Investigation of the Genomic and Pathogenic Features of the Potentially Zoonotic Streptococcus parasuis

Jianping Wang,Yuanmeihui Tao,Jing Yang,Dong Jin,Xueli Yi,Bin Luo,Han Zheng,Yan Wang,Pujun Liang

doi:10.3390/pathogens10070834

Abstract

Recently, Streptococcus suis reference strains of serotype 20, 22, and 26 were reclassified as Streptococcus parasuis. The public health significance of S. parasuis is underestimated due to the lack of clinical isolates. In the present study, we first reported two sporadic S. parasuis infections in humans, after using full-length 16S rRNA and housekeeping genes’ phylogeny and ANI values of genome sequence comparisons to determine the species of their isolates BS26 and BS27. Compared to highly pathogenic S. suis strain P1/7, S. parasuis strains BS26 and BS27 possessed a delayed capacity to initiate lethal infection, which may attribute to the later production of higher level of pro-inflammatory cytokines. Differed to S. suis strain P1/7, S. parasuis strains did not induce significant inflammatory response in the brain of mice. Histopathological changes in liver and lungs were widely present in mice infected with S. parasuis strains. Our data indicated that the pathogenic mechanism of S. parasuis may be different from that of S. suis. Three lineages in the core-genome phylogenetic tree and ten types of cps gene cluster were found in 13 S. parasuis genomes, indicating high heterogeneity of this species. The similarity of CPS structure and antibiotic-resistant genes relative to S. suis indicated the evolutionary affinity between the two species. Our data suggested S. parasuis is a potential zoonotic pathogen and poses severe threat to health of susceptible people. Further study on the epidemiology and public health significance of S. parasuis is urgently necessary.

Highlights

Streptococcus suis is an important zoonotic pathogen that causes primarily meningitis, sepsis, endocarditis, arthritis, and pneumonia in both pigs and humans [1,2]
Phylogenetic analysis using 16S rRNA gene sequences demonstrated that strains BS26 and BS27 were 98.9% similar to S. parasuis type strain SUT-286T but 96.6% similar to S. suis type strain NCTC10234T (Table S1)
A dendrogram was constructed from a similarity matrix using the 16S rRNA sequences from 16 S. parasuis strains, S. suis type strain NCTC10234T, and E. faecalis JCM 5803 (Figure 1)

Summary

Introduction

Streptococcus suis is an important zoonotic pathogen that causes primarily meningitis, sepsis, endocarditis, arthritis, and pneumonia in both pigs and humans [1,2]. S. suis reference strains of serotypes 20, 22, 26 were proposed as Streptococcus parasuis [5] and serotype 33 was reclassified as Streptococcus ruminantium [6]. The presence of S. parasuis in diseased pigs and calves with pneumonia or systemic infection (meningitis, arthritis, endocarditis, or septicemia) indicated that S. parasuis may be pathogenic to pigs and/or calves [7,8,9,10]. Strains BS26 and BS27 isolated from two patients and reported in the current study were classified as S. parasuis species by combining fulllength 16S rRNA and housekeeping genes’ phylogeny and ANI values of genome sequence comparisons. Additional 11 genomes of S. parasuis available in NCBI were included to investigate the phylogeny and genomic features of S. parasuis

Methods

Results

Conclusion