Reduction of Pathogens Using Hot Water and Lactic Acid on Beef Trimmings

Beef trimmings from young or mature beef cattle were obtained commercially. Trimmings within age type then were inoculated with about 6.0 log₁₀ CFU/mL of rifampicin-resistant. Escherichia coli O157:H7 and Salmonella typhimurium (ATCC 13311) were randomly assigned to 1 of 3 treatments (control; 95 °C hot water alone, or with 2% L-lactic acid). After treatment, trimmings were ground, held for 0, 14, 28, or 42 d in chub packages at 4 °C, and total aerobic plat counts, E. coli O157:H7, and S. typhimurium counts were determined. Non-inoculated trimmings were also treated and samples were evaluated for pH, fat, moisture, TBA, meat color by colorimeter, and meat color, and odor by trained sensory panels. Trimmings treated with water or hot water plus lactic acid reduced levels of E. coli O157:H7 and S. typhimurium and tended to be darker after treatment. Meat odor in the final product was not affected by treatment.     

Inactivation of Escherichia coli O157:H7, Salmonella typhimurium,and Listeria monocytogenes on Stored Iceberg Lettuce by Aqueous Chlorine Dioxide Treatment

ABSTRACT: Inactivation of Escherichia coli O157:H7, Salmonella typhimurium, and Listeria monocytogenes in iceberg lettuce by aqueous chlorine dioxide (ClO₂) treatment was evaluated. Iceberg lettuce samples were inoculated with approximately 7 log CFU/g of E. coli O157:H7, S. typhimurium, and L. monocytogenes. Iceberg lettuce samples were then treated with 0, 5, 10, or 50 ppm ClO₂ solution and stored at 4 °C. Aqueous ClO₂ treatment significantly decreased the populations of pathogenic bacteria on shredded lettuce (P < 0.05). In particular, 50 ppm ClO₂ treatment reduced E. coli O157:H7, S. typhimurium, and L. monocytogenes by 1.44, 1.95, and 1.20 log CFU/g, respectively. The D₁₀‐values of E. coli O157:H7, S. typhimurium, and L. monocytogenes in shredded lettuce were 11, 26, and 42 ppm, respectively. The effect of aqueous ClO₂ treatment on the growth of pathogenic bacteria during storage was evaluated, and a decrease in the population size of these pathogenic bacteria was observed. Additionally, aqueous ClO₂ treatment did not affect the color of lettuce during storage. These results suggest that aqueous ClO₂ treatment can be used to improve the microbial safety of shredded lettuce during storage.     

Viability of multi-strain mixtures of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 inoculated into the batter or onto the surface of a soudjouk-style fermented semi-dry sausage

The fate of Listeria monocytogenes, Salmonella typhimurium, or Escherichia coli O157:H7 were separately monitored both in and on soudjouk. Fermentation and drying alone reduced numbers of L. monocytogenes by 0.07 and 0.74 log₁₀ CFU/g for sausages fermented to pH 5.3 and 4.8, respectively, whereas numbers of S. typhimurium and E. coli O157:H7 were reduced by 1.52 and 3.51 log₁₀ CFU/g and 0.03 and 1.11 log₁₀ CFU/g, respectively. When sausages fermented to pH 5.3 or 4.8 were stored at 4, 10, or 21 °C, numbers of L. monocytogenes, S. typhimurium, and E. coli O157:H7 decreased by an additional 0.08–1.80, 0.88–3.74, and 0.68–3.17 log₁₀ CFU/g, respectively, within 30 days. Storage for 90 days of commercially manufactured soudjouk that was sliced and then surface inoculated with L. monocytogenes, S. typhimurium, and E. coli O157:H7 generated average D-values of ca. 10.1, 7.6, and 5.9 days at 4 °C; 6.4, 4.3, and 2.9 days at 10 °C; 1.4, 0.9, and 1.6 days at 21 °C; and 0.9, 1.4, and 0.25 days at 30 °C. Overall, fermentation to pH 4.8 and storage at 21 °C was the most effective treatment for reducing numbers of L. monocytogenes (2.54 log₁₀ CFU/g reduction), S. typhimurium (5.23 log₁₀ CFU/g reduction), and E. coli O157:H7 (3.48 log₁₀ CFU/g reduction). In summary, soudjouk-style sausage does not provide a favorable environment for outgrowth/survival of these three pathogens.     

Assessment of the ability of five culture media for the detection of Escherichia coli O157

Cattle are a common reservoir for Escherichia coli O157:H7. Prior to confirming its presence in a sample, proper isolation of E. coli O157 is necessary. Consequently, this study evaluated the ability of five commercial plating media to isolate E. coli O157 from 138 samples of fresh cattle faeces, water from water trough and pond, and surfaces of water trough and hay bunk. For the isolation of E. coli O157, samples were enriched in tryptic soya broth, followed by immunoseparation and then plating on SMAC, CT‐SMAC, CHROMagar^? O157, Tellurite CHROMagar^? O157 and Vancomycin Cefixime Cefsoludin CHROMagar^? O157. Real‐time PCR targeting genes stx₁, stx₂ and wzy_O157 was used to confirm selected isolates. When analysed together, CT‐SMAC and CHROMagar^? O157 were the best combination for isolating E. coli O157, giving 79% true‐positive results and only 0.05% false‐negative results.     

Kojic acid and tea polyphenols inactivate Escherichia coli O157:H7 in vitro and on salmon fillets by inflicting damage on cell membrane and binding to genomic DNA

The development of effective natural antibacterial agents is important due to the insecurity of synthetic antimicrobial agents and consumer preferences. In this study, kojic acid (KA) and tea polyphenols (TP) were found to exhibit synergistic inhibitory effect against Escherichia coli O157:H7 with a fractional inhibitory concentration index of 0.25. KA combined with TP at 25% of their minimum inhibitory concentrations (MICs) completely inactivated E. coli O157:H7 within 4 h. Subsequently, propidium iodide uptake tests, genomic DNA interaction analysis, molecular docking, field emission scanning electron microscopy and biofilm formation assay were conducted to understand the synergistic antibacterial mechanism of KA-TP. The results demonstrated that KA-TP attacked the cell membrane cooperatively, thus disturbing membrane integrity and cell structure, and KA could bind to the genomic DNA to affect the biofilm formation of E. coli O157:H7. Moreover, the contamination of E. coli O157:H7 on raw salmon fillets was eliminated to varying degrees after soaking treatments with KA and/or TP for 30 min. The depuration effect was further enhanced when KA combined with TP, and more than 2-log reduction of E. coli O157:H7 was obtained under the treatment of KA-TP at 2 MIC, suggesting that KA-TP may serve as a natural compound disinfectant for ready-to-eat aquatic products.     

Heat-Resistance of Escherichia Coli O157:H7 in Meat and Poultry as Affected by Product Composition

The effects of fat level and low fat formulation on survival of Escherichia coli O157:H7 isolate 204P heated in ground beef [7%, 10% and 20% fat], pork sausage [7%, 10%, and 30% fat], chicken (3% and 11% fat), and turkey (3% and 11% fat) were determined by D- and z-values. D-values for E. coli 0157:H7 in lowest fat products were lower than in traditional beef and pork products (P < 0.05). Overall, higher fat levels in all products resulted in higher D-values. D₆₀ values (min) ranged from 0.45–0.47 in beef, 0.37–0.55 in pork sausage, 0.38–0.55 in chicken and 0.55–0.58 in turkey. D₅₅ and D₅₀ values were respectively longer. Z-values ranged from 4.4–4.8°C. Product composition affected lethality of heat to E. coli O157:H7.     

Image Analysis Based Quantification of Bacterial Volume Change with High Hydrostatic Pressure

ABSTRACT: Scanning electron microscopy (SEM) images of Staphylococcus aureus 485 and Escherichia coli O157:H7 933 were taken after pressure treatments at 200 to 400 MPa. Software developed for this purpose was used to analyze SEM images and to calculate the change in view area and volume of cells. Significant increase in average cell view area and volume for S. aureus 485 was observed in response to pressure treatment at 400 MPa. Cell view area for E. coli O157:H7 933 significantly increased at 325 MPa, the maximum pressure treatment tested against this pathogen. In contrast to S. aureus, cells of E. coli O157:H7 exhibited significant increase in average view area and volume at 200 MPa. The pressure‐induced increase in these parameters may be attributed to modifications in membrane properties, for example, denaturation of membrane‐bound proteins and pressure‐induced phase transition of membrane lipid bilayer.     

Growth Inhibitory Effect of Chicken Egg Yolk Antibody (IgY) on Escherichia coli O157:H7

Escherichia coli O157:H7‐specific antibodies (immunoglobulin Y [IgY]) were isolated by the water‐dilution method from the egg yolk of chickens that were immunized with E. coli O157:H7 whole cells. The specific‐binding activity of IgY against E. coli O157:H7 as determined by the enzyme immuno assay showed high levels of activity against bacterial whole cells. IgY binding activity was further demonstrated to have an inhibitory effect on E. coli O157:H7 growth in a liquid medium. The antibacterial function of IgY appeared to result from the interaction of IgY with surface components of E. coli O157:H7, as proven from observation of immunofluorescence and immunoelectron microscopy.     

Thermal Inactivation of Escherichia coli O157:H7 in Cooked Turkey Products

Survival of Escherichia coli O157:H7 when heated in commercial-type turkey products was determined. Thermal death times (TDT) were determined at 52–60°C in ground turkey with no additives, 3% fat; ground turkey with no additives, 11% fat; turkey ham batter, 11% fat; turkey frank batter, 17% fat; and turkey sausage batter, 31% fat. Mean D₅₂-values ranged from 44.9 to 116 min; D₅₅-values from 6.63 to 39.4 min; D₅₇-values from 2.20 to 11.7 min; D₆₀-values from 0.68 to 5.86 min. At all temperatures, survival of E. coli O157:H7 was greater in formulated products than in turkey meat with no additives. Greatest survival occurred in the turkey frank batter. Using our z-value data, times to provide a 5 D kill of E. coli O157:H7 in turkey franks cooked at 60°C, 65.6°C, or 71°C would be 26, 3.1, or 0.37 min, respectively.     

Comparison of selective agar media and enrichment broths for recovering heat-stressedEscherichia coliO157:H7 from ground beef

Media for detecting and enumerating healthy as well as heat-injured cells ofEscherichia coliO157:H7 in foods are highly desired. This study was conducted to evaluate the performance of eight selective and two non-selective direct plating agar media for their ability to recoverE. coliO157:H7 cells from unheated and heated ground beef, and to compare the ability of five enrichment broths to recoverE. coliO157:H7 cells from heated ground beef. Ground beef was incoulated withE. coliO157:H7 and heated at 56°C for up to 30 min. Each agar was evaluated for its ability to support colony formation byE. coliO157:H7 surviving heat treatment, and each enrichment broth was evaluated for its ability to recover low numbers of surviving cells. Of the selective media tested, modified eosin methylene blue agar (MEMB) and Rainbow^TMagar O157 supported recovery of significantly (P≤0·05) higher numbers of heat-stressed cells ofE. coliO157:H7, regardless of heating time. CHROMagar^TMO157, sorbitol MacConkey agar (SMA) supplemented with cefixime and potassium tellurite (CT-SMAC), and SMA supplemented with cefixime and rhamnose (CR-SMAC) performed less favorably, even in recovering cells ofE. coliO157:H7 that had not been subjected to heat stress. SMA and BCM^TMO157:H7 agar were similar to CT-SMAC and CR-SMAC in their ability to recoverE. coliO157:H7 from heated beef. Tryptone bile X-glucuronide (TBX) agar performed significantly better than these media, but was inferior to MEMB agar and Rainbow^TMagar O157:H7. Enrichment using tryptone soya broth with novobiocin or a procedure using brain–heart infusion and tryptone phosphate broths recovered the highest population of heat stressedE. coliO157:H7. EZ Coli^TMenrichment broth was inferior to other broths in resuscitating injured cells and supporting subsequent growth.     

Survival of Escherichia coli O157:H7 in channel catfish pond and holding tank water

Survival of Escherichia coli O157:H7 in channel catfish (Ictalurus punctatus), pond and holding tank water was investigated. Water from three channel catfish ponds was inoculated with ampicillin/nalidixic acid-resistant E. coli O157:H7 transformed with a plasmid encoding for green fluorescent protein at 10⁵, 10⁶, and 10⁷ CFU/ml. Samples were taken from surface, internal organs, and skin scrape of fish and pond water for E. coli O157:H7 enumeration on brain heart infusion (BHI) agar containing ampicillin and nalidixic acid. To determine the survival of E. coli O157:H7 in catfish holding tank water from two farmers markets, the water was inoculated with 10⁷E. coli O157:H7 CFU/ml. E. coli O157:H7 were detected by direct plating for 33 and 69 d in pond and holding tank water, respectively. A rapid decrease of the pathogen was observed in the first 2 weeks to reach 2 log CFU/ml. When E. coli O157:H7 was not recovered by direct plating, the pathogen was isolated by enrichment in TSB for approximately another 30 d from pond and holding tank water. The populations of E. coli O157:H7 found in the internal organs and skin scrape were 5.5 log and 2.5 log CFU/ml, respectively. E. coli O157:H7 from internal organs and water were recovered for at least 12 d. Results suggest that E. coli O157:H7 can survive in channel catfish pond and holding tank water and channel catfish may become a potential carrier of the pathogen.     

Evaluation of Antibacterial Activity of Whey Protein Isolate Coating Incorporated with Nisin,Grape Seed Extract,Malic Acid,and EDTA on a Turkey Frankfurter System

ABSTRACT: The effectiveness of whey protein isolate (WPI) coatings incorporated with grape seed extract (GSE), nisin (N), malic acid (MA), and ethylenediamine tetraacetic acid (EDTA) and their combinations to inhibit the growth of Listeria monocytogenes, E. coli O157:H7, and Salmonella typhimurium were evaluated in a turkey frankfurter system through surface inoculation (approximately 10⁶ CFU/g) of pathogens. The inoculated frankfurters were dipped into WPI film forming solutions both with and without the addition of antimicrobial agents (GSE, MA, or N and EDTA, or combinations). Samples were stored at 4 °C for 28 d. The L. monocytogenes population (5.5 log/g) decreased to 2.3 log/g after 28 d at 4 °C in the samples containing nisin (6000 IU/g) combined with GSE (0.5%) and MA (1.0%). The S. typhimurium population (6.0 log/g) was decreased to approximately 1 log cycles after 28 d at 4 °C in the samples coated with WPI containing a combination of N, MA, GSE, and EDTA. The E. coli O157:H7 population (6.15 log/g) was decreased by 4.6 log cycles after 28 d in samples containing WPI coating incorporated with N, MA, and EDTA. These findings demonstrated that the use of an edible film coating containing nisin, organic acids, and natural extracts is a promising means of controlling the growth and recontamination of L. monocytogenes, S. typhimurium, and E. coli O157:H7 in ready‐to‐eat poultry products.     

Detection and Isolation of Low Levels of E. coli O157:H7 in Cilantro by Real-Time PCR, Immunomagnetic Separation, and Cultural Methods with and without an Acid Treatment

Abstract: Leafy greens such as cilantro, contaminated with Escherichia coli O157:H7, have been implicated in cases of human illnesses. High levels of microflora in fresh cilantro make recovery of low numbers of E. coli O157:H7 difficult. To improve upon current methods, immunomagnetic separation (IMS) techniques in combination with real‐time PCR (RTiPCR) and selective enrichment protocols were examined. Rinsates were prepared from cilantro samples inoculated with low (～0.02 CFU/g) and slightly higher (～0.05 CFU/g) levels of E. coli O157:H7. Rinsate portions were enriched in modified buffered peptone water with pyruvate (mBPWp) for 5 h at 37 °C. After 5 h, selective agents were added to samples and further incubated at 42 °C overnight. Detection and recovery were attempted at 5 and 24 h with and without IMS. IMS beads were screened by RTiPCR for simultaneous detection of stx1, stx2, and uidA SNP. Additionally, broth cultures and IMS beads were streaked onto selective agar plates (Rainbow^®agar, R&F^®E. coli O157 Chromogenic medium, TC‐SMAC and CHROMagar? 0157) for isolation of E. coli O157:H7. Both broth cultures and IMS beads were also acid treated in Trypticase Soy Broth pH 2 prior to plating to selective media to improve upon cultural recovery. Although E. coli O157 strains were detected in most samples by PCR after 5 h enrichment, cultural recovery was poor. However, after 24 h enrichment, both PCR and cultural recovery were improved. Acidification of the broths and the IMS beads prior to plating greatly improved recovery from 24 h enrichment broths by suppressing the growth of competing microorganisms. Practical Application: Detection and recovery of Escherichia coli O157:H7 in fresh produce matrices (e.g., cilantro) can be complicated by high background microflora present in these foods. Rapid detection by molecular methods combined with effective enrichment and isolation procedures such as using immunomagnetic separation (IMS) techniques can quickly identify potential hazards to public health. Additional techniques such as acidification of enrichment broths can exploit acid resistance characteristics of pathogens such as E. coli O157:H7, facilitating their isolation in complex food matrices.     

Sodium Lactate Affects Pathogens in Cooked Beef

Cooked, quartered beef top rounds containing either 1, 2, 3 or 4% sodium lactate were aseptically sampled and slice sections were inoculated with Listeria monocytogenes (ATCC 43256), Staphylococcus aureus (ATCC 27154), Salmonella typhimurium (ATCC 13311), Clostridium perfringens (ATCC 12924), or Escherichia coli O157:H7 (ATCC 43895). Inoculated slices were stored at 10°C for 0. 7. 14. 21 or 28 days.‘Three and 4% sodium lactate generally displayed lim-ited proliferation of S. typhimurium, L. monocytogenes and E. coli O157:H7 when compared with control roasts (0% sodium lactate) and roasts containing 2% sodium lactate.     

Fate of Escherichia coli O157:H7 in field-inoculated lettuce

Impact of drip and overhead sprinkler irrigation on the persistence of attenuated Escherichia coli O157:H7 in the lettuce phyllosphere was investigated using a split-plot design in four field trials conducted in the Salinas Valley, California, between summer 2007 and fall 2009. Rifampicin-resistant attenuated E. coli O157:H7 ATCC 700728 (BLS1) was inoculated onto the soil beds after seeding with a backpack sprayer or onto 2- or 4-week-old lettuce plant foliage with a spray bottle at a level of 7 log CFU ml⁻¹. When E. coli O157:H7 was inoculated onto 2-week-old plants, the organism was recovered by enrichment in 1 of 120 or 0 of 240 plants at 21 or 28 days post-inoculation, respectively. For the four trials where inoculum was applied to 4-week-old plants, the population size of E. coli O157:H7 declined rapidly and by day 7, counts were near or below the limit of detection (10 cells per plant) for 82% or more of the samples. However, in 3 out 4 field trials E. coli O157:H7 was still detected in lettuce plants by enrichment 4-weeks post-inoculation. Neither drip nor overhead sprinkler irrigation consistently influenced the survival of E. coli O157:H7 on lettuce.     

Antibacterial activities and total phenolic contents of grape pomace extracts

The aim of this study was to determine the total phenolic contents and antibacterial effects of grape pomace extracts (cultivars Emir and Kalecik karasi) against 14 bacteria, and the effects of the extracts on the growth and survival of two of the bacteria during storage. The total phenolic contents of grape pomace of Emir and Kalecik karasi cultivars extracted with acetone/water/acetic acid (90:9.5:0.5) were 68.77 and 96.25 mg GAE g^?1, respectively. The agar well diffusion method was used to test the antibacterial activity of the extracts at 1, 2.5, 5, 10 and 20% (w/v) concentrations in methanol on spoilage and pathogenic bacteria including Aeromonas hydrophila, Bacillus cereus, Enterobacter aerogenes, Enterococcus faecalis, Escherichia coli, Escherichia coli O157:H7. Mycobacterium smegmatis, Proteus vulgaris, Pseudomonas aeruginosa, Pseudomonas fluorescens, Salmonella enteritidis, Salmonella typhimurium, Staphylococcus aureus and Yersinia enterocolitica. All the bacteria tested were inhibited by extract concentrations of 2.5, 5, 10 and 20%, except for Y enterocolitica which was not inhibited by the 2.5% concentration. However, pomace extracts at 1% concentration had no antibacterial activity against some of the bacteria. According to the agar well diffusion method, E coli O157:H7 was the most sensitive of the bacteria. Generally, using the serial dilution method, while the extracts at 0.5% concentration had bacteriostatic activities on E coli O157:H7 and S aureus, the extracts appeared to have bactericidal effects at 1 and 2.5% concentrations. In accordance with this method, S aureus was more sensitive than E coli O157:H7 to the extracts. Copyright © 2004 Society of Chemical Industry     

Role of O-antigen on the Escherichia coli O157:H7 cells hydrophobicity, charge and ability to attach to lettuce

Environmental factors encountered during growing and harvesting may contribute to Escherichia coli O157:H7 contamination of lettuce. Limited nutrients and extended exposure to water may cause E. coli O157:H7 to shed its O antigen. Absence of the O157-polysaccharide antigen could affect the cell's physicochemical properties (hydrophobicity and cell charge) and ultimately influence its attachment to surfaces. The objectives of this study were to evaluate the effect of the E. coli O157:H7 O-antigen on the cell's overall hydrophobicity, charge and ability to attach to cut edge and whole leaf iceberg lettuce surfaces. Three strains of E. coli O157:H7 (86-24 wild type; F-12, mutant lacking the O-antigen and pRFBE, plasmid for O157 gene reintroduced) were examined for their hydrophobicity, overall charge and ability to attach to lettuce. Overall, E. coli O157:H7 attached at higher levels to cut surfaces over whole leaf surfaces (P = 0.008) for all strains and treatments. Additionally, the strain lacking the O-antigen (F12) — attached significantly less to lettuce (P = 0.015) than the strains expressing the antigen (WT and pRFBE). Cells lacking the O antigen (strain F-12) were also significantly more hydrophobic than strains 86-24 or pRFBE (P ≤ 0.05). Surface charge differed among the strains tested (P ≤ 0.05); however, it did not appear to influence bacterial attachment to lettuce surfaces. The charge was not fully restored in the pRFBE strain (expression of O-antigen reintroduced), therefore, no conclusions can be made pertaining to the effect of charge on attachment in this study. Results indicate that E. coli O157:H7 cells which lack the O-antigen have greater hydrophobicity and attach at lower concentrations than cells expressing the O-antigen, to iceberg lettuce surfaces.     

Production of biofilm and quorum sensing by Escherichia coli O157:H7 and its transfer from contact surfaces to meat,poultry, ready-to-eat deli,and produce products

Multistate outbreaks of Escherichia coli O157:H7 infections through consumption of contaminated foods including produce products have brought a great safety concern. The objectives of this study were to determine the effect of biofilm and quorum sensing production on the attachment of E. coli O157:H7 on food contact surfaces and to evaluate the transfer of the pathogen from the food contact to various food products. E. coli O157:H7 produced maximum levels of AI-2 signals in 12 h of incubation in tested meat, poultry, and produce broths and subsequently formed strong biofilm in 24 h of incubation. In general, E. coli O157:H7 formed stronger biofilm on stainless steel than glass. Furthermore, E. coli O157:H7 that had attached on the surface of stainless steel was able to transfer to meat, poultry, ready-to-eat deli, and produce products. Strong attachment of the transferred pathogen on produce products (cantaloupe, lettuce, carrot, and spinach) was detected (>10³ CFU/cm²) even after washing these products with water. Our findings suggest that biofilm formation by E. coli O157:H7 on food contact surfaces can be a concern for efficient control of the pathogen particularly in produce products that require no heating or cooking prior to consumption.     

Switchgrass extractives to mitigate Escherichia coli O157:H7 and Salmonella enterica serovar Typhimurium contamination of romaine lettuce at pre- and postharvest

The antimicrobial potential of switchgrass extractives (SE) was evaluated on cut lettuce leaves and romaine lettuce in planta, using rifampicin-resistant Escherichia coli O157:H7 and Salmonella Typhimurium strain LT2 as model pathogens. Cut lettuce leaves were swabbed with E. coli O157:H7 or S. Typhimurium followed by surface treatment with 0.8% SE, 0.6% sodium hypochlorite, or water for 1 to 45 min. For in planta studies, SE was swabbed on demarcated leaf surfaces either prior to or after inoculation of greenhouse-grown lettuce with E. coli O157:H7 or S. Typhimurium; the leaf samples were collected after 0, 24, and 48 h of treatment. Bacteria from inoculated leaves were enumerated on tryptic soy agar plates (and also on MacConkey's and XLT4 agar plates), and the recovered counts were statistically analyzed. Cut lettuce leaves showed E. coli O157:H7 reduction between 3.25 and 6.17 log CFU/leaf, whereas S. Typhimurium reductions were between 2.94 log CFU/leaf and 5.47 log CFU/leaf depending on the SE treatment durations, from initial levels of ∼7 log CFU/leaf. SE treatment of lettuce in planta, before bacterial inoculation, reduced E. coli O157:H7 and S. Typhimurium populations by 1.88 and 2.49 log CFU after 24 h and 3 h, respectively. However, SE treatment after bacterial inoculation of lettuce plants decreased E. coli O157:H7 populations by 3.04 log CFU (after 0 h) with negligible reduction of S. Typhimurium populations. Our findings demonstrate the potential of SE as a plant-based method for decontaminating E. coli O157:H7 on lettuce during pre- and postharvest stages in hurdle approaches.