[Presence of plasmids in Neisseria meningitidis].

The plasmid content of twenty-nine Neisseria meningitidis strains, isolated from CSF and blood cultures, was investigated by agarose gel electrophoresis. The strains (twenty-seven from serogroup B and two from serogroup C) were sensitive to antibiotics, but 50% were resistant to sulphonamide (MIC greater than or equal to 16 mg/l). Two serogroup-B strains from CSF harboured an extrachromosomal element. These two cryptic plasmids differed in size: 8.4 Kb for pNMT1 and 82 Kb for pNMT2.