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. Author manuscript; available in PMC: 2024 Apr 30.
Published in final edited form as: Nat Microbiol. 2023 Oct 16;8(11):2033–2049. doi: 10.1038/s41564-023-01493-w

Figure 4: Lactulose-mediated Bifidobacteria expansion is associated with exclusion of antibiotic-resistant Enterococcus species.

Figure 4:

(A) Relative abundance of potentially pathogenic taxa Enterococcus and Proteobacteria were plotted based on lactulose exposure (no lactulose, left; lactulose, right) and relative abundance of Bifidobacteria (< 10%, blue; ≥10%, red). Each point represents a single sample with the following sample sizes: total n = 262; no lactulose, < 10%, n=79; no lactulose, ≥10%, n=24; lactulose, < 10%, n=87; lactulose, ≥10%, n=72. Median and interquartile range are indicated by the horizontal line and box, respectively. The lower vertical line depicts Q1 – 1.5*IQR and the upper vertical line depicts Q3 + 1.5*IQR. Statistical comparisons between individual groups were analyzed using a two-tailed Wilcoxon rank sum test. P-values are adjusted for multiple comparisons using the Benjamini-Hochberg procedure and represented as follows: *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001. (B) A human-derived B. longum species was grown in BHIS media (blue) or BHIS supplemented with 50mM lactulose (red) or 50mM sucrose (green), and growth curves (OD600 over time) are shown. The growth curve shows mean +/− standard deviation for an experiment done in triplicate. This graph is representative of three independent experiments, also done in triplicate, all with consistent results. (C) Schematic of experimental design for B. longum (purple bacilli) and VRE (green cocci) co-culture. B. longum and VRE were grown to steady state and diluted to low density (OD600 = 0.05) prior to inoculation in either BHIS or BHIS supplemented with 50mM lactulose. Cultures were inoculated with both bacteria simultaneously (top) or B. longum was given either a 24-hour or 48-hour lead time prior to VRE inoculation (bottom). (D) After 24-hours of co-culture, serial dilutions of three replicates were plated for VRE c.f.u. counts. Each replicate is plotted as an individual point, and the median is represented by the horizontal line. *, p < 0.05 two-tailed student’s t-test. The plot is from one experiment that is representative of three independent experiments done in triplicate all with consistent results.