Fig 5

AIEC LF82 exacerbates intestinal inflammation in DSS-treated larvae. (A–D) H&E-stained longitudinal sections of the mid-intestine of larvae without (A and B) and with (C and D) prior DSS treatment, fed paramecia (para.) alone (A, C) or paramecia containing LF82 (B, D) at 2 (i), 24 (ii), and 48 (iii) hpi, n = 3. Black arrows point to goblet cells. Scale bars = 50 µm. (E) Representative confocal images of Tg(mpo::egfp) larvae fed paramecia only (i, iii) or LF82 (ii, iv) at 6 dpf. Larvae were imaged for 18 hours (3–20 hpi), neutrophils (green) and bacteria (red). Scale bars = 200 µm. (F) Quantification of neutrophils per intestine in UT- and DSS-treated fish fed with paramecia only (black) or para. containing LF82 (red); n ≥10. (G) qRT-PCR analyses of cxcl8, il1b, mmp9, and tnfa in DSS-treated (red) larvae infected with LF82- and DSS-treated larvae fed paramecia (black) relative to UT paramecia controls (onefold) at 6 dpf, n = 7. Unpaired two-tailed t-test. Mean ± SEM. (H) Survival of DSS-treated larvae that were uninfected (black), fed paramecia control (blue), or para. containing AIEC (red). N = 17. Kaplan-Meier and Mantel-Cox test, followed by a Bonferroni correction test. **, P ≤ 0.01; ***, P ≤ 0.001; ns, not statistically significant.