Objective To observe the effect of Qiguiyin Formula [Formula of Huangqi（Radix Astrangali）

Danggui（Angelica sinesis） and Jinyinhua（Lonicera Japonica）] on imipenem-resisting pseudomonas aeruginosa.Methods Serum pharmacological method was used to prepare drug-containing serum of Qiguiyin Formula.Imipenem-resisting pseudomonas aeruginosa（1643 strains） was cultured with conventional broth and was divided into the drug-containing group（0.8ml of MH broth+0.2ml of drug-containing serum）

blank ser um group（0.8ml of MH broth+0.2ml of blank serum） and the positive control group （1ml of MH broth）.Three groups were given passaged intervention to the 8th gener ation.The minimal inhibitory concentration（MIC） value of strains in each group to imipenem was determined with double dilution method and the inhibition zone diameter was compared.Imipenem-resisting pseudomonas aeruginosa strains was frozen

thawed and centrifuged.The enzyme crude extracts was collected.Cephaloridine was used as substr ate and divided into the drug-containing serum group（95μl of 0.1mM/L cephaloridine+3μ l of drug-containing serum+2μl of enzyme crude extracts） and blank serum group（95μl o f 0.1mM/L cephaloridine+3μl of blank serum+2μl of enzyme crude extracts）.The hyd r olysis rate of β-lactamase was determined.Results Th e MIC value of imipenem-resisting pseudomonas aeruginosa to imipenem in the drug-containing serum group

blank serum group an d positive control group was 8μg/ml

16μg/ml and 16μg/ml respectively.The inhibition zone diameter in the drug-containing serum group was significantly larger than that in the positive control g roup（P<0.05）.The hydrolysis rate of β-lactamase in the drug-containing serum group was significantly lower than that in the blank serum group（P<0.05）.Conclusion The sensitivity of imipenem-resisting pseudomonas aeruginosa to imipenem could be restored by the drug-containing serum of Qiguiyin Formula.The Qiguiyin Formula-containing serum of could reduce the hydrolysis rate of β-lactamase

which maybe the mechanism of its reversal effect on the resisting of imipenem-resistant ps eudomonas aeruginosa.