scholarly journals Hierarchical dose response of E. coli O157:H7 from human outbreaks incorporating heterogeneity in exposure

2007 ◽  
Vol 136 (6) ◽  
pp. 761-770 ◽  
Author(s):  
P. F. M. TEUNIS ◽  
I. D. OGDEN ◽  
N. J. C. STRACHAN
Keyword(s):  
Dose Response ◽  
Foodborne Pathogens ◽  
Poisson Model ◽  
Additional Parameter ◽  
Response Model ◽  
Susceptible Population ◽  
E Coli ◽  
Risk Assessment Models ◽  
Human Volunteers ◽  
Key Factor

SUMMARYThe infectivity of pathogenic microorganisms is a key factor in the transmission of an infectious disease in a susceptible population. Microbial infectivity is generally estimated from dose–response studies in human volunteers. This can only be done with mildly pathogenic organisms. Here a hierarchical Beta-Poisson dose–response model is developed utilizing data from human outbreaks. On the lowest level each outbreak is modelled separately and these are then combined at a second level to produce a group dose–response relation. The distribution of foodborne pathogens often shows strong heterogeneity and this is incorporated by introducing an additional parameter to the dose–response model, accounting for the degree of overdispersion relative to Poisson distribution. It was found that heterogeneity considerably influences the shape of the dose–response relationship and increases uncertainty in predicted risk. This uncertainty is greater than previously reported surrogate and outbreak models using a single level of analysis. Monte Carlo parameter samples (α, β of the Beta-Poisson model) can be readily incorporated in risk assessment models built using tools such as S-plus and @ Risk.

scholarly journals Implementing a New Dose-response Model for Estimating Infection Probability of Campylobacter Jejuni based on the Key Events Dose-response Framework

2021 ◽  
Author(s):  
Hiroki Abe ◽  
Kohei Takeoka ◽  
Yuto Fuchisawa ◽  
Kento Koyama ◽  
Shigenobu Koseki
Keyword(s):  
Campylobacter Jejuni ◽  
Dose Response ◽  
Cell Invasion ◽  
Foodborne Pathogens ◽  
Pathogenic Bacteria ◽  
Underlying Mechanism ◽  
Response Model ◽  
Response Relationship ◽  
Dose Response Relationship ◽  
Key Factor

Abstract Understanding the dose-response relationship between ingested pathogenic bacteria and infection probability is a key factor for appropriate risk assessment of foodborne pathogens. The objectives of this study were to develop and validate a novel mechanistic dose-response model for Campylobacter jejuni and simulate the underlying mechanism of foodborne illness during digestion. Bacterial behavior in the human gastrointestinal environment, including gastric reductions, transition to intestines, and invasion to intestinal tissues, was described using a Bayesian statistical model based on the reported experimental results of each process while considering physical food types (liquid or solid) and host age (young or elderly). Combining the models in each process, the relationship between pathogen intake and the cell invasion probability of C. jejuni was estimated and compared with reported epidemiological dose-response relationships. Taking food types into account, estimations of the cell invasion probability of C. jejuni successfully described the reported dose-response relationships from substantial accidents. The developed calculation framework is thus potentially applicable to other pathogens to quantify the dose-response relationship from experimental data obtained from digestion.

scholarly journals Levan-Capped Silver Nanoparticles for Bactericidal Formulations: Release and Activity Modelling

2019 ◽  
Vol 20 (6) ◽  
pp. 1502 ◽  
Author(s):  
Álvaro González-Garcinuño ◽  
Rubén Masa ◽  
María Hernández ◽  
Ángel Domínguez ◽  
Antonio Tabernero ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Dose Response ◽  
Bactericidal Activity ◽  
Lethal Dose ◽  
Response Model ◽  
Inhibition Activity ◽  
E Coli ◽  
Unique Model ◽  
Bacteria Inhibition ◽  
Silver Release

An environmentally friendly technique was used to produce levan-capped silver nanoparticles of about 30 nm (with a loading of 30%) that showed bactericide effect, for E. coli and B. subtilis. That effect was mathematically studied with a dose-response model (lethal dose of 12.4 ppm and 6.8 ppm respectively). These silver nanoparticles were subsequently introduced in a gel to create a silver release system with bacteria inhibition activity. Silver release from the gel and its bactericidal activity was theoretically studied to develop a unique model that is able to predict accurately both silver release and lethal dose for any type of bacteria. This model will be useful for performing predictions for future silver in gel applications.

DISTRIBUSI DAN IDENTIFIKASI POPULASI SINTRONG (Crossocephalum crepidiodes.Benth) RESISTEN PARAKUAT PADA LAHAN JAGUNG (Zea mays) DI KABUPATEN DAIRI

2017 ◽  
Vol 4 (2) ◽  
pp. 149-161
Author(s):  
Berton Sianturi
Keyword(s):  
Zea Mays ◽  
Dose Response ◽  
High Resistance ◽  
Block Design ◽  
Recommended Dose ◽  
Second Step ◽  
Resistance Level ◽  
Susceptible Population ◽  
Randomized Complete Block Design ◽  
Susceptible Populations

Crassocephalum crepidioides on Cornfields in Dairi Regency had been reported tobecome more difficult to control using paraquat. The objective of the research was todetermine the characteristics and the distribution of C.crepidioides resistant to paraquatin cornfields. The experiment was carried out in two steps, the first step was screeningthe population of C. crepidioides with paraquat at the recommended dose, and the secondstep, dose-response experiment for the resistance level of C. crepidioides population withdose 0, 76, 152, 304,5, 609, 1218, and 2436 g.ai /ha. In the first step experiment, paraquatdichloride was applied at 280 g.ai/ha. The treatments were arranged in a randomized blockdesign with 3 replication. The second step experiment was that the resistant populationsconfirmed in the first experiment were sprayed for their dose-response. The treatmentswere arranged in a randomized complete block design (CRBD). The results showed thatof 30 populations of C. crepidiodes, 19 populations (63.3%) were categorized to beresistant with the mortality ranging from 10.84% to 52.08%, and 11 populations (36.7%),was categorized as high resistance with mortality of 0% to 9.21%. The level ofresistance (R/S) of R-C25, R-C27, and R-C30 populations of C. crepidioides were 12,3,14,86, and 24,83 times consecutively, compared with the susceptible population. Thenumber of C. crepidioides chlorophyl leaves in susceptible populations was significantlylower than that of a resistant populations.

scholarly journals Estimating the tolerance of brachial plexus to hypofractionated stereotactic body radiotherapy: a modelling-based approach from clinical experience

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Irina Kapitanova ◽  
Sharmi Biswas ◽  
Sabrina Divekar ◽  
Eric J. Kemmerer ◽  
Robert A. Rostock ◽  
...  
Keyword(s):  
Brachial Plexus ◽  
Dose Response ◽  
Medical Center ◽  
Probit Model ◽  
Brachial Plexopathy ◽  
Maximum Point ◽  
Response Model ◽  
Clinical Practices ◽  
Karolinska Institute ◽  
Human Dose

Abstract Background Brachial plexopathy is a potentially serious complication from stereotactic body radiation therapy (SBRT) that has not been widely studied. Therefore, we compared datasets from two different institutions and generated a brachial plexus dose–response model, to quantify what dose constraints would be needed to minimize the effect on normal tissue while still enabling potent therapy for the tumor. Methods Two published SBRT datasets were pooled and modeled from patients at Indiana University and the Richard L. Roudebush Veterans Administration Medical Center from 1998 to 2007, as well as the Karolinska Institute from 2008 to 2013. All patients in both studies were treated with SBRT for apically located lung tumors localized superior to the aortic arch. Toxicities were graded according to Common Terminology Criteria for Adverse Events, and a probit dose response model was created with maximum likelihood parameter fitting. Results This analysis includes a total of 89 brachial plexus maximum point dose (Dmax) values from both institutions. Among the 14 patients who developed brachial plexopathy, the most common complications were grade 2, comprising 7 patients. The median follow-up was 30 months (range 6.1–72.2) in the Karolinska dataset, and the Indiana dataset had a median of 13 months (range 1–71). Both studies had a median range of 3 fractions, but in the Indiana dataset, 9 patients were treated in 4 fractions, and the paper did not differentiate between the two, so our analysis is considered to be in 3–4 fractions, one of the main limitations. The probit model showed that the risk of brachial plexopathy with Dmax of 26 Gy in 3–4 fractions is 10%, and 50% with Dmax of 70 Gy in 3–4 fractions. Conclusions This analysis is only a preliminary result because more details are needed as well as additional comprehensive datasets from a much broader cross-section of clinical practices. When more institutions join the QUANTEC and HyTEC methodology of reporting sufficient details to enable data pooling, our field will finally reach an improved understanding of human dose tolerance.

Screening of Commercial and Pecan Shell–Extracted Liquid Smoke Agents as Natural Antimicrobials against Foodborne Pathogens

2012 ◽  
Vol 75 (6) ◽  
pp. 1148-1152 ◽  
Author(s):  
ELLEN J. VAN LOO ◽  
D. BABU ◽  
PHILIP G. CRANDALL ◽  
STEVEN C. RICKE
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Salmonella Enteritidis ◽  
Antioxidant Properties ◽  
Inhibitory Effects ◽  
Natural Antimicrobials ◽  
E Coli ◽  
Liquid Smoke ◽  
Water Based ◽  
Smoke Sample

Liquid smoke extracts have traditionally been used as flavoring agents, are known to possess antioxidant properties, and serve as natural alternatives to conventional antimicrobials. The antimicrobial efficacies of commercial liquid smoke samples may vary depending on their source and composition and the methods used to extract and concentrate the smoke. We investigated the MICs of eight commercial liquid smoke samples against Salmonella Enteritidis, Staphylococcus aureus, and Escherichia coli. The commercial liquid smoke samples purchased were supplied by the manufacturer as water-based or concentrated extracts of smoke from different wood sources. The MICs of the commercial smokes to inhibit the growth of foodborne pathogens ranged from 0.5 to 6.0% for E. coli, 0.5 to 8.0% for Salmonella, and 0.38 to 6% for S. aureus. The MIC for each liquid smoke sample was similar in its effect on both E. coli and Salmonella. Solvent-extracted antimicrobials prepared using pecan shells displayed significant differences between their inhibitory concentrations depending on the type of solvent used for extraction. The results indicated that the liquid smoke samples tested in this study could serve as effective natural antimicrobials and that their inhibitory effects depended more on the solvents used for extraction than the wood source.

Changes in Aerobic Plate and Escherichia coli–Coliform Counts and in Populations of Inoculated Foodborne Pathogens on Inshell Walnuts during Storage

2016 ◽  
Vol 79 (7) ◽  
pp. 1143-1153 ◽  
Author(s):  
JOHN C. FRELKA ◽  
GORDON R. DAVIDSON ◽  
LINDA J. HARRIS
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Relative Humidity ◽  
Low Temperature ◽  
Foodborne Pathogens ◽  
Limit Of Detection ◽  
Sampling Time ◽  
E Coli ◽  
Plate Counts ◽  
Forced Air

ABSTRACT After harvest, inshell walnuts are dried using low-temperature forced air and are then stored in bins or silos for up to 1 year. To better understand the survival of bacteria on inshell walnuts, aerobic plate counts (APCs) and Escherichia coli–coliform counts (ECCs) were evaluated during commercial storage (10 to 12°C and 63 to 65% relative humidity) over 9 months. APCs decreased by 1.4 to 2.0 log CFU per nut during the first 5 months of storage, and ECCs decreased by 1.3 to 2.2 log CFU per nut in the first month of storage. Through the remaining 4 to 8 months of storage, APCs and ECCs remained unchanged (P > 0.05) or decreased by <0.15 log CFU per nut per month. Similar trends were observed on kernels extracted from the inshell walnuts. APCs and ECCs were consistently and often significantly higher on kernels extracted from visibly broken inshell walnuts than on kernels extracted from visibly intact inshell walnuts. Parameters measured in this study were used to determine the survival of five-strain cocktails of E. coli O157:H7, Listeria monocytogenes, and Salmonella inoculated onto freshly hulled inshell walnuts (~8 log CFU/g) after simulated commercial drying (10 to 12 h; 40°C) and simulated commercial storage (12 months at 10°C and 65% relative humidity). Populations declined by 2.86, 5.01, and 4.40 log CFU per nut for E. coli O157:H7, L. monocytogenes, and Salmonella, respectively, after drying and during the first 8 days of storage. Salmonella populations changed at a rate of −0.33 log CFU per nut per month between days 8 and 360, to final levels of 2.83 ± 0.79 log CFU per nut. E. coli and L. monocytogenes populations changed by −0.17 log CFU per nut per month and −0.26 log CFU per nut per month between days 8 and 360, respectively. For some samples, E. coli or L. monocytogenes populations were below the limit of detection by plating (0.60 log CFU per nut) by day 183 or 148, respectively; at least one of the six samples was positive at each subsequent sampling time by either plating or by enrichment.

Changes in Post-Traumatic Symptom Pattern during and after Exposure to Extreme War Stress: An Uncontrolled, Preliminary Study Supporting the Dose-Response Model

2010 ◽  
Vol 25 (1) ◽  
pp. 38-41 ◽  
Author(s):  
Menachem Ben-Ezra ◽  
Yuval Palgi ◽  
Amit Shrira ◽  
Dina Sternberg ◽  
Nir Essar
Keyword(s):  
Dose Response ◽  
Medical Center ◽  
External Stress ◽  
Response Model ◽  
Ptsd Symptoms ◽  
Post Traumatic Stress ◽  
War Stress ◽  
Symptom Pattern ◽  
Post Traumatic ◽  
Stress Influences

AbstractIntroduction:Exposure to prolonged war stress is understudied. While there is debate regarding the empirical data of the dose-response model for post-traumatic stress disorder (PTSD), little is known about how weekly changes in external stress influences the level of PTSD symptoms. The purpose of this study was to measure the relation between objective external stress and PTSD symptoms across time, and thus, gain a deeper understating of the dose-response model.Hypothesis:The study hypothesis postulates that the more severe the external stressor, the more severe the exhibition of traumatic symptoms.Methods:Thirteen special army administrative staff (SAAS) members from the Rambam Medical Center in Haifa attended seven intervention meetings during the war. These personnel answered a battery of questionnaires regarding demographics and PTSD symptoms during each session. A non-parametric test was used in order to measure the changes in PTSD symptoms between sessions. Pearson correlations were used in order to study the relationship between the magnitude of external stressors and the severity of PTSD symptoms.Results:The results suggested that there was a significant relationship between the magnitude of external stressors and the severity of PTSD symptoms. These results are in line with the dose-response model.Conclusions:The results suggest that a pattern of decline in PTSD symptoms confirm the dose-response model for PTSD.

Sequence of Colonization Determines the Composition of Mixed Biofilms by Escherichia coli O157:H7 and O111:H8 Strains†

2015 ◽  
Vol 78 (8) ◽  
pp. 1554-1559 ◽  
Author(s):  
RONG WANG ◽  
NORASAK KALCHAYANAND ◽  
JAMES L. BONO
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
Early Stage ◽  
Critical Role ◽  
The United States ◽  
Food Samples ◽  
E Coli ◽  
Cell Percentage ◽  
Composition And Structure ◽  
Biofilm Development

Bacterial biofilms are one of the potential sources of cross-contamination in food processing environments. Shiga toxin–producing Escherichia coli (STEC) O157:H7 and O111:H8 are important foodborne pathogens capable of forming biofilms, and the coexistence of these two STEC serotypes has been detected in various food samples and in multiple commercial meat plants throughout the United States. Here, we investigated how the coexistence of these two STEC serotypes and their sequence of colonization could affect bacterial growth competition and mixed biofilm development. Our data showed that E. coli O157:H7 strains were able to maintain a higher cell percentage in mixed biofilms with the co-inoculated O111:H8 companion strains, even though the results of planktonic growth competition were strain dependent. On solid surfaces with preexisting biofilms, the sequence of colonization played a critical role in determining the composition of the mixed biofilms because early stage precolonization significantly affected the competition results between the E. coli O157:H7 and O111:H8 strains. The precolonizer of either serotype was able to outgrow the other serotype in both planktonic and biofilm phases. The competitive interactions among the various STEC serotypes would determine the composition and structure of the mixed biofilms as well as their potential risks to food safety and public health, which is largely influenced by the dominant strains in the mixtures. Thus, the analysis of mixed biofilms under various conditions would be of importance to determine the nature of mixed biofilms composed of multiple microorganisms and to help implement the most effective disinfection operations accordingly.

scholarly journals On use of the multistage dose–response model for assessing laboratory animal carcinogenicity

2007 ◽  
Vol 48 (2) ◽  
pp. 135-147 ◽  
Author(s):  
Daniela K. Nitcheva ◽  
Walter W. Piegorsch ◽  
R.Webster West
Keyword(s):  
Dose Response ◽  
Laboratory Animal ◽  
Response Model
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