Investigation on the virulence of non-encapsulated Streptococcus pneumoniae using liquid agar pneumonia model.

Abstract

INTRODUCTION:

Since the introduction of pneumococcal conjugate vaccine, there have been warnings of an increase in infections caused by non-vaccine type of Streptococcus pneumoniae strains. Among them, nonencapsulated Streptococcus pneumoniae (NESp) has been reported to cause invasive infections, especially in children and the elderly. Due to low virulence, however, basic experimental reports on invasive infections are limited.

METHODS:

We applied a liquid-agar method to establish a mouse model of invasive NESp infection. Mice were intratracheally administered a bacterial suspension including agar. With this technique, we investigated the pathogenicity of NESp and the effect of Pneumococcal surface protein K (PspK), a specific surface protein antigen of NESp. NESp wild-type strain (MNZ11) and NESp pspK-deleted mutant strain (MNZ1131) were used in this study. The survival rate, number of bacteria, cytokine/chemokine levels in the bronchoalveolar lavage fluid, and histology of the lung tissue were evaluated.

RESULTS:

Mice that were intratracheally administered MNZ11 developed lethal pneumonia with bacteremia within 48 h. Conversely, MNZ1131 showed predominantly low lethality without significant pro-inflammatory cytokine production. NESp was found to cause severe pneumonia and bacteremia upon reaching the lower respiratory tract, and PspK was a critical factor of NESp for developing invasive infections.

CONCLUSIONS:

The current study demonstrated the ability of NESp to develop invasive diseases, especially in connection with PspK by use of a mouse pneumonia model.

• Authors: Hideki Sakatani, Masamitsu Kono, Gen Sugita, Denisa Nanushaj, Masayoshi Hijiya, Takuro Iyo, Tatsuya Shiga, Daichi Murakami, Norihito Kaku, Katsunori Yanagihara, Moon H Nahm, Muneki Hotomi
• Journal: Journal of infection and chemotherapy : official journal of the Japan Society of Chemotherapy (J Infect Chemother) Vol. 28 Issue 11 Pg. 1452-1458 (Nov 2022) ISSN: 1437-7780 [Electronic] Netherlands
• PMID: 35835387 (Publication Type: Journal Article)
• Copyright: Copyright © 2022 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Chemical References

• Cytokines
• Agar

Topics

• Agar (metabolism)
• Animals
• Bacteremia
• Cytokines (metabolism)
• Mice
• Pneumococcal Infections (microbiology)
• Pneumonia, Pneumococcal
• Streptococcus pneumoniae
• Virulence