Genomic and pathogenic investigations of Streptococcus suis serotype 7 population derived from a human patient and pigs

Abstract

Streptococcus suis is one of the important emerging zoonotic pathogens. Serotype 2 is most prevalent in patients worldwide. In the present study, we first isolated one S. suis serotype 7 strain GX69 from the blood culture of a patient with septicemia complicated with pneumonia in China. In order to deepen the understanding of S. suis serotype 7 population characteristics, we investigated the phylogenetic structure, genomic features, and virulence of S. suis serotype 7 population, including 35 strains and 79 genomes. Significant diversities were revealed in S. suis serotype 7 population, which were clustered into 22 sequence types (STs), five minimum core genome (MCG) groups, and six lineages. Lineages 1, 3a, and 6 were mainly constituted by genomes from Asia. Genomes of Lineages 2, 3b, and 5a were mainly from Northern America. Most of genomes from Europe (41/48) were clustered into Lineage 5b. In addition to strain GX69, 13 of 21 S. suis serotype 7 representative strains were classified as virulent strains using the C57BL/6 mouse model. Virulence-associated genes preferentially present in highly pathogenic S. suis serotype 2 strains were not suitable as virulence indicators for S. suis serotype 7 strains. Integrative mobilizable elements were widespread and may play a critical role in disseminating antibiotic resistance genes of S. suis serotype 7 strains. Our study confirmed S. suis serotype 7 is a non-negligible pathotype and deepened the understanding of the population structure of S. suis serotype 7, which provided valuable information for the improved surveillance of this serotype.

The characteristics of population structure and antimicrobial resistance of Streptococcus suis serotype 8, a non‐negligible pathotype

“…Although we cannot gain these strains to perform animal infection experiments due to their NCBI source, their pathogenicity deserves attention. In addition, the pathogenic potential of S. suis varies by serotypes and MLST: in serotype 2 strains, ST1 was the most associated with disease in both pigs and humans in Europe, Asia, Africa and South America, and ST7 (a single locus variant of ST1) was only endemic to China, which was responsible for human outbreaks in 1998 and 2005 in this country (Segura et al., 2020); in serotype 9 strains, ST16 included one isolate from a human patient and one from a diseased pig, harbouring more virulence genes (Willemse et al., 2019); in serotype 7 strains, ST373 presented a higher zoonotic potential (Liang et al., 2021). In this study, three serotype 8 representative strains belonging to ST1241 were selected, and all of them were defined as virulent strains in the zebrafish and mice infection experiments.…”

“…Genes mrp , sly and epf were not virulence indicators for serotype 7 strains. Instead, their distribution was linked to serotype 7 evolution (Liang et al., 2021). We did not observe the correlation between the genotype of putative virulence‐associated genes and the virulence phenotype in serotype 8 strains.…”

The antimicrobial systems of Streptococcus suis promote niche competition in pig tonsils

“…Liang et al . reported that four representative strains of S. suis serotype 7 isolated from healthy pig tonsils were identified as virulent strains; two of them belonged to ST373, the same sequence type with serotype 7 human isolate GX69, suggesting we should be aware of the public health threat posed by S. suis serotype 7 ST373 strains [ 13 ]. Wang et al .…”

Genomic Characterization of Streptococcus suis Serotype 24 Clonal Complex 221/234 From Human Patients

“…Among the 29 described serotypes of S. suis , serotype 2 is the most common cause of human infections ( Goyette-Desjardins et al, 2014 ; Okura et al, 2016 ). However, human cases have also been reported due to the rare serotypes 4, 5, 7, 9, 14, 16, 21, 24, and 31 ( Nghia et al, 2008 ; Callejo et al, 2014 ; Goyette-Desjardins et al, 2014 ; Hatrongjit et al, 2015 ; Kerdsin et al, 2017 ; Liang et al, 2021 ).…”

“…Among 29 serotypes, WGS has been applied to the serotype 2 strains worldwide for, as examples, characterization of outbreaks, evaluation of S. suis reinfection, determining the population structure of S. suis strains, and identifying pathotypes or virulence traits ( Estrada et al, 2019 ; Hatrongjit et al, 2020 ). Several studies have also been conducted on serotypes other than serotype 2 including serotypes 3–9, 14, 16, 19, 20, 21, 22, 26, and unencapsulated strains, although most of them were of swine origin ( Hu et al, 2011 ; Wang et al, 2013a , b , 2014 ; Baig et al, 2015 ; Yoshida et al, 2017 ; Zheng et al, 2018 ; Niemann et al, 2019 ; Stevens et al, 2019 ; Bunk et al, 2021 ; Liang et al, 2021 ; Nicholson et al, 2021 ). To date, there has been no WGS performed on S. suis serotype 24 strains recovered from humans.…”