Reduction of Salmonella spp. and Strains of Escherichia coli O157:H7 by Gamma Radiation of Inoculated Sprouts

Abstract

There have been several recent outbreaks of salmonellosis and infections with Escherichia coli O157:H7 linked to the consumption of raw sprouts. Use of ionizing radiation was investigated as a means to reduce or to totally inactivate 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 doses 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 isolates or with E. coli O157:H7 cocktails made with either meat or vegetable isolates. The radiation D values for the Salmonella spp. cocktails on sprouts were 0.54 and 0.46 kGy, respectively, for the meat and vegetable isolates. The radiation D values for the E. coli O157:H7 cocktails on sprouts were 0.34 and 0.30 kGy, respectively, for the meat and vegetable isolates. Salmonella was not detected by enrichment culture on sprouts grown from alfalfa seeds naturally contaminated with Salmonella after the sprouts were irradiated 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.

Irradiation Sensitivity of Planktonic and Biofilm-Associated Escherichia coli O157:H7 Isolates Is Influenced by Culture Conditions

“…The D 10 values of 43894 ranged from 14 to 27% less than those of the other two strains. Straindependent response to irradiation is a well-documented phenomenon and has been previously observed with E. coli O157:H7 irradiated on a variety of food and nonfood substrates (14,17,21,24). However, this is the first direct examination of the role of isolate specificity with regard to the radiation sensitivity of biofilm-associated E. coli O157:H7 cells.…”

“…The radiation dose value required to reduce the population by one log or 90% (D 10 ) for E. coli O157:H7 depends on the isolate, the suspending food product, and the conditions of treatment (13,14,21). When inoculated onto fresh sprouts of radish, alfalfa, or broccoli seeds, E. coli O157:H7 showed a D 10 value range of 0.27 to 0.34 kGy, depending on the type of sprout examined (17). On different types of lettuce, D 10 values of between 0.12 and 0.14 kGy were reported, depending on the suspending type of lettuce (13).…”

“…Escherichia coli O157:H7 is a food-borne pathogen associated with a variety of food products, including meats, leafy vegetables, sprouts, and other foods (1,13,14,17,21). E. coli O157:H7 and other human pathogens such as Staphylococcus aureus, Salmonella spp., and Listeria monocytogenes are known to adhere to food surfaces and to inert surfaces such as stainless steel, plastic, glass, and cement (4,5,9,10,18,19).…”

Sensitivity of Planktonic and Biofilm-Associated Salmonella spp. to Ionizing Radiation

“…are important food-borne pathogens, responsible for food-borne illness (FBI) associated with a variety of food products (16,18,19,24). Numerous studies have documented the ability of Salmonella spp.…”

Evaluation of Aerated Steam Treatment of Alfalfa and Mung Bean Seeds To Eliminate High Levels of Escherichia coli O157:H7 and O178:H12, Salmonella enterica, and Listeria monocytogenes

“…Yet studies have shown that this results in a median reduction of only 2.5 log CFU/g (20). Other sanitizing treatments include ionizing radiation (21), high hydrostatic pressure (22) in combination with mild heat (23), supercritical carbon dioxide (24), hot water (25)(26)(27), and dry heat (28). There is, however, no decontamination method available to date to ensure elimination of pathogens in all types of seeds without reducing seed germination or sprout yields (2).…”