Plasmid deoxyribonucleic acid in throat and cerebrospinal fluid isolates of Neisseria meningitidis

Ten strains of Neisseria meningitides, isolated either from cerebrospinal fluid or from throat cultures, were typed and screened for the presence of plasmid DNA. Three group C strains, isolated in the same area, each harboured a plasmid of similar molecular weight (approx. 8.5 Md). No evidence of plasmid DNA was found in the other strains (whether of the same group but isolated in another area, or of other groups).