Inactivation of Stressed Escherichia coli O157:H7 Cells on the Surfaces of Rocket Salad Leaves by Chlorine and Peroxyacetic Acid

2014 ◽  
Vol 77 (1) ◽  
pp. 32-39 ◽  
Author(s):  
ANAS A. AL-NABULSI ◽  
TAREQ M. OSAILI ◽  
HEBA M. OBAIDAT ◽  
REYAD R. SHAKER ◽  
SADDAM S. AWAISHEH ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Deionized Water ◽  
Escherichia Coli O157 ◽  
Apparent Difference ◽  
Peroxyacetic Acid ◽  
Surface Disinfection ◽  
E Coli ◽  
Leafy Greens ◽  
Foodborne Outbreaks ◽  
Stressed Cells

Because Escherichia coli O157:H7 has been frequently associated with many foodborne outbreaks caused by consumption of leafy greens (lettuce, spinach, and celery), this study investigated the ability of deionized water, chlorine, and peroxyacetic acid to detach or inactivate stressed and unstressed cells of E. coli O157:H7 contaminating the surfaces of rocket salad leaves. E. coli O157:H7 cells stressed by acid, cold, starvation, or NaCl exposure, as well as unstressed cells, were inoculated on the surfaces of rocket salad leaves at 4°C. The effectiveness of two sanitizers (200 ppm of chlorine and 80 ppm of peroxyacetic acid) and deionized water for decontaminating the leaves treated with stressed and unstressed E. coli O157:H7 were evaluated during storage at 10 or 25°C for 0.5, 1, 3, and 7 days. It was found that washing with 80 ppm of peroxyacetic acid was more effective and reduced unstressed and stressed cells of E. coli O157:H7 by about 1 log CFU per leaf on the leaves. There was no apparent difference in the ability of stressed and unstressed cells to survive surface disinfection with the tested agents. Treatments to reduce viable E. coli O157:H7 cells on rocket leaves stored at 25°C were more effective than when used on those stored at 10°C. Washing with peroxyacetic acid or chlorine solution did not ensure the safety of rocket leaves, but such treatments could reduce the likelihood of water-mediated transfer of E. coli O157:H7 during washing and subsequent processing.

Tracking an Escherichia coli O157:H7–Contaminated Batch of Leafy Greens through a Pilot-Scale Fresh-Cut Processing Line

2014 ◽  
Vol 77 (9) ◽  
pp. 1487-1494 ◽  
Author(s):  
ANNEMARIE L. BUCHHOLZ ◽  
GORDON R. DAVIDSON ◽  
BRADLEY P. MARKS ◽  
EWEN C. D. TODD ◽  
ELLIOT T. RYSER
Keyword(s):  
Escherichia Coli ◽  
Membrane Filtration ◽  
Fluorescent Protein ◽  
Pilot Scale ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Leafy Greens ◽  
Iceberg Lettuce ◽  
Processing Line ◽  
Fresh Cut

Cross-contamination of fresh-cut leafy greens with residual Escherichia coli O157:H7–contaminated product during commercial processing was likely a contributing factor in several recent multistate outbreaks. Consequently, radicchio was used as a visual marker to track the spread of the contaminated product to iceberg lettuce in a pilot-scale processing line that included a commercial shredder, step conveyor, flume tank, shaker table, and centrifugal dryer. Uninoculated iceberg lettuce (45 kg) was processed, followed by 9.1 kg of radicchio (dip inoculated to contain a four-strain, green fluorescent protein–labeled nontoxigenic E. coli O157:H7 cocktail at 106 CFU/g) and 907 kg (2,000 lb) of uninoculated iceberg lettuce. After collecting the lettuce and radicchio in about 40 bags (~22.7 kg per bag) along with water and equipment surface samples, all visible shreds of radicchio were retrieved from the bags of shredded product, the equipment, and the floor. E. coli O157:H7 populations were quantified in the lettuce, water, and equipment samples by direct plating with or without prior membrane filtration on Trypticase soy agar containing 0.6% yeast extract and 100 ppm of ampicillin. Based on triplicate experiments, the weight of radicchio in the shredded lettuce averaged 614.9 g (93.6%), 6.9 g (1.3%), 5.0 g (0.8%), and 2.8 g (0.5%) for bags 1 to 10, 11 to 20, 21 to 30, and 31 to 40, respectively, with mean E. coli O157:H7 populations of 1.7, 1.2, 1.1, and 1.1 log CFU/g in radicchio-free lettuce. After processing, more radicchio remained on the conveyor (9.8 g; P < 0.05), compared with the shredder (8.3 g), flume tank (3.5 g), and shaker table (0.1 g), with similar E. coli O157:H7 populations (P > 0.05) recovered from all equipment surfaces after processing. These findings clearly demonstrate both the potential for the continuous spread of contaminated lettuce to multiple batches of product during processing and the need for improved equipment designs that minimize the buildup of residual product during processing.

Reduction of Escherichia coli O157:H7 Counts on Whole Fresh Apples by Treatment with Sanitizers

2000 ◽  
Vol 63 (6) ◽  
pp. 703-708 ◽  
Author(s):  
MARCY A. WISNIEWSKY ◽  
BONITA A. GLATZ ◽  
MARK L. GLEASON ◽  
CHERYLL A. REITMEIER
Keyword(s):  
Escherichia Coli ◽  
Chlorine Dioxide ◽  
Phosphate Buffer ◽  
Phosphate Buffer Solution ◽  
Escherichia Coli O157 ◽  
Peroxyacetic Acid ◽  
Water Control ◽  
Buffer Solution ◽  
E Coli ◽  
Log Reduction

The objectives of this study were to determine if washing of whole apples with solutions of three different sanitizers (peroxyacetic acid, chlorine dioxide, or a chlorine-phosphate buffer solution) could reduce a contaminating nonpathogenic Escherichia coli O157:H7 population by 5 logs and at what sanitizer concentration and wash time such a reduction could be achieved. Sanitizers were tested at 1, 2, 4, 8, and 16 times the manufacturer's recommended concentration at wash times of 5, 10, and 15 min. Whole, sound Braeburn apples were inoculated with approximately 1 × 108 or 7 × 106 CFU per apple, stored for 24 h, then washed with sterile water (control) or with sanitizers for the prescribed time. Recovered bacteria were enumerated on trypticase soy agar. Washing with water alone reduced the recoverable population by almost 2 logs from the starting population; this can be attributed to physical removal of organisms from the apple surface. No sanitizer, when used at the recommended concentration, reduced the recovered E. coli population by 5 logs under the test conditions. The most effective sanitizer, peroxyacetic acid, achieved a 5-log reduction when used at 2.1 to 14 times its recommended concentration, depending on the length of the wash time. The chlorine-phosphate buffer solution reduced the population by 5 logs when used at 3 to 15 times its recommended concentration, depending on wash time. At no concentration or wash time tested did chlorine dioxide achieve the 5-log reduction.

Effects of Water Source, Dilution, Storage, and Bacterial and Fecal Loads on the Efficacy of Electrolyzed Oxidizing Water for the Control of Escherichia coli O157:H7

2004 ◽  
Vol 67 (7) ◽  
pp. 1377-1383 ◽  
Author(s):  
S. M. L. STEVENSON ◽  
S. R. COOK ◽  
S. J. BACH ◽  
T. A. McALLISTER
Keyword(s):  
Escherichia Coli ◽  
Bactericidal Activity ◽  
Storage Temperature ◽  
Uv Light ◽  
Tap Water ◽  
Organic Matter Content ◽  
Water Source ◽  
Deionized Water ◽  
Escherichia Coli O157 ◽  
E Coli

To evaluate the potential of using electrolyzed oxidizing (EO) water for controlling Escherichia coli O157:H7 in water for livestock, the effects of water source, electrolyte concentration, dilution, storage conditions, and bacterial or fecal load on the oxidative reduction potential (ORP) and bactericidal activity of EO water were investigated. Anode and combined (7:3 anode:cathode, vol/vol) EO waters reduced the pH and increased the ORP of deionized water, whereas cathode EO water increased pH and lowered ORP. Minimum concentrations (vol/vol) of anode and combined EO waters required to kill 104 CFU/ml planktonic suspensions of E. coli O157:H7 strain H4420 were 0.5 and 2.0%, respectively. Cathode EO water did not inhibit H4420 at concentrations up to 16% (vol/vol). Higher concentrations of anode or combined EO water were required to elevate the ORP of irrigation or chlorinated tap water compared with that of deionized water. Addition of feces to EO water products (0.5% anode or 2.0% combined, vol/vol) significantly reduced (P < 0.001) their ORP values to <700 mV in all water types. A relationship between ORP and bactericidal activity of EO water was observed. The dilute EO waters retained the capacity to eliminate a 104 CFU/ml inoculation of E. coli O157:H7 H4420 for at least 70 h regardless of exposure to UV light or storage temperature (4 versus 24°C). At 95 h and beyond, UV exposure reduced ORP, significantly more so (P < 0.05) in open than in closed containers. Bactericidal activity of EO products (anode or combined) was lost in samples in which ORP value had fallen to ≤848 mV. When stored in the dark, the diluted EO waters retained an ORP of >848 mV and bactericidal efficacy for at least 125 h; with refrigeration (4°C), these conditions were retained for at least 180 h. Results suggest that EO water may be an effective means by which to control E. coli O157:H7 in livestock water with low organic matter content.

Infrequent Internalization of Escherichia coli O157:H7 into Field-Grown Leafy Greens

2010 ◽  
Vol 73 (3) ◽  
pp. 500-506 ◽  
Author(s):  
MARILYN C. ERICKSON ◽  
CATHY C. WEBB ◽  
JUAN CARLOS DIAZ-PEREZ ◽  
SHARAD C. PHATAK ◽  
JOHN J. SILVOY ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Irrigation Water ◽  
Field Studies ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Leafy Greens ◽  
Contaminated Irrigation Water ◽  
Green Fluorescent ◽  
Field Plots ◽  
Spinach Leaves

Several sources of contamination of fresh produce by Escherichia coli O157:H7 (O157) have been identified and include contaminated irrigation water and improperly composted animal waste; however, field studies evaluating the potential for internalization of O157 into leafy greens from these sources have not been conducted. Irrigation water inoculated with green fluorescent plasmid–labeled Shiga toxin–negative strains (50 ml of 102, 104, or 106 CFU of O157 per ml) was applied to soil at the base of spinach plants of different maturities in one field trial. In a second trial, contaminated compost (1.8 kg of 103 or 105 CFU of O157 per g) was applied to field plots (0.25 by 3.0 m) prior to transplantation of spinach, lettuce, or parsley plants. E. coli O157:H7 persisted in the soil up to harvest (day 76 posttransplantation) following application of contaminated irrigation water; however, internalized O157 was not detected in any spinach leaves or in roots exposed to O157 during the early or late growing season. Internalized O157 was detected in root samples collected 7 days after plants were contaminated in mid-season, with 5 of 30 samples testing positive for O157 by enrichment; however, O157 was not detected by enrichment in surface-disinfected roots on days 14 or 22. Roots and leaves from transplanted spinach, lettuce, and parsley did not internalize O157 for up to 50 days in the second trial. These results indicate that internalization of O157 via plant roots in the field is rare and when it does occur, O157 does not persist 7 days later.

Effect of Modified Atmosphere Packaging on the Persistence and Expression of Virulence Factors of Escherichia coli O157:H7 on Shredded Iceberg Lettuce†

2011 ◽  
Vol 74 (5) ◽  
pp. 718-726 ◽  
Author(s):  
MANAN SHARMA ◽  
SUDESNA LAKSHMAN ◽  
SEAN FERGUSON ◽  
DAVID T. INGRAM ◽  
YAGUANG LUO ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Virulence Factors ◽  
Modified Atmosphere Packaging ◽  
Ambient Air ◽  
Modified Atmosphere ◽  
Escherichia Coli O157 ◽  
Atmospheric Conditions ◽  
E Coli ◽  
Leafy Greens ◽  
Fresh Cut

Fresh-cut leafy greens contaminated with Escherichia coli O157:H7 have caused foodborne outbreaks. Packaging conditions, coupled with abusive storage temperatures of contaminated lettuce, were evaluated for their effect on the potential virulence of E. coli O157:H7. Shredded lettuce was inoculated with 5.58 and 3.98 log CFU E. coli O157:H7 per g and stored at 4 and 15°C, respectively, for up to 10 days. Lettuce was packaged under treatment A (modified atmosphere packaging conditions used for commercial fresh-cut produce, in gas-permeable film with N2), treatment B (near–ambient air atmospheric conditions in a gas-permeable film with microperforations), and treatment C (high-CO2 and low-O2 conditions in a gas-impermeable film). E. coli O157:H7 populations from each treatment were determined by enumeration of numbers on MacConkey agar containing nalidixic acid. RNA was extracted from packaged lettuce for analysis of expression of virulence factor genes stx2, eae, ehxA, iha, and rfbE. E. coli O157:H7 populations on lettuce at 4°C under all treatments decreased, but most considerably so under treatment B over 10 days. At 15°C, E. coli O157:H7 populations increased by at least 2.76 log CFU/g under all treatments. At 15°C, expression of eae and iha was significantly greater under treatment B than it was under treatments A and C on day 3. Similarly, treatment B promoted significantly higher expression of stx2, eae, ehxA, and rfbE genes on day 10, compared with treatments A and C at 15°C. Results indicate that storage under near–ambient air atmospheric conditions can promote higher expression levels of O157 virulence factors on lettuce, and could affect the severity of E. coli O157:H7 infections associated with leafy greens.

Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on Plastic Kitchen Cutting Boards by Electrolyzed Oxidizing Water

1999 ◽  
Vol 62 (8) ◽  
pp. 857-860 ◽  
Author(s):  
KUMAR S. VENKITANARAYANAN ◽  
GABRIEL O. I. EZEIKE ◽  
YEN-CON HUNG ◽  
MICHAEL P. DOYLE
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Laminar Flow ◽  
Foodborne Pathogens ◽  
Deionized Water ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Laminar Flow Hood ◽  
Cutting Boards ◽  
Temperature Time

One milliliter of culture containing a five-strain mixture of Escherichia coli O157:H7 (∼1010 CFU) was inoculated on a 100-cm2 area marked on unscarred cutting boards. Following inoculation, the boards were air-dried under a laminar flow hood for 1 h, immersed in 2 liters of electrolyzed oxidizing water or sterile deionized water at 23°C or 35°C for 10 or 20 min; 45°C for 5 or 10 min; or 55°C for 5 min. After each temperature–time combination, the surviving population of the pathogen on cutting boards and in soaking water was determined. Soaking of inoculated cutting boards in electrolyzed oxidizing water reduced E. coli O157:H7 populations by ≥5.0 log CFU/100 cm2 on cutting boards. However, immersion of cutting boards in deionized water decreased the pathogen count only by 1.0 to 1.5 log CFU/100 cm2. Treatment of cutting boards inoculated with Listeria monocytogenes in electrolyzed oxidizing water at selected temperature–time combinations (23°C for 20 min, 35°C for 10 min, and 45°C for 10 min) substantially reduced the populations of L. monocytogenes in comparison to the counts recovered from the boards immersed in deionized water. E. coli O157:H7 and L. monocytogenes were not detected in electrolyzed oxidizing water after soaking treatment, whereas the pathogens survived in the deionized water used for soaking the cutting boards. This study revealed that immersion of kitchen cutting boards in electrolyzed oxidizing water could be used as an effective method for inactivating foodborne pathogens on smooth, plastic cutting boards.

Growth of Escherichia coli O157:H7 and Listeria monocytogenes in Packaged Fresh-Cut Romaine Mix at Fluctuating Temperatures during Commercial Transport, Retail Storage, and Display

2014 ◽  
Vol 77 (2) ◽  
pp. 197-206 ◽  
Author(s):  
WENTING ZENG ◽  
KEITH VORST ◽  
WYATT BROWN ◽  
BRADLEY P. MARKS ◽  
SANGHYUP JEONG ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Large Scale ◽  
Microbial Growth ◽  
Escherichia Coli O157 ◽  
Temperature Profiles ◽  
E Coli ◽  
Leafy Greens ◽  
Retail Display ◽  
Fluctuating Temperatures

Temperature abuse during commercial transport and retail sale of leafy greens negatively impacts both microbial safety and product quality. Consequently, the effect of fluctuating temperatures on Escherichia coli O157:H7 and Listeria monocytogenes growth in commercially-bagged salad greens was assessed during transport, retail storage, and display. Over a 16-month period, a series of time-temperature profiles for bagged salads were obtained from five transportation routes covering four geographic regions (432 profiles), as well as during retail storage (4,867 profiles) and display (3,799 profiles). Five different time-temperature profiles collected during 2 to 3 days of transport, 1 and 3 days of retail storage, and 3 days of retail display were then duplicated in a programmable incubator to assess E. coli O157:H7 and L. monocytogenes growth in commercial bags of romaine lettuce mix. Microbial growth predictions using the Koseki-Isobe and McKellar-Delaquis models were validated by comparing the root mean square error (RMSE), bias, and the acceptable prediction zone between the laboratory growth data and model predictions. Monte Carlo simulations were performed to calculate the probability distribution of microbial growth from 8,122,127,472 scenarios during transport, cold room storage, and retail display. Using inoculated bags of retail salad, E. coli O157:H7 and L. monocytogenes populations increased a maximum of 3.1 and 3.0 log CFU/g at retail storage. Both models yielded acceptable RMSEs and biases within the acceptable prediction zone for E. coli O157:H7. Based on the simulation, both pathogens generally increased <2 log CFU/g during transport, storage, and display. However, retail storage duration can significantly impact pathogen growth. This large-scale U.S. study—the first using commercial time/temperature profiles to assess the microbial risk of leafy greens—should be useful in filling some of the data gaps in current risk assessments for leafy greens.

scholarly journals Outbreaks of Escherichia coli O157:H7 Infections Linked to Romaine Lettuce in Canada from 2008 to 2018: An Analysis of Food Safety Context

2020 ◽  
Vol 83 (8) ◽  
pp. 1444-1462 ◽  
Author(s):  
GENEVIÈVE COULOMBE ◽  
ANGELA CATFORD ◽  
AMALIA MARTINEZ-PEREZ ◽  
ENRICO BUENAVENTURA
Keyword(s):  
Escherichia Coli ◽  
The United States ◽  
Escherichia Coli O157 ◽  
Romaine Lettuce ◽  
E Coli ◽  
Leafy Greens ◽  
Iceberg Lettuce ◽  
Canadian Population ◽  
The Difference ◽  
Commercial Distribution

ABSTRACT Foodborne diseases are a major cause of illness in Canada. One of the main pathogens causing cases and outbreaks of foodborne illness in Canada is Escherichia coli O157:H7. From 2008 to 2018, 11 outbreaks of E. coli O157:H7 infection in Canada were linked to leafy greens, including 7 (63.6%) linked to romaine lettuce, 2 (18.2%) linked to iceberg lettuce, and 2 (18.2%) linked to other or unspecified types of leafy greens. The consumption of lettuce in Canada, the behavior of E. coli O157:H7 on lettuce leaves, and the production practices used for romaine and iceberg lettuce do not seem to explain why a higher number of outbreaks of E. coli O157:H7 infection were linked to romaine than to iceberg lettuce. However, the difference in the shape of iceberg and romaine lettuce heads could be an important factor. Among the seven outbreaks linked to romaine lettuce in Canada between 2008 and 2018, an eastern distribution of cases was observed. Cases from western provinces were reported only twice. The consumption of romaine and iceberg lettuce by the Canadian population does not seem to explain the eastern distribution of cases observed, but the commercial distribution, travel distances, and the storage practices used for lettuce may be important factors. In the past 10 years, the majority of the outbreaks of E. coli O157:H7 infection linked to romaine lettuce occurred during the spring (March to June) and fall (September to December). The timing of these outbreaks may be explained by the availability of lettuce in Canada, the growing region transition periods in the United States, and the seasonality in the prevalence of E. coli O157:H7. The consumption of romaine lettuce by the Canadian population does not explain the timing of the outbreaks observed. HIGHLIGHTS

scholarly journals Efficacy of Electrolyzed Oxidizing Water for Inactivating Escherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes

1999 ◽  
Vol 65 (9) ◽  
pp. 4276-4279 ◽  
Author(s):  
Kumar S. Venkitanarayanan ◽  
Gabriel O. Ezeike ◽  
Yen-Con Hung ◽  
Michael P. Doyle
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Salmonella Enteritidis ◽  
Sampling Time ◽  
Deionized Water ◽  
Escherichia Coli O157 ◽  
Water Control ◽  
E Coli ◽  
Complete Inactivation ◽  
Control Samples

ABSTRACT The efficacy of electrolyzed oxidizing water for inactivatingEscherichia coli O157:H7, Salmonella enteritidis, and Listeria monocytogenes was evaluated. A five-strain mixture of E. coli O157:H7,S. enteritidis, or L. monocytogenes of approximately 108 CFU/ml was inoculated in 9 ml of electrolyzed oxidizing water (treatment) or 9 ml of sterile, deionized water (control) and incubated at 4 or 23°C for 0, 5, 10, and 15 min; at 35°C for 0, 2, 4, and 6 min; or at 45°C for 0, 1, 3, and 5 min. The surviving population of each pathogen at each sampling time was determined on tryptic soy agar. At 4 or 23°C, an exposure time of 5 min reduced the populations of all three pathogens in the treatment samples by approximately 7 log CFU/ml, with complete inactivation by 10 min of exposure. A reduction of ≥7 log CFU/ml in the levels of the three pathogens occurred in the treatment samples incubated for 1 min at 45°C or for 2 min at 35°C. The bacterial counts of all three pathogens in control samples remained the same throughout the incubation at all four temperatures. Results indicate that electrolyzed oxidizing water may be a useful disinfectant, but appropriate applications need to be validated.

Preharvest Internalization of Escherichia coli O157:H7 into Lettuce Leaves, as Affected by Insect and Physical Damage

2010 ◽  
Vol 73 (10) ◽  
pp. 1809-1816 ◽  
Author(s):  
MARILYN C. ERICKSON ◽  
JEAN LIAO ◽  
ALISON S. PAYTON ◽  
DAVID G. RILEY ◽  
CATHY C. WEBB ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Insect Pests ◽  
Enteric Pathogen ◽  
Escherichia Coli O157 ◽  
Physical Damage ◽  
E Coli ◽  
Leafy Greens ◽  
Different Populations ◽  
Pathogen Exposure ◽  
Spinach Leaves

Environmental pests may serve as reservoirs and vectors of zoonotic pathogens to leafy greens; however, it is unknown whether insect pests feeding on plant tissues could redistribute these pathogens present on the surface of leaves to internal sites. This study sought to differentiate the degree of tissue internalization of Escherichia coli O157:H7 when applied at different populations on the surface of lettuce and spinach leaves, and to ascertain whether lettuce-infesting insects or physical injury could influence the fate of either surface or internalized populations of this enteric pathogen. No internalization of E. coli O157:H7 occurred when lettuce leaves were inoculated with 4.4 log CFU per leaf, but it did occur when inoculated with 6.4 log CFU per leaf. Internalization was statistically greater when spinach leaves were inoculated on the abaxial (underside) than when inoculated on the adaxial (topside) side, and when the enteric pathogen was spread after surface inoculation. Brief exposure (~18 h) of lettuce leaves to insects (5 cabbage loopers, 10 thrips, or 10 aphids) prior to inoculation with E. coli O157:H7 resulted in significantly reduced internalized populations of the pathogen within these leaves after approximately 2 weeks, as compared with leaves not exposed to insects. Surface-contaminated leaves physically injured through file abrasions also had significantly reduced populations of both total and internalized E. coli O157:H7 as compared with nonabraded leaves 2 weeks after pathogen exposure.

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