Volatile compounds from Escherichia coli O157 : H7 and their absorption bystrawberry fruit

Volatile compounds emitted by cultures of two strains of the pathogenic bac terium Escherichia coli 0157:H7 and a nonpathogenic strain of E. coli were trapped on Super-Q porous polymer and identified by GC-MS. The predominant compound produced by all three strains was indole with lesser amounts of ot her components including methyl ketones, 2-heptanone, 2-nonanone, 2-undecan one, and 2-tridecanone. The vapor-phase profiles of these strains were simi lar for most chemicals identified but differed with regard to ketones. Stra wberry fruit was shown to be a suitable host for E. coli 0157:H7 with the p opulation of the bacterium either increasing or remaining stable after 3 da ys depending on inoculation level. Headspace analysis of the volatile compo unds from inoculated fruit yielded no detectable quantity of indole. Strawb erry fruit readily absorbed indole and other volatile compounds produced by the bacteria and in some cases metabolized the compounds to new volatile p roducts. Thus, headspace "marker" compounds indicating possible bacterial c ontamination of fruit were largely removed from the vapor phase by the stra wberries.