The aim of this study was to test the antibacterial activity of selected isolate spices against pathogens microorganisms by two types of contact mothods(liquid and vapour-phase contact).The isolate spices were tested against an array of four types of Gram-negative bacteria (Escherichia coli,Salmonella typhimurium,Shigella flexneri,Vibrio parahaemolyticus) and three types of Gram-positive bacteria (Bacillus cereus,Listeria monocytogenes,Staphylococcus aureus).The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of different isolate spices were determined by the broth dilution method in liquid contact method and the disc volatilization method was used in the vapour-phase contact method.The results show that the antimicrobial activity of the six isolate spices in the liquid contact assay are as follows:thymol > salicylaldehyde > cinnamaldehyde > citral > eugenol > linalool.The MIC values of thymol and salicylaldehyde were both 0.125 μL/mL.The value of cinnamaldehyde and citral were in the range of 0.25 to 0.5 μL/mL,and the value of eugenol and linalool were 0.25-2.0 μL/mL.cinnamaldehyde and citral range from 0.25-0.5 μL/mL,eugenol for 0.25-2.0 μL/mL and linalool for 0.25-2.0 μL/mL.In the vapour-phase contact assay,the antimicrobial activity was in the order of thymol and salicylaldehyde > linalool > cinnamaldehyde > citral > eugenol.The MIC values of thymol and salicylaldehyde were both 0.125 μL/mL,linalool values ranged from 0.25 to 1.0 μL/mL,citral were mostly 0.5-1.0 μL/mL and cinnamaldehyde ranged from 0.5 to 1.0 μL/mL,while eugenol only effective against V. parahaemolyticus in the test range.According to the analysis of variance of repeated measurement by the MIC values,thymol and salicylaldehyde were significantly difference between the liquid contact method and the vapour-phase contact method,P<0.05,and the liquid contact method was significantly better than the vapour-phase contact method.The analysis of MBC values,linalool and salicylaldehyde had significant differences in the two contact methods, P<0.05,in which the liquid contact method of linalool and salicylaldehyde was significantly better than vapour-phase contact method,while eugenol was the opposite.In conclusion,the different assay methods between isolate spices and pathogens would lead to various antimicrobial effects.Therefore,the development of new antimicrobial agents using the antimicrobial properties of isolate spices requires a comprehensive evaluation of their antibacterial properties.