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Abstract

Immunology and Infection

Constructing Mutants in Serotype 1 Streptococcus pneumoniae strain 519/43

Published: September 11th, 2020

DOI:

10.3791/61594

1Faculty of Infections and Tropical Diseases, Department of Infection Biology, London School of Hygiene and Tropical Medicine, 2Division of Medicine, University College London, 3Division of Infection and Immunity, University College London UCL

Abstract

Streptococcus pneumoniae serotype 1 remains a huge problem in low-and-middle income countries, particularly in sub-Saharan Africa. Despite its importance, studies in this serotype have been hindered by the lack of genetic tools to modify it. In this study, we describe a method to genetically modify a serotype 1 clinical isolate (strain 519/43). Interestingly, this was achieved by exploiting the Pneumococcus’ ability to naturally acquire DNA. However, unlike most pneumococci, the use of linear DNA was not successful; to mutate this important strain, a suicide plasmid had to be used. This methodology has provided the means for a deeper understanding of this elusive serotype, both in terms of its biology and pathogenicity. To validate the method, the major known pneumococcal toxin, pneumolysin, was mutated because it has a well-known and easy to follow phenotype. We showed that the mutant, as expected, lost its ability to lyse red blood cells. By being able to mutate an important gene in the serotype of interest, we were able to observe different phenotypes for loss of function mutants upon intraperitoneal and intranasal infections from the ones observed for other serotypes. In summary, this study proves that strain 519/43 (serotype 1) can be genetically modified.

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Keywords Serotype 1 Streptococcus Pneumoniae

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