Rifampicin-resistant meningococci causing invasive disease: detection of point mutations in the rpoB gene and molecular characterization of the strains

Mutations in the rpoB gene affecting two amino acids were found in eight ri fampicin-resistant Neisseria meningitidis group B and C strains isolated in Italy. The Asp542-->Val substitution, documented for the first time in N. meningitidis, was found in four of the isolates; the His552-->Tyr or Asn su bstitution in the other four resistant strains. Mutations in the mtr gene d id not seem to be involved in the resistance since the same mutations occur red in both resistant and susceptible strains. Two different clusters were identified among these resistant strains, without any correlation with the specific mutations detected in the rpoB gene.