Inactivation of Escherichia coli O157:H7 by cinnamic aldehyde purified from Cinnamomum cassia shoot

Escherichia coli O157:H7 is a pathogen, which causes the hemorrhagic colitis, hemolytic uremic syndrome and thrombotic thrombocytopenic purpura in humans. Control of the bacterial cells in foods is an important factor to reduce outbreaks of the foodborne diseases. In this study, cinnamic aldehyde possessing antimicrobial activity against the bacterial cells was purified from the extract of cinnamon (Cinnamomum cassia Blume) shoot by sequential fractionation with various solvents and silica gel column chromatography. When E coli O157:H7 cells were incubated at 37degreesC for 12 It in the presence of 500 mug ml(-1) of the purified from cinnamic aldehyde, the viable counts decreased dramatically (from 4.9 x 10(6) to 1.0 x 10(2) cfu ml(-1)). In the presence of 1000 mug ml(-1) of the substance, most of the cells were killed after 2 It of incubation suggesting that the antimicrobial activity of cinnamic aldehyde is bacteriocidal in E coli. Scanning electron microscopic observations revealed that the bacterial cells treated with the cinnamic aldehyde suffered from severe damages in their surface structure. Minimal inhibitory concentration of the cinnamic aldehyde was determined to be 250 mug ml(-1) against E coli strains O157:H7 and O26 or 500 mug ml(-1) against strains ATCC11105 and 0111. (C) 2003 Elsevier Ltd. All rights reserved.