Figure 4.

Comparison of virulence of capsule-deficient Kp7De mutant and its parental Kp486 strain. Adhesion (A) and time-dependent internalization (B) by the A549 lung epithelial cells expressed in CFU per well and shown as the mean ± SEM (n = 4). (C) Phagocytosis by the human monocyte cell line THP1 determined by flow cytometry. UV-killed FITC-labeled bacterial cells were mixed with monocytes at a 100:1 ratio. Quantification of cellular uptake of bacterial cells by phagocytes is expressed as the geometric mean fluorescence intensity (gMFI) from the gated sample with phagocytosing cells ± SEM (n = 3). (D) Time-dependent bactericidal effect of 50% NHS or heat-inactivated NHS for 3 h at 37 °C. The percentage of survival was determined as the number of bacteria that survived relatively to the initial bacterial loading (n = 3). Asterisks indicate a statistically significant difference (p < 0.05).