Comparison of chemical treatments to eliminate enterohemorrhagic Escherichia coli O157:H7 on alfalfa seeds.
The focus of this study was to determine the efficacy of various chemicals in eliminating 2.04 to 3.23 log10 CFU/g of Escherichia coli O157:H7 from alfalfa seeds and to determine the survivability of the pathogen on seeds stored for prolonged periods at three temperatures. Significant (P < or = 0.05) reductions in populations of E. coli O157:H7 on inoculated seeds were observed after treatments with 500 and 1,000 ppm of active chlorine (as Ca[OCl]2) for 3 but not 10 min and with > or =2,000 ppm of Ca(OCl)2 regardless of pretreatment with a surfactant. Treatment with 20,000 ppm of active chlorine failed to kill 2.68 log10 CFU/g of seeds. Acidified NaClO2 (500 ppm) was effective in reducing populations of the pathogen by >2 logs per g. Acidified ClO2 significantly reduced populations of E. coli O157:H7 on seeds at concentrations > or =100 ppm, and 500 ppm of ClO2 reduced the pathogen from 2.7 log10 CFU/g to <0.5 CFU/g. Chlorine (as NaOCl) was not effective at concentrations < or =1,000 ppm; significant reduction was achieved only after treatment with 2,000 ppm for 3 or 10 min. Notable reduction in populations was observed after treatment with 30 or 70% C2H3OH, but there was a dramatic decrease in germination percentage. Treatment with 0.2% H2O2 significantly reduced populations, and the organism was not detected by direct plating after treatment with > or =1% H2O2. Significant reduction in population of E. coli O157:H7 occurred after treatment with 1% trisodium phosphate, 40 ppm of Tsunami and Vortexx, and 1% Vegi-Clean. A significant decrease in the number of E. coli O157:H7 on dry seeds was observed within 1 week of storage at 25 and 37 degrees C, but not at 5 degrees C. Between 1 and 38 weeks, populations on seeds stored at 5 degrees C remained relatively constant. The pathogen was recovered from alfalfa seeds initially containing 3.04 log 10 CFU/g after storage at 25 or 37 degrees C for 38 weeks but not 54 weeks.
Center for Food Safety and Quality Enhancement, Department of Food Science and Technology, University of Georgia, Griffin 30223-1797, USA.
P J
PJ
Taormina
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LR
Beuchat
D017610:Calcium Compounds; D002713:Chlorine; D015169:Colony Count, Microbial; D004202:Disinfectants; D004203:Disinfection / Q000379:methods; D019453:Escherichia coli O157 / Q000254:growth & development*; D000431:Ethanol; D006863:Hydrogen-Ion Concentration; D000455:Medicago sativa / Q000382:microbiology* / Q000502:physiology; D010710:Phosphates; D011136:Polysorbates; D012639:Seeds / Q000382:microbiology*; D012973:Sodium Hypochlorite; D013696:Temperature
D017610:Calcium Compounds; D004202:Disinfectants; D010710:Phosphates; D011136:Polysorbates; C004488:calcium hypochlorite; D000431:Ethanol; D002713:Chlorine; D012973:Sodium Hypochlorite; C018279:sodium phosphate