Genetic Isolation of Meningococci of the Electrophoretic Type 37 Complex

Abstract

Neisseria meningitidis (the meningococcus) is a naturally competent bacterial species in which intra- and interspecific horizontal gene transfer is a major source of genetic diversity. In strains of the electrophoretic type 37 (ET-37) complex and of the A4 cluster, we identified genomic DNA coding for a novel restriction-modification system and for the tail of a previously unidentified prophage. Furthermore, a novel 7.2-kb DNA segment restricted to clones of the ET-37 complex and the A4 cluster was isolated and shown to occur both as a plasmid (pJS-B) and as a chromosomal integration. Neither the genomic loci nor pJS-B was present in ET-5 complex, lineage 3, or serogroup A meningococci. The differential distribution of the DNA segments described herein, as well as of opcA, porB, nmeAI, nmeBI , and nmeDI described previously, supports the concept of genetic isolation of hypervirulent lineages responsible for most cases of serogroup C disease worldwide.