Fig. 4

Biofilm formation, expression of the csuCD genes, and interactions with host cells in A. baumannii strains. a Biofilms formed on 5 ml polystyrene tubes were stained with crystal violet. The amount of crystal violet eluted from the biofilms with ethanol was quantified as the OD₅₇₀ normalized to total bacterial growth (OD₆₀₀). The data are presented as mean ± SD of three independent experiments. ** p < 0.01 compared to wild-type ATCC 17978. b Transcription levels of csuC and csuD in the three A. baumannii strains were determined using qPCR. Data are mean ± SD expression levels of the target genes in each strain relative to expression of these genes in A. baumannii ATCC 17978. The data were obtained from three independent experiments. c Adherence to and invasion of A549 cells by A. baumannii strains. A549 cells were infected with the A. baumannii strains at MOI 100 for 3 h, and then the cell monolayers were lysed with Triton X-100. Dilutions of the bacterial lysates were plated on LB agar, and CFUs were counted. The data are presented as mean ± SD of three independent experiments