Fig 2. Inhibition of A. baumannii adhesion and motility by LL-37.

(A) Motility of A. baumannii on semisolid agar. Three microliters of cells from mid-log phase were spotted onto the middle of semisolid agar containing different concentrations of LL-37 and incubated at 37°C for 7 hr. (B) Cell motility was quantified using the Image J program (http://imagej.nih.gov/ij/). The whole area of the entire colony and the original spot was measured. Cell motility was obtained by subtracting the area of the original spot from the area of the entire colony. The relative percentage of motility was obtained by comparing the motility of cells treated with LL-37 to of the motility of the control without LL-37 treatment. The results of both (A) and (B) showed that A. baunmannii motility was reduced by increasing concentrations of LL-37. (C) Cell adhesion to a polystyrene surface. Cells were mixed with different concentrations of LL-37 in RPMI-1640 and incubated at 37°C for 1 hr. Adherent cells were detected by crystal violet staining, and relative adhesion was represented as a percentage. (D) Non-adherent floating cells were collected by centrifugation, serially diluted and spotted onto an LB agar plate. The results indicated that A. baumannii cell attachment was decreased with treatment of increasing concentrations of LL-37 and that most non-adherent cells were alive. Both adhesion and motility experiments were performed in triplicates (N = 3). The Student’s t-test (**, p<0.01) was used to determine the statistical significance of the experimental data.