Validation of Predictive Mathematical Models Describing Growth of Staphylococcus aureus

1996 ◽  
Vol 59 (1) ◽  
pp. 11-15 ◽  
Author(s):  
ISABEL WALLS ◽  
VIRGINIA N. SCOTT ◽  
DANE T. BERNARD
Keyword(s):  
Staphylococcus Aureus ◽  
Mathematical Models ◽  
Growth Kinetics ◽  
Growth Rates ◽  
Close Agreement ◽  
Growth Conditions ◽  
Lag Phase ◽  
Growth Data ◽  
Gompertz Equation ◽  
Ph Range

An investigation was performed on the growth of Staphylococcus aureus in a commercially available, sterile, homogeneous food at 12°C with 1.2 and 5.9% NaCl; at 25°C with 10.4% NaCl; and at 20 and 35°C with 1.2, 5.3, 12.5, and 15.8% NaCl; over a pH range of 5.5 to 7.5. Growth data were fitted to the Gompertz equation and the resulting growth kinetics were compared with predictions from the Pathogen Modeling Program (PMP) and Food MicroModel (FMM). For the PMP, predicted lag-phase durations varied from 0.5 to 130 h longer than the observed values. In general, close agreement with growth rates was obtained but there was a 10-fold difference in one case. For FMM, predicted lag-phase durations ranged from 27 h shorter to 47 h longer than the observed values. Again, close agreement with growth rates was obtained, but in one case a fivefold difference was observed. In general, for the sterile foods used under the growth conditions tested, the models underestimated the growth of S. aureus. This implies that while the models can be used as a guide to indicate growth rates in foods they should not be relied upon as the sole determinant of the product's safety.

Validation of Predictive Mathematical Models Describing the Growth of Listeria monocytogenes

1997 ◽  
Vol 60 (9) ◽  
pp. 1142-1145 ◽  
Author(s):  
ISABEL WALLS ◽  
VIRGINIA N. SCOTT
Keyword(s):  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Microbial Growth ◽  
Lag Phase ◽  
Growth Data ◽  
Ph Values ◽  
Gompertz Equation ◽  
Generation Times ◽  
Different Temperatures ◽  
Good Agreement

Growth of Listeria monocytogenes and Listeria innocua in commercially available sterile homogeneous foods was investigated at different temperatures, pH values, and NaCl concentrations. Growth data were fitted to the Gompertz equation and the resulting growth kinetics were compared with predictions from the Pathogen Modeling Program and Food MicroModel. In general, good agreement was obtained when comparing growth rates and generation times for both models. Differences were observed when comparing lag phases, which ranged from 117 h shorter to 4.9 h longer than predicted for L. monocytogenes. Despite differences in lag phase, under most conditions, the models gave good predictions of microbial growth. Predictive modeling appears to be a useful tool in determining growth rates of Listeria in foods.

Growth kinetics ofStaphylococcus aureuson Brie and Camembert cheeses

2014 ◽  
Vol 81 (2) ◽  
pp. 252-256 ◽  
Author(s):  
Heeyoung Lee ◽  
Kyungmi Kim ◽  
Soomin Lee ◽  
Minkyung Han ◽  
Yohan Yoon
Keyword(s):  
Growth Kinetics ◽  
Storage Temperature ◽  
Model Performance ◽  
Lag Phase ◽  
Square Root ◽  
Growth Data ◽  
Phase Duration ◽  
Mannitol Salt Agar ◽  
Staph Aureus ◽  
Kinetics Of

In this study, we developed mathematical models to describe the growth kinetics ofStaphylococcus aureuson natural cheeses. A five-strain mixture ofStaph. aureuswas inoculated onto 15 g of Brie and Camembert cheeses at 4 log CFU/g. The samples were then stored at 4, 10, 15, 25, and 30 °C for 2–60 d, with a different storage time being used for each temperature. Total bacterial andStaph. aureuscells were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data ofStaph. aureusto calculate kinetic parameters such as the maximum growth rate in log CFU units (rmax; log CFU/g/h) and the lag phase duration (λ; h). The effects of temperature on the square root ofrmaxand on the natural logarithm of λ were modelled in the second stage (secondary model). Independent experimental data (observed data) were compared with prediction and the respective root mean square error compared with theRMSEof the fit on the original data, as a measure of model performance. The total growth of bacteria was observed at 10, 15, 25, and 30 °C on both cheeses. Thermaxvalues increased with storage temperature (P<0·05), but a significant effect of storage temperature on λ values was only observed between 4 and 15 °C (P<0·05). The square root model and linear equation were found to be appropriate for description of the effect of storage temperature on growth kinetics (R2=0·894–0·983). Our results indicate that the models developed in this study should be useful for describing the growth kinetics ofStaph. aureuson Brie and Camembert cheeses.

scholarly journals Anaerobic Conditions Induce Expression of Polysaccharide Intercellular Adhesin in Staphylococcus aureus and Staphylococcus epidermidis

2001 ◽  
Vol 69 (6) ◽  
pp. 4079-4085 ◽  
Author(s):  
Sarah E. Cramton ◽  
Martina Ulrich ◽  
Friedrich Götz ◽  
Gerd Döring
Keyword(s):  
Staphylococcus Aureus ◽  
Staphylococcus Epidermidis ◽  
Biofilm Formation ◽  
Extracellular Polysaccharide ◽  
Growth Conditions ◽  
Anaerobic Conditions ◽  
Anaerobic Environment ◽  
Specific Mrna

ABSTRACT Products of the intercellular adhesion (ica) operon in Staphylococcus aureus and Staphylococcus epidermidis synthesize a linear β-1,6-linked glucosaminylglycan. This extracellular polysaccharide mediates bacterial cell-cell adhesion and is required for biofilm formation, which is thought to increase the virulence of both pathogens in association with prosthetic biomedical implants. The environmental signal(s) that triggers ica gene product and polysaccharide expression is unknown. Here we demonstrate that anaerobic in vitro growth conditions lead to increased polysaccharide expression in both S. aureus and S. epidermidis, although the regulation is less stringent inS. epidermidis. Anaerobiosis also dramatically stimulates ica-specific mRNA expression inica- and polysaccharide-positive strains of both S. aureus and S. epidermidis.These data suggest a mechanism whereby ica gene expression and polysaccharide production may act as a virulence factor in an anaerobic environment in vivo.

scholarly journals Modified Gompertz equation for electrotherapy murine tumor growth kinetics: predictions and new hypotheses

BMC Cancer ◽  
2010 ◽  
Vol 10 (1) ◽  
Author(s):  
Luis E Bergues Cabrales ◽  
Juan J Godina Nava ◽  
Andrés Ramírez Aguilera ◽  
Javier A González Joa ◽  
Héctor M Camué Ciria ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Growth Kinetics ◽  
Murine Tumor ◽  
Gompertz Equation ◽  
Tumor Growth Kinetics

Impact of pH on growth of Staphylococcus epidermidis and Staphylococcus aureus in vitro

2021 ◽  
Vol 70 (9) ◽  
Author(s):  
Vidula Iyer ◽  
Janhavi Raut ◽  
Anindya Dasgupta
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Kinetics ◽  
Staphylococcus Epidermidis ◽  
Type Species ◽  
Ph Dependence ◽  
Skin Microbiome ◽  
Content Type ◽  
Link Type ◽  
Kinetics Of

The pH of skin is critical for skin health and resilience and plays a key role in controlling the skin microbiome. It has been well reported that under dysbiotic conditions such as atopic dermatitis (AD), eczema, etc. there are significant aberrations of skin pH, along with a higher level of Staphylococcus aureus compared to the commensal Staphylococcus epidermidis on skin. To understand the effect of pH on the relative growth of S. epidermidis and S. aureus , we carried out simple in vitro growth kinetic studies of the individual microbes under varying pH conditions. We demonstrated that the growth kinetics of S. epidermidis is relatively insensitive to pH within the range of 5–7, while S. aureus shows a stronger pH dependence in that range. Gompertz’s model was used to fit the pH dependence of the growth kinetics of the two bacteria and showed that the equilibrium bacterial count of S. aureus was the more sensitive parameter. The switch in growth rate happens at a pH of 6.5–7. Our studies are in line with the general hypothesis that keeping the skin pH within an acidic range is advantageous in terms of keeping the skin microbiome in balance and maintaining healthy skin.

Modelling the colonisation of maize by toxigenic and non-toxigenic Aspergillus flavus strains: implications for biological control

2008 ◽  
Vol 1 (3) ◽  
pp. 333-340 ◽  
Author(s):  
H. Abbas ◽  
R. Zablotowicz ◽  
H. Bruns
Keyword(s):  
Biological Control ◽  
Aspergillus Flavus ◽  
Growth Parameters ◽  
Biological Control Agent ◽  
Cyclopiazonic Acid ◽  
Aflatoxin Contamination ◽  
Tween 20 ◽  
Lag Phase ◽  
Gompertz Equation ◽  
Aflatoxin Accumulation

To successfully exploit biological control it is desirable to understand how the introduced agent colonises the host and interferes with establishment of the pest. This study assessed field colonisation of maize by Aspergillus flavus strains as biological control agents to reduce aflatoxin contamination. Maize (corn, Zea mays L.) ears were inoculated with A. flavus using a pin-bar technique in 2004 and 2005. Non-aflatoxigenic strains K49 (NRRL 30797) & CT3 (NRRL 30798) and toxigenic F3W4 (NRRL 30798) were compared against a carrier control (0.2% aqueous Tween 20). Ten ears were sampled over 12 to 20 days, visually assessed, and curves fit to a three compartment Gompertz equation or other best appropriate regressions. Aflatoxin was determined by HPLC and cyclopiazonic acid (CPA) by LC/MS. The Gompertz model describes growth parameters, e.g. growth constant, lag phase and maximum colonisation characterised patterns of maize colonisation for most inoculated treatments. Aflatoxin accumulation in maize inoculated with F3W4 was about 35,000 ng/g in 2004 and 2005, with kinetics of aflatoxin accumulation in 2005 well described by the Gompertz equation. Less than 200 ng/g was observed in maize inoculated with strains CT3 & K49 and accumulation was described by a linear or logistic model. Maize inoculated with strains CT3 and F3W4 accumulated a maximum of 220 and 169 µg/kg CPA, respectively, compared to 22 and 0.2 µg/kg in the control and K49 inoculated, respectively. This technique can be used to elucidate colonisation potential of non-toxigenic A. flavus in maize in relation to biological control of aflatoxin. The greatest reduction of aflatoxin and CPA in maize inoculated with strain K49 and Gompertz parameters on colonisation indicates its superiority to CT3 as a biological control agent. The dynamics of maize colonisation by A. flavus strains and subsequent mycotoxin accumulation generated by using the pin-bar technique has implications for characterising the competence of biocontrol strains for reducing aflatoxin contamination.

scholarly journals Growth of Listeria monocytogenes in Thawed Frozen Foods

2017 ◽  
Vol 80 (3) ◽  
pp. 447-453 ◽  
Author(s):  
Ai Kataoka ◽  
Hua Wang ◽  
Philip H. Elliott ◽  
Richard C. Whiting ◽  
Melinda M. Hayman
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Growth Rates ◽  
Storage Temperature ◽  
Growth Parameters ◽  
Quadratic Model ◽  
Lag Phase ◽  
Frozen Foods ◽  
Phase Duration ◽  
Primary Model

ABSTRACT The growth characteristics of Listeria monocytogenes inoculated onto frozen foods (corn, green peas, crabmeat, and shrimp) and thawed by being stored at 4, 8, 12, and 20°C were investigated. The growth parameters, lag-phase duration (LPD) and exponential growth rate (EGR), were determined by using a two-phase linear growth model as a primary model and a square root model for EGR and a quadratic model for LPD as secondary models, based on the growth data. The EGR model predictions were compared with growth rates obtained from the USDA Pathogen Modeling Program, calculated with similar pH, salt percentage, and NaNO2 parameters, at all storage temperatures. The results showed that L. monocytogenes grew well in all food types, with the growth rate increasing with storage temperature. Predicted EGRs for all food types demonstrated the significance of storage temperature and similar growth rates among four food types. The predicted EGRs showed slightly slower rate compared with the values from the U.S. Department of Agriculture Pathogen Modeling Program. LPD could not be accurately predicted, possibly because there were not enough sampling points. These data established by using real food samples demonstrated that L. monocytogenes can initiate growth without a prolonged lag phase even at refrigeration temperature (4°C), and the predictive models derived from this study can be useful for developing proper handling guidelines for thawed frozen foods during production and storage.

Does Economic Growth Pay Political Dividends in India?

2019 ◽  
Vol 67 (1-2) ◽  
pp. 166-169
Author(s):  
Vasant V. Bang ◽  
Alok Kumar Mishra
Keyword(s):  
Economic Growth ◽  
Growth Rates ◽  
Regression Equations ◽  
Economic Policies ◽  
Growth Data ◽  
Parliamentary Elections ◽  
Independent Variables ◽  
Economic Development And Growth ◽  
Bharatiya Janata Party ◽  
Ruling Party

Since independence in 1947, India has witnessed several changes in economic policies of governments. Economic reforms were started in India in 1984 and were accelerated later in 1991. It is believed that Bharatiya Janata Party won the 2014 parliamentary elections on the promise of economic development and growth. In this article, an attempt has been made to investigate the link between economic and electoral performances in Indian elections. The data for 1951–2014 period has been analysed by establishing regression equations using vote percentage received by a ruling party as dependent variable and sectoral economic growth during the ruling tenure as independent variables. Comparisons have been made between the pre- and post-1984 eras. An important contribution of this article is that it highlights the fact that electoral performances can be better explained using sectoral growth data as compared to overall GDP growth rates. The article also highlights a significant role played by volatility in growth rates.

Dynamic Predictive Model for Growth of Bacillus cereus from Spores in Cooked Beans

2017 ◽  
Vol 81 (2) ◽  
pp. 308-315 ◽  
Author(s):  
Vijay K. Juneja ◽  
Abhinav Mishra ◽  
Abani K. Pradhan
Keyword(s):  
Bacillus Cereus ◽  
Growth Rates ◽  
Linear Models ◽  
Growth Models ◽  
Maximum Growth ◽  
Effect Of Temperature ◽  
Coefficient Of Determination ◽  
Growth Data ◽  
Three Phase ◽  
Primary Model

ABSTRACT Kinetic growth data for Bacillus cereus grown from spores were collected in cooked beans under several isothermal conditions (10 to 49°C). Samples were inoculated with approximately 2 log CFU/g heat-shocked (80°C for 10 min) spores and stored at isothermal temperatures. B. cereus populations were determined at appropriate intervals by plating on mannitol–egg yolk–polymyxin agar and incubating at 30°C for 24 h. Data were fitted into Baranyi, Huang, modified Gompertz, and three-phase linear primary growth models. All four models were fitted to the experimental growth data collected at 13 to 46°C. Performances of these models were evaluated based on accuracy and bias factors, the coefficient of determination (R2), and the root mean square error. Based on these criteria, the Baranyi model best described the growth data, followed by the Huang, modified Gompertz, and three-phase linear models. The maximum growth rates of each primary model were fitted as a function of temperature using the modified Ratkowsky model. The high R2 values (0.95 to 0.98) indicate that the modified Ratkowsky model can be used to describe the effect of temperature on the growth rates for all four primary models. The acceptable prediction zone (APZ) approach also was used for validation of the model with observed data collected during single and two-step dynamic cooling temperature protocols. When the predictions using the Baranyi model were compared with the observed data using the APZ analysis, all 24 observations for the exponential single rate cooling were within the APZ, which was set between −0.5 and 1 log CFU/g; 26 of 28 predictions for the two-step cooling profiles also were within the APZ limits. The developed dynamic model can be used to predict potential B. cereus growth from spores in beans under various temperature conditions or during extended chilling of cooked beans.

scholarly journals Coriolis effects on the elliptical instability in cylindrical and spherical rotating containers

2007 ◽  
Vol 585 ◽  
pp. 323-342 ◽  
Author(s):  
M. LE BARS ◽  
S. LE DIZÈS ◽  
P. LE GAL
Keyword(s):  
Growth Rates ◽  
Close Agreement ◽  
Unstable Mode ◽  
Quantitative Agreement ◽  
Fixed Rate ◽  
Elliptical Instability ◽  
Normal Mode Theory ◽  
Set Up ◽  
First Time ◽  
Selection Of

The effects of the Coriolis force on the elliptical instability are studied experimentally in cylindrical and spherical rotating containers placed on a table rotating at a fixed rate $\tilde{\Omega}^G$. For a given set-up, changing the ratio ΩG of global rotation $\tilde{\Omega}^G$ to flow rotation $\tilde{\Omega}^F$ leads to the selection of various unstable modes due to the presence of resonance bands, in close agreement with the normal-mode theory. No instability occurs when ΩG varies between −3/2 and −1/2 typically. On decreasing ΩG toward −1/2, resonance bands are first discretized for ΩG<0 and progressively overlap for −1/2 ≪ ΩG < 0. Simultaneously, the growth rates and wavenumbers of the prevalent stationary unstable mode significantly increase, in quantitative agreement with the viscous short-wavelength analysis. New complex resonances have been observed for the first time for the sphere, in addition to the standard spin-over. We argue that these results have significant implications in geo- and astrophysical contexts.

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