Genetic structure of Neisseria meningitidis populations in relation to serogroup, serotype, and outer membrane protein pattern

Abstract

The genetic structure of populations of Neisseria meningitidis was examined by an analysis of electrophoretically demonstrable allelic variation at 15 genes encoding enzymes in 650 isolates of eight serogroups (A, B, C, W135, X, Y, Z, and 29E) and 38 nonserogroupable isolates. A total of 331 distinctive multilocus genotypes (electrophoretic types, ETs) was identified, among which mean genetic diversity per locus (H = 0.547) was greater than in Escherichia coli and other bacterial species thus far studied. The intercontinental distribution of some ETs and the recovery of organisms of identical genotype over periods of many years strongly suggest that the genetic structure of N. meningitdis is basically clonal as a consequence of low rates of recombination of chromosomal genes. Variation among strains in serogroup, serotype, and the electrophoretic pattern of the major outer membrane proteins has little relationship to the complex structure of populations revealed by enzyme electrophoresis, which involves 14 major lineages of clones diverging from one another at genetic distances greater than 0.50. Genetic diversity among ETs of isolates of the same serogroup was, on average, 84% of that in the total sample. Clones of serogroup A were unusual in being genotypically less heterogeneous than those of other serogroups and in forming a single phylogenetic group. Isolates of the same serotype or outer membrane protein pattern were also highly heterogeneous; on average, 87 and 97%, respectively, of the total species diversity was represented by ETs of the same serotype or outer membrane protein.

Phylogenetic and epidemiological analysis ofNeisseria meningitidisusing DNA probes

“…The division of UK B15:P1.16R strains into two types (G and P) as suggested by others [12,13,24,25] is supported by this work. This differs from our earlier findings in which we were unable to differentiate Gloucester and Plymouth strains.…”

Molecular epidemiology of recent United Kingdom isolates ofNeisseria meningitidisserogroup C

“…Again, characterization of 94 United Kingdom meningococcal strains by ribotyping and by REA using Bgl II showed that ribotyping gave lower discrimination (11). Twenty-eight of those strains which were included in this study were subtyped by PFGE into 8 subtypes whereas by ribotyping they were subtyped into only 4 ribotypes [11]. Three strains that had been ribotyped [11] (Figs.…”

“…Currently the most widely used method for identifying bacterial clones is MLEE which has been successfully applied to the study of genetic relationships among meningococcal strains [4,31]. MLEE typing offers both the ability to discriminate and to estimate genetic relatedness among isolates.…”

“…Most disease isolates within the serogroup B and C meningococci have been assigned by multilocus enzyme electrophoresis (MLEE) to one of three genetically distinct lineages, each containing a number of related electrophoretic types [4]. Serogroup C organisms are responsible for sporadic and endemic disease, being intermediate between genetically diverse serogroup B meningococci and the relative genetic and antigenic stability of clones of serogroup A [5,6].…”

“…Serological classification is phenotypically based and suffers from the deficiency that groupings based on it may contain strains that are genotypically dissimilar. MLEE indexes the genotype and has been widely used to study genetic relationships among meningococci [4,8,9]. [8,11,12] such techniques often produce complex patterns that are difficult to interpret.…”