Tigecycline Suppresses the Virulence Factors of Multidrug-Resistant Acinetobacter baumannii Allowing Human Neutrophils to Act

PURPOSE: To determine the ability of human neutrophils to kill multidrug-resistant Acinetobacter baumannii (MDRAB) in the presence of tigecycline (TGC). METHODS: Clinical isolates of MDRAB were cultured with human neutrophils and H(2)O(2) in the presence of TGC. The numbers of viable bacteria, catalase activity, gene expression at the K locus of the MDRAB, reactive oxygen species (ROS) production, and granule exocytosis in human neutrophils were determined. RESULTS: There was a time-dependent increase in the numbers of MDRAB after co-culturing with human neutrophils, whereas there was a significant decrease in the MDRAB numbers when co-cultured with both, human neutrophils and TGC for 6 h. The presence or absence of TGC did not affect total ROS production or the expression of CD11b, CD15, and CD63 on human neutrophils occurred when co-cultured with MDRAB. TGC significantly suppressed catalase activity and gene expression at the K locus of MDRAB, and significantly reduced the thickness of the capsule. Additionally, the bacterial viability of TGC-treated MDRAB cultured with H(2)O(2) was lower than that without H(2)O(2) after 6 h of culture. CONCLUSION: TGC significantly suppressed the expression of catalase and the capsule in MDRAB without adverse effects on neutrophil function, allowing human neutrophils to kill MDRAB. TGC is an effective antibiotic for treating MDRAB infections.