May 30, 2020

pspK acquisition contributes to the loss of capsule in pneumococci: molecular characterisation of non-encapsulated pneumococci

Microbes and Infection
Takeaki WajimaNorihisa Noguchi

Abstract

With the introduction of the pneumococcal conjugate vaccine (PCV), the number of cases of non-vaccine type pneumococci and non-encapsulated Streptococcus pneumoniae (NESp) infection have increased. In order to clarify how pspK-harbouring NESp might have emerged, we characterised NESp and analysed the correlation between transformation and non-encapsulation. A total of 26 NESp strains were used in this study. The genetic backgrounds were compared using multilocus sequence typing (MLST). The ΔpspK::ermB strain, in which pspK was replaced by ermB in NESp was constructed by homologous recombination. The genomic DNA of the ΔpspK::ermB strain was transformed into two types of encapsulated S. pneumoniae via transformation. The fitness of the parent and non-encapsulated transformants was compared using the growth curve. All NESp had pspK instead of capsular coding regions and were classified into 14 types by MLST, which indicated that NESp had several genetic backgrounds. Transformation of ΔpspK::ermB genomic DNA resulted in 10-4‒10-5 non-encapsulated transformants. Non-encapsulated transformants could grow faster than the encapsulated parent strain. The acquisition of pspK region via transformation contributed to the loss of encapsula...Continue Reading

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Mentioned in this Paper

Pneumococcal conjugate vaccine
Non-Encapsulated Neoplasm
Study
Open Reading Frames
Genes
Microbial Anatomical Capsule Structure
RNA, Untranslated
Streptococcus pneumoniae
Genomic DNA
Multilocus Sequence Typing

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