Microevolution and epidemic spread of serogroup A Neisseria meningitidis--a review.

An extensive and representative strain collection of serogroup A Neisseria meningitidis was established. These bacteria were obtained from different endemic and epidemic/pandemic sources and include strains from diseased patients and healthy carriers. The genetic relationships of the bacteria were defined by multi-locus enzyme electrophoresis and sequence polymorphisms of genetically variable antigens have been analyzed in closely-related groupings. The results are interpreted as reflecting a balance of recombination events, which disrupt clonal relationships, and sequential bottlenecks, which purify the bacterial population of genetic variants during epidemic spread.