Fig. 1: NsrP negatively regulates virulence in NMEC RS218.

a Northern blotting was performed with a specific probe directed against NsrP sRNA in the NMEC WT, ΔNsrP, and ΔNsrP complemented (cNsrP) strains. 5S rRNA was used as a loading control. b The genomic position of the NsrP sequence in the NMEC RS218 genome. c Northern blotting for NsrP in RNA preparations from NMEC WT, and Δhfq. d, e Bacterial counts in the blood (CFU/mL, d) and meningitis development (e) were determined 4 h after intravenous injection of 1 × 10⁶ CFU of the WT, ΔNsrP, or cNsrP strain (n = 8 for each group in d). CSF culture positivity was defined as meningitis (e). f H&E staining of brain sections was performed 4 h after intravenous injection of 1 × 10⁶ CFU of the WT or ΔNsrP strain. The right panels are higher-magnification images of the boxed regions, showing meningeal thickening and neutrophil infiltration (arrows). Scale bar, 100 μm. The images shown are representative of three independent experiments. g Survival curves of 2- to 5-day-old rats subcutaneously injected with 1 × 10⁵ CFU of the WT or ΔNsrP strain (n = 16 for each group). The number of living animals was recorded every 8 h. ns, nonsignificant. The two-tailed Mann–Whitney U-test (d), and the log-rank (Mantel–Cox) test (g) were applied.