Acinetobacter baumannii has developed resistance to various antimicrobial drugs, and its drug-resistant strains cause nosocomial infections. Controlling these infections has become a global clinical challenge.

Vizantin is an insoluble adjuvant that activates macrophages and lymphocytes. Recently, 2,2',3,3',4,4'-hexasulfated-vizantin (sulfated vizantin), which enables solubilization of vizantin, was developed by the present team. Sulfated vizantin was found to enhance bactericidal activity against multi-drug resistant Pseudomonas aeruginosa in RAW264.7 cells. In addition, spread of P. aeruginosa was inhibited in RAW264.7 cells treated with sulfated vizantin. When only sulfated vizantin and P. aeruginosa were incubated, sulfated vizantin did not affect growth of P. aeruginosa. Formation of DNA-based extracellular traps (ETs), a novel defense mechanism in several types of innate immune cells, helps to eliminate pathogens. In the present study, ET-forming macrophages constituted the majority of immune cells. Sulfated vizantin induced ET formation in RAW264.7 cells, whereas a Ca-chelating reagent, EDTA, and T-type calcium channel blocker, tetrandrine, inhibited ET formation and attenuated inhibition of spread of P. aeruginosa in sulfated vizantin-treated cells. Thus, sulfated vizantin induces ET formation in phagocytic cells in a Ca-dependent manner, thus preventing spread of P. aeruginosa. Hence, sulfated vizantin may be useful in the management of infectious diseases.

Pseudomonas aeruginosa is an opportunistic pathogen that causes severe infections, such as pneumonia and bacteremia. Several studies demonstrated that flagellar motility is an important virulence factor for P. aeruginosa infection. In this study, we determined whether sulfated vizantin affects P. aeruginosa flagellar motility in the absence of direct antimicrobial activity. We found that 100 μM sulfated vizantin suppressed P. aeruginosa PAO1 from penetrating through an artificial mucin layer by affecting flagellar motility, although it did not influence growth nor bacterial protease activity. To further clarify the mechanism in which sulfated vizantin suppresses the flagellar motility of P. aeruginosa PAO1, we examined the effects of sulfated vizantin on the composition of the flagellar filament and mRNA expression of several flagella-related genes, finding that sulfated vizantin did not influence the composition of the flagellar complex (fliC, motA, and motB) in P. aeruginosa PAO1, but significantly decreased mRNA expression of the chemotaxis-related genes cheR1, cheW, and cheZ. These results indicated that sulfated vizantin is an effective inhibitor of flagellar motility in P. aeruginosa.