Showing papers by "Ulrich Vogel published in 2000"

Rapid serogroup switching in Neisseria meningitidis.

Abstract: To the Editor: In Neisseria meningitidis, the horizontal transfer of siaD genes encoding polysialyltransferases has been shown to result in capsular serogroup switching in vitro.1 The presence of c...

Molecular basis for distinction of the ET-15 clone within the ET-37 complex of Neisseria meningitidis.

Abstract: The species Neisseria meningitidis comprises a large variety of genetically different clones, which are defined either by multilocus enzyme electrophoresis (MLEE) (2) or by multilocus sequence typing (MLST) (5) of housekeeping genes. One cluster of related clones causing predominantly epidemic serogroup C disease, i.e., the electrophoretic type 37 (ET-37) complex, has been defined by MLEE. A particular clone of the ET-37 complex, ET-15, arose several years ago in Canada (1, 6) and has spread worldwide since then (4). ET-15 meningococci tend to be more virulent than other members of the ET-37 complex, and attack and fatality rates, as well as the proportion of sequelae, have been reported to exceed the rates observed for other members of the ET-37 complex (3, 4, 6). Therefore, attempts to distinguish ET-15 from other clones of the ET-37 complex have been made to guide public health actions undertaken in case of outbreaks of ET-15 disease. Until now, ET-15 meningococi could be solely identified by MLEE, because this new clone differed by a rarely occurring FumC allele (FumC2) from most other ET-37 complex strains, which express a FumC1 allele (1). However, the use of MLEE is restricted to a few specialized laboratories worldwide. Pulsed-field gel electrophoresis (PFGE) using the enzyme SpeI revealed restriction patterns which are specific to ET-15 (J. Jelfs, R. Munro, F. Ashton, N. Rawlinson, and D. A. Caugant, Abstr. 11th Int. pathog. Neisseria Conf., p. 5, 1998), but PFGE is far too time-consuming to be a viable alternative to MLEE. Sequencing of the fumC gene has been added to the original MLST scheme for meningococci in order to distinguish ET-15, but no sequence information specific to ET-15 meningococci was found in the part of the gene sequenced by MLST (fumC gene position 776 to 1,230) (http://mlst.zoo.ox.ac.uk/). We therefore compared the sequences upstream of position 776 of the fumC gene of ET-15 meningococci with those of other members of the ET-37 complex. For this purpose, the fumC gene was amplified using the primers fumC-A1 and fumC-A2 (1). The PCR product was sequenced using the primer fumC-P3 (5′-CGTAAAAGCCCTGCGCGAC-3′). At position 640 we observed a point mutation in the fumC gene of ET-15 meningococci, which showed an A instead of a G in other ET-37 complex strains. This nonsynonymous change results in the expression of a basic lysine instead of an acidic glutamate (Fig. ​(Fig.1).1). We suggest that this mutation is responsible for the different MLEE migration pattern of the ET-15 FumC. The point mutation was consistantly found in 13 ET-15 strains from various geographical origins, but not in seven ET-37 complex strains other than ET-15 (Table ​(Table1).1). Thus, the point mutation at posiiton 640 of the fumC gene is a clone-specific characteristic which permits the distintion of ET-15 from other ET-37 complex strains. We therefore suggest that sequencing of the fumC gene should include position 640 in order to identify this especially virulent variant. FIG. 1 Nonsynonymous change at position 640 in the fumC gene of ET-15 strains. TABLE 1 ET-37 complex strains used in this study

Differential distribution of novel restriction-modification systems in clonal lineages of Neisseria meningitidis

Abstract: Using representational difference analysis, we isolated novel meningococcal restriction-modification (R-M) systems. NmeBI, which is a homologue of the R-M system HgaI of Pasteurella volantium, was present in meningococci of the ET-5 complex and of lineage III. NmeAI was found in serogroup A, ET-37 complex, and cluster A4 meningococci. NmeDI was harbored by meningococci of the ET-37 complex and of cluster A4, but not by serogroup A meningococci. Two of the R-M systems, NmeBI and NmeDI, were located at homologous positions between the phenylalanyl-tRNA synthetase genes pheS and pheT, which appeared to be a preferential target for the insertion of foreign DNA in meningococci. The distribution of the three R-M systems was tested with 103 meningococcal strains comprising 49 sequence types. The vast majority of the strains had either NmeBI, NmeAI, or both NmeAI and NmeDI. Using cocultivation experiments, we could demonstrate that NmeBI, which was present in ET-5 complex meningococci, was responsible for a partial restriction of DNA transfer from meningococci of the ET-37 complex to meningococci of the ET-5 complex.

Distribution of the meningococcal insertion sequence IS1301 in clonal lineages of Neisseria meningitidis.

Abstract: The distribution of the meningococcal insertion sequence IS1301 was analysed in 496 strains of different serogroups and clonal lineages of Neisseria meningitidis, and in 64 neisserial strains other than N. meningitidis. IS1301 was found in meningococci, but not in apathogenic Neisseria sp. and Neisseria gonorrhoeae. The copy numbers of IS1301 varied between 2 and 17 per genome. IS1301 positive strains were mostly found among the serogroups 29E, W135, X, and Y. Clonal lineages of serogroup A, B, and C meningococci associated with epidemic meningococcal disease were rarely positive for IS1301.