Internalization of Escherichia coli O157:H7 following Spraying of Cut Shoots When Leafy Greens Are Regrown for a Second Crop

2013 ◽  
Vol 76 (12) ◽  
pp. 2052-2056 ◽  
Author(s):  
MARILYN C. ERICKSON ◽  
CATHY C. WEBB ◽  
JUAN CARLOS DÍAZ-PÉREZ ◽  
LINDSEY E. DAVEY ◽  
ALISON S. PAYTON ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Irrigation Water ◽  
Tissue Repair ◽  
Contamination Level ◽  
Contaminated Water ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Leafy Greens ◽  
Spraying Plants ◽  
High Level

Both spinach and lettuce were grown to harvest, cut, and then regrown after spraying the cut shoots with irrigation water contaminated with Escherichia coli O157:H7. Plant tissue was collected on the day of spraying and again 2 and 14 days later for analysis of total and internalized E. coli O157:H7 populations. Internalization of E. coli O157:H7 occurred on the day of spraying, and larger populations were internalized as the level in the spray increased. Tissue repair was slow and insufficient to prevent infiltration of E. coli O157:H7; internalized E. coli O157:H7 in shoots cut 5 days prior to exposure to E. coli O157:H7–contaminated water were not significantly different from levels in shoots cut on the same day of spraying with contaminated water (P > 0.05). Two days after spraying plants with a high level of E. coli O157:H7 (7.3 log CFU/ml), levels of internalized E. coli O157:H7 decreased by ca. 2.6 and 1.3 log CFU/g in Tyee and Bordeaux spinach, respectively, whereas populations of internalized E. coli O157:H7 decreased very little (ca. 0.4 log CFU/g) in lettuce plants that had been sprayed either on the same day as cutting or 1 day after cutting. When cut plants were sprayed with irrigation water at a lower contamination level (4.5 log CFU/ml), internalized E. coli O157:H7 was not detected in either spinach or lettuce plants 2 days later and therefore would not likely be of concern when the crop was harvested.

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.

Persistence of Escherichia coli O157:H7 on Lettuce Plants following Spray Irrigation with Contaminated Water

2003 ◽  
Vol 66 (12) ◽  
pp. 2198-2202 ◽  
Author(s):  
ETHAN B. SOLOMON ◽  
HOAN-JEN PANG ◽  
KARL R. MATTHEWS
Keyword(s):  
Escherichia Coli ◽  
Irrigation Water ◽  
Sampling Period ◽  
Repeated Exposure ◽  
Human Consumption ◽  
Contaminated Water ◽  
Escherichia Coli O157 ◽  
Plant Leaves ◽  
E Coli ◽  
Spray Irrigation

Irrigation water collected at farms growing crops for human consumption was artificially contaminated with E. coli O157: H7 and used to irrigate lettuce plants. Plants in a growth chamber were spray irrigated either once or intermittently with water contaminated with 102 or 104 CFU of E. coli O157:H7 per ml and were then sampled over a 30-day period. Only plants exposed to 102 CFU/ml on day 1 did not harbor the pathogen at the end of the sampling period. All other treatments resulted in contaminated plants at harvest. Plants irrigated with 104 CFU/ml contained high levels (up to 5 log CFU/g) of the pathogen at harvest. The results obtained in this study underscore the assertion that spray irrigation (the application of water directly to plant leaves) is linked to the contamination of crops and suggest that repeated exposure increases the E. coli O157:H7 level on the plant.

Transfer of Escherichia coli O157:H7 from Soil, Water, and Manure Contaminated with Low Numbers of the Pathogen to Lettuce Plants

2009 ◽  
Vol 72 (11) ◽  
pp. 2308-2312 ◽  
Author(s):  
GABRIEL MOOTIAN ◽  
WEN-HSUAN WU ◽  
KARL R. MATTHEWS
Keyword(s):  
Escherichia Coli ◽  
Contaminated Soil ◽  
Human Health Risk ◽  
Contaminated Water ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Leafy Greens ◽  
Entire Plant ◽  
Sources Of Contamination ◽  
Amended Soil

The sources of contamination of leafy greens remain unclear, but it is evident that contaminated water, soil amendments, and wildlife likely contribute. The objective of the present study was to determine transfer of low numbers of Escherichia coli O157:H7 from soil, manure-amended soil, and water to growing lettuce plants. Lettuce plants, young (12 days of age) or mature (30 days of age), were grown in soil, manure-amended soil, or irrigated with water containing 101, 102, 103, or 104 CFU E. coli O157:H7 per g or ml. Harvested plants were processed to determine whether E. coli O157:H7 was associated with the entire plant or within internal locations. Young plants (12 days) were harvested at 1, 10, 20, and 30 days postexposure. No samples were positive for E. coli O157:H7 after direct plating of serial dilutions. Enrichment of all samples from young plants exposed to contaminated soil, manure-amended soil, and irrigation water demonstrated that approximately 21% (113 of 552) of plants were positive for E. coli O157:H7. Approximately 30% (36 of 120) of the mature plants initially irrigated with or grown in contaminated soil (including manure-amended soil) for 15 days were positive for E. coli O157:H7. Based on sterilization of surface tissue, E. coli O157:H7 was in protected locations of lettuce tissue. The results suggest that lettuce exposed to, and grown in the presence of, low numbers of E. coli O157:H7 may become contaminated and thus present a human health risk.

Surface and Internalized Escherichia coli O157:H7 on Field-Grown Spinach and Lettuce Treated with Spray-Contaminated Irrigation Water

2010 ◽  
Vol 73 (6) ◽  
pp. 1023-1029 ◽  
Author(s):  
MARILYN C. ERICKSON ◽  
CATHY C. WEBB ◽  
JUAN CARLOS DIAZ-PEREZ ◽  
SHARAD C. PHATAK ◽  
JOHN J. SILVOY ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Irrigation Water ◽  
Enrichment Culture ◽  
Field Studies ◽  
Plate Count ◽  
Escherichia Coli O157 ◽  
Adaxial Side ◽  
Abaxial Side ◽  
E Coli ◽  
Contaminated Irrigation Water

Numerous field studies have revealed that irrigation water can contaminate the surface of plants; however, the occurrence of pathogen internalization is unclear. This study was conducted to determine the sites of Escherichia coli O157:H7 contamination and its survival when the bacteria were applied through spray irrigation water to either field-grown spinach or lettuce. To differentiate internalized and surface populations, leaves were treated with a surface disinfectant wash before the tissue was ground for analysis of E. coli O157:H7 by direct plate count or enrichment culture. Irrigation water containing E. coli O157:H7 at 102, 104, or 106 CFU/ml was applied to spinach 48 and 69 days after transplantation of seedlings into fields. E. coli O157:H7 was initially detected after application on the surface of plants dosed at 104 CFU/ml (4 of 20 samples) and both on the surface (17 of 20 samples) and internally (5 of 20 samples) of plants dosed at 106 CFU/ml. Seven days postspraying, all spinach leaves tested negative for surface or internal contamination. In a subsequent study, irrigation water containing E. coli O157:H7 at 108 CFU/ml was sprayed onto either the abaxial (lower) or adaxial (upper) side of leaves of field-grown lettuce under sunny or shaded conditions. E. coli O157:H7 was detectable on the leaf surface 27 days postspraying, but survival was higher on leaves sprayed on the abaxial side than on leaves sprayed on the adaxial side. Internalization of E. coli O157:H7 into lettuce leaves also occurred with greater persistence in leaves sprayed on the abaxial side (up to 14 days) than in leaves sprayed on the adaxial side (2 days).

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.

Fate of Escherichia coli O157:H7 and Other Coliforms in Commercial Mayonnaise and Refrigerated Salad Dressing

1995 ◽  
Vol 58 (1) ◽  
pp. 13-18 ◽  
Author(s):  
ERROL V. RAGHUBEER ◽  
JIM S. KE ◽  
MICHAEL L. CAMPBELL ◽  
RICHARD S. MEYER
Keyword(s):  
Escherichia Coli ◽  
Storage Temperature ◽  
Enterobacter Aerogenes ◽  
Antimicrobial Effect ◽  
Coliform Bacteria ◽  
Escherichia Coli O157 ◽  
Salad Dressing ◽  
E Coli ◽  
Survival Pattern ◽  
High Level

Commercial mayonnaise and refrigerated ranch salad dressing were inoculated at two levels with two strains of Escherichia coli O157:H7, a non-pathogenic E. coli, and the non-fecal coliform Enterobacter aerogenes. Results showed that at the high inoculation level (>106 colony forming units [CFU]/g) in mayonnaise stored at room temperature (ca. 22°C) both strains of O157:H7 were undetected at 96 h. At the high inoculation level, all strains of coliform bacteria tested survived longer in salad dressing stored at 4°C than in mayonnaise stored at 22°C. The O157:H7 strains were still present at low levels after 17 days. The survival time in the low-level inoculum (104CFU/g) study decreased, but the survival pattern in the two products was similar to that observed in the high-level inoculum study. Slight differences in survival among strains were observed. The greater antimicrobial effect of mayonnaise may be attributable to differences in pH, water activity (aw), nutrients, storage temperature, and the presence of lysozyme in the whole eggs used in the production of commercial mayonnaise. Coliform bacteria survived longer in refrigerated salad dressing than in mayonnaise particularly at the high-level inoculum. Both mayonnaise (pH 3.91) and salad dressing (pH 4.51) did not support the growth of any of the microorganisms even though survival was observed.

A Comparison of the Survival in Feces and Water of Escherichia coli O157:H7 Grown under Laboratory Conditions or Obtained from Cattle Feces

2006 ◽  
Vol 69 (1) ◽  
pp. 6-11 ◽  
Author(s):  
L. SCOTT ◽  
P. McGEE ◽  
J. J. SHERIDAN ◽  
B. EARLEY ◽  
N. LEONARD
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogen ◽  
Hemorrhagic Colitis ◽  
Contaminated Water ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Cattle Feces ◽  
Oral Inoculation ◽  
Before And After ◽  
Uremic Syndrome

Escherichia coli O157:H7 is an important foodborne pathogen that can cause hemorrhagic colitis and hemolytic uremic syndrome. Cattle feces and fecally contaminated water are important in the transmission of this organism on the farm. In this study, the survival of E. coli O157:H7 in feces and water was compared following passage through the animal digestive tract or preparation in the laboratory. Feces were collected from steers before and after oral inoculation with a marked strain of E. coli O157:H7. Fecal samples collected before cattle inoculation were subsequently inoculated with the marked strain of E. coli O157:H7 prepared in the laboratory. Subsamples were taken from both animal and laboratory-inoculated feces to inoculate 5-liter volumes of water. E. coli O157:H7 in feces survived up to 97 days, and survival was not affected by the method used to prepare the inoculating strain. E. coli O157:H7 survived up to 109 days in water, and the bacteria collected from inoculated cattle were detected up to 10 weeks longer than the laboratory-prepared culture. This study suggests that pathogen survival in low-nutrient conditions may be enhanced by passage through the gastrointestinal tract.

Transfer of Escherichia coli O157:H7 to Romaine Lettuce due to Contact Water from Melting Ice

2008 ◽  
Vol 71 (2) ◽  
pp. 252-256 ◽  
Author(s):  
JIN KYUNG KIM ◽  
MARK A. HARRISON
Keyword(s):  
Escherichia Coli ◽  
Tap Water ◽  
Sampling Site ◽  
Contaminated Water ◽  
Escherichia Coli O157 ◽  
Romaine Lettuce ◽  
E Coli ◽  
Ice Melt ◽  
Leaf Surfaces ◽  
Shipping Containers

Ice can be used to chill romaine lettuce and maintain relative humidity during transportation. Escherichia coli O157:H7 may contaminate water used for ice. The objective of this study was to determine the potential for E. coli O157:H7 contamination of romaine lettuce from either ice contaminated with the pathogen or by transfer from lettuce surfaces via melting ice. In experiment 1, lettuce was spot inoculated with E. coli O157:H7 and chilled with ice prepared from uncontaminated tap water. In experiment 2, water inoculated with this pathogen was frozen and used to ice lettuce. Three heads of lettuce were stacked in each container and stored at 4 or 20°C. After the ice melted, E. coli O157:H7 attachment to and recovery from the lettuce leaves were determined. For experiment 1, the population of E. coli O157:H7 attached to inoculated sites averaged 3.8 and 5.5 CFU/cm2 at 4 and 20°C, respectively. Most of the uninoculated sites became contaminated with the pathogen due to ice melt. For experiment 2, 3.5 to 3.8 log CFU E. coli O157:H7 per cm2 was attached to the top leaf on the first head. After rinsing with chlorinated water (200 μg/ml), E. coli O157:H7 remained on the surface of the top head (1.8 to 2.0 log CFU/cm2). There was no difference in numbers of E. coli O157:H7 recovered from each sampling site at 4 and 20°C. Results show that E. coli O157:H7 can be transferred onto other produce layers in shipping containers from melted ice made of contaminated water and from contaminated to uncontaminated leaf surfaces.

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.

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