Relative Efficacy of Sodium Hypochlorite Wash Versus Irradiation To Inactivate Escherichia coli O157:H7 Internalized in Leaves of Romaine Lettuce and Baby Spinach†

2007 ◽  
Vol 70 (11) ◽  
pp. 2526-2532 ◽  
Author(s):  
BRENDAN A. NIEMIRA
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Ionizing Radiation ◽  
Sodium Hypochlorite ◽  
Escherichia Coli O157 ◽  
Romaine Lettuce ◽  
E Coli ◽  
Perfusion Process ◽  
Scanning Electron ◽  
Spinach Leaves

Pathogenic bacteria that become internalized in leaf tissues are protected from the antimicrobial effects of surface treatments. Ionizing radiation is known to penetrate food tissues, but the efficacy of the process against internalized bacteria is unknown. Leaves of Romaine lettuce and baby spinach were cut into pieces, submerged in a cocktail mixture of three isolates of Escherichia coli O157:H7, and subjected to a vacuum perfusion process to force the bacterial cells into the intercellular spaces in the leaves. Scanning electron microscopy was used to evaluate the efficacy of the perfusion process. The inoculated leaves were then treated with a 3-min water wash, a 3-min wash with a sodium hypochlorite sanitizing solution (300 or 600 ppm), or various doses of ionizing radiation (0.25 to 1.5 kGy). Leaves were stomached to recover the internalized pathogen cells, which were enumerated. The vacuum perfusion effectively forced bacteria into the leaf vasculature and apoplast, as confirmed by scanning electron microscopy. For spinach leaf pieces, neither the water nor the sodium hypochlorite washes resulted in significant reductions of E. coli O157:H7 cells relative to the untreated control. For Romaine lettuce leaf pieces, 300 and 600 ppm sodium hypochlorite each resulted in less than 1-log reduction; water wash was ineffective. Ionizing radiation, in contrast, significantly reduced the pathogen population, with 4-log (Romaine lettuce) or 3-log (spinach) reductions at the highest dose tested. In Romaine leaves, the reduction was dose dependent across the range of doses tested, with a D10-value (the amount of irradiation necessary to reduce the population by 1 log unit) of 0.39 kGy. In spinach leaves, the pathogen had a biphasic response, with a D10-value of 0.27 kGy in the range of 0 to 0.75 kGy but only slight additional reductions from 0.75 to 1.5 kGy. In this study, ionizing radiation but not chemical sanitizers effectively reduced viable E. coli O157:H7 cells internalized in leafy green vegetables, but the response of the pathogen to irradiation was more complex in spinach leaves than in Romaine lettuce leaves.

Evidence for Escherichia coli O157:H7 Attachment to Water Distribution Pipe Materials by Scanning Electron Microscopy

2002 ◽  
Vol 65 (12) ◽  
pp. 1970-1975 ◽  
Author(s):  
MAFU AKIER ASSANTA ◽  
DENIS ROY ◽  
MARIE-JOSÉE LEMAY ◽  
DIANE MONTPETIT
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Scanning Electron Microscopy ◽  
Water Distribution ◽  
Escherichia Coli O157 ◽  
Exposure Condition ◽  
Copper Surfaces ◽  
E Coli ◽  
Plastic Surfaces ◽  
Scanning Electron

Scanning electron microscopy observation was used to investigate the adhesion of Escherichia coli O157:H7 on water distribution pipe surfaces such as copper and polyethylene plastic at different contact times and storage temperatures. Our results indicated that E. coli cells could easily attach to both surface types after exposures as short as 1 or 4 h at ambient (20°C) and refrigeration temperatures (4°C). Also, we found that copper surfaces have a higher number of attached E. coli cells than plastic surfaces. The number of cells attached to each type of material depended on the nature of the water distribution pipe surfaces and the length of contact time. In addition, the surface energy value of each surface estimated by contact angle measurements using water, ∝-bromonaphthalene, and dimethyl sulfoxide as wetting agents showed that both copper (41.2 megajoules [MJ]·m−2) and plastic (45.8 MJ·m−2) have a low energy surface. In no cases could evidence of extracellular material be observed on surfaces with either exposure condition.

scholarly journals Enterohemorrhagic Escherichia coli O157:H7 Present in Radish Sprouts

1998 ◽  
Vol 64 (4) ◽  
pp. 1532-1535 ◽  
Author(s):  
Yoshinori Itoh ◽  
Yoshiko Sugita-Konishi ◽  
Fumiko Kasuga ◽  
Masaaki Iwaki ◽  
Yukiko Hara-Kudo ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Scanning Electron Microscopy ◽  
Outer Surface ◽  
Immunofluorescence Microscopy ◽  
Enterohemorrhagic Escherichia Coli ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Radish Sprouts ◽  
Scanning Electron

ABSTRACT Using cultivation, immunofluorescence microscopy, and scanning electron microscopy, we demonstrated the presence of viable enterohemorrhagic Escherichia coli O157:H7 not only on the outer surfaces but also in the inner tissues and stomata of cotyledons of radish sprouts grown from seeds experimentally contaminated with the bacterium. HgCl2 treatment of the outer surface of the hypocotyl did not kill the contaminating bacteria, which emphasized the importance of either using seeds free from E. coli O157:H7 in the production of radish sprouts or heating the sprouts before they are eaten.

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.

scholarly journals N-halamine antibacterial nanofibrous mats based on polyacrylonitrile and N-halamine for protective face masks

2019 ◽  
Vol 14 ◽  
pp. 155892501984322 ◽  
Author(s):  
Chengbo Huang ◽  
Ying Liu ◽  
Zhiguang Li ◽  
Rong Li ◽  
Xuehong Ren ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Scanning Electron Microscopy ◽  
Air Permeability ◽  
Escherichia Coli O157 ◽  
Electrospinning Technique ◽  
Antibacterial Materials ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Biocidal Properties ◽  
Scanning Electron

The main objective of this study was to develop antibacterial materials based on polyacrylonitrile for potential application in protective face masks to combat airborne pathogens. To achieve biocidal properties, 1-chloro-2, 2, 5, 5-tetramethyl-4-imidazolidinone as a kind of N-halamine was introduced into the polyacrylonitrile nanofibers by an electrospinning technique to form nanofibers by an electrospinning technique to form polyacrylonitrile/1-chloro-2, 2, 5, 5-tetramethyl-4-imidazolidinone-5% nanofibers. Scanning electron microscopy and Fourier transformed infrared spectroscopy were employed to characterize the structure of nanofibers. The antimicrobial efficacies of electrospinning nanofibers with 1-chloro-2, 2, 5, 5-tetramethyl-4-imidazolidinone against both Staphylococcus aureus and Escherichia coli O157:H7 were evaluated at different contact times. The antimicrobial efficacies against bioaerosol of S. aureus were also performed. The polyacrylonitrile/1-chloro-2, 2, 5, 5-tetramethyl-4-imidazolidinone-5% nanofibers possess excellent antimicrobial efficacies against bacteria bioaersol, and it has good air permeability.

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.

Behavior of Escherichia coli O157:H7 on Damaged Leaves of Spinach, Lettuce, Cilantro, and Parsley Stored at Abusive Temperatures

2010 ◽  
Vol 73 (2) ◽  
pp. 212-220 ◽  
Author(s):  
ROWAIDA K. KHALIL ◽  
JOSEPH F. FRANK
Keyword(s):  
Escherichia Coli ◽  
Pathogenic Bacteria ◽  
Leaf Damage ◽  
Escherichia Coli O157 ◽  
Oxidation Reactions ◽  
Leaf Extracts ◽  
Romaine Lettuce ◽  
Growth And Survival ◽  
E Coli ◽  
Additional Information

Recent foodborne illness outbreaks associated with the consumption of leafy green produce indicates a need for additional information on the behavior of pathogenic bacteria on these products. Previous research indicates that pathogen growth and survival is enhanced by leaf damage. The objective of this study was to compare the behavior of Escherichia coli O157:H7 on damaged leaves of baby Romaine lettuce, spinach, cilantro, and parsley stored at three abusive temperatures (8, 12, and 15°C). The damaged portions of leaves were inoculated with approximately 105 CFU E. coli O157:H7 per leaf. The pathogen grew on damaged spinach leaves held for 3 days at 8 and 12°C (P < 0.05), with the population increasing by 1.18 and 2.08 log CFU per leaf, respectively. E. coli O157:H7 did not grow on damaged Romaine leaves at 8 or 12°C, but growth was observed after 8 h of storage at 15°C, with an increase of less than 1.0 log. Growth of E. coli O157:H7 on Romaine lettuce held at 8 or 12°C was enhanced when inocula were suspended in 0.05% ascorbic acid, indicating the possibility of inhibition by oxidation reactions associated with tissue damage. Damaged cilantro and Italian parsley leaves held at 8°C for 4 days did not support the growth of E. coli O157:H7. Behavior of the pathogen in leaf extracts differed from behavior on the damaged tissue. This study provides evidence that the damaged portion of a leafy green is a distinct growth niche that elicits different microbial responses in the various types of leafy greens.

Impact of Preinoculation Culture Conditions on the Behavior of Escherichia coli O157:H7 Inoculated onto Romaine Lettuce (Lactuca sativa) Plants and Cut Leaf Surfaces

2009 ◽  
Vol 72 (7) ◽  
pp. 1553-1559 ◽  
Author(s):  
CHRISTOPHER G. THEOFEL ◽  
LINDA J. HARRIS
Keyword(s):  
Escherichia Coli ◽  
High Standard ◽  
Culture Conditions ◽  
Escherichia Coli O157 ◽  
Late Stationary Phase ◽  
Romaine Lettuce ◽  
Preparation Methods ◽  
E Coli ◽  
Leaf Surfaces ◽  
Inoculum Preparation

Inoculum preparation methods can impact growth or survival of organisms inoculated into foods, thus complicating direct comparison of results among studies. The objective of this study was to evaluate preinoculation culture preparation for impact on Escherichia coli O157:H7 inoculated onto leaves of romaine lettuce plants and cut leaf surfaces. E. coli O157:H7 was grown quiescently or shaken at 15, 25, or 37°C to different growth phases in tryptic soy or M9 minimal salts broth or agar. Cells were harvested, washed, and suspended in 0.1% peptone, Milli Q water, or well water and refrigerated for 0 or 18 h. Prepared inoculum was spotted onto cut romaine lettuce (10 μl; 3 × 104 CFU/10 g) or onto romaine lettuce plants (20 μl; 3 × 106 CFU per leaf). Cut lettuce was sealed in 100-cm2 bags (made from a commercial polymer film) and incubated at 5 or 20°C. Lettuce plants were held at 23°C for 24 h. For all tested conditions, levels of E. coli O157:H7 increased at 20°Concut lettuce and decreased on cut lettuce stored at 5°C or on leaves of lettuce plants. At 20°C, preinoculation culture conditions had little impact on growth of E. coli O157:H7 on cut lettuce. However, survival at 5°C was significantly better (P < 0.05) for cultures grown at 15 or 37°C in minimal medium and to late stationary phase. Impact of preinoculation handling on survival on lettuce plants was less clear due to relatively high standard deviations observed among samples.

Factors Influencing Attachment of Escherichia coli O157:H7 to Beef Tissues and Removal Using Selected Sanitizing Rinses‡

1996 ◽  
Vol 59 (5) ◽  
pp. 453-459 ◽  
Author(s):  
PINA M. FRATAMICO ◽  
FRANKIE J. SCHULTZ ◽  
ROBERT C. BENEDICT ◽  
ROBERT L. BUCHANAN ◽  
PETER H. COOKE
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Surface Structures ◽  
Escherichia Coli O157 ◽  
Adipose Tissues ◽  
E Coli ◽  
Factors Influencing ◽  
Significant Difference ◽  
Phosphate Buffered Saline ◽  
Scanning Electron

Attachment of E. coli O157:H7 and E. coli K12 to beef tenderloin filet, chuck, and adipose tissues was studied. Most attachment occurred within 1 min of incubation; the number of attached organisms depended on the concentration of bacteria in the liquid inoculum. Similar levels of E. coli bound to the three types of beef tissues tested. E. coli O157:H7 was heavily piliated; however, there was no significant difference between levels of bound E. coli O157:H7 and E. coli K12, indicating that these surface structures apparently are not involved in attachment. Scanning electron photomicrographs of meat tissue and of purified collagen suggested that bacteria attached primarily to collagen fibers. Rinsing solutions consisting of 10% trisodium phosphate (TSP), 2% acetic acid (HAc), phosphate-buffered saline (PBS) and combinations of each were tested for effectiveness in reducing the number of attached E. coli. The level of bacteria removed from tenderloin tissue following TSP, HAc, or PBS rinses did not differ considerably. When beef tissues were stored at 4°C for 18 h after the various rinse combinations, TSP rinse treatments reduced the levels of E. coli K12 and O157:H7 attached to adipose tissue up to 3.4 and 2.7 log units, respectively, compared to PBS rinse treatments. Therefore, TSP may be effective for reducing populations of E. coli O157:H7 on beef carcass tissue.

Comparative Examination of Escherichia coli O157:H7 Survival on Romaine Lettuce and in Soil at Two Independent Experimental Sites

2012 ◽  
Vol 75 (3) ◽  
pp. 480-487 ◽  
Author(s):  
GREG BEZANSON ◽  
PASCAL DELAQUIS ◽  
SUSAN BACH ◽  
ROBIN McKELLAR ◽  
ED TOPP ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Nalidixic Acid ◽  
Abiotic Factors ◽  
Decay Rates ◽  
Escherichia Coli O157 ◽  
Production Environment ◽  
Romaine Lettuce ◽  
Ecological Fitness ◽  
E Coli ◽  
Significant Difference

Little is known about the influence of abiotic factors such as climate and soil chemistry on the survival of Escherichia coli O157:H7 in field lettuce. We applied a nalidixic acid–resistant derivative of strain ATCC 700728 to field-grown romaine lettuce in two regions in Canada characterized by large variances in soil type and climate. Surviving populations in soil and on lettuce leaves were estimated on sorbitol MacConkey agar supplemented with nalidixic acid. Data were fitted with the Weibull decline function to permit comparison of decay rates in the two experimental sites. E. coli O157:H7 populations fell from 105 to <102 CFU/g on leaves, and <103 CFU/g in soil within 7 days after inoculation. Analysis revealed there was no significant difference between decay rates at the two experimental sites in either environment. The results of this study suggest that the inherent ecological fitness of E. coli O157:H7 ATCC 700728 determines the extent of survival in the production environment.

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

Sign in / Sign up

Export Citation Format

Share Document