Figure 6.

Klebsiella pneumoniae RYC492 virulence correlates with a more prominent and irregular capsule and with increased biofilm formation ability. (A) K. pneumoniae cells were subjected to classical capsule staining with India ink, and observed and photographed using confocal microscopy. Pictures of 3 representative cells of each bacterial strain are presented. The capsule corresponds to the white area between the bacillary cell and the black background. Scale bar, 2 μm. (B) Biofilm formation assessment of K. pneumoniae strains or E. coli DH5α upon growth in a 96-well plate during 18 h. Bacterial cells adhered to the wells were stained with crystal violet, where biofilm formation is proportional to the absorbance of the bound stain (measured at 590 nm). The values shown correspond to the mean of three independent experiments and the error bars represent the standard deviation. RYC492 strain showed a significantly higher ability to form biofilms than Kp 700603 (one-way ANOVA, ^****p < 0.0001), and then the rest of the bacterial strains tested.