Fig. 4: Circulating OMVs Serve as an Early Markers of Bacterial Infections.

a Analysis of circulating PmBF⁺ EVs levels in germ-free (GF) and conventional mice (SPF) mice by nano-flow cytometry (Bars represent the mean ± SD, n = 3 biological replicates). b Schematic diagram of the construction of a mouse model of colonized bacteria clearance, d: days (Created with BioRender.com). c Analysis of circulating PmBF⁺ EVs levels in mice models before (Control group) or after intestinal flora cleared (Bars represent the mean ± SD, n = 3 biological replicates). d Schematic diagram of the construction of mouse models of bacterial infections and blood were collected from mice after intranasally injection with 8 × 10⁷ CFU bacteria at 2, 6, 12, 24 h (Created with BioRender.com). e Blood bacterial culture plates for mouse models after E. coli infections for 2, 6, 12, 24 h, control group mice was treated with PBS. f Quantitative analysis of circulating PmBF⁺ EVs changes in mouse models after E. coli infections for 2, 6, 12, 24 h, control group mice was treated with PBS (The center line of each box indicates the median. The bottom and top bonds of the box show the 25th and 75th percentiles, respectively. Whiskers extend to the minimum and maximum values, n = 5 biological replicates). g Comparison of bacterial cultures and circulating OMVs positivity rates in mouse models after E. coli infections for 2, 6, 12, 24 h, control group mice was treated with PBS (Elements Created with BioRender.com). h Expression analysis of mCherry in wide-type or mCherry-E. coli derived OMVs (Bars represent the mean ± SD, n = 3 biological replicates). i Analysis of circulating mCherry⁺ EVs in mice models infected with mCherry-E. coli, control group mice was treated with PBS. The Y-axis indicates the percentage of serum mCherry⁺ EVs to total EVs. (Bars represent the mean ± SD, n = 3 biological replicates). j Blood bacterial culture plates as well as LB medium. Positive control: live mCherry-E. coli; PBS: blood of mice treated by PBS; mCherry-E. coli: blood of mice treated by mCherry-E. coli. No viable bacterial colonies were observed in group PBS and mCherry-E. coli. k Dynamic monitoring of circulating PmBF⁺ EVs levels at different time points post-infection in mice. Antibiotic treatment was initiated at 12 h post-infection, with administration every 12 h thereafter (Bars represent the mean ± SD, n = 3 biological replicates). l Illustration of the effect of different points in time of treatment on mouse infection models survival rate (Created with BioRender.com). m Mouse survival curves. a, c, h, i was determined by a two-tailed unpaired t-test; f, k were determined by one-way ANOVA with multiplicity adjusted P value; Survival analysis was performed using the Log-rank (Mantel-Cox) test to compare the survival curves between groups (*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; ns: P ≥ 0.05). Source data are provided as a Source Data file.