A Study to Evaluate the Need for Comminution in the Preparation of Food Materials for Testing of Listeria monocytogenes, Staphylococcus Species, and Generic Escherichia coli

2020 ◽  
Vol 103 (6) ◽  
pp. 1639-1645
Author(s):  
Patricia Hanson ◽  
Nicole Mitchell ◽  
S Brian Caudle ◽  
Lyndsey Caulkins ◽  
Cameron Owens ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Sampling Method ◽  
Sampling Error ◽  
Food Samples ◽  
Test Portion ◽  
Target Analytes ◽  
Wide Range ◽  
Current Sampling ◽  
Selection Of

Abstract Background Comminution reduces the sampling error arising from distributional heterogeneity of the target contaminant/target analyte in the material, facilitating the selection of a more representative test portion. A laboratory sampling method incorporating comminution prior to selection of the test portion (Sampling Method B) was compared to current sampling methods that used no comminution step (Sampling Method A). Objective This required the development of an efficient process for comminution of food samples prior to removal of the test portion for the detection and isolation of Listeria monocytogenes and the enumeration of Staphylococcus species and Escherichia coli. Method From December 2016 to December 2017, 2742 tests were conducted on 778 unique food samples. For all food samples, a test portion (TPA) was first removed using Sampling Method A, and then the remainder of the material was comminuted and a second test portion (TPB) was removed using Sampling Method B and tested alongside the first portion. Results Across all food matrices and microbial targets, 17 additional targets were detected using only Sampling Method B, and positive detections of target analytes increased by 77% using Sampling Method B from the test portions taken using Sampling Method A. Conclusion Utilizing a sample preparation method that includes a comminution step resulted in an increased number of pathogen detections. Highlights The introduction of a comminution step in the preparation of food samples for detection of three common microbial contaminants resulted in an increase in the rate of detection of natural contaminates in a variety of ready to eat foods. An efficient aseptic process for commutation that can be adapted to a wide range of laboratory settings was identified.

scholarly journals Identification of Surface Protein Biomarkers of Listeria monocytogenes via Bioinformatics and Antibody-Based Protein Detection Tools

2016 ◽  
Vol 82 (17) ◽  
pp. 5465-5476 ◽  
Author(s):  
Cathy X. Y. Zhang ◽  
Brian W. Brooks ◽  
Hongsheng Huang ◽  
Franco Pagotto ◽  
Min Lin
Keyword(s):  
Monoclonal Antibodies ◽  
Listeria Monocytogenes ◽  
Surface Protein ◽  
Protein Detection ◽  
Food Samples ◽  
Surface Proteins ◽  
Content Type ◽  
Selective Enrichment ◽  
Wide Range ◽  
Serotype 4B

ABSTRACTThe Gram-positive bacteriumListeria monocytogenescauses a significant percentage of the fatalities among foodborne illnesses in humans. Surface proteins specifically expressed in a wide range ofL. monocytogenesserotypes under selective enrichment culture conditions could serve as potential biomarkers for detection and isolation of this pathogen via antibody-based methods. Our study aimed to identify such biomarkers. Interrogation of theL. monocytogenesserotype 4b strain F2365 genome identified 130 putative or known surface proteins. The homologues of four surface proteins, LMOf2365_0578, LMOf2365_0581, LMOf2365_0639, and LMOf2365_2117, were assessed as biomarkers due to the presence of conserved regions among strains ofL. monocytogeneswhich are variable among otherListeriaspecies. Rabbit polyclonal antibodies against the four recombinant proteins revealed the expression of only LMOf2365_0639 on the surface of serotype 4b strain LI0521 cells despite PCR detection of mRNA transcripts for all four proteins in the organism. Three of 35 monoclonal antibodies (MAbs) to LMOf2365_0639, MAbs M3643, M3644, and M3651, specifically recognized 42 (91.3%) of 46L. monocytogeneslineage I and II isolates grown in nonselective brain heart infusion medium. While M3644 and M3651 reacted with 14 to 15 (82.4 to 88.2%) of 17L. monocytogeneslineage I and II isolates, M3643 reacted with 22 (91.7%) of 24 lineage I, II, and III isolates grown in selective enrichment media (UVM1, modified Fraser, Palcam, and UVM2 media). The three MAbs exhibited only weak reactivities (the optical densities at 414 nm were close to the cutoff value) to some otherListeriaspecies grown in selective enrichment media. Collectively, the data indicate the potential of LMOf2365_0639 as a surface biomarker ofL. monocytogenes, with the aid of specific MAbs, for pathogen detection, identification, and isolation in clinical, environmental, and food samples.IMPORTANCEL. monocytogenesis traditionally divided into at least 12 serotypes. Currently, there are no monoclonal antibodies (MAbs) available that are capable of binding to the surface ofL. monocytogenesstrains representing all 12 serotypes. Such antibodies would be useful and are needed for the development of methods to detect and isolateL. monocytogenesfrom food samples. In our study, we aimed to identify surface proteins that possess regions of well-conserved amino acid sequences among various serotypes and then to employ them as antigen targets (biomarkers) for the development of MAbs. Through bioinformatics and protein expression analysis, we identified one of the four putative surface protein candidates, LMOf2365_0639, encoded by the genome of theL. monocytogenesserotype 4b strain F2365, as a useful surface biomarker. Extensive assessment of 35 MAbs raised against LMOf2365_0639 in our study revealed three MAbs (M3643, M3644, and M3651) that recognized a wide range ofL. monocytogenesisolates.

Use of Randomized Branch and Importance Sampling to Estimate Loblolly Pine Biomass

1989 ◽  
Vol 13 (4) ◽  
pp. 181-184 ◽  
Author(s):  
Roger A. Williams
Keyword(s):  
Importance Sampling ◽  
Loblolly Pine ◽  
Sampling Method ◽  
Sampling Error ◽  
Total Biomass ◽  
Tree Biomass ◽  
Individual Tree ◽  
Wide Range ◽  
Pinus Taeda L ◽  
Source Of Error

Abstract A previously developed sampling method utilizing randomized branch and importance sampling for the purpose of quickly estimating tree biomass was tested on five loblolly pine (Pinus taeda L.) trees. Results show a wide range of per-tree sampling error, ranging from 5.3 to 28.9%. Largevariation in foliage content among selected branches per treee may be a major source of error. However, the sampling error for the total biomass of the five trees tested was only 3.3%. This sampling method appears to be reliable and efficient in obtaining precise estimates of the total biomassof a population of trees. Increased sampling intensity per tree is necessary to obtain precise estimates of individual tree biomass. South. J. Appl. For. 13(4):181-184.

scholarly journals An Improved Cloning Vector for Construction of Gene Replacements in Listeria monocytogenes

2003 ◽  
Vol 69 (5) ◽  
pp. 3020-3023 ◽  
Author(s):  
Guojie Li ◽  
S. Kathariou
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Plasmid Vector ◽  
Gene Replacement ◽  
Direct Selection ◽  
Genetic Studies ◽  
Food Borne ◽  
Food Borne Illness ◽  
Selection For ◽  
Selection Of

ABSTRACT Listeria monocytogenes is a gram-positive, facultative intracellular bacterium implicated in severe food-borne illness (listeriosis) in humans. The construction of well-defined gene replacements in the genome of L. monocytogenes has been instrumental to several genetic studies of the virulence and other attributes of the organism. Construction of such mutations by currently available procedures, however, tends to be labor intensive, and gene replacement mutants are sometimes difficult to recover due to lack of direct selection for the construct. In this study we describe the construction and use of plasmid vector pGF-EM, which can be conjugatively transferred from Escherichia coli S17-1 to L. monocytogenes and which provides the genetic means for direct selection of gene replacements.

Incidence of Enterohemorrhagic Escherichia coli, Escherichia coli O157, Salmonella, and Listeria monocytogenes in Retail Fresh Ground Beef, Sprouts, and Mushrooms

2006 ◽  
Vol 69 (2) ◽  
pp. 441-443 ◽  
Author(s):  
M. SAMADPOUR ◽  
M. W. BARBOUR ◽  
T. NGUYEN ◽  
T.-M. CAO ◽  
F. BUCK ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Ground Beef ◽  
Food Samples ◽  
Enterohemorrhagic Escherichia Coli ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Pcr Assays ◽  
Retail Food

The objective of this study was to determine the prevalence of enterohemorrhagic Escherichia coli (EHEC), E. coli O157, Salmonella, and Listeria monocytogenes in retail food samples from Seattle, Wash. A total of 2,050 samples of ground beef (1,750 samples), mushrooms (100 samples), and sprouts (200 samples) were collected over a 12-month period and analyzed for the presence of these pathogens. PCR assays, followed by culture confirmation were used to determine the presence or absence of each organism. Of the 1,750 ground beef samples analyzed, 61 (3.5%) were positive for EHEC, and 20 (1.1%) of these were positive for E. coli O157. Salmonella was present in 67 (3.8%) of the 1,750 ground beef samples. Of 512 ground beef samples analyzed, 18 (3.5%) were positive for L. monocytogenes. EHEC was found in 12 (6.0%) of the 200 sprout samples, and 3 (1.5%) of these yielded E. coli O157. Of the 200 total sprout samples, 14 (7.0%) were positive for Salmonella and none were positive for L. monocytogenes. Among the 100 mushroom samples, 4 (4.0%) were positive for EHEC but none of these 4 samples were positive for E. coli O157. Salmonella was detected in 5 (5.0%) of the mushroom samples, and L. monocytogenes was found in 1 (1.0%) of the samples.

scholarly journals Assessment of Photodynamic Destruction of Escherichia coli O157:H7 and Listeria monocytogenes by Using ATP Bioluminescence

2003 ◽  
Vol 69 (11) ◽  
pp. 6393-6398 ◽  
Author(s):  
N. A. Romanova ◽  
L. Y. Brovko ◽  
L. Moore ◽  
E. Pometun ◽  
A. P. Savitsky ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Yeast Cells ◽  
Bacterial Cells ◽  
E Coli ◽  
Intracellular Atp ◽  
Microdilution Method ◽  
Wide Range ◽  
Atp Bioluminescence ◽  
Time Courses

ABSTRACT Antimicrobial photodynamic therapy was shown to be effective against a wide range of bacterial cells, as well as for fungi, yeasts, and viruses. It was shown previously that photodestruction of yeast cells treated with photosensitizers resulted in cell destruction and leakage of ATP. Three photosensitizers were used in this study: tetra(N-methyl-4-pyridyl)porphine tetratosylate salt (TMPyP), toluidine blue O (TBO), and methylene blue trihydrate (MB). A microdilution method was used to determine MICs of the photosensitizers against both Escherichia coli O157:H7 and Listeria monocytogenes. To evaluate the effects of photodestruction on E. coli and L. monocytogenes cells, a bioluminescence method for detection of ATP leakage and a colony-forming assay were used. All tested photosensitizers were effective for photodynamic destruction of both bacteria. The effectiveness of photosensitizers (in microgram-per-milliliter equivalents) decreased in the order TBO > MB > TMPyP for both organisms. The MICs were two- to fourfold higher for E. coli O157:H7 than for L. monocytogenes. The primary effects of all of the photosensitizers tested on live bacterial cells were a decrease in intracellular ATP and an increase in extracellular ATP, accompanied by elimination of viable cells from the sample. The time courses of photodestruction and intracellular ATP leakage were different for E. coli and L. monocytogenes. These results show that bioluminescent ATP-metry can be used for investigation of the first stages of bacterial photodestruction.

scholarly journals Heterologous Expression of Pediocin PA-1 inEscherichia coli

2019 ◽  
Author(s):  
Nguyen Pham Anh Thu ◽  
Dao Thi Hong Thuy ◽  
Nguyen Hieu Nghia ◽  
Dang Thi Phuong Thao
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Heterologous Expression ◽  
Enterococcus Faecalis ◽  
High Efficiency ◽  
Expression System ◽  
Temperature Stability ◽  
Food Preservation ◽  
Soluble Form ◽  
Wide Range

AbstractPediocin PA-1 is an antimicrobial peptide which has a strongly activity against some Gram – positive pathogens such asListeria monocytogenes, Staphylococcus aureus, Enterococcus faecalis…With the broad inhibitory spectrum as well as pH and temperature stability, pediocin has a potential application in food preservation as well as pharmaceutical industry. For higher manufactory efficiency, pediocin has been expressed in both prokaryote and eukaryote heterologous expression system, mostly on Escherichia coli with different strategies. Here, we show a new strategy to produce pediocin fromEscherichia coliBL21(DE3) system as fusion form by using a vector containing NusA tag. Our results showed that NusA fused pediocin almost presented in soluble form with high efficiency (79.8 mg/l obtained by Ni-NTA purification). After remove the fusion tag, recombinant pediocin showed antimicrobial activity againstListeria monocytogenesATCC 13932 as 23.5×103Au/mg as well as againstEnterococcus faecalis, Lactobacillus plantarum, and Streptococcus thermophilus, especiallyVibrio parahaemolyticus– a Gram-negative bacteria which have not been reported in antimicrobial spectrum of pediocin on Bactibase. Recombinant pediocin is recorded to be stable to a wide range of pH (1-12 for 1 hour) and temperature (100°C for 15 min) as well as sensitive to protease treatment as the nature pediocin. These characteristics opened a prospect of using pediocin as bio-preservative compound in food industry.

scholarly journals Selection of Sampling Keys for Cryptographic Tests

2021 ◽  
pp. 1-14
Author(s):  
George Marinakis
Keyword(s):  
Computer Security ◽  
Sampling Method ◽  
Sampling Error ◽  
Data Encryption ◽  
Algorithm Performance ◽  
Real Performance ◽  
Security Information ◽  
Selection Methodology ◽  
Equivalent Keys ◽  
Selection Of

Abstract The keys of modern cryptographic algorithms have an enormous size, so the testing of the algorithm performance for all key combinations, will take practically an infinite time. To avoid this, the sampling method is used, where a much smaller number of keys is tested and then the estimation of the algorithm performance for all the keys is calculated with a predetermined sampling error. For each sampling key, an output sample of the algorithm must be generated and tested. Therefore, in order to have sampling results as close as possible to the real performance of the algorithm, the key question is whether the selection of the keys should be random or it must follow some rules. If the selection of the keys is completely random, there is a high probability that the tests will not find some "weak" or "equivalent" keys, which give non-random or similar outputs and therefore reduce the total number of active keys. But if the sampling keys are selected with some specific criteria, there is a much greater probability of detecting any weak or equivalent key. In this study an optimal key selection methodology is proposed, which combines the random and the non-random key selection. Keywords: Cryptography, Data encryption, Communication security, Computer security, Data security, Information security.

scholarly journals Application of bacteriophage as food preservative to control enteropathogenic Escherichia coli (EPEC)

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Diana Elizabeth Waturangi ◽  
Cecillia Pingkan Kasriady ◽  
Geofany Guntama ◽  
Amelinda Minerva Sahulata ◽  
Diana Lestari ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Tolerance ◽  
Food Samples ◽  
Multiplicity Of Infection ◽  
Enteropathogenic Escherichia Coli ◽  
Food Matrix ◽  
Food Preservative ◽  
Ph Tolerance ◽  
Wide Range

Abstract Objectives This study was conducted to characterize lytic bacteriophages infecting enteropathogenic Escherichia coli (EPEC) on several types of food and analyze their ability as phage biocontrol to be used as a food preservative. Characterization was done for bacteriophage morphology and stability, along with the determination of minimum multiplicity of infection (miMOI), and application of bacteriophage in the food matrix. Results Out of the five samples, BL EPEC bacteriophage exhibited the highest titer of 2.05  ×  109 PFU/mL, with a wide range of pH tolerance, and high thermal tolerance. BL EPEC also showed the least reduction after 168 h of incubation, with a rate of 0.90  ×  10–3 log10 per hour. Bacteriophages from BL EPEC and CS EPEC showed an ideal value of miMOI of 0.01. As a food preservative, BL EPEC bacteriophage was able to reduce bacteria in food samples with a reduction above 0.24 log10 in lettuce and approximately 1.84 log10 in milk. From this study we found that BL EPEC bacteriophage showed the greatest potential to be used as phage biocontrol to improve food safety

COMBINATORIAL POLYNOMIALLY COMPUTABLE CHARACTERISTICS OF SUBSTITUTIONS AND THEIR PROPERTIES

2020 ◽  
Vol 7 (2) ◽  
pp. 34-41
Author(s):  
VLADIMIR NIKONOV ◽  
◽  
ANTON ZOBOV ◽  
Keyword(s):  
Mathematical Expectation ◽  
Point Of View ◽  
Small Range ◽  
Computational Point ◽  
Wide Range ◽  
Bijective Function ◽  
The Difference ◽  
Element Base ◽  
Selection Of

The construction and selection of a suitable bijective function, that is, substitution, is now becoming an important applied task, particularly for building block encryption systems. Many articles have suggested using different approaches to determining the quality of substitution, but most of them are highly computationally complex. The solution of this problem will significantly expand the range of methods for constructing and analyzing scheme in information protection systems. The purpose of research is to find easily measurable characteristics of substitutions, allowing to evaluate their quality, and also measures of the proximity of a particular substitutions to a random one, or its distance from it. For this purpose, several characteristics were proposed in this work: difference and polynomial, and their mathematical expectation was found, as well as variance for the difference characteristic. This allows us to make a conclusion about its quality by comparing the result of calculating the characteristic for a particular substitution with the calculated mathematical expectation. From a computational point of view, the thesises of the article are of exceptional interest due to the simplicity of the algorithm for quantifying the quality of bijective function substitutions. By its nature, the operation of calculating the difference characteristic carries out a simple summation of integer terms in a fixed and small range. Such an operation, both in the modern and in the prospective element base, is embedded in the logic of a wide range of functional elements, especially when implementing computational actions in the optical range, or on other carriers related to the field of nanotechnology.

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