scholarly journals Quantitative Interaction Effects of Carbon Dioxide, Sodium Chloride, and Sodium Nitrite on Neurotoxin Gene Expression in Nonproteolytic Clostridium botulinum Type B

2004 ◽  
Vol 70 (5) ◽  
pp. 2928-2934 ◽  
Author(s):  
Maria Lövenklev ◽  
Ingrid Artin ◽  
Oskar Hagberg ◽  
Elisabeth Borch ◽  
Elisabet Holst ◽  
...  
Keyword(s):  
Gene Expression ◽  
Carbon Dioxide ◽  
Growth Rate ◽  
Sodium Chloride ◽  
Optical Density ◽  
Sodium Nitrite ◽  
Clostridium Botulinum ◽  
Lag Phase ◽  
Type B ◽  
Phase Duration

ABSTRACT The effects of carbon dioxide, sodium chloride, and sodium nitrite on type B botulinum neurotoxin (BoNT/B) gene (cntB) expression in nonproteolytic Clostridium botulinum were investigated in a tryptone-peptone-yeast extract (TPY) medium. Various concentrations of these selected food preservatives were studied by using a complete factorial design in order to quantitatively study interaction effects, as well as main effects, on the following responses: lag phase duration (LPD), growth rate, relative cntB expression, and extracellular BoNT/B production. Multiple linear regression was used to set up six statistical models to quantify and predict these responses. All combinations of NaCl and NaNO2 in the growth medium resulted in a prolonged lag phase duration and in a reduction in the specific growth rate. In contrast, the relative BoNT/B gene expression was unchanged, as determined by the cntB-specific quantitative reverse transcription-PCR method. This was confirmed when we measured the extracellular BoNT/B concentration by an enzyme-linked immunosorbent assay. CO2 was found to have a major effect on gene expression when the cntB mRNA levels were monitored in the mid-exponential, late exponential, and late stationary growth phases. The expression of cntB relative to the expression of the 16S rRNA gene was stimulated by an elevated CO2 concentration; the cntB mRNA level was fivefold greater in a 70% CO2 atmosphere than in a 10% CO2 atmosphere. These findings were also confirmed when we analyzed the extracellular BoNT/B concentration; we found that the concentrations were 27 ng · ml−1 · unit of optical density−1 in the 10% CO2 atmosphere and 126 ng · ml−1 · unit of optical density−1 in the 70% CO2 atmosphere.

Effects and Interactions of Temperature, pH, Atmosphere, Sodium Chloride, and Sodium Nitrite on the Growth of Listeria monocytogenes

1989 ◽  
Vol 52 (12) ◽  
pp. 844-851 ◽  
Author(s):  
ROBERT L. BUCHANAN ◽  
HEIDI G. STAHL ◽  
RICHARD C. WHITING
Keyword(s):  
Listeria Monocytogenes ◽  
Sodium Chloride ◽  
Sodium Nitrite ◽  
Exponential Growth ◽  
Chloride Content ◽  
Lag Phase ◽  
Growth Data ◽  
Phase Duration ◽  
Degree Of Protection ◽  
Cured Meats

The effects and interactions of temperature (5, 19, 28, 37°C), initial pH (6.0 and 7.5), atmosphere (aerobic and anaerobic), sodium chloride content (0.5 and 4.5%), and sodium nitrite concentration (0, 50, 100, 200, 1000 μg/ml) on the growth of Listeria monocytogenes Scott A were determined using Tryptose Phosphate Broth. Growth data were analyzed by regression analysis to generate “best-fit” Gompertz equations, which were used subsequently to calculate lag phase duration, exponential growth rate, generation time, and maximum population density values. The data indicated that the growth kinetics of L. monocytogenes was dependent on the interaction of the five variables, particularly in regard to exponential growth rates and lag phase durations. The data suggest that sodium nitrite can have significant bacteriostatic activity against L. monocytogenes and may provide cured meats with a degree of protection against this microorganism, particularly if employed in conjunction with a combination of acidic pH, vacuum packaging, high salt concentrations, and adequate refrigeration.

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.

Validation and Analysis of Modeled Predictions of Growth of Bacillus cereus Spores in Boiled Rice

2000 ◽  
Vol 63 (2) ◽  
pp. 268-272 ◽  
Author(s):  
DANA M. McELROY ◽  
LEE-ANN JAYKUS ◽  
PEGGY M. FOEGEDING
Keyword(s):  
Growth Rate ◽  
Bacillus Cereus ◽  
Exponential Growth ◽  
Generation Time ◽  
Time Lag ◽  
Lag Phase ◽  
Exponential Growth Rate ◽  
Phase Duration ◽  
Margin Of Safety ◽  
Fail Safe

The growth of psychrotrophic Bacillus cereus 404 from spores in boiled rice was examined experimentally at 15, 20, and 30°C. Using the Gompertz function, observed growth was modeled, and these kinetic values were compared with kinetic values for the growth of mesophilic vegetative cells as predicted by the U.S. Department of Agriculture's Pathogen Modeling Program, version 5.1. An analysis of variance indicated no statistically significant difference between observed and predicted values. A graphical comparison of kinetic values demonstrated that modeled predictions were “fail safe” for generation time and exponential growth rate at all temperatures. The model also was fail safe for lag-phase duration at 20 and 30°C but not at l5°C. Bias factors of 0.55, 0.82, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, indicated that the model generally was fail safe and hence provided a margin of safety in its growth predictions. Accuracy factors of 1.82, 1.60, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, quantitatively demonstrated the degree of difference between predicted and observed values. Although the Pathogen Modeling Program produced reasonably accurate predictions of the growth of psychrotrophic B. cereus from spores in boiled rice, the margin of safety provided by the model may be more conservative than desired for some applications. It is recommended that if microbial growth modeling is to be applied to any food safety or processing situation, it is best to validate the model before use. Once experimental data are gathered, graphical and quantitative methods of analysis can be useful tools for evaluating specific trends in model prediction and identifying important deviations between predicted and observed data.

scholarly journals Growth characterisation of Staphylococcus aureus in milk: a quantitative approach

2009 ◽  
Vol 27 (No. 6) ◽  
pp. 433-453 ◽  
Author(s):  
A. Medveďová ◽  
Ľ. Valík ◽  
Z. Sirotná ◽  
D. Liptáková
Keyword(s):  
Staphylococcus Aureus ◽  
Growth Rate ◽  
Incubation Temperature ◽  
Food Poisoning ◽  
Raw Milk ◽  
Lag Phase ◽  
Phase Duration ◽  
Temperature Range ◽  
Root Model ◽  
Toxigenic Strains

<i>Staphylococcus aureus</i> is a pathogenic bacterium that induces several of human illnesses. The staphylococcal enterotoxin (SE) production as the results of previous growth of toxigenic strains is the most crucial problem which may lead to the staphylococcal food poisoning outbreaks in humans. That is why the growth of three strains of <i>Staphylococcus aureus</i> was characterised in milk and modelled in dependence of temperature. For the lag phase duration of <i>S. aureus</i> 2064, the Davey model was used with the following result: ln(1/lag) = 1.973 – 87.92/<i>T</i> + 285.09/<i>T</i><sup>2</sup> (<i>R</i><sup>2</sup> = 0.962). The dependence of the growth rate on incubation temperature was modelled by the Ratkowsky square root model and Gibson in sub-optimal and whole temperature range, respectively. The validation of both models showed high significance of the growth rate data fitting. The optimal temperature of <i>T</i><sub>opt</sub> = 38.5°C was resulted from Gibson model for the <i>S. aureus</i> 2064 growth in milk. For practical purpose, the time necessary for the increase of <i>S. aureus</i> by 3 log counts was also calculated within the growth temperature range. These data may provide useful information e.g. for the producers using raw milk in their artisanal cheese practice as the specific strains were used in this study.

Control of Nonproteolytic Clostridium botulinum Types B and E in Crab Analogs by Combinations of Heat Pasteurization and Water Phase Salt

2002 ◽  
Vol 65 (1) ◽  
pp. 130-139 ◽  
Author(s):  
M. E. PETERSON ◽  
R. N. PARANJPYE ◽  
F. T. POYSKY ◽  
G. A. PELROY ◽  
M. W. EKLUND
Keyword(s):  
Sodium Chloride ◽  
Clostridium Botulinum ◽  
Frozen Storage ◽  
Toxin Production ◽  
Water Phase ◽  
Type B ◽  
C Storage ◽  
Time Period ◽  
Heat Pasteurization ◽  
G Prior

Water phase sodium chloride (WPS) levels of 1.8 to 3.0% in combination with heat pasteurization for 15 min at temperatures of 75, 80, 85, and 90°C were evaluated as methods for the inactivation or inhibition of nonproteolytic, psychrotrophic Clostridium botulinum types B and E in crab analogs (imitation crab legs) subsequently stored at 10 and 25°C. Samples inoculated with 102 type B or E spores per g prior to pasteurization remained nontoxic for 120 days at 10°C and for 15 days at 25°C. With 104 type E spores per g and 80°C pasteurization, ≥2.4 and 2.7% WPS was required for inhibition at 10 and 25°C storage, respectively. Pasteurization at 85°C decreased the inhibitory level of WPS to 2.1% at 10°C and to 2.4% at 25°C. When the inoculum was 104 type B spores per g, samples with 2.7% WPS were toxic after 80 days of storage at 10°C. Samples inoculated with 103 type B spores per g and processed at 85°C remained nontoxic for 15 days at 25°C with a WPS of ≥2.4%. When pasteurization was carried out before inoculation and packaging, 1.8% WPS prevented toxin production by 102 and 104 type E spores per g for 30 days at 10°C, and this time period increased as the WPS concentrations increased. Three percent WPS prevented toxin production by 104 type E spores per g in vacuum-packaged analogs stored 110 days at 10°C. Pasteurization processes used in these experiments, however, do not inactivate the heat-resistant proteolytic types of Clostridium botulinum. Therefore, the most important factor controlling the growth of this bacterium is continuous refrigeration below 3.0°C or frozen storage of the finished product.

Risk of Growth and Toxin Production by Clostridium botulinum Nonproteolytic Types B, E, and F in Salmon Fillets Stored Under Modified Atmospheres at Low and Abused Temperatures

1987 ◽  
Vol 50 (4) ◽  
pp. 330-336 ◽  
Author(s):  
GENERO W. GARCIA ◽  
CONSTANTIN GENIGEORGIS ◽  
SEPPO LINDROTH
Keyword(s):  
Clostridium Botulinum ◽  
Storage Time ◽  
Toxin Production ◽  
Lag Phase ◽  
Type B ◽  
Inoculum Level ◽  
Modified Atmospheres ◽  
Botulinum Type ◽  
Best Fit ◽  
Design Experiments

In factorial design experiments we inoculated fresh salmon fillets with a spore pool of 13 nonproteolytic strains of Clostridium botulinum type B, E, and F at 6 levels (10−1 to 104/50 g of fillet), and incubated at 1, 4, 8, 12 and 30°C under modified atmospheres (MA) of vacuum, 100% CO2 and 70% CO2 + 30% air for up to 60 d. The earliest time we detected toxin in the fillets at 30, 12 and 8°C, irrespective of MA, was after 1, 3–9 and 6–12 d of storage and required 100–103, 101–103, 101–102 spores/fillet. The probability (P) of toxin production was significantly (P&lt;0.05) affected by temperature (T), MA storage time (ST), MA × T, MA × ST and T × ST. Only type B toxin was detected in the toxic fillets. No toxin was detected in fillets stored at 4°C for up to 60 d. Toxin detection coincided with spoilage at 30°C, but preceded spoilage at 8 and 12°C, and followed spoilage at 4°C. Using linear and logistic regression analysis, best fit equations were derived relating the length of the lag phase and P of toxin production to T, ST, MA and spore inoculum level.

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.

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