OBJECTIVE: To probe into the protective effect of Chaihu Guizhi decoction on pan-drug-resistant Acinetobacter baumannii（ PDR-AB） invading human lung cancer A549 cells and its possible mechanism. METHODS: A model of PDR-AB invading human lung cancer A549 cells was established

and Chaihu Guizhi decoction was used to conduct intervention. Through detecting cell survival rate

PDR-AB adhesion rate and invasion rate

concentrations of tumor necrosis factor α（ TNF-α） and interleukin 6（ IL-6） concentration

forming ability of PDR-AB biofilm and other indicators

and the protective effect of Chaihu Guizhi decoction on PDR-AB invading human lung cancer A549 cells was inspected. RESULTS: Compared with the model group

Chaihu Guizhi decoction had protective effect on PDR-AB invading human lung cancer A549 cells

which can significantly improve the survival rate of human lung cancer A549 cells（ 30

15 and 7. 5 mg/ml

P < 0. 05）; significantly inhibit the adhesion of PDR-AB to A549 cells（ P < 0. 05 when the concentration of Chaihu Guizhi decoction was 7. 5 mg/ml; P < 0. 01 when the concentration of Chaihu Guizhi decoction was 30 and 15 mg/ml）; significantly inhibit the invasion effect of PDR-AB on A549 cells（ P < 0. 05 when the concentration of Chaihu Guizhi decoction was 30 mg/ml）; significantly inhibit the formation of PDR-AB biofilm（ P <0. 05 when the concentration of Chaihu Guizhi decoction was 15 mg/ml; P <0. 01 when the concentration of Chaihu Guizhi decoction was 30 mg/ml）; significantly reduce the release levels of TNF-α and IL-6（ P < 0. 01 when the concentration of Chaihu Guizhi decoction was 30 and 15 mg/ml）

with statistically significant differences. CONCLUSIONS:Chaihu Guizhi decoction has a certain protective effect on PDR-AB invading human lung cancer A549 cells.