Comparative Genome Analysis of Streptococcus suis Serotype 9 Isolates from China, The Netherland, and the U.K.

Streptococcus suis (S. suis) is an important swine pathogen and an emerging zoonotic agent worldwide. Serotype 9 is the most prevalent serotype in several European countries but it is relatively rare in China. In this study, through the investigation of the serotypes of 279 S. suis strains isolated from China from 2015 to 2017, it was found that serotype 9 is the second most prevalent serotype (43 out of 279), behind serotype 2 (83 out of 279). Next, the 43 serotype 9 isolates were sequenced and compared with those from the Netherland (28) and the U.K. (eight). For the purpose of comparison, the strain D12 (GCA_000231905), which has completed genome sequences, was also incorporated. Phylogenetic tree analysis showed that the strains from China and the U.K. were heterogeneous. In contrast, all but one from the Netherland belonged to the same clade. The dominant clades of Chinese strains (33) and strains from the Netherland (27) were very similar. Both of them may have originated from the same strain about 70 years ago. Then, the distributions of virulence-associated genes and antibiotic resistance genes among different clades and sources were analyzed. By comparison, strains from the Netherland carried more virulence-associated genes and those from the U.K. had more antibiotic resistance genes. Additionally, some virulence-associated genes (salK and salR) and antibiotic resistance genes (lincomycin and spectinomycin) existed only in several Chinese strains. In conclusion, our data displayed the population characteristics and differences of S. suis serotype 9 between China and Europe, suggesting that they have taken different evolutionary paths.

Role of Maturation of Lipoproteins in the Pathogenesis of the Infection Caused by Streptococcus suis Serotype 2

Streptococcus suis serotype 2 is an important porcine bacterial pathogen associated with multiple pathologies in piglets. Bacterial lipoproteins (LPPs) have been described as playing important roles in the pathogenesis of the infection of other Gram-positive bacteria as adhesins, pro-inflammatory cell activators and/or virulence factors. In the current study, we aimed to evaluate the role of the prolipoprotein diacylglyceryl transferase (Lgt) and lipoprotein signal peptidase (Lsp) enzymes, which are responsible for LPP maturation, on the pathogenesis of the infection caused by two different sequence types (STs) of S. suis serotype 2 strains (virulent ST1 and highly virulent ST7). Through the use of isogenic Δlgt, Δlsp and double Δlgt/Δlsp mutants, it was shown that lack of these enzymes did not influence S. suis adhesion/invasion to porcine respiratory epithelial cells. However, in the absence of the Lsp and/or Lgt, a significant reduction in the capacity of S. suis to activate phagocytic cells and induce pro-inflammatory mediators (in vitro and in vivo) was observed. In general, results obtained with the double mutant did not differ in comparison to single mutants, indicating lack of an additive effect. Finally, our data suggest that these enzymes play a differential role in virulence, depending on the genetic background of the strain and being more important for the highly virulent ST7 strain.

Peptidomics Analysis of Virulent Peptides Involved in Streptococcus suis Pathogenesis

Streptococcus suis (S. suis) is a zoonotic pathogen causing severe streptococcal disease worldwide. S. suis infections in pigs and humans are frequently associated with the virulent S. suis serotype 2 (SS2). Though various virulence factors of S. suis have been proposed, most of them were not essentially accounted for in the experimental infections. In the present study, we compared the peptidomes of highly virulent SS2 and SS14 in humans, the swine causative serotypes SS7 and SS9, and the rarely reported serotypes SS25 and SS27, and they were cultured in a specified culture medium containing whole blood to simulate their natural host environment. LC-MS/MS could identify 22 unique peptides expressed in the six S. suis serotypes. Under the host-simulated environment, peptides from the ABC-type phosphate transport system (SSU05_1106) and 30S ribosomal protein S2 (rpsB) were detected in the peptidome of virulent SS2 and SS14. Therefore, we suggest that these two proteins or their derived peptides might be involved in the survival of S. suis when simulated with a blood environment.

KẾT QUẢ XÁC ĐỊNH ĐÁP ỨNG MIỄN DỊCH ĐỐI VỚI AUTOVACCINE PHÒNG BỆNH LIÊN CẦU KHUẨN Ở LỢN TẠI TỈNH THÁI NGUYÊN

Nghiên cứu được triển khai với mục đích xác định đáp ứng miễn dịch ở lợn sau tiêm Autovaccine phòng bệnh liên cầu khuẩn do vi khuẩn Streptococcus suis (S.suis) serotype 2, serotype 7 và serotype 9 gây ra ở lợn nuôi tại huyện Phú Bình và khu vực thị xã Phổ Yên, tỉnh Thái Nguyên. Nghiên cứu sử dụng phản ứng ngưng kết hồng cầu gián tiếp (Indirect Haemaglunation Test-IHA) và phương pháp tách huyết thanh để xác định mức độ đáp ứng miễn dịch và hiệu giá kháng thể ở lợn thí nghiệm. Kết quả xác định đáp ứng miễn dịch sau tiêm cho thấy, Autovaccine chế tạo từ các thành phần kháng nguyên vi khuẩn S. suis serotype 2, 7 và 9 bước đầu đã đạt được yêu cầu kích thích sản sinh kháng thể tốt đối với lợn thí nghiệm, miễn dịch tạo ra đạt yêu cầu của một Autovaccine theo tiêu chuẩn của Tổ chức Thú y Thế giới (OIE) với hiệu giá ngưng kết đạt ≥ 1/16 sau tiêm 120 ngày.

Evaluation of the immunoprotective effects of IF-2 GTPase and SSU05-1022 as Streptococcus suis candidate subunit vaccine

Aim: This study aims to develop a subunit vaccine with high cross-protection for Streptococcus suis. Materials & methods: Four-week-old female BALB/c mice were first immunized with a single and mixed protein. Various indicators, such as antibody titers and various cytokine levels, were further analyzed. Results: The results showed that purified recombinant proteins IF-2 and 1022 had a good protective effect against lethal doses of S. suis serotype 2 and S. suis serotype 9. This study showed immunization with recombinant proteins. Conclusion: IF-2 and 1022 can enhance cross-protection against S. suis serotypes 2 and 9.