Fig. 3: Cytotoxicity assessment of biofilm-forming sessile and planktonic L. monocytogenes. | npj Biofilms and Microbiomes

Fig. 3: Cytotoxicity assessment of biofilm-forming sessile and planktonic L. monocytogenes.

From: Biofilm-isolated Listeria monocytogenes exhibits reduced systemic dissemination at the early (12–24 h) stage of infection in a mouse model

Fig. 3

a Flow cytometric analysis of Ped-2E9 (B cell hybridoma) cells treated with biofilm-isolated (B) and planktonic (P) cells of L. monocytogenes (Lm) F4244 and 10403S and corresponding mutant strains at MOI 10. Annexin V-PE-positive and 7-AAD-negative events (Q3) were identified as cells in the early phase of apoptosis. Events with both Annexin V-PE and 7-AAD positive (Q2) or both negative (Q4) were identified as dead or live cells, respectively. L. innocua (Lin) F4248 was also tested as a nonpathogenic negative control. b Quantitative comparison of overall damage of Ped-2E9 caused by bacteria. Each bar represents the percentage of Annexin V-PE-positive events, which included early apoptosis (Q3) or dead (Q2) cells. Biofilm-isolated bacteria of both strains were significantly less cytotoxic than their planktonic counterparts. Bars marked with different letters are significantly different at P < 0.05. c Lactate dehydrogenase (LDH) released from Caco-2 cells (a colorectal adenocarcinoma) treated with both sessile or planktonic cells. Bacteria were incubated with cells at MOI 10 at 37 °C for 2 h. Data are the average of at least three independent experiments performed in triplicate. All error bars represent SEM. A pairwise Student’s t-test was used for statistical analysis. *P < 0.05.

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