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The Streptococcus suis (S. suis) is an important zoonotic pathogen that causes streptococcal disease in pigs and poses a threat to humans. This study provides an understanding of the prevalence of   S.suis in eastern China and provides guidance for clinical prophylaxis. From 2021 to 2023, a total of 143 strains of S. suis were isolated from 1642 lung tissue and nasal swabs from healthy and suspected infected pigs in Shandong Province, China, using the Phenotypic tests and PCR technique. The isolates were then tested for serotype, virulence-related genes, and resistance genes. Among the 143 isolates, type 2 was the predominant serotype with 98 isolates (98/143, 68.5%), followed by type 5 with 22 isolates (22/143, 15.3%), type 4 with 6 isolates (6/143, 4.2%), type 19 with 4 isolates (4/143, 2.8%) and type 21 with 5 isolates (5/143, 3.5%), respectively. A minimum of 78.3% of the strains exhibited the presence of virulence-related genes including pgda , dlta , mann , fbps , orf2 , and sspa , whereas the virulence-associated genes Sum , Sly , and Salkr are not widely prevalent. For the detection of resistance genes, it was found that the tetO gene had a high detection rate of 70.1% (101/143), whereas neither the pbp2b gene nor the cat1 and cat2 genes were detected. Antimicrobial susceptibility testing revealed that 96.5% (138/143) of the isolates exhibited multidrug resistance (MDR). And polypeptide B was found to be tolerated by 125 of the 143 strains (87.4%). Although we did not detect the β-lactam resistance gene in any of the 143 strains, an average of 39.2% of the strains were resistant to β-lactam antibiotics. The results of the current study is thought it may be help to understand the prevalence of S. suis and provide important insights into treatment and prevention.

Background Streptococcus suis is divided into 29 serotypes based on a serological reaction against the capsular polysaccharide (CPS). Multiplex PCR tests targeting the cps locus are also used to determine S. suis serotypes, but they cannot differentiate between serotypes 1 and 14, and between serotypes 2 and 1/2. Here, we developed a pipeline permitting in silico serotype determination from whole-genome sequencing (WGS) short-read data that can readily identify all 29  S. suis serotypes. Results We sequenced the genomes of 121 strains representing all 29 known S. suis serotypes. We next combined available software into an automated pipeline permitting in silico serotyping of strains by differential alignment of short-read sequencing data to a custom S. suis cps loci database. Strains of serotype pairs 1 and 14, and 2 and 1/2 could be differentiated by a missense mutation in the cpsK gene . We report a 99 % match between coagglutination- and pipeline-determined serotypes for strains in our collection. We used 375 additional S. suis genomes downloaded from the NCBI’s Sequence Read Archive (SRA) to validate the pipeline. Validation with SRA WGS data resulted in a 92 % match. Included pipeline subroutines permitted us to assess strain virulence marker content and obtain multilocus sequence typing directly from WGS data. Conclusions Our pipeline permits rapid and accurate determination of S. suis serotype, and other lineage information, directly from WGS data. By discriminating between serotypes 1 and 14, and between serotypes 2 and 1/2, our approach solves a three-decade longstanding S. suis typing issue.

Purpose Streptococcus suis serotype 14 is the second most prevalent serotype being highly prevalent in Southeast Asia. This study aimed to characterize genetic background, population structure, virulent genes, antimicrobial-resistant genes, and virulence of human S. suis serotype 14. Methods Genomes of 11 S. suis serotype 14 were sequenced by short- and long-read sequencing platforms. The genomes were analyzed for genetic relationship, virulence-associated genes, and antimicrobial-resistant genes. Antimicrobial susceptibility was conducted and the virulence was tested based on cell assay. Results All isolates belonged to clonal complex (CC) 1, with nine sequence type (ST) 105 isolates and each isolate of ST1 and ST237. They were susceptible to penicillin, whereas tetracycline and macrolide were resistance due to tetO and ermB . Genomic analysis revealed that the serotype 14-ST105 isolates were closely related to zoonotic serotype 14-ST105 isolates from Vietnam and the serotype 1-ST105 Thai strain. The serotype 14-ST1 isolate was closely related to pig-diseased serotype 1-ST1 isolates from UK and USA, whereas the serotype 14-ST237 isolate was related to serotype 1-ST237 strains recovered from healthy pig from Thailand. Of 150 virulence-associated genes, 13 were absent from the serotype 14 isolates, including atl1 , atlAss , hhly3 , nisK , nisR , pnuC , salK , salR , sp1 , srtG , virB4 , virD4 , and zmp . The virulence of strain 32481, a representative S. suis serotype 14-ST105 isolate showed reduced adhesion and invasion of two epithelial cell lines (A549 and HeLa) when compared to the serotype 2-ST1 strain P1/7, whereas apoptosis was similar. Conclusion This study highlighted the pathogenic potential of virulent serotype 14-ST105 strains and the need for increased monitoring of S. suis serotypes other than for serotype 2.

Streptococcus suis serotype 14 is the second most prevalent serotype after serotype 2, and is highly prevalent in Southeast Asia. Among the serotype 14 strains, sequence type (ST) 105 is found in humans and pigs. We analysed the genome sequences of S. suis ST105 to identify unique sequences to develop a multiplex PCR (mPCR) -gel electrophoresis and mPCR-lateral flows trip (LFS) for epidemiological purposes. The ST105 genome was closely related to the ST1 genomes. All ST105 of Thai and Vietnamese strains were highly homologous. Of the 1818 genes found in all compared genomes, 36 unique sequences were detected only in the ST105 strain. Of these, two unique sequences encoding hypothetical proteins were selected as PCR targets. Only S. suis ST105 strains were positive for both mPCRs. mPCR-LFS had fewer complications, lower costs, and less time for testing, than those of mPCR-gel electrophoresis. This comparative genomic study demonstrates the usefulness of identifying unique sequences of ST105 S. suis . These unique sequences could be used to develop diagnostic or screening tools, such as PCR, for the detection of specific strains or clones for epidemiological purposes.

Streptococcus suis is an economically important pathogen of pigs as well as a zoonotic cause of human disease. Serotyping is used for further characterization of isolates; some serotypes seem to be more virulent and more widely spread than others. This study characterizes a collection of German field isolates of Streptococcus suis from pigs dating from 1996 to 2016 with respect to capsular genes (cps) specific for individual serotypes and pathotype by multiplex PCR and relates results to the clinical background of these isolates. The most prominent finding was the reduction in prevalence of serotype-2/serotype-1/2 among invasive isolates during this sampling period, which might be attributed to widely implemented autogenous vaccination programs in swine against serotype 2 in Germany. In diseased pigs (systemically ill; respiratory disease) isolates of serotype-1/serotype-14, serotype-2/serotype-1/2, serotype 3 to 5 and 7 to 9 were most frequent while in carrier isolates a greater variety of cps types was found. Serotype-1/serotype-14 seemed to be preferentially located in joints, serotype 4 and serotype 3 in the central nervous system, respectively. The virulence associated extracellular protein factor was almost exclusively associated with invasive serotype-1/serotype-14 and serotype-2/serotype-1/2 isolates. In contrast, lung isolates of serotype-2/serotype-1/2 mainly harbored the gene for muramidase-released protein. Serotype 4 and serotype 9 isolates from clinically diseased pigs most frequently carried the muramidase-released protein gene and the suilysin gene. When examined by transmission electron microscopy all but one of the isolates which were non-typable by molecular and serological methods showed various amounts of capsular material indicating potentially new serotypes among these isolates. Given the variety of cps types/serotypes detected in pigs, not only veterinarians but also medical doctors should consider other serotypes than just serotype 2 when investigating potential human cases of Streptococcus suis infection.

Streptococcus suis, a swine pathogen that causes zoonotic infections in Europe and Asia, has increasingly been observed in South America. We reviewed all available reports from the continent and identified S. suis cases in Argentina, Brazil, Chile, French Guiana, and Uruguay. We also identified 8 novel infections from Argentina, bringing the total documented human cases in South America to 47. We reclassified 1 previously reported infection as S. parasuis. Among the 47 S. suis cases, 40 (85%) patients had meningitis, 2 (4%) had toxic shock-like illness, 2 (4%) had nonshock sepsis, 1 (2%) had arthritis, and 1 (2%) had endocarditis. The case-fatality rate was 4% (2/47). Infections were primarily linked to pig or pork exposure, although some occurred after consuming undercooked meat. Case distribution varied by country, and Argentina reported a disproportionately high number of cases despite a smaller swine industry. Our findings highlight the need for more consistent regional S. suis surveillance.

Streptococcus suis is a major pathogen in pigs, causing diseases like meningitis, septicemia, and pneumonia, and has become a serious zoonosis in humans, particularly in countries with intensive swine production. Human infections have risen significantly, especially in Thailand, where serotype 2 is most commonly associated with disease in both pigs and humans. Traditional methods of identifying S. suis and its serotypes, such as bacterial culture, biochemical testing, and agglutination tests, face challenges due to variability and limited antisera availability, leading to the need for alternative approaches. In this study, we developed a novel RPA-NALFIA assay targeting the recN and cps2J genes of S. suis serotype 2. This method demonstrated accurate identification without cross-reactivity among 28 other bacterial species, with a detection limit of 10 3  CFU/mL, comparable to PCR methods. Food safety concerns are heightened by the discovery of S. suis contamination in pork, a major infection route when consumed undercooked. Our surveillance in central Thailand revealed that 49.3% of pork samples were contaminated with S. suis , with serotype 2 detected in 2.6% of samples. The RPA-NALFIA method proved effective, showing 100% sensitivity and 97.5% specificity. This assay offers rapid, reliable detection suitable for point-of-care testing in resource-limited settings.

Background: Streptococcus suis is a zoonotic pathogen that infects pigs and can occasionally cause serious infections in humans. S. suis infections occur sporadically in human Europe and North America, but a recent major outbreak has been described in China with high levels of mortality. The mechanisms of S. suis pathogenesis in humans and pigs are poorly understood. Methodology/Principal Findings: The sequencing of whole genomes of S. suis isolates provides opportunities to investigate the genetic basis of infection. Here we describe whole genome sequences of three S. suis strains from the same lineage: one from European pigs, and two from human cases from China and Vietnam. Comparative genomic analysis was used to investigate the variability of these strains. S. suis is phylogenetically distinct from other Streptococcus species for which genome sequences are currently available. Accordingly, approximately 40% of the approximately 2 Mb genome is unique in comparison to other Streptococcus species. Finer genomic comparisons within the species showed a high level of sequence conservation; virtually all of the genome is common to the S. suis strains. The only exceptions are three approximately 90 kb regions, present in the two isolates from humans, composed of integrative conjugative elements and transposons. Carried in these regions are coding sequences associated with drug resistance. In addition, small-scale sequence variation has generated pseudogenes in putative virulence and colonization factors. Conclusions/Significance: The genomic inventories of genetically related S. suis strains, isolated from distinct hosts and diseases, exhibit high levels of conservation. However, the genomes provide evidence that horizontal gene transfer has contributed to the evolution of drug resistance.

Streptococcussuis is an important zoonotic agent causing severe diseases in pigs and humans. To date, 33 serotypes of S. suis have been identified based on antigenic differences in the capsular polysaccharide. The capsular polysaccharide synthesis (cps) locus encodes proteins/enzymes that are responsible for capsular production and variation in the capsule structures are the basis of S. suis serotyping. Multiplex and/or simplex PCR assays have been developed for 15 serotypes based on serotype-specific genes in the cps gene cluster. In this study, we developed a set of multiplex PCR (mPCR) assays to identify the 33 currently known S. suis serotypes. To identify serotype-specific genes for mPCR, the entire genomes of reference strains for the 33 serotypes were sequenced using whole genome high-throughput sequencing, and the cps gene clusters from these strains were identified and compared. We developed a set of 4 mPCR assays based on the polysaccharide polymerase gene wzy, one of the serotype-specific genes. The assays can identify all serotypes except for two pairs of serotypes: 1 and 14, and 2 and 1/2, which have no serotype-specific genes between them. The first assay identifies 12 serotypes (serotypes 1 to 10, 1/2, and 14) that are the most frequently isolated from diseased pigs and patients; the second identifies 10 serotypes (serotypes 11 to 21 except 14); the third identifies the remaining 11 serotypes (serotypes 22 to 31, and 33); and the fourth identifies a new cps cluster of S. suis discovered in this study in 16 isolates that agglutinated with antisera for serotypes 29 and 21. The multiplex PCR assays developed in this study provide a rapid and specific method for molecular serotyping of S. suis.

is a significant and emerging zoonotic pathogen. ST1 and ST7 strains are the primary agents responsible for human infections in China, including the Guangxi Zhuang Autonomous Region (GX). To enhance our understanding of ST1 population characteristics, we conducted an investigation into the phylogenetic structure, genomic features, and virulence levels of 73 ST1 human strains from GX between 2005 and 2020. The ST1 GX strains were categorized into three lineages in phylogenetic analysis. Sub-lineage 3-1a exhibited a closer phylogenetic relationship with the ST7 epidemic strain SC84. The strains from lineage 3 predominantly harboured 89K-like pathogenicity islands (PAIs) which were categorized into four clades based on sequence alignment. The acquirement of 89K-like PAIs increased the antibiotic resistance and pathogenicity of corresponding transconjugants. We observed significant diversity in virulence levels among the 37 representative ST1 GX strains, that were classified as follows: epidemic (E)/highly virulent (HV) (32.4%, 12/37), virulent plus (V+) (29.7%, 11/37), virulent (V) (18.9%, 7/37), and lowly virulent (LV) (18.9%, 7/37) strains based on survival curves and mortality rates at different time points in C57BL/6 mice following infection. The E/HV strains were characterized by the overproduction of tumour necrosis factor (TNF)-α in serum and promptly established infection at the early phase of infection. Our research offers novel insights into the population structure, evolution, genomic features, and pathogenicity of ST1 strains. Our data also indicates the importance of establishing a scheme for characterizing and subtyping the virulence levels of strains.