the MIC. The strain was characterized using monoclonal antibodies as B: Non Typeable: P1. 5, 10.1 The antibiotic susceptibility was determined by the agar dilution method with Mueller–Hinton agar (Difco Laboratories, Detroit, MI, USA) supplemented with 5% sheep blood, with a final inoculum of the strain of 105 cfu/spot.1 Cultures were incubated for 24 h at 37°C under a 5% CO2 atmosphere. The MIC was defined as the lowest concentration at which no growth was visible on agar plates. Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 were used as quality control organisms. The MICs of sulphamide, ciprofloxacin, rifampicin, penicillin, ampicillin, ceftriaxone and cefotaxime were 100, 0.12, 0.06, 0.06, 0.25, 0.0007 and 0.003 mg/L, respectively. The data thus indicate that the strain might be defined as resistant to sulphamide, with decreased susceptibility to ciprofloxacin (taking into account that all Spanish meningococcal strains show MICs of ciprofloxacin between 0.007 and 0.003 mg/L) and susceptible to the rest of the tested drugs. The emergence of meningococcal strains with reduced susceptibility to ciprofloxacin has been reported on only two previous occasions: in 1999 from a meningococcal carrier in France and in 2000 from a female nursing student with invasive disease in Wollongong, New South Wales, Australia.2 In Neisseria gonorrhoeae, the most important mechanisms contributing to ciprofloxacin resistance involve mutations in the quinolone resistance determining region (QRDR) of the gyrA gene and the analogous region of the parC locus.3 Neisseria meningitidis and N. gonorrhoeae share high DNA homology.4 PCR amplification and sequencing of the equivalent region of the gyrA gene in two susceptible N. meningitidis strains also isolated in Spain and included in our study with MICs of 0.003 mg/L of ciprofloxacin, revealed three nucleotide differences according to the N. gonorrhoeae sequence.5 These differences were previously described by Shultz et al.2 in 2000. One of these alterations encoded a conservative Ser to Thr amino acid substitution at position 91 and the other two changes, Ala-92 and Val-93, respectively, were synonymous. The meningococcal strain that we are describing contained a mutation, not previously defined, that resulted in a Thr to Ile substitution at position 91. The alterations found in the strains from France and Australia were both at position Asp-95, resulting in Gly and Asn changes, respectively.2 This alteration in the N. gonorrhoeae gyrA gene has been described previously and is associated with an increase in ciprofloxacin MICs.3,5 No alterations in the QRDR of the parC gene were found in this meningococcal strain when we compared it with the parC gene of susceptible meningococcal strains and a gonococcal isolate, also susceptible to this antibiotic. The appearance of a new mutation site in the gyrA gene of this species indicates that meningococci develop mechanisms of resistance to quinolones in a similar way to N. gonorrhoeae and other microorganisms.3,5 In Spain, the emergence of meningococcal strains showing decreased susceptibility to this antibiotic might have implications in chemoprophylaxis because ciprofloxacin is used occasionally to eradicate meningococci from nasopharyngeal carriers. Thus, continuous surveillance is necessary to monitor the emergence and spread of resistance to ciprofloxacin and other quinolones and to guide appropriate public health interventions in preventing drug-resistant meningococci.