scholarly journals Estimation of Microbial Contamination of Food from Prevalence and Concentration Data: Application to Listeria monocytogenes in Fresh Vegetables

2006 ◽  
Vol 73 (1) ◽  
pp. 250-258 ◽  
Author(s):  
Amélie Crépet ◽  
Isabelle Albert ◽  
Catherine Dervin ◽  
Frédéric Carlin
Keyword(s):  
Listeria Monocytogenes ◽  
Standard Deviation ◽  
Mixture Model ◽  
Microbial Contamination ◽  
Concentration Data ◽  
Minimally Processed ◽  
Prevalence Studies ◽  
Lower Estimation ◽  
Fresh Vegetables ◽  
Sensitivity Rate

ABSTRACT A normal distribution and a mixture model of two normal distributions in a Bayesian approach using prevalence and concentration data were used to establish the distribution of contamination of the food-borne pathogenic bacteria Listeria monocytogenes in unprocessed and minimally processed fresh vegetables. A total of 165 prevalence studies, including 15 studies with concentration data, were taken from the scientific literature and from technical reports and used for statistical analysis. The predicted mean of the normal distribution of the logarithms of viable L. monocytogenes per gram of fresh vegetables was −2.63 log viable L. monocytogenes organisms/g, and its standard deviation was 1.48 log viable L. monocytogenes organisms/g. These values were determined by considering one contaminated sample in prevalence studies in which samples are in fact negative. This deliberate overestimation is necessary to complete calculations. With the mixture model, the predicted mean of the distribution of the logarithm of viable L. monocytogenes per gram of fresh vegetables was −3.38 log viable L. monocytogenes organisms/g and its standard deviation was 1.46 log viable L. monocytogenes organisms/g. The probabilities of fresh unprocessed and minimally processed vegetables being contaminated with concentrations higher than 1, 2, and 3 log viable L. monocytogenes organisms/g were 1.44, 0.63, and 0.17%, respectively. Introducing a sensitivity rate of 80 or 95% in the mixture model had a small effect on the estimation of the contamination. In contrast, introducing a low sensitivity rate (40%) resulted in marked differences, especially for high percentiles. There was a significantly lower estimation of contamination in the papers and reports of 2000 to 2005 than in those of 1988 to 1999 and a lower estimation of contamination of leafy salads than that of sprouts and other vegetables. The interest of the mixture model for the estimation of microbial contamination is discussed.

Coliforms and Prevalence of Escherichia coli and Foodborne Pathogens on Minimally Processed Spinach in Two Packing Plants

2008 ◽  
Vol 71 (12) ◽  
pp. 2398-2403 ◽  
Author(s):  
SANJA ILIC ◽  
JOSEPH ODOMERU ◽  
JEFFREY T. LeJEUNE
Keyword(s):  
Escherichia Coli ◽  
Standard Deviation ◽  
Foodborne Pathogens ◽  
The United States ◽  
Total Coliform ◽  
Minimally Processed ◽  
Minimal Processing ◽  
E Coli ◽  
Fresh Vegetables ◽  
Shigella Spp

Minimally processed spinach has been recently associated with outbreaks of foodborne illnesses. This study investigated the effect of commercial minimal processing of spinach on the coliform and Escherichia coli counts and the prevalence of E. coli O157:H7, Salmonella, Shigella spp., and Listeria monocytogenes on two types of spinach before and after minimal processing. A total of 1,356 spinach samples (baby spinach, n = 574; savoy spinach, n = 782) were collected daily in two processing plants over a period of 14 months. Raw spinach originated from nine farms in the United States and three farms in Canada. Overall, the proportion of samples positive for coliforms increased from 53% before minimal processing to 79% after minimal processing (P < 0.001). Average total coliform counts also increased significantly after processing, especially in baby spinach (mean ± standard deviation, 1.16 ± 0.14 log CFU/g to 2.37 ± 0.08 log CFU/g following processing; P < 0.001). E. coli was isolated from 8.9% of the samples (mean ± standard deviation, 1.81 ± 0.14 log CFU/g), and no difference in prevalence or CFU counts after processing (P < 0.1) was observed. E. coli O157:H7 and Shigella spp. were not isolated from any of the samples. Salmonella and L. monocytogenes were isolated from 0.4 and 0.7% of samples, respectively. Results demonstrate that commercial minimal processing of spinach based on monitored chlorine washing and drying may not decrease microbial load on spinach leaves as expected. Further research is needed to identify the most appropriate measures to control food safety risk under commercial minimal processing of fresh vegetables.

scholarly journals Advanced Killing Potential of Thymol against a Time and Temperature Optimized Attached Listeria monocytogenes Population in Lettuce Broth

Biomolecules ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Dimitra Kostoglou ◽  
Parthena Tsaklidou ◽  
Ioannis Iliadis ◽  
Nikoletta Garoufallidou ◽  
Georgia Skarmoutsou ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Benzalkonium Chloride ◽  
Planktonic Cells ◽  
Antimicrobial Efficiency ◽  
Fresh Vegetables ◽  
Viable Bacteria ◽  
Steel Surfaces ◽  
Polymerase Chain ◽  
Killing Action ◽  
Foodborne Infections

Fresh vegetables and salads are increasingly implicated in outbreaks of foodborne infections, such as those caused by Listeria monocytogenes, a dangerous pathogen that can attach to the surfaces of the equipment creating robust biofilms withstanding the killing action of disinfectants. In this study, the antimicrobial efficiency of a natural plant terpenoid (thymol) was evaluated against a sessile population of a multi-strain L. monocytogenes cocktail developed on stainless steel surfaces incubated in lettuce broth, under optimized time and temperature conditions (54 h at 30.6 °C) as those were determined following response surface modeling, and in comparison, to that of an industrial disinfectant (benzalkonium chloride). Prior to disinfection, the minimum bactericidal concentrations (MBCs) of each compound were determined against the planktonic cells of each strain. The results revealed the advanced killing potential of thymol, with a concentration of 625 ppm (= 4 × MBC) leading to almost undetectable viable bacteria (more than 4 logs reduction following a 15-min exposure). For the same degree of killing, benzalkonium chloride needed to be used at a concentration of at least 20 times more than its MBC (70 ppm). Discriminative repetitive sequence-based polymerase chain reaction (rep-PCR) also highlighted the strain variability in both biofilm formation and resistance. In sum, thymol was found to present an effective anti-listeria action under environmental conditions mimicking those encountered in the salad industry and deserves to be further explored to improve the safety of fresh produce.

Prevalence and level of Listeria monocytogenes and other Listeria sp. in ready-to-eat minimally processed and refrigerated vegetables

2012 ◽  
Vol 29 (4) ◽  
pp. 707-712 ◽  
Author(s):  
Mira Kovačević ◽  
Jelena Burazin ◽  
Hrvoje Pavlović ◽  
Mirela Kopjar ◽  
Vlasta Piližota
Keyword(s):  
Listeria Monocytogenes ◽  
Minimally Processed

Effect of Gamma Radiation on the Reduction of Salmonella strains, Listeria monocytogenes, and Shiga Toxin–Producing Escherichia coli and Sensory Evaluation of Minimally Processed Spinach (Tetragonia expansa)

2014 ◽  
Vol 77 (10) ◽  
pp. 1768-1772 ◽  
Author(s):  
ANA CAROLINA B. REZENDE ◽  
MARIA CRYSTINA IGARASHI ◽  
MARIA TERESA DESTRO ◽  
BERNADETTE D. G. M. FRANCO ◽  
MARIZA LANDGRAF
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Gamma Radiation ◽  
Shiga Toxin ◽  
Radiation Doses ◽  
Minimally Processed ◽  
Tetragonia Expansa ◽  
Effects Of Irradiation On ◽  
Spinach Leaves

This study evaluated the effects of irradiation on the reduction of Shiga toxin–producing Escherichia coli (STEC), Salmonella strains, and Listeria monocytogenes, as well as on the sensory characteristics of minimally processed spinach. Spinach samples were inoculated with a cocktail of three strains each of STEC, Salmonella strains, and L. monocytogenes, separately, and were exposed to gamma radiation doses of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 kGy. Samples that were exposed to 0.0, 1.0, and 1.5 kGy and kept under refrigeration (4°C) for 12 days were submitted to sensory analysis. D10-values ranged from 0.19 to 0.20 kGy for Salmonella and from 0.20 to 0.21 for L. monocytogenes; for STEC, the value was 0.17 kGy. Spinach showed good acceptability, even after exposure to 1.5 kGy. Because gamma radiation reduced the selected pathogens without causing significant changes in the quality of spinach leaves, it may be a useful method to improve safety in the fresh produce industry.

scholarly journals Mechanical Vibration Signal Denoising Using Quantum-Inspired Standard Deviation Based on Subband Based Gaussian Mixture Model

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Aidong Xu ◽  
Wenqi Huang ◽  
Peng Li ◽  
Huajun Chen ◽  
Jiaxiao Meng ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Gaussian Mixture Model ◽  
Mixture Model ◽  
Mechanical Vibration ◽  
Vibration Signal ◽  
Gaussian Mixture ◽  
Wavelet Coefficients ◽  
Denoising Method ◽  
Reduction Effect ◽  
Thresholding Function

Aiming at improving noise reduction effect for mechanical vibration signal, a Gaussian mixture model (SGMM) and a quantum-inspired standard deviation (QSD) are proposed and applied to the denoising method using the thresholding function in wavelet domain. Firstly, the SGMM is presented and utilized as a local distribution to approximate the wavelet coefficients distribution in each subband. Then, within Bayesian framework, the maximum a posteriori (MAP) estimator is employed to derive a thresholding function with conventional standard deviation (CSD) which is calculated by the expectation-maximization (EM) algorithm. However, the CSD has a disadvantage of ignoring the interscale dependency between wavelet coefficients. Considering this limit for the CSD, the quantum theory is adopted to analyze the interscale dependency between coefficients in adjacent subbands, and the QSD for noise-free wavelet coefficients is presented based on quantum mechanics. Next, the QSD is constituted for the CSD in the thresholding function to shrink noisy coefficients. Finally, an application in the mechanical vibration signal processing is used to illustrate the denoising technique. The experimental study shows the SGMM can model the distribution of wavelet coefficients accurately and QSD can depict interscale dependency of wavelet coefficients of true signal quite successfully. Therefore, the denoising method utilizing the SGMM and QSD performs better than others.

Effect of Ozone on the Inactivation of Yersinia enterocolitica and the Reduction of Natural Flora on Potatoes

2006 ◽  
Vol 69 (10) ◽  
pp. 2357-2363 ◽  
Author(s):  
MARÍA VICTORIA SELMA ◽  
DAVID BELTRÁN ◽  
ELISEO CHACÓN-VERA ◽  
MARÍA ISABEL GIL
Keyword(s):  
Listeria Monocytogenes ◽  
Yersinia Enterocolitica ◽  
Disease Outbreaks ◽  
Wash Water ◽  
Foodborne Disease ◽  
Pathogenic Microorganisms ◽  
Psychrotrophic Bacteria ◽  
Fresh Vegetables ◽  
Natural Flora ◽  
Soil Irrigation

Fresh vegetables contaminated with Yersinia enterocolitica have been implicated in foodborne disease outbreaks. Surfaces of vegetables can become contaminated with pathogenic microorganisms through contact with soil, irrigation water, fertilizers, equipment, humans, and animals. One approach to reduce this contamination is to treat fresh produce with sanitizers. In this study, the ability of ozone to inactivate Y. enterocolitica inoculated in water and on potato surfaces was evaluated. Furthermore, the efficacy of ozone in reducing natural flora on whole potato was determined. Total aerobic mesophilic and psychrotrophic bacteria, total coliforms, and Listeria monocytogenes were enumerated. Finally, several disinfection kinetic models were considered to predict Y. enterocolitica inactivation with ozone. Treatments with ozone (1.4 and 1.9 ppm) for 1 min decreased the Y. enterocolitica population in water by 4.6 and 6.2 log CFU ml−1, respectively. Furthermore, ozonated water (5 ppm) for 1 min decreased Y. enterocolitica and L. monocytogenes from potato surfaces by 1.6 and 0.8 log CFU g−1, respectively. Therefore, ozone can be an effective treatment for disinfection of wash water and for reduction of potato surface contamination.

Comparison of Four Commercial DNA Extraction Kits for PCR Detection of Listeria monocytogenes, Salmonella, Escherichia coli O157:H7, and Staphylococcus aureus in Fresh, Minimally Processed Vegetables

2008 ◽  
Vol 71 (10) ◽  
pp. 2110-2114 ◽  
Author(s):  
P. ELIZAQUÍVEL ◽  
R. AZNAR
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Listeria Monocytogenes ◽  
Dna Extraction ◽  
Pcr Detection ◽  
Escherichia Coli O157 ◽  
Minimally Processed ◽  
Green Pepper ◽  
Minimally Processed Vegetables ◽  
And Staphylococcus Aureus

Four commercial DNA extraction methods, PrepMan Ultra (Applied Biosystems), InstaGene Matrix (BioRad), DNeasy Tissue kit (Qiagen), and UltraClean (MoBio), were tested for PCR detection of Listeria monocytogenes, Escherichia coli O157: H7, Salmonella, and Staphylococcus aureus in fresh, minimally processed vegetables. For comparative purposes, sensitivity assays with specific PCRs were carried out after DNA extraction with the four methods in green pepper, broccoli, and onion artificially inoculated with the four pathogens separately. As confirmed by statistical analysis, the DNeasy Tissue kit rendered the highest sensitivity values in the three matrices assayed for Salmonella, L. monocytogenes, and E. coli O157:H7 and in onion for S. aureus. Despite being the most expensive of the methods compared, the DNeasy Tissue Kit can be successfully applied for any of the four most commonly studied pathogens, thus saving time and overall reducing the cost of the analysis.

scholarly journals Listeria Monocytogenes Contamination Study in Food from Plant Origin in the Market

2019 ◽  
Vol 4 (3) ◽  
Keyword(s):  
Listeria Monocytogenes ◽  
Microbial Contamination ◽  
Chemical Contamination ◽  
Minimal Processing ◽  
Traditional Markets ◽  
Fresh Food ◽  
Accredited Laboratories ◽  
Pathogenic Microbes ◽  
Random Method ◽  
Bean Sprouts

Fresh food from plants is fresh food that is consumed directly or after cutting, I have minimal processing. Therefore PSAT to be consumed must be safe from aspects of microbial contamination and physical chemical contamination. There are several types of pathogenic microbes, which can contaminate PSAT and can cause disease disorders. One microbe, which includes pathogenic microbes and potentially contaminates PSAT, is Listeria monocytogenes. Microbes Listeria monocytogenes are pathogenic in certain groups of people in small amounts. To know the prevalence of Listeria monocytogenes, studies were carried out, by taking samples at locations, and selected commodities. The locations chosen are West Java, Banten and DKI Jakarta in two traditional markets in each province. While the selected commodities are bean sprouts, tomatoes and cabbage. Sampling was carried out by random method, with the population in accordance with the number of vegetable traders in that location. Testing of samples for Listeria monocytogenes contamination is carried out in accredited laboratories. From the results of testing of 300 (three hundred) samples, consisting of 100 samples of bean sprouts, 100 samples of tomatoes, and 100 samples of cabbage, all test samples were declared negative or unexposed to Listeria monocytogenes.

Radiation Processing To Ensure Safety of Minimally Processed Carrot (Daucus carota) and Cucumber (Cucumis sativus): Optimization of Dose for the Elimination of Salmonella Typhimurium and Listeria monocytogenes

2006 ◽  
Vol 69 (2) ◽  
pp. 444-448 ◽  
Author(s):  
V. S. DHOKANE ◽  
S. HAJARE ◽  
R. SHASHIDHAR ◽  
A. SHARMA ◽  
J. R. BANDEKAR
Keyword(s):  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Escherichia Coli O157 ◽  
Radiation Processing ◽  
Minimally Processed ◽  
Shigella Species ◽  
Storage Studies ◽  
D Values ◽  
Minimally Processed Vegetables ◽  
Control Samples

Minimally processed vegetables are in demand, because they offer convenience to consumers. However, these products are often unsafe because of possible contamination with pathogens, such as Salmonella, Escherichia coli O157:H7, and Shigella species. Therefore, this study was carried out to optimize the radiation dose necessary to ensure the safety of precut carrot and cucumber. Decimal reduction doses (D-values) of Salmonella Typhimurium MTCC 98 were ca. 0.164 kGy in carrot samples and 0.178 kGy in cucumber samples. D-values of Listeria monocytogenes were determined to be 0.312 and 0.345 kGy in carrot and cucumber samples, respectively. Studies of inoculated, packaged, minimally processed carrot and cucumber samples showed that treatment with a 1-kGy dose of gamma radiation eliminated up to 4 log CFU/g of Salmonella Typhimurium and 3 log CFU/g of L. monocytogenes. However, treatment with a 2-kGy dose was necessary to eliminate these pathogens by 5 log CFU/g. Storage studies showed that both Salmonella Typhimurium and L. monocytogenes were able to grow at 10°C in inoculated control samples. Neither of these pathogens could be recovered from radiation-processed samples after storage for up to 8 days.

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