Reduction of Salmonella spp. and strains of Escherichia coli O157 : H7 by gamma radiation of inoculated sprouts

There have been several recent outbreaks of salmonellosis and infections wi th Escherichia coli O157:H7 linked to the consumption of raw sprouts. Use o f ionizing radiation was investigated as a means to reduce or to totally in activate these pathogens, if present, on the sprouts. The radiation D value , which is the amount of irradiation in kilograys for a 1-log reduction in cell numbers, for these pathogens was established using a minimum of five d oses at 19 +/- 1 degrees C. Before inoculation, the sprouts were irradiated to 6 kGy to remove the background microflora. The sprouts were inoculated either with Salmonella spp. cocktails made with either meat or vegetable is olates or with E. coli O157:H7 cocktails made with either meat or vegetable isolates. The radiation D values for the Salmonella spp. cocktails on spro uts were 0.54 and 0.46 kGy, respectively, for the meat and vegetable isolat es. The radiation D values for the E. coli O157:H7 cocktails on sprouts wer e 0.34 and 0.30 kGy, respectively, for the meat and vegetable isolates. Sal monella was not detected by enrichment culture on sprouts grown from alfalf a seeds naturally contaminated with Salmonella after the sprouts were irrad iated to a dose of 0.5 kGy or greater. Ionizing radiation is a process that can be used to reduce the population of pathogens on sprouts.