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

Moyne, Anne-Laure; Sudarshana, Mysore R.; Blessington, Tyann; Koike, S. T.; Cahn, Michael; Harris, Linda J.

doi:10.1016/j.fm.2011.02.001

Cited by 98 publications

(95 citation statements)

References 27 publications

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“…Dudley, unpublished data). E. coli ATCC 700728 is an O157:H7 strain that has been cured of Shiga toxin-converting phage (47). Each culture was grown in tryptic soy broth (TSB; Difco, Sparks, MD) under aerobic conditions at 37°C in an orbital shaker.…”

Section: Discussionmentioning

confidence: 99%

Critical Concentration of Lecithin Enhances the Antimicrobial Activity of Eugenol against Escherichia coli

Zhang

Dudley

Davidson

et al. 2017

Appl Environ Microbiol

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Lecithin is a natural emulsifier used in a wide range of food and nonfood applications to improve physical stability, with no known bioactive effects. In this study, the effect of lecithin on the antimicrobial performance of a constant eugenol concentration was tested against three Escherichia coli strains (C600, 0.1229, and O157:H7 strain ATCC 700728). This is the first study, to our knowledge, focusing on lecithin at concentrations below those commonly used in foods to improve the stability of oil in water emulsions (Յ10 mg/100 ml). For all three cultures, significant synergistic antimicrobial effects were observed when E. coli cultures were exposed to a constant eugenol concentration (ranging from 0.043 to 0.050% [wt/wt]) together with critical lecithin concentrations ranging from 0.5 to 1 mg/100 ml. Increasing the concentration of lecithin above 1 mg/100 ml (up to 10 mg/100 ml lecithin) diminished the antibacterial effect to values similar to those with eugenol-only treatments. The formation of aggregates (Ͻ100 nm) at the critical lecithin concentration was observed using cryo-transmission electron microscopy (cryo-TEM), together with a reduction in light absorbance at 284 nm. At critically low concentrations of lecithin, the formation of nanoscale aggregates is responsible for improving eugenol antimicrobial effects.IMPORTANCE Essential oils (EOs) are effective natural antimicrobials. However, their hydrophobicity and strong aromatic character limit the use of essential oils in food systems. Emulsifiers (e.g., lecithin) increase the stability of EOs in water-based systems but fail to consistently improve antimicrobial effects. We demonstrate that lecithin, within a narrow critical concentration window, can enhance the antimicrobial properties of eugenol. This study highlights the potential bioactivity of lecithin when utilized to effectively control foodborne pathogens.

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Section: Discussionmentioning

confidence: 99%

Critical Concentration of Lecithin Enhances the Antimicrobial Activity of Eugenol against Escherichia coli

Zhang

Dudley

Davidson

et al. 2017

Appl Environ Microbiol

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“…The possible routes of fecal transmission of pathogens under field conditions are numerous, but application of DNA-based fingerprint methods such as pulsed-field gel electrophoresis (PFGE) can help track the source of fecal bacteria (45). Surveys on the type and concentrations of pathogens on vegetables and their survival under natural field conditions are still scarce, although increasing (38). The reported level of human pathogens in produce seems to vary considerably, e.g., between regions (3,32,41,50).…”

mentioning

confidence: 99%

Escherichia coli Contamination of Lettuce Grown in Soils Amended with Animal Slurry

Jensen¹,

Storm²,

Forslund³

et al. 2013

Journal of Food Protection

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A pilot study was conducted to assess the transfer of Escherichia coli from animal slurry fertilizer to lettuce, with E. coli serving as an indicator of fecal contamination and as an indicator for potential bacterial enteric pathogens. Animal slurry was applied as fertilizer to three Danish agricultural fields prior to the planting of lettuce seedlings. At harvest, leaves (25 g) of 10 lettuce heads were pooled into one sample unit (n = 147). Soil samples (100 g) were collected from one field before slurry application and four times during the growth period (n = 75). E. coli was enumerated in slurry, soil, and lettuce on 3M Petrifilm Select E. coli Count Plates containing 16 mg/liter streptomycin, 16 mg/liter ampicillin, or no antimicrobial agent. Selected E. coli isolates (n = 83) originating from the slurry, soil, and lettuce were genotyped by pulsed-field gel electrophoresis (PFGE) to determine the similarity of isolates. The slurry applied to the fields contained 3.0 to 4.5 log CFU/g E. coli. E. coli was found in 36 to 54% of the lettuce samples, streptomycin-resistant E. coli was found in 10.0 to 18.0% of the lettuce samples, and ampicillin-resistant E. coli in 0 to 2.0% of the lettuce samples (the detection limit was 1 log CFU/g). The concentration of E. coli exceeded 2 log CFU/g in 19.0% of the lettuce samples. No E. coli was detected in the soil before the slurry was applied, but after, E. coli was present until the last sampling day (harvest), when 10 of 15 soil samples contained E. coli. A relatively higher frequency of E. coli in lettuce compared with the soil samples at harvest suggests environmental sources of fecal contamination, e.g., wildlife. The higher frequency was supported by the finding of 21 different PFGE types among the E. coli isolates, with only a few common PFGE types between slurry, soil, and lettuce. The frequent finding of fecal-contaminated lettuce indicates that human pathogens such as Salmonella and Campylobacter can be present and represent food safety hazards.

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“…The concentration of each of the cultures used for the preparation of inoculums was adjusted to similar value 8.2 to 8.4 log CFU /mL . The combination of rifampicin resistant strains and rifampicin containing non-selective media such as tripticase soy agar TSA were commonly used to measure survivability of bacteria in foods because of its high selectivity and high efficacy of injured bacteria detection Moyne et al, 2011 .…”

Section: Methodsmentioning

confidence: 99%

Fate of <i>Escherichia coli</i> O157 Cells Inoculated into Lightly Pickled Chinese Cabbage during Processing, Storage and Incubation in Artificial Gastric Juice

et al. 2016

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Fate of Escherichia coli O157 cells was evaluated when inoculated into each step after production of lightly pickled Chinese cabbage. The efficacy of surface sterilization by 100 mg/L of chlorine water for 10 min on raw leaves 6.0 log CFU/g was 2.2 log CFU/g reduction. No meaningful change of the population of E. coli O157 3.5 log CFU/g to 1.5 log MPN/g contaminated into 19 kinds of products was observed. These results indicated the difficulty of estimating the viable count of the cells between contaminated on farms and further processing and storage steps. The population of E. coli O157 3 log CFU/g to 1 log MPN/g inoculated into the Chinese cabbage products was reduced less than 0.6 log CFU/g after 2 h-incubation at 37 in artificial gastric juice. Prevention from initial contamination of E. coli O157 on the ingredients of Chinese cabbage products is important to reduce the risk of food poisoning because the reduction of the bacterial counts after processing and consumption are limited.

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

Cited by 98 publications

References 27 publications

Critical Concentration of Lecithin Enhances the Antimicrobial Activity of Eugenol against Escherichia coli

Critical Concentration of Lecithin Enhances the Antimicrobial Activity of Eugenol against Escherichia coli

Escherichia coli Contamination of Lettuce Grown in Soils Amended with Animal Slurry

Fate of <i>Escherichia coli</i> O157 Cells Inoculated into Lightly Pickled Chinese Cabbage during Processing, Storage and Incubation in Artificial Gastric Juice

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