Decomposition of Growth Curves into Growth Rate and Acceleration: a Novel Procedure to Monitor Bacterial Growth and the Time-Dependent Effect of Antimicrobials

2021 ◽  
Author(s):  
M. Luisa Navarro-Pérez ◽  
M. Coronada Fernández-Calderón ◽  
Virginia Vadillo-Rodríguez
Keyword(s):  
Growth Rate ◽  
Mathematical Models ◽  
Bacterial Growth ◽  
Time Course ◽  
Antimicrobial Agents ◽  
Numerical Procedure ◽  
Growth Curves ◽  
Predictive Microbiology ◽  
Insight Into ◽  
Over Time

In this paper, a simple numerical procedure is presented to monitor the growth of Streptococcus sanguinis over time in the absence and presence of propolis, a natural antimicrobial. In particular, it is shown that the real-time decomposition of growth curves obtained through optical density measurements into growth rate and acceleration can be a powerful tool to precisely assess a large range of key parameters [ i.e. lag time ( t 0 ), starting growth rate ( γ 0 ), initial acceleration of the growth ( a 0 ), maximum growth rate ( γ max ), maximum acceleration ( a max ) and deceleration ( a min ) of the growth and the total number of cells at the beginning of the saturation phase ( N s )] that can be readily used to fully describe growth over time. Consequently, the procedure presented provides precise data of the time course of the different growth phases and features, which is expected to be relevant, for instance, to thoroughly evaluate the effect of new antimicrobial agents. It further provides insight into predictive microbiology, likely having important implications to assumptions adopted in mathematical models to predict the progress of bacterial growth. Importance: The new and simple numerical procedure presented in this paper to analyze bacterial growth will possibly allow identifying true differences in efficacy among antimicrobial drugs for their applications in human health, food security, and environment, among others. It further provides insight into predictive microbiology, likely helping in the development of proper mathematical models to predict the course of bacterial growth under diverse circumstances.

Growth Curves of S. elongatus under salt stress and low carbon v1

2021 ◽  
Author(s):  
Akashdutta not provided
Keyword(s):  
Growth Rate ◽  
Salt Stress ◽  
Growth Curves ◽  
Toxic Waste ◽  
Physiological Adaptation ◽  
Phase Cell ◽  
Lag Phase ◽  
Low Carbon ◽  
Over Time ◽  
Number Of Cells

When liquid media is inoculated with bacteria and the cell population is counted at intervals, it is possible to plot a typical bacterial growth curve that shows the increase in the number of cells over time. Such growth curves show four distinct phases of growth: Lag phase: There is slow growth or lack of growth due to the physiological adaptation of cells to culture conditions or the dilution of exoenzymes (due to initial low cell densities). Log or exponential phase: Optimal growth rates are seen in this phase. Cell numbers double at discrete time intervals known as the mean generation time. Stationary phase: During this phase, the growth (cell division) and death of cells occur at the same rate, resulting in the number of cells being constant. The reduced growth rate is usually due to a lack of nutrients and/or a buildup of toxic waste constituents. Decline or death phase: Here, the death rate exceeds the growth rate, resulting in a net loss of viable cells. This is one of the simplest methods used to analyze trends in growth because it uses a spectrophotometer to track changes in the optical density (OD) over time. In other words, as the number of cells in a sample increases, the transmission of light through the sample will decrease. Growth curves for certain freshwater cyanobacterial species are carried out under salt stress to account for sucrose production in the particular strain. This is because sucrose is naturally produced intracellularly in these strains to balance the osmotic pressure of a saline environment.

scholarly journals Comparisons between Antimicrobial Pharmacodynamic Indices and Bacterial Killing as Described by Using the Zhi Model

1998 ◽  
Vol 42 (7) ◽  
pp. 1731-1737 ◽  
Author(s):  
S. Corvaisier ◽  
P. H. Maire ◽  
M. Y. Bouvier d’yvoire ◽  
X. Barbaut ◽  
N. Bleyzac ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Time Course ◽  
Composite Index ◽  
Relative Number ◽  
Good Sensitivity ◽  
Time Curve ◽  
Bacterial Killing ◽  
Concentration Time ◽  
Time Courses ◽  
Over Time

ABSTRACT Various suggestions have been made for empirical pharmacodynamic indices of antibiotic effectiveness, such as areas under the drug concentration-time curve in serum (AUC), AUC>MIC, AUC/MIC, area under the inhibitory curve (AUIC), AUC above MIC, and time above MIC (T>MIC). In addition, bacterial growth and killing models, such as the Zhi model, have been developed. The goal of the present study was to compare the empirical behavior of the Zhi model of bacterial growth and killing with the other empirical pharmacodynamic indices described above by using simulated clinical data analyzed with the USC*PACK PC clinical programs for adaptive control of drug therapy, with one model describing a concentration-dependent antibiotic (tobramycin) and another describing a concentration-independent antibiotic (ticarcillin). The computed relative number of CFU was plotted against each pharmacodynamic index, with each axis parameterized over time. We assumed that a good pharmacodynamic index should present a clear and continuous relationship between the time course of its values and the time course of the bacterial killing as seen with the Zhi model. Preliminary work showed that some pharmacodynamic indices were very similar. A good sensitivity to the change in the values of the MIC was shown for AUC/MIC and also forT>MIC. In addition, the time courses of some other pharmacodynamic indices were very similar. Since AUC/MIC is easily calculated and shows more sensitivity, it appeared to be the best of the indices mentioned above for the concentration-dependent drug, because it incorporated and used the MIC the best. T>MIC appeared to be the best index for a concentration-independent drug. We also propose a new composite index, weighted AUC (WAUC), which appears to be useful for both concentration-dependent and concentration-independent drugs.

scholarly journals The problem of predicting food intake during the period of adaptation to a new food: a model

2003 ◽  
Vol 89 (3) ◽  
pp. 383-399 ◽  
Author(s):  
Emma C. Whittemore ◽  
Gerry C. Emmans ◽  
Ilias Kyriazakis
Keyword(s):  
Growth Rate ◽  
Food Intake ◽  
Time Course ◽  
Live Weight ◽  
Growth Function ◽  
Rate Of Change ◽  
Published Data ◽  
Potential Growth ◽  
Dry Food ◽  
Over Time

A model is described which aims to predict intake immediately following a change from one food to another that is higher in bulk content; it deals with the transition from one ‘equilibrium’ intake to another. The system considered is an immature pig fedad libitumon a single homogeneous food, which is balanced for nutrients and contains no toxins so that the first limiting resource is always energy. It is assumed that an animal has a desired rate of food intake (DFI) which is that needed to meet the energy requirements for protein and lipid deposition and for maintenance. DFI may not be achieved if a bulk constraint to intake exists. Where a bulk constraint operates intake is calculated as constrained food intake (CFI) where CFI=Cwhc/WHC k/ (where WHC is the water-holding capacity of the food (kg wate/g dry food) and Cwhcis the animal's capacity for WHC (unit/g live weight per d)). Where intake is not constrained it is assumed that genetic potential will be achieved. Potential growth rate is described by the Gompertz growth function. Where intake is constrained, growth will be less than the potential. Constrained growth rate is predicted as (d/t)con=(EI−Em)/egk/ where W is pig weight (kg), EI is energy intake (M/), Emis the energy required for maintenance (M/) and egis the energy required for unit gain (M/g). The value of egdepends on weight and the fattening characteristics of the pig. Actual growth is predicted to be the lesser of potential and constrained growth. To deal with adaptation it is assumed that the time taken to reach equilibrium depends on the difference in WHC values between the previous and current food and that the capacity to consume food bulk is related to the WHC of the current food. It is proposed that the capacity for WHC on the first day on a new food will be equal to the current capacity for WHC on the last day of the previous food. Thus Cwhc=(FI×WHC)/W /g, where FI is food intake (k/). Thereafter Cwhcwill gradually increase over time to a maximum of 0·27 /g. The rate of change in Cwhcis made to be the same for all pigs and all foods. The increase in capacity over time is assumed to be linear at the rate of 0·01 unit/. The model was tested using published data. Qualitatively the predictions of the model were in close agreement with the relevant observed data in at least some cases. It is concluded that the underlying theoretical assumptions of the model are reasonable. However, the model fails to predict initial intake when changed to foods high in wheat-bran content and fails to predict the intake of a non-limiting food where compensatory increases in intake and gain occur. The model could be adapted to overcome the first failure by taking into account the time course of digestive efficiency following a change in food. To deal with the second would require a sufficient understanding of the time course of compensatory growth.

scholarly journals Methods to optimize energy consumption in Conarc furnaces

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Aashay Wanjari
Keyword(s):  
Energy Consumption ◽  
Mathematical Models ◽  
Raw Materials ◽  
Maximum Efficiency ◽  
Steelmaking Process ◽  
The Past ◽  
Annual Productivity ◽  
Produce Steel ◽  
Insight Into ◽  
Over Time

AbstractOver the past few decades, steelmaking has reached its zenith in terms of annual productivity, and relevant processes have been developed over time to produce steel with maximum efficiency in a shorter time. One of the prominent steelmaking practices used extensively in contemporary industries is the Conarc Steelmaking Practice, which involves the use of electrical and chemical Energy to carry out melting and decarburization in respective shells. This article reviews the factors that affect the energy consumption in Conarc furnaces and provides insight into the technologies developed to alleviate energy consumption and make the steelmaking process optimal in terms of energy consumption and requirement. This article also accentuates relevant systems and melting practices for the raw materials, which can be utilized in the Conarc Steelmaking practice to make the entire process less energy-intensive. Oxygen-enhanced combustion and thermophotovoltaic systems can alleviate energy consumption substantially while maintaining steel quality at the same time, as discussed in the paper. Additionally, some mathematical models have been discussed that facilitate in formulating an energy optimal and financial steelmaking process.

Growth Curves of S. elongatus under salt stress and high carbon v1

2021 ◽  
Author(s):  
Akashdutta not provided
Keyword(s):  
Carbon Dioxide ◽  
Growth Rate ◽  
Salt Stress ◽  
Growth Curves ◽  
Toxic Waste ◽  
Physiological Adaptation ◽  
Phase Cell ◽  
Lag Phase ◽  
Over Time ◽  
Number Of Cells

When liquid media is inoculated with bacteria and the cell population is counted at intervals, it is possible to plot a typical bacterial growth curve that shows the increase in the number of cells over time. Such growth curves show four distinct phases of growth:1 Lag phase: There is slow growth or lack of growth due to the physiological adaptation of cells to culture conditions or the dilution of exoenzymes (due to initial low cell densities). Log or exponential phase: Optimal growth rates are seen in this phase. Cell numbers double at discrete time intervals known as the mean generation time. Stationary phase: During this phase, the growth (cell division) and death of cells occur at the same rate, resulting in the number of cells being constant. The reduced growth rate is usually due to a lack of nutrients and/or a buildup of toxic waste constituents. Decline or death phase: Here, the death rate exceeds the growth rate, resulting in a net loss of viable cells. This is one of the simplest methods used to analyze trends in growth because it uses a spectrophotometer to track changes in the optical density (OD) over time. In other words, as the number of cells in a sample increases, the transmission of light through the sample will decrease.2 Growth curves for certain freshwater cyanobacterial species are carried out under salt stress to account for sucrose production in the particular strain. This is because sucrose is naturally produced intracellularly in these strains to balance the osmotic pressure of a saline environment.3 This experiment was carried out in two iterations: one at 0.04% of carbon dioxide - i.e, ambient carbon dioxide from the atmosphere - and the other with bicarbonate added to be equivalent to 0.6% of carbon dioxide. Find our results for these iterations here.

scholarly journals Quantitative evaluation of medium filth (najs mutawassitah) in halalan toyyibah food

2016 ◽  
Vol 15 (1) ◽  
Author(s):  
Ibrahim Abu Bakar ◽  
Ainin Azwani Abdul Rafa ◽  
Norrakiah Abdullah Sani
Keyword(s):  
Growth Rate ◽  
Health Risk ◽  
Ambient Temperature ◽  
Quantitative Evaluation ◽  
Health Risks ◽  
Bacterial Growth ◽  
Growth Curves ◽  
Lag Time ◽  
Lag Times

Introduction: This study was conducted to evaluate the quantity of medium filth (najs mutawassitah) and the growth rate of faecal borne bacteria in self prepared fried rice toward the standardization of ‘halalan toyyibah’ food. Methods: The samples of fried rice were cooked with the application of hygienic practices. A specific quantity of human stools were then purposely inoculated into the samples. The growth curves of the bacteria were determined using NanoDrop 1000 UV-VIS Spectrophotometer at 630nm where the initial and end of lag times for each of the bacterial growth were determined. Results: The results showed that if the contamination of human stools in the food is in small quantity (1-2 drops), it may have no health risk at all (within lag time). If the human stools are in higher volume (more than 2 drops, or about 1 ml) then it may start to contaminate the food and could then lead to health risks. If foods are contaminated with small amounts (about 0.1 ml) of human stools and left at ambient temperature (about 37o C) for about 4 hours, the same thing will happen. Conclusions: If the level of health risk is translated according to Shariah law, foods which are contaminated with higher amount (more than 2 drops, or about 1 ml) of human stools or contaminated with small amounts (1-2 drops) of human stools, but are left (about 4 hours) at ambient temperature can be considered as shubhah/makhrooh to be eaten.

scholarly journals Growth of Staphylococcus aureus 2064 described by predictive microbiology: From primary to secondary models

2019 ◽  
Vol 12 (2) ◽  
pp. 175-181
Author(s):  
Alžbeta Medveďová ◽  
Adriana Havlíková ◽  
Ľubomír Valík
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Rate ◽  
Specific Growth Rate ◽  
Water Activity ◽  
Goodness Of Fit ◽  
Specific Growth ◽  
Growth Curves ◽  
Extended Model ◽  
Predictive Microbiology ◽  
Temperature Range

Abstract The growth of Staphylococcus aureus 2064 isolate in model nutrient broth was studied as affected by temperature and water activity using principles and models of predictive microbiology. Specific rates resulting from growth curves fitted by the Baranyi model were modelled by the secondary Ratkowsky model for suboptimal temperature range (RTKsub) as well as the Ratkowsky extended model (RTKext) and cardinal model (CM) in the whole temperature range. With the biological background of the RTKext model, cardinal values of temperature Tmin = 6.06 °C and Tmax = 47.9 °C and water activity aw min = 0.859 were calculated and validated with cardinal values estimated by CM (Tmin = 7.72 °C, Tmax = 46.73 °C, aw min = 0.808). CM also provided other cardinal values, Topt = 40.63 °C, aw opt = 0.994, as well as optimal specific growth rate of 1.97 h–1 (at Topt and aw opt). To evaluate the goodness of fit of all models, mathematical and graphical validation was performed and the statistical indices proved appropriateness of all the secondary models used.

Probiotics Slow the Growth of Pathogenic Bacteria

2019 ◽  
Vol 14 (1) ◽  
pp. 28-31 ◽  
Author(s):  
Rowles H. L.
Keyword(s):  
Growth Rate ◽  
Bacterial Infections ◽  
Pathogenic Bacteria ◽  
Diarrheal Disease ◽  
Growth Curves ◽  
Mortality Rates ◽  
Controlled Delivery ◽  
E Coli ◽  
Multiple Strains ◽  
Commercial Probiotics

Probiotics are live microorganisms, which when ingested in sufficient amounts, confer health benefits to the host by improving the gut microflora balance. The purpose of this research was to determine whether commercial probiotic products containing multitude of commensal bacteria would reduce the growth rate of pathogenic bacteria, specifically Escherichia coli and Salmonella typhimurium. Growth curves were established, and the growth rates were compared for samples of E. coli, S. typhimurium, Nature’s Bounty Controlled Delivery probiotic, Sundown Naturals Probiotic Balance probiotic, and cocultures of the pathogenic bacteria mixed with the probiotics. The findings of this research were that the commercial probiotics significantly reduced the growth rate of E. coli and S. typhimurium when combined in cocultures. Probiotics containing multiple strains may be taken prophylactically to reduce the risk of bacterial infections caused by E. coli and S. typhimurium. Probiotics could be used to reduce the high global morbidity and mortality rates of diarrheal disease.

Dualities, Dialectics, and Paradoxes in Organizational Life

2018 ◽  
Keyword(s):  
Dynamic Systems ◽  
Empirical Studies ◽  
Organizational Studies ◽  
Organizational Life ◽  
Organizational Processes ◽  
Organization Studies ◽  
Process Studies ◽  
Convergence And Divergence ◽  
Insight Into ◽  
Over Time

Organizational contradictions and process studies offer interwoven and complementary insights. Studies of dialectics, paradox, and dualities depict organizational contradictions that are oppositional as well as interrelated such that they persistently morph and shift over time. Studies of process often examine how contradictions fuel emergent, dynamic systems and stimulate novelty, adaptation, and transformation. Drawing from rich conversations at the Eighth International Symposium on Process Organization Studies, the contributors to this volume unpack these relationships in more depth. The chapters explore three main, connected themes through both conceptual and empirical studies, including (1) offering insight into how process theorizing advances understandings of organizational contradictions; (2) shedding light on how dialectics, paradoxes, and dualities fuel organizational processes that affect persistence and transformation; and (3) exploring the convergence and divergence of dialectics, paradox, and dualities lenses. Taken together, this book offers key insights in order to inform persistent, contradictory dynamics in organizations and organizational studies.

The Oxford Handbook of the Brazilian Economy

2018 ◽  
Keyword(s):  
Direct Investment ◽  
Global Economy ◽  
Iron Ore ◽  
Structural Features ◽  
Economic Importance ◽  
Closed Economy ◽  
Current Characteristics ◽  
Insight Into ◽  
Contemporary Context ◽  
Over Time

Brazil constitutes a globally vital but troubled economy. It accounts for the largest GDP in Latin America and ranks among the world’s largest exporters of critical commodities including iron ore, soya, coffee, and beef. In recent years Brazil’s global economic importance has been magnified by a surge in both outward and inward foreign direct investment. This has served to further internationalize what has been historically a relatively closed economy. The purpose of this Handbook is to offer real insight into the Brazil’s economic development in contemporary context, understanding its most salient characteristics and analyzing its structural features across various dimensions. At a more granular level, this volume accomplishes the following tasks. First, it provides an understanding of the economy’s evolution over time and the connection of its current characteristics to this evolution. Second, it analyzes Brazil’s broader place in the global economy, and considers the ways in which this role has changed, and is likely to change, over coming years. Third, reflecting contemporary concerns, the volume offers an understanding, not only of how one of the world’s key economies has developed and transformed itself, but also of the ways in which this process has yet to be completed. The volume thus analyzes the current challenges facing the Brazilian economy and the kinds of issues that need to be tackled for these to be addressed.

Sign in / Sign up

Export Citation Format

Share Document