Resistance testing of meningococci: the recommendations of the European Monitoring Group on Meningococci

One of the most controversial topics concerning Neisseria meningitidis is the definition of antimicrobial resistance. A process of harmonization, promoted by the European Monitoring Group on Meningococci (EMGM), is already in progress. There are several aspects of the MIC definition for meningococcal strains for which a consensus is needed, as follows. (1) What methods can be used? At present, both the Etest and agar dilution methods are recommended by the EMGM. Microdilution, also a recommended method, is not used across Europe. (2) What media produce the most reliable data? The use of Mueller-Hinton medium supplemented with 5% blood is recommended for the MIC determination of N. meningitidis by both Etest and agar dilution method. (3) What is the minimum set of antimicrobial agents to be tested? A minimum set should include rifampicin, ciprofloxacin (or another quinolone), penicillin, ampicillin and ceftriaxone. (4) What are the most suitable breakpoints for definition? There is no widely accepted robust evidence base for the definition of breakpoints. Although progress has been made in achieving a standardized methodology, we are still far from obtaining common breakpoints for antimicrobial resistance definition. These differences will imply inability for building a common epidemiologic figure about drug resistance.