Identification of meningococcal serosubtypes by polymerase chain reaction

The polymerase chain reaction was used as the basis of a novel typing method for Neisseria meningitidis. Southern hybridization experiments demonstrated that it was possible to identify genes encoding different serological variants of the meningococcal class 1 outer membrane protein by probing with polymerase chain reaction products corresponding to known epitopes. A set of 14 defined variable regions was prepared in bacteriophage M13mp19 by the cloning of polymerase chain reaction products. The phage were dot blotted onto membrane filters, which were used as targets for hybridization of radiolabeled amplified class 1 outer membrane protein genes. Thus, the presence of many different subtype-specific epitopes could be investigated in one experiment. This technique was evaluated with a set of serological reference strains, mainly of serogroup B organisms, and provided an alternative, rapid, and comprehensive typing system that was capable of distinguishing known serosubtypes and also of defining currently untypeable strains independently of sodium dodecyl sulfate-polyacrylamide gel electrophoresis or serological analysis. An additional advantage of this technique was that in the case of an unknown serosubtype (i.e., one that did not hybridize with any of the known samples), the DNA amplified from the original sample could be used to determine the nucleotide sequence of the novel serosubtype and to clone the corresponding variable region into bacteriophage M13. It may be possible to develop this procedure for the diagnostic detection and typing of meningococci directly from clinical samples even when culture is not possible because of antibiotic treatment of an acute case.