Clonal diversity of Neisseria meningitidis from a population of asymptomatic carriers

Abstract

Genetic diversity and relationships among 109 isolates ofNeisseria meningitidis obtained from throat cultures of healthy individuals in Norway in 1984 were assessed by analyzing electrophoretically demonstrable alielic variation at 15 enzyme-encoding chromosomal genes. Seventy-eight distinctive electrophoretic types (ETs), representing multilocus genotypes, were identified. The mean genetic diversity per locus among the 78 ETs (0.538) was equivalent to that among 19 ETs represented by 66 isolates collected from patients with meningococcal disease in Norway in the first 5 months of 1984. The clonal composition of the collection of carrier strains was, however, quite different from that of strains from patients. The two groups of clones, the ET-5 complex and the ET-37 complex, that were responsible for 91% of the cases of systemic disease in Norway in 1984 were identified in only 7 and 9%, respectively, of the throat cultures from healthy individuals, and their frequencies in the human population sampled were only 0.7% for clones of the ET-5 complex and 0.9% for those of the ET-37 complex. The complex of clones that was most frequently represented by isolates from carriers (19%) has never been recovered from patients with meningococcal disease in Norway or elsewhere, which suggests that these clones have a low virulence potential. Children attending the same day care center or school seldom harbored the same clone in their throats.

In vivo expression of Neisseria meningitidis proteins homologous to the Haemophilus influenzae Hap and Hia autotransporters

“…2.1. Bacterial strains, plasmids and growth conditions N. meningitidis strain H44/76 (B:15:P1.7,16) was originally isolated from the cerebrospinal £uid of a meningitis patient in Norway and was shown to belong to the ET-5 group of strains associated with many cases of disease [16]. Cultures of the strain were started from frozen stocks and grown overnight in Tryptic soy broth.…”

“…The genome sequences of N. meningitidis serogroup A strain Z2491 [6] and serogroup B strain MC58 [7] were searched for genes putatively encoding autotransporters by homology searching using the sequences of 28 autotransporters from 10 di¡erent bacterial species (Table 1). This list was based upon the sequences described by [16] and [10], and, additionally, TibA [17], PssA [18] and Vag8 [19] were included. Database searches were performed using the web sites of The Sanger Centre (http://www.…”

Lessons from meningococcal carriage studies

“…Patient strains are encapsulated and five of these serogroups (A, B, C, W135, and Y) cause more than 90% of the invasive disease worldwide (Pollard, 2004). In contrast, c. 50% of the strains isolated from carriers lack capsule and are therefore serologically not serogroupable (Caugant et al, 1988;Ala'Aldeen et al, 2000). There are two essential reasons for the lack of capsule -the deletion of the capsule locus (the capsule nul or cnl meningococci) or down-regulation of the expression of the capsule either temporarily or permanently by one of a number of genetic mechanisms (Claus et al, 2002).…”

Multilocus sequence typing for global surveillance of meningococcal disease

“…Comparisons of meningococci isolated from asymptomatic carriage and disease have demonstrated that meningococcal populations are genetically and antigenically highly diverse (Caugant et al, 1987a, but that a minority of genotypes and antigenic types, the 'hyperinvasive lineages', account for the majority of disease (Caugant et al, 1988;Urwin et al, 2004;Yazdankhah et al, 2004). Detailed and accurate isolate characterization is therefore a particularly important element in studies of meningococcal epidemiology, population biology and evolution.…”