Survival curves.

<p>Survival curves of zebrafish infected with wild-type and lysogenic SS2-4 were compared using GraphPad Prism 5 software. Each experimental group contained 15 zebrafish, and each experiment was performed in triplicate. A, The survival rates of zebrafish infected with 10⁸CFU/fish of wild-type and lysogenic SS2-4; B, The survival rates of zebrafish infected with 10⁷CFU/fish of wild-type and lysogenic SS2-4; C, The survival rates of zebrafish infected with 10⁶CFU/fish of wild-type and lysogenic SS2-4.</p

Bacterial load of zebrafish infected with wild-type or lysogenic SS2-4.

<p>Three infected fish from each dose group were sacrificed at 2, 14, and 23 h post-infection. A, B, C, D: the bacterial load of fish infected with wild-type and lysogenic SS2-4 at 10⁸ CFU/fish, 10⁷ CFU/fish, 10⁶ CFU/fish, 10⁵ CFU/fish, respectively. The Student's <i>t</i>-test was performed for comparison of the bacterial load at each dose between wild-type and lysogenic SS2-4 using GraphPad Prism 5 software.</p

Sensitivity to lysozyme.

<p>Viable bacteria after incubation with lysozyme (3 h). First and second columns: initial bacterial viability of wild-type and lysogenic SS2-4; third and fourth columns: bacterial viability of wild-type and lysogenic SS2-4 after incubation with lysozyme (3 h).</p

Confirmation of prophage integration by Southern hybridization.

<p>Southern gel transfer (right) and Southern hybridization (left) of SMP DNA fractions. Lanes: 1–3, SMP, wild-type SS2-4 and lysogenic SS2-4, <i>Pst</i>I digested; 4–6, SMP, wild-type SS2-4 and lysogenic SS2-4, <i>Spe</i>I digested; M, Marker.</p

Mortality and LD₅₀ of wild-type and lysogenic SS2-4.

<p>Average LD₅₀ 2.13×10⁵ (wild-type SS2-4) and 6.64×10⁴ (lysogenic SS2-4).</p

Virulence testing.

<p>Survival of wild-type and lysogenic isolates was determined in zebrafish. Left: average LD₅₀ of zebrafish challenged with wild-type SS2-4; right: average LD₅₀ of zebrafish challenged with lysogenic SS2-4. The Student's <i>t</i>-test was performed for comparison of the LD₅₀ of the two strains using GraphPad Prism 5 software. <i>P</i> = 0.006; degrees of freedom, 2; Standard error of the mean (SEM) of LD₅₀ of wild-type and lysogenic isolates was 11,360 and 1,510, respectively. A significant difference in the LD₅₀ was identified between the wild-type and lysogenic SS2-4.</p

Growth curves of wild-type and lysogenic SS2-4 strains.

<p>The initial concentration of bacteria was 10⁶ CFU/ml. Number of bacteria was estimated by plate counts. The growth rate of the lysogen was more rapid than that of the wild-type and a higher plateau was maintained during the stationary phase.</p

Primer sequences used in this study.

<p>Primer sequences used in this study.</p

Comparison of wild-type and lysogenic SS2-4 cell morphology.

<p>(a) Wild-type SS2-4 in mid-log growth phase; (b) Lysogenic SS2-4 in mid-log growth phase; (c) Wild-type SS2-4 in the stationary growth phase; (d) Lysogenic SS2-4 in the stationary growth phase; (e) Wild-type SS2-4 in the declining growth phase; (f) Lysogenic SS2-4 in the declining growth phase. In all three phases, the lysogenic strain had a shorter chain than the wild-type strain.</p

Synthesis of Galabiose-chitosan Conjugate as Potent Inhibitor of Streptococcus suis Adhesion

The aim of this work is to construct a safe and effective drug candidate against Streptococcus suis infection. A panel of chitosan-based polymer conjugates with branched galabiose (Galα1−4Gal) side chains was synthesized as inhibitors of S. suis adhesion. The synthesis was achieved by using an aldehyde-functionalized galabiose derivative to graft it onto chitosan amino groups. Structural compositions of the conjugates were verified by 1H NMR spectroscopy and CHN elemental analyses. Potent inhibitory activities of the conjugates against S. suis adhesion to human erythrocytes were determined at low nanomolar concentration by HAI assay. An SPR study revealed a high affinity binding (Kd = 39.6 nM) of the conjugate with BSI-B4 lectin. By using biocompatible chitosan as the scaffold for presenting S. suis-specific galabiose units, as well as the concise route tailored for the conjugate syntheses, the present study provides a practical way for explorations of new anti-S. suis therapies