Invasive meningococci with reduced susceptibility to penicillin in Portugal

Sir, Since the description of the first clinical isolate of Neisseria meningitidis with reduced susceptibility to penicillin (MRSP),1 similar findings have been reported from a number of countries.2,3 At the same time, the frequency of serogroup C meningococci has increased in Europe.4 Twenty-seven MRSP invasive strains recovered from the collection of the Antibiotic Resistance Unit at the National Institute of Health in Lisbon were analysed. MRSP were defined as strains with a penicillin MIC of 0.12–1 mg/L. MICs of penicillin and of ampicillin (Wyeth Lederle Portugal), cefotaxime (Hoechst Marion Rousel), ceftriaxone (Roche Pharmaceuticals), ciprofloxacin (Bayer Portugal) and rifampicin (Novartis Farma) were determined by an agar dilution method according to NCCLS guidelines.5 Serogroup determination was carried out by a slide agglutination method with specific antisera (Murex Biotech, Dartford, UK). β-Lactamase production was assessed on all isolates by chromogenic cephalosporin assay (Oxoid, Basingstoke, UK). Ampicillin was found to be less active than penicillin against meningococci (Table). None of the isolates produced β-lactamase. All meningococci were fully susceptible to cefotaxime, ceftriaxone, ciprofloxacin and rifampicin. Most of the MRSP isolates were from serogroup C (19/27, 70.4%), but 6/27 (22.2%) belonged to serogroup B and 2/27 (7.4%) belonged to serogroup W135. These results suggest that ceftriaxone or cefotaxime should become the antibiotic of choice for treating meningococcal meningitis in the face of the possible development of penicillin resistance. As there appears to be no immediate risk of resistance to rifampicin or ciprofloxacin, these antibiotics should continue to be used for prophylaxis among contacts. In this study we demonstrate a high prevalence of MRSP in serogroup C, which indicates that meningococcal group C conjugate (MCC) vaccine in national prophylaxis programmes could be very useful in countries with such a high prevalence. Immunization with effective vaccines is the best approach for controlling meningococcal disease, and the MCC vaccine has been demonstrated to have an effect on the epidemiological pattern of serogroup C infection.6 Our data highlight the importance of serotype and resistance surveillance for these pathogens in helping to define health policies. Improvements in the submission of meningococcal isolates to national reference laboratories are crucial for maximizing the efficacy of this surveillance. MICs of penicillin and ampicillin for 27 meningococci with reduced susceptibility to penicillin MICs of penicillin and ampicillin for 27 meningococci with reduced susceptibility to penicillin The authors would like to thank the pharmaceutical companies represented in Portugal, cited in the text, for having supplied antibiotic powders.