Clonal spread of serogroup A meningococci: a paradigm for the analysis of microevolution in bacteria

Abstract

Extensive epidemiological analyses of epidemics of meningococcal meningitis have resulted in large, well‐defined strain collections which represent the local diversity and global spread of serogroup A bacteria. Several genes for cell surface proteins are conserved during spread, with a few exceptions: analysis of these exceptions has revealed some of the phenomena which can lead to microevolution. Micro‐evolution is so rapid with serogroup A meningococcal that several independent recombination events have been documented within the last few decades. In a few cases, the recombinant bacteria have become established by clonal replacement plus epidemic spread. Comparison with other bacteria indicates that serogroup A meningococcal provide a number of advantages for analysis of microevolution.