Reduction of Escherichia coli O157:H7 and Salmonella after application of various sanitizing treatments to harvesting knives.

Consumption of food contaminated with Escherichia coli O157:H7 and Salmonella can cause enteric disease in consumers. If not properly sanitized, knives used during animal harvest can spread these and other pathogens. This study evaluated the reduction of E. coli O157:H7 and Salmonella on harvesting knives after nonthermal sanitation. Knives were inoculated in cocktails of E. coli O157:H7 or Salmonella and treated by 30-s immersions in ambient-temperature solutions (unless temperature was specified) of 1.1 % sodium metasilicate (SMS), 200 ppm of quaternary ammonium compounds (QAC), 200 ppm of chlorine (Cl(2)), 5 % lactic acid (LA), 82.2°C water, and 21°C water. Initial and treated counts were determined by plating onto MacConkey and xylose lysine desoxycholate for E. coli O157:H7 and Salmonella, respectively. Initial counts were determined by sampling one side of the knife blade, while treated counts were sampled from the opposite side. Plates were incubated for 24 to 48 h at 37°C. Mean attachment of E. coli O157:H7 and Salmonella was 4.51 and 5.09 log CFU/cm(2), respectively. Mean log reductions on knives inoculated with E. coli O157:H7 were 1.16, 3.51, 3.38, 1.38, 3.82, and 2 0.41 CFU/cm(2) after treatment in SMS, QAC, Cl(2), LA, 82.2°C water, and 21°C water, respectively (P ≤ 0.05). Knives inoculated with Salmonella showed reductions of 0.78, 3.42, 3.40, 2.91, 4.12, and 0.36 log CFU/cm(2) after treatment in SMS, QAC, Cl(2), LA, 82.2°C water, and 21°C water, respectively (P ≤ 0.05). Results indicate that some ambient-temperature sanitizing agents have the potential to significantly reduce E. coli O157:H7 and Salmonella populations on knives used during animal harvest.

Reduction of Escherichia coli O157:H7 in Fresh Spinach, using lactic acid bacteria and chlorine as a multihurdle intervention.

A 12-day shelf life study was conducted at 7 degrees C to determine whether Escherichia coli O157:H7 on spinach can be controlled effectively by selected strains of lactic acid bacteria (LAB) alone or in combination with chlorine as a multihurdle intervention. The multihurdle intervention consisted of both LAB and chlorine and was applied to spinach as a rinse and evaluated in comparison to LAB alone and chlorine and water rinses. Reductions achieved by all treatments also were compared with those observed for an inoculated control. The spinach was inoculated by submersion in a solution containing an E. coli O157:H7 cocktail at 1.0 x 10(6) CFU/ml. LAB were applied postharvest at a concentration of 2.0 x 10(8) CFU/ml, and 200 ppm of chlorine was used for the chlorine rinse. All spinach samples were packaged in commercial packaging, held in a retail display case, and tested for E. coli O157:H7 on days 0, 1, 3, 6, 9, and 12 using the Neo-Grid filtration system and CHROMagar. Survival of LAB throughout the shelf life also was determined. Significant reductions in pathogen populations were achieved by water (P = 0.0008), LAB (P < 0.0001), chlorine (P < 0.0001), and multihurdle (P < 0.0001) treatments when compared with controls. The multihurdle treatment produced the greatest reduction from control populations, a reduction of 1.91 log CFU/ml. This reduction was significantly greater than that achieved with water (P < 0.0001), LAB (P = 0.0025), and chlorine (P < 0.0001) alone, indicating that the application of chlorine and LAB is most effective as a combination treatment. The results obtained from this study indicate that the industry standard chlorine wash may be more effective when applied in combination with LAB.