Population structure of the Yersinia pseudotuberculosis complex according to multilocus sequence typing.

Multilocus sequence analysis of 417 strains of Yersinia pseudotuberculosis revealed that it is a complex of four populations, three of which have been previously assigned species status [Y. pseudotuberculosis sensu stricto (s.s.), Yersinia pestis and Yersinia similis] and a fourth population, which we refer to as the Korean group, which may be in the process of speciation. We detected clear signs of recombination within Y. pseudotuberculosis s.s. as well as imports from Y. similis and the Korean group. The sources of genetic diversification within Y. pseudotuberculosis s.s. were approximately equally divided between recombination and mutation, whereas recombination has not yet been demonstrated in Y. pestis, which is also much more genetically monomorphic than is Y. pseudotuberculosis s.s. Most Y. pseudotuberculosis s.s. belong to a diffuse group of sequence types lacking clear population structure, although this species contains a melibiose-negative clade that is present globally in domesticated animals. Yersinia similis corresponds to the previously identified Y. pseudotuberculosis genetic type G4, which is probably not pathogenic because it lacks the virulence factors that are typical for Y. pseudotuberculosis s.s. In contrast, Y. pseudotuberculosis s.s., the Korean group and Y. pestis can all cause disease in humans.

Monitoring of Bordetella isolates circulating in Saint Petersburg, Russia between 2001 and 2009.

Bordetella isolates in the Saint Petersburg region have been monitored since 1998. Over the past ten years, concomitant with the increase in pertussis whole-cell vaccine coverage, the incidence of whooping cough has decreased. However, this decrease exists only for Bordetella pertussis infections, as the incidence of Bordetella parapertussis confirmed cases has remained stable, suggesting that pertussis-vaccine-induced immunity is not protective against parapertussis, as expected. B. pertussis and B. parapertussis clinical isolates were analyzed using serotyping, immunoblotting, pulsed-field gel electrophoresis of chromosomal DNA (after digestion with XbaI) and sequencing of virulence genes. The bacterial population is now similar to that observed in other European countries.

Evaluation of ribotyping as a tool for molecular typing of Yersinia pseudotuberculosis strains of worldwide origin.

Yersinia pseudotuberculosis is a gram-negative bacterium that infects a wide range of animals, including humans, and is transmitted by the fecal-oral route. This species is found globally and is responsible for human outbreaks, mainly in cold countries. The aim of this study was to evaluate the potential of ribotyping for the molecular typing of worldwide isolates. For this purpose, 80 strains of Y. pseudotuberculosis belonging to the six classical serotypes and nine subserotypes and isolated from various countries and different hosts were analyzed. Combination of the EcoRI and EcoRV ribopatterns allowed the delineation of 27 ribotypes. In most instances, ribotypes were associated with specific subserotypes and allowed their subdivision. No association between the ribotype and the geographical origin of the strains was observed, arguing for a global spread of this organism. Similarly, no marked association between the ribotype and the type of host was noted, confirming the circulation of this pathogen in the environment, different animal species, and human hosts. Y. pseudotuberculosis exhibited ribopatterns very close to those of Y. pestis, although not completely identical. Altogether, the present study demonstrates that ribotyping may be a useful tool for molecular typing of global isolates of Y. pseudotuberculosis but that it has some limitations due to the small number of hybridizing bands that generate the diversity of the profiles.

Comparison of the Bordetella pertussis and Bordetella parapertussis isolates circulating in Saint Petersburg between 1998 and 2000 with Russian vaccine strains.

We analyzed the Bordetella pertussis and Bordetella parapertussis isolates circulating in Saint Petersburg that were collected between 1998 and 2000 and compared them with isolates collected 40 years ago and Russian vaccine strains. The analysis involved serotyping, pulsed-field gel electrophoresis of chromosomal DNA after digestion with XbaI and SpeI, and sequencing of the ptxS1 and prn genes, which encode the S1 subunit of the pertussis toxin and the major adhesin pertactin, respectively. The Russian isolates were classified in five of the six pulsed-field gel electrophoresis groups identified in other European countries. The B. pertussis isolates currently circulating in Saint Petersburg differed from the Russian whole-cell vaccine strains and the isolates collected in the prevaccine era. However, their repartition in the major pulsed-field gel electrophoresis groups was slightly different from that of isolates collected in countries that have had a high level of vaccine coverage for a long time, probably because the level of vaccine coverage in Saint Petersburg has increased only recently, after decreasing until the early 1990s. Most of the B. parapertussis isolates studied were similar to those circulating in France. However, some variants were observed, perhaps because B. parapertussis infections are more common in children in this area.