scholarly journals Survival of LA-MRSA in Dust from Swine Farms

2018 ◽  
Vol 62 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Louise Feld ◽  
Hans Bay ◽  
Øystein Angen ◽  
Anders Rhod Larsen ◽  
Anne Mette Madsen
Keyword(s):  
Staphylococcus Aureus ◽  
Exponential Decay ◽  
Half Life ◽  
Storage Time ◽  
Decay Constant ◽  
Airborne Dust ◽  
Swine Farms ◽  
Exponential Decay Model ◽  
Staphylococcus Equorum ◽  
Rate Of Decay

AbstractDust is suspected to be an important factor in transmission of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) between pigs and pig farmers and their families. The aim of this study was to determine the rate of decay for Staphylococcus aureus and LA-MRSA in dust from swine farms. Electrostatic dust fall collectors (EDCs) were used for passive sampling of settling airborne dust in 11 stable sections from six swine farms. Extraction, plating, identification, and enumeration of cultivable S. aureus and LA-MRSA from the EDCs were performed after storage for 0–30 days postsampling. The survival of S. aureus was measured in 196 dust samples from all farms, and data were used to estimate the decay constant λ according to a model for exponential decay: N(t) = N0 × e−λt. The number of S. aureus colonies was up to 600-fold higher than the number of LA-MRSA colonies on MRSA selective agar. The data showed a good fit to the model (λ = 0.13, r2 = 0.86) even with a large difference in initial concentrations of S. aureus between stables. The loads of S. aureus and LA-MRSA in the dust were significantly reduced by storage time, and the half-life was 5 days for both S. aureus and LA-MRSA. In dust samples with high initial concentrations, LA-MRSA and S. aureus could still be cultivated 30 days after sampling. On all farms MRSA isolates belonged to the clonal complex (CC) 398, and at one farm some isolates also belonged to CC30. A screening for other Staphylococcus species in the farm dust revealed 13 different species numerically dominated by Staphylococcus equorum. Based on the exponential decay model, S. equorum had a half-life of 4 days. In conclusion, the presence of MRSA in airborne dust from five of six farms indicates that dust might be an important vehicle for transmission of LA-MRSA. LA-MRSA and S. aureus was found to survive well in farm dust with half-lives of 5 days, and dependent on the initial concentration they could be found in farm dust for weeks. The 99.9% die-off rate was 66 days for LA-MRSA. Thus, farm dust can pose an exposure risk for humans in the farm environment, but also when transported to other environments. On the other hand, the risk will decrease by time. These results provide important knowledge to diminish spread from farm environments to other environments on, e.g., tools or clothing, and in relation to cleaning of emptied LA-MRSA-positive stables.

Tree windthrow and forest soil turnover

1989 ◽  
Vol 19 (3) ◽  
pp. 386-389 ◽  
Author(s):  
D. A. Norton
Keyword(s):  
Forest Soil ◽  
Exponential Decay ◽  
Half Life ◽  
Soil Development ◽  
Turnover Time ◽  
Important Influence ◽  
Plant Distribution ◽  
Canopy Trees ◽  
Decay Model ◽  
Exponential Decay Model

Soil turnover as a result of tree windthrow has an important influence on soil development and plant distribution in forests. Estimates of the time needed for soil turnover in a given area are often made, but unless these take into account the potential for reestablishment of canopy trees onto sites previously affected by windthrow, they are likely to substantially underestimate turnover time. Soil turnover is not a regular, uniform process, but rather results in a mosaic of soils with different turnover histories. Because soil turnover follows an exponential decay model, some area of soil will never be turned over. As it is therefore not possible to define the time when all the soil in an area has been turned over, it is proposed that soil turnover half-life (the time at which half the soil has been turned over) be used as a measure of soil turnover.

scholarly journals Half-life of Ingested Antibodies in Anopheles Stephensi Mosquito Is Less Than 10 Hours

2021 ◽  
Author(s):  
Kazutoyo Miura ◽  
Deng Bingbing ◽  
Yonas T Gebremicale ◽  
Thao P Pham ◽  
Ababacar Diouf ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Mechanism Of Action ◽  
Half Life ◽  
Human Monoclonal Antibody ◽  
Critical Role ◽  
Target Antigen ◽  
Multiple Time ◽  
Human Red Blood Cells ◽  
Exponential Decay Model ◽  
Multiple Time Points

Abstract Background: A transmission-blocking vaccine (TBV) can be a useful tool to reduce malaria infection in an endemic area. For a TBV, elicited antibody (either by itself or working with complement) has a critical role in the mechanism of action, which for most known TBV targets, blockade will occur within the mosquito. However, no study has quantitively assessed the longevity of ingested antibody in Anopheles mosquito vectors. Methods: A mixture of mouse or human monoclonal antibody (mAb), human red blood cells and human serum were fed to An. stephensi mosquitoes, and their midguts were collected at multiple time points (0 to 48 hours; 12 mosquitoes at each time point) after feeds. The reactivity of antibodies against target antigen (integrity of antigen-binding region of the antibody) in each midgut was assessed by ELISA. For one mouse mAb, integrity of antibody constant region was also determined by western blot (WB) with a mouse-specific secondary antibody.Results: First, the half-life of mouse anti-Pfs25 mAb, 4B7, was determined both by ELISA and WB in three independent assays. When the ELISA and WB signals were plotted against time after feed, both data reasonably fit one-phase exponential decay models (R2 B 0.70), and the half-lives were estimated as 8.6 hours by ELISA and 4.7 hours by WB. To determine whether the longevity was affected by target antigens or species of antibody, two human anti-Pfs25 mAbs (AB1245 and AB2544), one human anti-Pfs48/45 mAb (TB31F), and one mouse anti-Pfs230 mAb (15A4-1B12) were examined by ELISA in two or three independent assays. The ELISA results of each additional mAb also reasonably fit to a one-phase exponential decay model (R2 a 0.78), and the half-lives of those mAbs were similar to that of 4B7 (7.2 to 9.3 hours), except AB1245 which showed a half-life of 4.6 hours. Conclusions: Depending on the methods of detection and mAbs used, the longevity of ingested antibody varied around 2-fold, but all estimated half-lives were < 10 hours. These data suggest a TBV with antibody dependent mechanism of action(s) is more likely to succeed when targeting earlier stages of parasites (or parasite interaction) in mosquitoes.

scholarly journals Longitudinal Study to Assess the Quantitative Use of Fundus Autofluorescence for Monitoring Disease Progression in Choroideremia

2021 ◽  
Vol 10 (2) ◽  
pp. 232
Author(s):  
Adam M Dubis ◽  
Wei S Lim ◽  
Jasleen K Jolly ◽  
Maria Toms ◽  
Robert E MacLaren ◽  
...  
Keyword(s):  
Disease Progression ◽  
Exponential Decay ◽  
Half Life ◽  
Fundus Autofluorescence ◽  
Area Measurement ◽  
Timely Manner ◽  
Measurement Variability ◽  
Slow Progression ◽  
Exponential Decay Model

Background: Characterisation of preserved autofluorescence (PAF) area in choroideremia (CHM) and its validity for monitoring disease progression in clinical trials is of importance. Methods: Eighty patients with molecularly confirmed CHM were recruited. PAF area was measured manually by 2 graders and half-life was calculated based on exponential decay model. Results: Mean age at baseline and follow-up examination was 38.1 (range, 10–69) and 40.7 (range, 11–70) years. Mean follow-up interval was 29 months (range, 6–104). The median LogMAR visual acuity was 0.10 (OD) and 0.18 (OS). Interobserver repeatability for PAF area was −0.99 to 1.03 mm2 (−6.46 to 6.49% of area). There was a statistically significant relationship between age and rate of PAF area loss (r2 = 0.28, p = 0.012). The half-life for PAF area was 13.7 years (range, 1.7–216.0 years). The correlation between half-life and age was stronger than between half-life and log transformed baseline PAF area, although neither was statistically significant. Conclusions: The intra- and inter-observer PAF area measurement variability provides a baseline change, which must be overcome in a clinical trial if this metric were to be used. Treatments must slow progression to alter the exponential decay in a timely manner accounting for naturally slow progression patterns.

scholarly journals A psychrometric model to assess the biological decay of the SARS-CoV-2 virus in aerosols

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e11024
Author(s):  
Clive B. Beggs ◽  
Eldad J. Avital
Keyword(s):  
Air Temperature ◽  
Vapour Pressure ◽  
Half Life ◽  
Analytical Study ◽  
Decay Constant ◽  
Meteorological Data ◽  
Environmental Parameters ◽  
Published Data ◽  
Reasonable Accuracy ◽  
The Impact

There is increasing evidence that the 2020 COVID-19 pandemic has been influenced by variations in air temperature and humidity. However, the impact that these environmental parameters have on survival of the SARS-CoV-2 virus has not been fully characterised. Therefore, an analytical study was undertaken using published data to develop a psychrometric model to assess the biological decay rate of the virus in aerosols. This revealed that it is possible to describe with reasonable accuracy (R2 = 0.718, p < 0.001) the biological decay constant for the SARS-CoV-2 virus using a regression model with enthalpy, vapour pressure and specific volume as predictors. Applying this to historical meteorological data from London, Paris and Milan over the pandemic period, produced results which indicate that the average half-life of the virus in aerosols outdoors was in the region 13–22 times longer in March 2020, when the outbreak was accelerating, than it was in August 2020 when epidemic in Europe was at its nadir. However, indoors, this variation is likely to be much less. As such, this suggests that changes in virus survivability due the variations in the psychrometric qualities of the air might influence the transmission of SARS-CoV-2.

scholarly journals An Exponential Decay Model for the Deterministic Correlations in Axial Compressors

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Yangwei Liu ◽  
Yumeng Tang ◽  
Baojie Liu ◽  
Lipeng Lu
Keyword(s):  
Exponential Decay ◽  
Equation System ◽  
Time Averaging ◽  
Mean Flow ◽  
Flow Solver ◽  
Axial Compressors ◽  
Routine Design ◽  
Proposed Model ◽  
Exponential Decay Model ◽  
Two Stages

The unsteady blade row interaction (UBRI) is inherent and usually has a large effect on performance in multistage axial compressors. The effect could be considered by using the average-passage equation system (APES) in steady-state environment by introducing the deterministic correlations (DC). How to model the DC is the key in APES method. The primary purpose of this study is to develop a DC model for compressor routine design. The APES technique is investigated by using a 3D viscous unsteady and time-averaging Computational fluid dynamics (CFD) flow solver developed in our previous studies. Based on DC characteristics and its effects on time-averaged flow, an exponential decay DC model is proposed and implemented into the developed time-averaging solver. Steady, unsteady, and time-averaging simulations are conducted on the investigation of the UBRI and the DC model in the first transonic stage of NASA 67 and the first two stages of a multistage compressor. The DC distributions and mean flow fields from the DC model are compared with the unsteady simulations. The comparison indicates that the proposed model can take into account the major part of UBRI and provide significant improvements for predicting compressor characteristics and spanwise distributions of flow properties in axial compressors, compared with the steady mixing plane method.

scholarly journals Exponential Decay Model of TVOC Emission from Indoor Building Materials

2020 ◽  
Vol 435 ◽  
pp. 012035
Author(s):  
Y Zhang ◽  
Y R Niu ◽  
Y Liu ◽  
Y F Wu ◽  
J X Jiang ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Building Materials ◽  
Decay Model ◽  
Exponential Decay Model

scholarly journals Engineering of Long-Circulating Peptidoglycan Hydrolases Enables Efficient Treatment of Systemic Staphylococcus aureus Infection

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Anna M. Sobieraj ◽  
Markus Huemer ◽  
Léa V. Zinsli ◽  
Susanne Meile ◽  
Anja P. Keller ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Human Blood ◽  
Half Life ◽  
Multidrug Resistant ◽  
Life Extension ◽  
Drug Resistant ◽  
Content Type ◽  
Peptidoglycan Hydrolases ◽  
Life Threatening

ABSTRACT Staphylococcus aureus is a human pathogen causing life-threatening diseases. The increasing prevalence of multidrug-resistant S. aureus infections is a global health concern, requiring development of novel therapeutic options. Peptidoglycan-degrading enzymes (peptidoglycan hydrolases, PGHs) have emerged as a highly effective class of antimicrobial proteins against S. aureus and other pathogens. When applied to Gram-positive bacteria, PGHs hydrolyze bonds within the peptidoglycan layer, leading to rapid bacterial death by lysis. This activity is highly specific and independent of the metabolic activity of the cell or its antibiotic resistance patterns. However, systemic application of PGHs is limited by their often low activity in vivo and by an insufficient serum circulation half-life. To address this problem, we aimed to extend the half-life of PGHs selected for high activity against S. aureus in human serum. Half-life extension and increased serum circulation were achieved through fusion of PGHs to an albumin-binding domain (ABD), resulting in high-affinity recruitment of human serum albumin and formation of large protein complexes. Importantly, the ABD-fused PGHs maintained high killing activity against multiple drug-resistant S. aureus strains, as determined by ex vivo testing in human blood. The top candidate, termed ABD_M23, was tested in vivo to treat S. aureus-induced murine bacteremia. Our findings demonstrate a significantly higher efficacy of ABD_M23 than of the parental M23 enzyme. We conclude that fusion with ABD represents a powerful approach for half-life extension of PGHs, expanding the therapeutic potential of these enzybiotics for treatment of multidrug-resistant bacterial infections. IMPORTANCE Life-threatening infections with Staphylococcus aureus are often difficult to treat due to the increasing prevalence of antibiotic-resistant bacteria and their ability to persist in protected niches in the body. Bacteriolytic enzymes are promising new antimicrobials because they rapidly kill bacteria, including drug-resistant and persisting cells, by destroying their cell wall. However, when injected into the bloodstream, these enzymes are not retained long enough to clear an infection. Here, we describe a modification to increase blood circulation time of the enzymes and enhance treatment efficacy against S. aureus-induced bloodstream infections. This was achieved by preselecting enzyme candidates for high activity in human blood and coupling them to serum albumin, thereby preventing their elimination by kidney filtration and blood vessel cells.

scholarly journals Exponential Decay to Thermoelastic Systems over Noncylindrical Domains

2011 ◽  
Vol 2011 ◽  
pp. 1-10
Author(s):  
Luci Harue Fatori ◽  
Michelle Klaiber
Keyword(s):  
Exponential Decay ◽  
Moving Boundary ◽  
Uniform Rate ◽  
Rate Of Decay

This paper is concerned with linear thermoelastic systems defined in domains with moving boundary. The uniform rate of decay of the energy associated is proved.

Activities: An Interest in Radioactivity

1996 ◽  
Vol 89 (3) ◽  
pp. 209-230
Author(s):  
Jane B. Kennedy
Keyword(s):  
Exponential Decay ◽  
Exponential Growth ◽  
Half Life ◽  
Core Curriculum ◽  
Equal Access ◽  
Compound Interest

Introduction: This activity explores exponential growth and decay, emphasizing the paired concepts of doubling and half-life. Exponential growth is derived from actual computations to obtain compound interest, whereas exponential decay is modeled by the use of “radioactive” dice. The activity is based on the concept of the differentiated core curriculum, which asserts that all students should be guaranteed equal access to the same curricular topics but recognizes that all students may not explore the content to the same depth or at the same level of formalism.

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