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[Objectives] This study aims to investigate the role of oligosaccharide repeat unit polymerase Wzy on the pathogenicity of Streptococcus suis serotype Chz. [Methods] The genetic diversity of S.suis capsular polysaccharides(CPS)gene cluster was explored by ACT comparative genomics method. The gene wzy and cpsB mutant strains were then constructed respectively, and the CPS thickness was identified by TEM. The cell and animal experiments were applied to verifing the effects of Wzy on bacterial pathogenicity. [Results] The mutant strain exhibited the reduced capsular-like substance and a stronger biofilm-forming ability compared with the wild-type strain. Cell experiments showed that the mutant strain had stronger adhesion to mouse brain microvascular endothelial cells(bEnd.3), while was more sensitive to the phagocytosis of mouse macrophages RAW264.7. In addition, the deletion of gene wzy significantly attenuated the bacterial pathogenicity and proliferation in vivo. [Conclusions] Polymerase Wzy affects the pathogenicity of Streptococcus suis. [ABSTRACT FROM AUTHOR]

[Objectives]The purpose of this study was to predict and identify the integrative and conjugative elements(ICE)in the clinical isolates of Streptococcus suis serotype Chz AH681 and HN136,to detect the cyclization activity of the them, and to explore the relationship between the ICE and drug-resistant gene transfer and the mechanism of multiple drug resistance. [Methods]The minimum inhibitory concentration method was used to determine the drug resistance in the two strains of clinical isolates of S. suis serotype Chz. ICE in these strains were predicted using bioinformatics methods, and localized consulting the location characteristics of reported S. suis ICE. The cyclization and conjugating tests were performed to detect the activity of predicted ICE. The relationship of ICE in S. suis was analyzed by constructing evolutionary tree. [Results]Both AH681 and HN136 were multi-drug resistant strains. They all had obviously exogenous islands. Among them,73 kb and 115 kb gene islands possessed typical characteristics of integrated conjugative elements and the 73 kb(ICESsuAH681)and 115 kb(ICESsuHN136)gene islands belong to the ICESa2603 family. Further analysis revealed that the ICESsuAH681 contained tetracycline resistance gene tet(O), the macrolide antibiotic resistance gene erm(B), the fluoroquinolone export ATP-binding protein gene, the bacteriocin operon gene and the arsenate reductase gene; ICESsuHN136 contained tet(O), erm(B)and the bacteriocin gene cluster. The cyclization test confirmed that the ICESsuAH681 could be cut off from the genome and formed rings autonomously, but the conjugon in P1/7 strain containing ICESsuAH681 was not obtained. No circular form of ICESsuHN136 was detected. The evolutionary relationship analysis showed that the well-bounded ICE in S. suis had six major branches, among which ICESsuAH681 was more closely related to ICE in the ICESa2603 family. [Conclusions]This study confirmed that ICESsuAH681,which came from a multidrug-resistant strain of S. suis serotype Chz and carried resistance genes such as tet(O), erm(B)and arsc, could be removed from the genome and cycled. It was an active ICE and a member of the ICESa2603 family. [ABSTRACT FROM AUTHOR]