Figure 5

Sodium butyrate addition shows similar protective effect of P. pentosaceus YC in pathogen resistance on zebrafish. (A) Intestinal butyrate levels of zebrafish fed on commercial diet supplemented with 0 mmol/kg (CON) and 10 mmol/kg (SB10) sodium butyrate (n = 3). (B) Survival curve of zebrafish from CON and SB10 groups following 10⁸ CFU/ml A. hydrophila challenge. Each curve represents the sum of three independent tanks. ***p < 0.001 by Mantel–Cox test. (C) ELISA analysis of intestinal IL-1β level of zebrafish from CON and SB10 groups (n = 6). (D) Representative Western blot of intestinal IL-1β of zebrafish from the CON and SB10 group. (E) Survival curve of zebrafish following 10⁹ CFU/ml A. hydrophila challenge. Zebrafish were pretreated with 10 mmol/kg sodium butyrate for 1 week and then gavaged with PBS (SB-Mock), 50 µM non-targeting (SB-NC), or il1b (SB-il1b siRNA) siRNA. Asterisks indicate significant differences between SB-Mock and SB-il1b siRNA. *p < 0.05 by Mantel–Cox test. (F) Flow cytometry analysis of zebrafish intestinal neutrophils stained with anti-CD11b and anti-Ly6G antibodies (n = 3). Numbers indicate the percentage of CD11b⁺Ly6G⁺ neutrophils in intestinal cells. Data are represented as mean ± SEM. *p < 0.05; **p < 0.01; ***p < 0.001 by Student’s t-test.