Escherichia coli O157:H7 Biofilm Formation on Romaine Lettuce and Spinach Leaf Surfaces Reduces Efficacy of Irradiation and Sodium Hypochlorite Washes

2010 ◽  
Vol 75 (5) ◽  
pp. M270-M277 ◽  
Author(s):  
Brendan A. Niemira ◽  
Peter H. Cooke
Keyword(s):  
Escherichia Coli ◽  
Sodium Hypochlorite ◽  
Biofilm Formation ◽  
Escherichia Coli O157 ◽  
Romaine Lettuce ◽  
Leaf Surfaces ◽  
Spinach Leaf

scholarly journals Inhibition of Escherichia coli O157:H7 and Salmonella enterica Isolates on Spinach Leaf Surfaces Using Eugenol-Loaded Surfactant Micelles

Foods ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 575
Author(s):  
Songsirin Ruengvisesh ◽  
Chris R. Kerth ◽  
T. Matthew Taylor
Keyword(s):  
Escherichia Coli ◽  
Salmonella Enterica ◽  
Limit Of Detection ◽  
Sodium Dodecyl ◽  
Microbial Pathogens ◽  
Escherichia Coli O157 ◽  
Human Pathogens ◽  
Surfactant Micelles ◽  
Leaf Surfaces ◽  
Spinach Leaf

Spinach and other leafy green vegetables have been linked to foodborne disease outbreaks of Escherichia coli O157:H7 and Salmonella enterica around the globe. In this study, the antimicrobial activities of surfactant micelles formed from the anionic surfactant sodium dodecyl sulfate (SDS), SDS micelle-loaded eugenol (1.0% eugenol), 1.0% free eugenol, 200 ppm free chlorine, and sterile water were tested against the human pathogens E. coli O157:H7 and Salmonella Saintpaul, and naturally occurring microorganisms, on spinach leaf surfaces during storage at 5 °C over 10 days. Spinach samples were immersed in antimicrobial treatment solution for 2.0 min at 25 °C, after which treatment solutions were drained off and samples were either subjected to analysis or prepared for refrigerated storage. Whereas empty SDS micelles produced moderate reductions in counts of both pathogens (2.1–3.2 log10 CFU/cm2), free and micelle-entrapped eugenol treatments reduced pathogens by >5.0 log10 CFU/cm2 to below the limit of detection (<0.5 log10 CFU/cm2). Micelle-loaded eugenol produced the greatest numerical reductions in naturally contaminating aerobic bacteria, Enterobacteriaceae, and fungi, though these reductions did not differ statistically from reductions achieved by un-encapsulated eugenol and 200 ppm chlorine. Micelles-loaded eugenol could be used as a novel antimicrobial technology to decontaminate fresh spinach from microbial pathogens.

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.

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 &lt; 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.

Nanoemulsified carvacrol as a novel washing treatment reduces Escherichia coli O157:H7 on spinach and lettuce

2021 ◽  
Author(s):  
Chi-Hung Chen ◽  
Hsin-Bai Yin ◽  
Zi Teng ◽  
Suyeun Byun ◽  
Yongguang Guan ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Fresh Produce ◽  
Cell Aggregation ◽  
The United States ◽  
Water Soluble ◽  
Escherichia Coli O157 ◽  
Romaine Lettuce ◽  
Iceberg Lettuce ◽  
Leaf Surfaces ◽  
Study Support

Fresh produce continues to be the main source of foodborne illness outbreaks in the United States implicating bacterial pathogens such as Escherichia coli O157:H7 (EHEC). The efficacy of nanoemulsified carvacrol (NCR) as a washing treatment in reducing EHEC on fresh produce was investigated. Fresh baby spinach, Romaine lettuce, and Iceberg lettuce leaves (2.5 cm diameter cores) were spot-inoculated with a five-strain cocktail of nalidixic acid resistant EHEC at ~ 6 log CFU/cm 2 . After air-drying for 1 h, 20 pieces of each inoculated produce leaves were immersed in water-based treatment solutions (200 ml/group), including water alone, 25 or 50 ppm free chlorine, and 0.25% or 0.75% NCR for 2 minutes. Inoculated produce leaves without any treatment served as baseline. Produce leaves were stored at 10°C and surviving EHEC populations were enumerated on days 0, 2, 7 and 14. The viability of EHEC following NCR treatments on the fresh produce was visualized under fluorescence microscope. NCR treatment at 0.75% immediately reduced EHEC populations on Iceberg lettuce by 1.3 log CFU/cm 2 as compared to the produce treated with water alone (P&lt;0.05). Antimicrobial activity of NCR against EHEC was comparable to chlorine treatments on day 0 for all produce (P&gt;0.05). After 14-days of storage at 10°C, populations of EHEC on 0.75% NCR treated Romaine lettuce were reduced by 2.3 log CFU/cm 2 as compared to the recovery from 50 ppm chlorine treated samples (P&lt;0.05). Microscopic images revealed that EHEC cells were observed to be clustered on the baseline samples, indicating the development of cell aggregation, as compared to the scattered cells seen on NCR-treated leaf surfaces. Treatments with NCR did not significantly affect the color on the fresh produce leaves during the 14 days of storage at 10°C. Results of this study support the potential use of NCR as a water soluble natural antimicrobial wash treatment for controlling EHEC on fresh produce.

Characterization of interactions between Escherichia coli O157:H7 with epiphytic bacteria in vitro and on spinach leaf surfaces

2012 ◽  
Vol 153 (3) ◽  
pp. 351-357 ◽  
Author(s):  
Gabriela Lopez-Velasco ◽  
Heather A. Tydings ◽  
Renee R. Boyer ◽  
Joseph O. Falkinham ◽  
Monica A. Ponder
Keyword(s):  
Escherichia Coli ◽  
Escherichia Coli O157 ◽  
Epiphytic Bacteria ◽  
Leaf Surfaces ◽  
Spinach Leaf

Infrared Sensor–Based Aerosol Sanitization System for Controlling Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on Fresh Produce

2014 ◽  
Vol 77 (6) ◽  
pp. 977-980 ◽  
Author(s):  
SANG-OH KIM ◽  
JAE-WON HA ◽  
KI-HWAN PARK ◽  
MYUNG-SUB CHUNG ◽  
DONG-HYUN KANG
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Fresh Produce ◽  
Sensor Technology ◽  
Escherichia Coli O157 ◽  
Full Time ◽  
Infrared Sensor ◽  
Leaf Surfaces ◽  
Spinach Leaf

An economical aerosol sanitization system was developed based on sensor technology for minimizing sanitizer usage, while maintaining bactericidal efficacy. Aerosol intensity in a system chamber was controlled by a position-sensitive device and its infrared value range. The effectiveness of the infrared sensor–based aerosolization (ISA) system to inactivate Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on spinach leaf surfaces was compared with conventional aerosolization (full-time aerosol treated), and the amount of sanitizer consumed was determined after operation. Three pathogens artificially inoculated onto spinach leaf surfaces were treated with aerosolized peracetic acid (400 ppm) for 15, 30, 45, and 60 min at room temperature (22 ± 2°C). Using the ISA system, inactivation levels of the three pathogens were equal or better than treatment with conventional full-time aerosolization. However, the amount of sanitizer consumed was reduced by ca. 40% using the ISA system. The results of this study suggest that an aerosol sanitization system combined with infrared sensor technology could be used for transportation and storage of fresh produce efficiently and economically as a practical commercial intervention.

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.

Heat and Drought Stress during Growth of Lettuce (Lactuca sativa L.) Does Not Promote Internalization of Escherichia coli O157:H7

2009 ◽  
Vol 72 (12) ◽  
pp. 2471-2475 ◽  
Author(s):  
GUODONG ZHANG ◽  
LI MA ◽  
LARRY R. BEUCHAT ◽  
MARILYN C. ERICKSON ◽  
VANESSA H. PHELAN ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Heat Stress ◽  
Fluorescent Protein ◽  
Escherichia Coli O157 ◽  
Romaine Lettuce ◽  
E Coli ◽  
Leaf Surfaces ◽  
Green Fluorescent ◽  
And Control ◽  
Photoperiod Control

Studies were done to determine the effect of heat stress on internalization of Escherichia coli O157:H7 in lettuce subjected to different watering practices during growth. Iceberg and romaine lettuce were grown in sandy soil in an environmental chamber at 23°C during the day and 7°C at night, with a 12-h photoperiod. Thirty days after transplanting seedlings, potting soil was inoculated with a five-strain mixture of green fluorescent protein–labeled E. coli O157:H7 at populations of 4 and 6 log CFU/g of soil. Lettuce plants were exposed to one of two temperature stress regimes: 36°C during the day and 15°C at night for 2 days, or 32°C during the day and 15°C at night for 3 days, both with a 12-h photoperiod. Control plants were held at 23°C during the day and 7°C at night for 3 days. Plants were either watered daily or not watered during the heat stress and control treatments. E. coli O157:H7 was detected by enrichment in all inoculated soil and rhizosphere samples from plants grown in inoculated soil. Less E. coli O157:H7 was detected in inoculated heat-stressed soil than in control soil. From inoculated pots, all leaf surfaces and macerated leaves that had been surface sanitized were negative for E. coli O157:H7. All surface-sanitized macerated roots from control samples and from 143 of 144 samples of inoculated samples were negative for E. coli O157:H7. Heat stress during growth of lettuce did not promote or enhance internalization of E. coli O157:H7, regardless of the moisture content in the soil.

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