Abstract: The cellular fatty acid compositions of 19 strains of foodborne pathogenic bacteria, were extracted with organic reagent, isolated through thin layer chromatography and determined by capillary gas chromatography-mass spectrometry (GC-MS). The result indicated that the cellular fatty acid compositions of Salmonella, Escherichia coli, Vibrio and Shigella all contain tetradecanoic acid, hexadecanoic acid and octadecenoic acid, the total content is around 90%, in which the hexadecanoic acid is the most, above 40%, next is the octadecenoic acid, around 30%. The difference of the fatty acid compositions is prominent among the four genus. Escherichia coli O157 is absent of tridecanoic acid and pentadecanoic acid, and Vibrio parahaem olyticus is lack of dodecanoic acid and tridecanoic acid, while Shigella contains unique cyclopentanetridecanoic acid. These characters could be the basis of classification and identification respectively. There are difference in the location of double bonds between the type strains and local strains, so they could be distinguished by these variation.

Key words: total ion current, fatty acid methyl ester, gas chromatography-mass spectrometry, pathogenic bacteria ..