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Figure 1 | BMC Microbiology

Figure 1

From: Klebsiella pneumoniae triggers a cytotoxic effect on airway epithelial cells

Figure 1

K. pneumoniae triggers a cytotoxic effect during infection of A549 carcinoma lung epithelial cells. A. Infection of A549 lung epithelial cells with K. pneumoniae 52145. MOIs used were 200:1 (top), 500:1 (middle) and 1000:1 (bottom panel and detail). Infections were carried out for 5 h in all cases. Non infected cells are shown for comparison (top left). Cells were fixed and stained for immunofluorescence. Actin cytoskeleton was labelled with phalloidin-RRX (red). White arrows show cell rounding and cytotoxicity. B. A549 epithelial cells were infected with K. pneumoniae strains 52145, 43816 and 1850 at MOI 500:1 for 4 h. Infected cells were fixed and stained with phalloidin-RRX for immunofluorescence as indicated above. C. UV killed K. pneumoniae 52145 was used to infect cells at MOI 500:1 during 4 h (top). K. pneumoniae 52145 was used for a mock infection (MOI 500:1). After 4 h the bacterial suspension was UV irradiated and used to infect a confluent cell monolayer for 4 h (middle). To assess the need of presence of live bacteria to induce cell rounding, infection was carried out at MOI 500:1 during 4 h, after which the supernatant was collected, centrifuged and filtered (0.2 Tm, nitrocellulose) to obtain a primed bacteria-free medium, which was then added to a new epithelium monolayer for 4 h (bottom). Infected cells were fixed and stained for immunofluorescence as described above.

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