Characterization of Streptococcus suis serotype 2 isolates from China.

Streptococcus suis (S. suis) is a major pathogen in the pig industry and an important zoonotic agent that causes severe invasive diseases in humans. Previous studies based on multilocus sequence typing (MLST) and the associations between sequence types and genotypes or virulence suggested that North American S. suis serotype 2 isolates are composed of multiple populations. This study investigated the population structure of S. suis serotype 2 isolates in China. We constructed a phylogenetic tree for S. suis serotype 2 isolates based on 16S rRNA gene typing and MLST, studied associations between clades and sources, analyzed the genotype distributions of virulence markers [muramidase-released protein (MRP), extracellular protein factor (EF), and suilysin (SLY)] in different clades, computed the selection pressures for these virulence marker genes, and verified the associations between clades and virulence. There were two primary clades (populations) in the phylogenetic tree of S. suis serotype 2. The two populations were associated with different tissue tropisms. The genotypic distributions and selection pressures of MRP, EF, and SLY were different between the two populations, which suggested that they had different evolutionary paths. The two populations also displayed differences in virulence in experimentally infected mice. The results provide insights into the population structure of S. suis serotype 2 isolates in China and suggest that S. suis serotype 2 clade 1 is an overlooked population that deserves further evaluation.

Complete genome sequence of an H10N5 avian influenza virus isolated from pigs in central China.

An avian H10N5 influenza virus, A/swine/Hubei/10/2008/H10N5, was isolated from pigs in the Hubei Province of central China. Homology and phylogenetic analyses of all eight gene segments demonstrated that the strain was wholly of avian origin and closely homologous to the Eurasian lineage avian influenza virus. To our knowledge, this is the first report of interspecies transmission of an avian H10N5 influenza virus to domestic pigs under natural conditions.

Comparative genomic analysis of Streptococcus suis reveals significant genomic diversity among different serotypes.

BACKGROUND: Streptococcus suis (S. suis) is a major swine pathogen and an emerging zoonotic agent. Serotypes 1, 2, 3, 7, 9, 14 and 1/2 are the most prevalent serotypes of this pathogen. However, almost all studies were carried out on serotype 2 strains. Therefore, characterization of genomic features of other serotypes will be required to better understand their virulence potential and phylogenetic relationships among different serotypes. RESULTS: Four Chinese S. suis strains belonging to serotypes 1, 7, 9 and 1/2 were sequenced using a rapid, high-throughput approach. Based on the 13 corresponding serotype strains, including 9 previously completed genomes of this bacterium, a full comparative genomic analysis was performed. The results provide evidence that (i) the pan-genome of this species is open and the size increases with addition of new sequenced genomes, (ii) strains of serotypes 1, 3, 7 and 9 are phylogenetically distinct from serotype 2 strains, but all serotype 2 strains, plus the serotype 1/2 and 14 strains, are very closely related. (iii) all these strains, except for the serotype 1 strain, could harbor a recombinant site for a pathogenic island (89 K) mediated by conjugal transfer, and may have the ability to gain the 89 K sequence. CONCLUSIONS: There is significant genomic diversity among different strains in S. suis, and the gain and loss of large amount of genes are involved in shaping their genomes. This is indicated by (i) pairwise gene content comparisons between every pair of these strains, (ii) the open pan-genome of this species, (iii) the observed indels, invertions and rearrangements in the collinearity analysis. Phylogenetic relationships may be associated with serotype, as serotype 2 strains are closely related and distinct from other serotypes like 1, 3, 7 and 9, but more strains need to be sequenced to confirm this.

Comparative genomics study of multi-drug-resistance mechanisms in the antibiotic-resistant Streptococcus suis R61 strain.

BACKGROUND: Streptococcus suis infections are a serious problem for both humans and pigs worldwide. The emergence and increasing prevalence of antibiotic-resistant S. suis strains pose significant clinical and societal challenges. RESULTS: In our study, we sequenced one multi-drug-resistant S. suis strain, R61, and one S. suis strain, A7, which is fully sensitive to all tested antibiotics. Comparative genomic analysis revealed that the R61 strain is phylogenetically distinct from other S. suis strains, and the genome of R61 exhibits extreme levels of evolutionary plasticity with high levels of gene gain and loss. Our results indicate that the multi-drug-resistant strain R61 has evolved three main categories of resistance. CONCLUSIONS: Comparative genomic analysis of S. suis strains with diverse drug-resistant phenotypes provided evidence that horizontal gene transfer is an important evolutionary force in shaping the genome of multi-drug-resistant strain R61. In this study, we discovered novel and previously unexamined mutations that are strong candidates for conferring drug resistance. We believe that these mutations will provide crucial clues for designing new drugs against this pathogen. In addition, our work provides a clear demonstration that the use of drugs has driven the emergence of the multi-drug-resistant strain R61.

Complete genome sequence of Streptococcus suis serotype 3 strain ST3.

Streptococcus suis is a zoonotic pathogen causing economic loss in the swine industry and is also a threat to human health. To date, the mechanism of pathogenesis is not fully understood. Here, we report the complete genome sequence of S. suis strain ST3 of serotype 3, which provides opportunities to reveal genetic basis of infection of S. suis non-serotype 2 strains.

Complete genome sequence of Streptococcus suis serotype 14 strain JS14.

Streptococcus suis is an important zoonotic agent leading to a variety of diseases in swine and can be transmitted to human beings upon close contact. Here, we report the complete genome sequence of S. suis serotype 14 strain JS14 which was isolated from a diseased pig in Jiangsu Province, China.

Characterization of Streptococcus suis isolates from the diseased pigs in China between 2003 and 2007.

The aim of this study was to illustrate the characteristics of 407 strains of Streptococcus suis (S. suis) isolated from diseased pigs in China. The results revealed that S. suis, with 56.6% of the Streptococci isolates, had replaced Streptococcus equi subsp. zooepidemicus as the predominant agent. Among the strains investigated, serotype 2 (43.2%) was most prevalent, followed by serotypes 3 (14.7%) and 4, 8, 5, 7, 1/2 (3.2-6.4%). Serotype 2 was more frequently isolated from swine with systemic infection, while serotype 3 was significantly associated with pneumonia. A high percentage of S. suis serotype 2 strains (54%) belonged to the genotype sly+ mrp+ epf+, which is a highly virulent strain, as confirmed by mice infection test. Biofilm producers only had lowly virulence compared to strains with the same genotype, indicating that biofilm could be associated with virulence but be not the character of virulent strains. The present study contributes to understanding the characteristics of Streptococcus suis and controlling Streptococcal disease in China.