Streptococcus pneumoniae serotypes 8 and 22F causing invasive pneumococcal disease in the Czech Republic in 2014-2020: whole genome sequencing (WGS) analysis.

Aim: An analysis is presented of whole genome data of Streptococcus pneumoniae serotypes 8 and 22F isolated in the Czech Republic from invasive pneumococcal disease (IPD) in 2014-2020. New multivalent pneumococcal conjugate vaccines (PCVs) are effective against these serotypes. Recently, serotypes 8 and 22F have been among the leading causes of IPD in the Czech Republic. S. pneumoniae isolates from the Czech Republic were compared with those of the same serotypes recovered in other countries in the same period and available in the international database PubMLST.

Material and methods: Isolates from IPD of serotypes 8 (22 isolates) and 22F (21 isolates) recovered in the Czech Republic in 2014-2020 were subjected to whole genome sequencing (WGS). The genomes were analysed and compared using the international database PubMLST.

Results: Most of the studied Czech serotype 8 isolates belong to two main subpopulations. The first subpopulation, dominated by ST-53 isolates, is part of a highly abundant group of genetically close European and non-European isolates that are clearly separated on the phylogenetic network. The second subpopulation of Czech serotype 8 isolates (dominated by ST-404) is more genetically variable and forms a separate lineage on the global phylogenetic network, with no other European isolates. Czech isolates of serotype 22F are a homogeneous population with a clear predominance of ST-433, which belongs to a genetically close European population.

Conclusion: The analysis of WGS data of IPD isolates of serotypes 8 and 22F provided a detailed insight into the genetic relationships between the Czech populations of these serotypes. It also allowed comparison of the Czech populations with the matched populations from other European and non-European countries. The obtained results add to the body of knowledge about the spread of genetic lineages causing IPD in the Czech Republic in the post-vaccination period and provide a basis for considering whether the use of the new multivalent PCVs in the Czech Republic would be beneficial.