FIG 4.

The surface polysaccharides protect K. kingae against antimicrobial peptides. K. kingae strains KK01 csaA and KK01 csaA pam were incubated with human neutrophils preincubated with a protease inhibitor (PI) cocktail at an MOI of 0.1 for 30 min in the presence of 1% HSA or 1% NHS (A and B). Black bars indicate survival in the absence of neutrophils, white bars represent survival in the presence of neutrophils, and gray bars represent survival in the presence of neutrophils pretreated with PI. (C to E) K. kingae strains and E. coli strain DH5α were incubated with various concentrations of antimicrobial peptides (polymyxin B, cathelicidin LL-37, or HNP-1 to HNP-3), as indicated, for 30 min. A total of three biological replicates were performed (n = 3). Survival was determined by calculating the number of recovered CFU by the number of CFU in the inoculum.