Microscopic observation of internalized <i>S</i>. <i>aureus</i>.

<p>Internalization of <i>S</i>. <i>aureus</i> N305 as observed by transmission electron microscopy. <i>S</i>. <i>aureus</i> N305 (at an MOI of 100:1) was incubated for 2 h with bMEC either alone (A, B) or in the presence of <i>L</i>. <i>casei</i> BL23 wt (C, D) or <i>srtA2</i> mutant (E, F) strains, at an MOI of 2,000:1.</p

Impact of <i>L</i>. <i>casei</i> BL380 (BL23 <i>bnaG</i>) on <i>S</i>. <i>aureus</i> internalization into bMEC.

<p>Internalization rates of <i>S</i>. <i>aureus</i> N305 after 2 h of interaction with bMEC and co-incubation with <i>L</i>. <i>casei</i> BL23 and <i>L</i>. <i>casei</i> BL380 (<i>bnaG</i>) at an MOI of 2,000:1. <i>S</i>. <i>aureus</i> was used at an MOI of 100:1. The internalization assay of <i>S</i>. <i>aureus</i> alone was used as a reference. Internalization rates were then defined as the internalized <i>S</i>. <i>aureus</i> population in the presence of the different <i>L</i>. <i>casei</i> strains relative to the internalized <i>S</i>. <i>aureus</i> population of the reference experiment. Data are presented as means ± standard deviations. Each experiment was done in triplicate, and differences between groups were compared using one-way ANOVA with Bonferroni's Multiple Comparison Test. *: P < 0.05.</p

Resistance of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> strains to H₂O₂.

<p>Resistance of <i>L</i>. <i>casei</i> BL23 wt (●, ○) and <i>srtA2</i> (■, □) strains to H₂O₂ was evaluated in the stationary phase of growth of <i>L</i>. <i>casei</i> (24h—MRS). The residual population was evaluated at 0, 10, 20 and 30 min after exposure to 0.25% (●, ■) and 0.5% H₂O₂ (○, □). Data are presented as means ± standard deviations. Each experiment was done in triplicate, and differences between groups were compared using Student’s t-test. *: P < 0.05.</p

Internalization of wild type and mutant strains of <i>L</i>. <i>casei</i> BL23 into bMEC.

<p><i>L</i>. <i>casei</i> populations internalized into bMEC were determined after 2 h of interaction at an MOI 2,000:1. The internalization assay of the <i>L</i>. <i>casei</i> BL23 wild type (wt) strain was used as a reference. Internalization rates were defined as the internalized population of mutant strains relative to the internalized <i>L</i>. <i>casei</i> BL23 wt strain population. Data are presented as mean ± standard deviations. Each experiment was done in triplicate and differences between groups were compared using Student’s t-test. *: P < 0.05.</p

Auto-aggregation capacities of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> strains.

<p>Strains were grown in UF milk medium for 48 h at 37°C. Auto-aggregation was evaluated by spectrophotometry (600 nm) and expressed as the auto-aggregation percentage. Cell suspension OD after growth (48 h) and homogenization was used as a reference (100%). Data are presented as means ± standard deviations. Each experiment was done in triplicate, and differences between groups were compared using Student’s t-test. *: P < 0.05.</p

Cell surface proteome of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> mutant as determined by enzymatic shaving.

<p>Cell surface proteome of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> mutant as determined by enzymatic shaving.</p

Contribution of sortase SrtA2 to <i>Lactobacillus casei</i> BL23 inhibition of <i>Staphylococcus aureus</i> internalization into bovine mammary epithelial cells - Fig 4

<p><b>Internalization of <i>L</i>. <i>casei</i> BL23 wt (A) and <i>srtA2</i> mutant (B) strains as observed by transmission electron microscopy</b>. Degradation vesicles (white arrows) were observed in a greater proportion in cells containing mutant <i>srtA2</i>.</p

Modulation of cytokine IL-8 production by LAB isolates.

<p>A: modulation of IL-8 production by the PS cell line in the presence of LAB isolates (MOI 100:1). Bars represent the mean IL-8 production ± standard deviation for four assays (two biological and two technical replicates), normalized with regard to IL-8 production by unstimulated PS cells (76 +/-16 pg/mL as a mean); B: modulation of IL-8 production by the <i>E</i>. <i>coli</i>-stimulated PS cell line in the presence of LAB isolates. <i>E</i>. <i>coli</i> was used at MOI 1:1 and LAB at MOI 100:1. Bars represent the mean IL-8 production ± standard deviation for four assays, normalized with regard to IL-8 production by <i>E</i>. <i>coli</i>-stimulated PS cells (368 ± 88 pg/mL as a mean). Differences in IL-8 production with regard to the reference condition were assessed using the Mann-Whitney test (* p < 0.05).</p

Internalization of lactic acid bacteria into bovine mammary epithelial cells.

<p>Lactic acid bacteria populations internalized into bMEC were determined after 2 h of interaction at a MOI of 400:1 (A) and 2000:1 (B), respectively. Data are presented as mean population per well (i.e., corresponding to 2.5x10⁵ bMEC) ± standard deviation. Each experiment was done in triplicate and differences between strains were assessed using one-way analysis of variance, followed by Tukey’s range test. Letters a, b, c and d indicate homogeneous statistical processing groups that were significantly different according to Tukey’s range test.</p