scholarly journals Influence of Stress on Individual Lag Time Distributions of Listeria monocytogenes

2005 ◽  
Vol 71 (6) ◽  
pp. 2940-2948 ◽  
Author(s):  
L. Guillier ◽  
P. Pardon ◽  
J.-C. Augustin
Keyword(s):  
Listeria Monocytogenes ◽  
Food Industry ◽  
Single Cells ◽  
Lag Time ◽  
Exponential Growth Phase ◽  
The Mean ◽  
Stressed Cells ◽  
Lag Times ◽  
The Times ◽  
Applied Stresses

ABSTRACT The effects of nine common food industry stresses on the times to the turbidity (T d) distribution of Listeria monocytogenes were determined. It was established that the main source of the variability of T d for stressed cells was the variability of individual lag times. The distributions of T d revealed that there was a noticeable difference in response to the stresses encountered by the L. monocytogenes cells. The applied stresses led to significant changes of the shape, the mean, and the variance of the distributions. The variance of T d of wells inoculated with single cells issued from a culture in the exponential growth phase was multiplied by at least 6 and up to 355 for wells inoculated with stressed cells. These results suggest stress-induced variability may be important in determining the reliability of predictive microbiological models.

scholarly journals Single-Cell and Population Lag Times as a Function of Cell Age

2008 ◽  
Vol 74 (8) ◽  
pp. 2534-2536 ◽  
Author(s):  
Carmen Pin ◽  
József Baranyi
Keyword(s):  
Escherichia Coli ◽  
Single Cell ◽  
Doubling Time ◽  
Single Cells ◽  
Lag Time ◽  
Exponential Phase ◽  
Cell Age ◽  
Generation Times ◽  
Lag Times ◽  
The Times

ABSTRACT After inoculation, the times to the first divisions are longer and more widely distributed for those Escherichia coli single cells that spent more time in the stationary phase prior to inoculation. The second generation times are still longer than the typical generation times in the exponential phase, and this extended the apparent lag time of the cell population. The greater the variability of the single-cell interdivision intervals, the shorter are both the lag time and the doubling time of the population.

scholarly journals Indirect Measurement of the Lag Time Distribution of Single Cells of Listeria innocua in Food

2006 ◽  
Vol 72 (4) ◽  
pp. 2533-2538 ◽  
Author(s):  
M. D'Arrigo ◽  
G. D. García de Fernando ◽  
R. Velasco de Diego ◽  
J. A. Ordóñez ◽  
S. M. George ◽  
...  
Keyword(s):  
Time Distribution ◽  
Single Cells ◽  
Dairy Product ◽  
Lag Time ◽  
Indirect Measurement ◽  
Food Samples ◽  
Linear Mapping ◽  
Listeria Innocua ◽  
Exponential Growth Phase ◽  
Lag Times

ABSTRACT The distribution of log counts at a given time during the exponential growth phase of Listeria innocua measured in food samples inoculated with one cell each was applied to estimate the distribution of the single-cell lag times. Three replicate experiments in broth showed that the distribution of the log counts is a linear mapping of the distribution of the detection times measured by optical density. The detection time distribution reflects the lag time distribution but is shifted in time. The log count distribution was applied to estimate the distributions of the lag times in a liquid dairy product and in liver paté after different heat treatments. Two batches of ca. 100 samples of the dairy product were inoculated and heated at 55°C for 45 min or at 62°C for 2 min, and an unheated batch was incubated at 4°C. The final concentration of surviving bacteria was ca. 1 cell per sample. The unheated cells showed the shortest lag times with the smallest variance. The mean and the variance of the lag times of the surviving cells at 62°C were greater than those of the cells treated at 55°C. Three batches of paté samples were heated at 55°C for 25 min, 62°C for 81 s, or 65°C for 20 s. A control batch was inoculated but not heated. All paté samples were incubated at 15°C. The distribution of the lag times of the cells heated at 55°C was not significantly different from that of the unheated cells. However, at the higher temperatures, 62°C and 65°C, the lag duration was longer and its variance greater.

scholarly journals The implications of lag times between nitrate leaching losses and riverine loads for water quality policy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. W. McDowell ◽  
Z. P. Simpson ◽  
A. G. Ausseil ◽  
Z. Etheridge ◽  
R. Law
Keyword(s):  
Water Quality ◽  
Mean Transit Time ◽  
Lag Time ◽  
Practice Change ◽  
N Leaching ◽  
N Losses ◽  
Leaching Losses ◽  
Nitrate N ◽  
The Mean ◽  
Lag Times

AbstractUnderstanding the lag time between land management and impacts on riverine nitrate–nitrogen (N) loads is critical to understand when action to mitigate nitrate–N leaching losses from the soil profile may start improving water quality. These lags occur due to leaching of nitrate–N through the subsurface (soil and groundwater). Actions to mitigate nitrate–N losses have been mandated in New Zealand policy to start showing improvements in water quality within five years. We estimated annual rates of nitrate–N leaching and annual nitrate–N loads for 77 river catchments from 1990 to 2018. Lag times between these losses and riverine loads were determined for 34 catchments but could not be determined in other catchments because they exhibited little change in nitrate–N leaching losses or loads. Lag times varied from 1 to 12 years according to factors like catchment size (Strahler stream order and altitude) and slope. For eight catchments where additional isotope and modelling data were available, the mean transit time for surface water at baseflow to pass through the catchment was on average 2.1 years less than, and never greater than, the mean lag time for nitrate–N, inferring our lag time estimates were robust. The median lag time for nitrate–N across the 34 catchments was 4.5 years, meaning that nearly half of these catchments wouldn’t exhibit decreases in nitrate–N because of practice change within the five years outlined in policy.

scholarly journals Significance of Inoculum Size in the Lag Time ofListeria monocytogenes

2000 ◽  
Vol 66 (4) ◽  
pp. 1706-1710 ◽  
Author(s):  
Jean-Christophe Augustin ◽  
Agnès Brouillaud-Delattre ◽  
Laurent Rosso ◽  
Vincent Carlier
Keyword(s):  
Listeria Monocytogenes ◽  
Food Industry ◽  
Lag Time ◽  
Inoculum Size ◽  
Nutrient Concentrations ◽  
Predictive Microbiology ◽  
Oflisteria Monocytogenes

ABSTRACT The lag time of Listeria monocytogenes growing under suboptimal conditions (low nutrient concentrations, pH 6, and 6.5°C) was extended when the inoculum was severely stressed by starvation and the inoculum size was very small. Predictive microbiology should deal with bacterial stress and stochastic approaches to improve its value for the agro-food industry.

scholarly journals Studies of the Commitment Step in the Germination of Spores of Bacillus Species

2010 ◽  
Vol 192 (13) ◽  
pp. 3424-3433 ◽  
Author(s):  
Xuan Yi ◽  
Peter Setlow
Keyword(s):  
Spore Germination ◽  
Dipicolinic Acid ◽  
Lag Time ◽  
Bacillus Species ◽  
Lytic Enzymes ◽  
Large Heterogeneity ◽  
Heat Activation ◽  
Lag Times ◽  
The Times ◽  
Insight Into

ABSTRACT Spores of Bacillus species are said to be committed when they continue through nutrient germination even when germinants are removed or their binding to spores' nutrient germinant receptors (GRs) is both reversed and inhibited. Measurement of commitment and the subsequent release of dipicolinic acid (DPA) during nutrient germination of spores of Bacillus cereus and Bacillus subtilis showed that heat activation, increased nutrient germinant concentrations, and higher average levels of GRs/spore significantly decreased the times needed for commitment, as well as lag times between commitment and DPA release. These lag times were also decreased dramatically by the action of one of the spores' two redundant cortex lytic enzymes (CLEs), CwlJ, but not by the other CLE, SleB, and CwlJ action did not affect the timing of commitment. The timing of commitment and the lag time between commitment and DPA release were also dependent on the specific GR activated to cause spore germination. For spore populations, the lag times between commitment and DPA release were increased significantly in spores that germinated late compared to those that germinated early, and individual spores that germinated late may have had lower appropriate GR levels/spore than spores that germinated early. These findings together provide new insight into the commitment step in spore germination and suggest several factors that may contribute to the large heterogeneity among the timings of various events in the germination of individual spores in spore populations.

scholarly journals The generation time, lag time, and minimum temperature of growth of coliform organisms on meat, and the implications for codes of practice in abattoirs

1985 ◽  
Vol 94 (3) ◽  
pp. 289-300 ◽  
Author(s):  
M. G. Smith
Keyword(s):  
Minimum Temperature ◽  
Generation Time ◽  
Time Lag ◽  
Safety Margin ◽  
Lag Time ◽  
Time Limits ◽  
Codes Of Practice ◽  
Generation Times ◽  
Lag Times ◽  
The Times

SUMMARYThe growth of coliform organisms on meat tissue from sheep carcasses processed in a commercial abattoir was investigated. The results indicated that for practical purposes the minimum temperature of growth of these organisms on meat may be taken as 8 °C. Equations were derived relating the generation time and the lag time of coliform organisms in raw blended mutton to the temperature at which the meat is held. Estimates of growth obtained with these equations were found to agree closely with the experimental results, especially at temperatures above 10 °C, and allowed the generation times and the lag times for all temperatures up to 40 °C to be calculated. These times were also found to agree closely with the times determined using a strain ofEscherichia coliinoculated into blended mutton tissue. A strain ofSalmonella typhimuriuminoculated in the same way into blended mutton tissue gave longer generation and lag times at temperatures below 15 °C. Therefore, it is believed that the calculated tables of lag and generation times included in this paper can be used to determine the length of time raw chilled meat may be held afterwards at temperatures above the minimum temperature of growth without an increase in the number of any salmonella organisms present, and these times include a safety margin at each temperature.The study indicates that the mandatory codes of practice presently applied in commercial abattoirs are too stringent. Maintaining the temperature of boning rooms at 10 °C or less does not appear to be necessary providing the meat is processed within the calculated time limits. A relaxation of the restrictions on boning room temperatures would decrease costs, increase worker comfort and safety and would not compromise the bacteriological safety of the meat produced.

scholarly journals Influence of Stress on Single-Cell Lag Time and Growth Probability for Listeria monocytogenes in Half Fraser Broth

2009 ◽  
Vol 75 (10) ◽  
pp. 3069-3076 ◽  
Author(s):  
Claire Dupont ◽  
Jean-Christophe Augustin
Keyword(s):  
Listeria Monocytogenes ◽  
Single Cell ◽  
Physiological State ◽  
False Negative ◽  
Lag Time ◽  
Enrichment Broth ◽  
A Cell ◽  
Lag Times ◽  
The Impact ◽  
Growth Probability

ABSTRACT The impacts of 12 common food industry stresses on the single-cell growth probability and single-cell lag time distribution of Listeria monocytogenes were determined in half Fraser broth, the primary enrichment broth of the International Organization for Standardization detection method. First, it was determined that the ability of a cell to multiply in half Fraser broth is conditioned by its history (the probability for a cell to multiply can be decreased to 0.05), meaning that, depending on the stress in question, the risk of false-negative samples can be very high. Second, it was established that when cells are injured, the single-cell lag times increase in mean and in variability and that this increase represents a true risk of not reaching the detection threshold of the method in the enrichment broth. No relationship was observed between the impact on single-cell lag times and that on growth probabilities. These results emphasize the importance of taking into account the physiological state of the cells when evaluating the performance of methods to detect pathogens in food.

Listeria monocytogenes: biofilm formation and persistence in food-processing environments

Biofilms ◽  
2004 ◽  
Vol 1 (2) ◽  
pp. 107-121 ◽  
Author(s):  
T. Møretrø ◽  
S. Langsrud
Keyword(s):  
Listeria Monocytogenes ◽  
Food Processing ◽  
Food Industry ◽  
Single Cells ◽  
Processing Plant ◽  
Production Environment ◽  
Adhesive Properties ◽  
Free Living ◽  
Survival And Growth ◽  
Cleaning And Disinfection

Listeria monocytogenes is ubiquitous in nature and a major concern for the food industry, since it is the causal agent of the serious foodborne illness listeriosis. This organism can be introduced through many routes to food-processing environments and may become established on food-processing equipment. Subsequently, food products may become contaminated during processing. In addition, the bacterium can grow at refrigeration temperatures. Biofilms are regarded as important with respect to the survival and growth of microorganisms in the food industry. Microorganisms growing in biofilms are protected against cleaning and disinfection and are difficult to eradicate. Listeria monocytogenes may grow in biofilms that protect them against environmental stress and can be isolated from surfaces after cleaning and disinfection. For each individual food-processing plant, a limited number of clones of L. monocytogenes may become established and persist for years. Persistent strains adhere to surfaces and form biofilms more readily compared to sporadically found strains, suggesting that adherence to surfaces is important for survival and persistence of L. monocytogenes in food-processing environments. Listeria monocytogenes can adhere to all the materials commonly used in the food industry. In biofilms L. monocytogenes is significantly more resistant to disinfection than its free-living counterparts and thick, complex biofilms are more difficult to remove than adherent single cells of L. monocytogenes. Several novel approaches to avoid adhesion of L. monocytogenes have been proposed, but high costs, practical difficulties or resistance problems limit their practical use. Despite considerable research on the adhesive properties and resistance of L. monocytogenes enabling its survival in the food production environment, a final solution for avoiding establishment of the bacterium has not yet been found.

Effect of Sodium Polyphosphates on Growth of Listeria monocytogenes

1993 ◽  
Vol 56 (7) ◽  
pp. 577-580 ◽  
Author(s):  
LAURA L. ZAIKA ◽  
ANNA H. KIM
Keyword(s):  
Listeria Monocytogenes ◽  
Food Additives ◽  
Brain Heart Infusion ◽  
Lag Time ◽  
Inhibitory Effect ◽  
Average Chain Length ◽  
Medium Ph ◽  
Test Conditions ◽  
Lag Times ◽  
Free Media

Evaluation of sodium polyphosphates (SPP), multifunctional food additives, indicated that only the higher polymers sodaphos, hexaphos, and glass H (average chain length = 6, 13, and 21, respectively) significantly inhibited growth of Listeria monocytogenes. The effect of the three compounds (0–2%) on growth of L. monocytogenes was studied in brain heart infusion + 0.3% glucose medium, pH 6.0, at 28, 19, 10, and 5°C. The organism grew well under all test conditions in the absence of SPP. Hexaphos and glass H were considerably more inhibitory than sodaphos. The most pronounced effect of SPP was on lag times, which increased with increasing SPP concentration and decreasing temperature. At 10°C, addition of 0.3% hexaphos or glass H increased lag time from 22 h to 197 and 186 h, respectively, and no growth was observed after 40 d in the presence of 2.0% of these compounds. Addition of 2.0% NaCl increased the inhibitory effect of SPP but had little effect on growth in SPP-free media. Results suggest that high molecular weight SPP may be useful in controlling the growth of L. monocytogenes, particularly at low temperatures and in combination with NaCl.

An exploration of food industry led reformulation on fortified food staples in Ireland

2020 ◽  
Author(s):  
Daragh McMenemy ◽  
Frances Kelly ◽  
Mary Rose Sweeney
Keyword(s):  
Food Industry ◽  
Saturated Fat ◽  
Microsoft Excel ◽  
Nutrient Profile ◽  
Fortified Food ◽  
Prevalence Of Obesity ◽  
The Mean ◽  
Total Fat ◽  
Food Staples ◽  
Serving Sizes

Abstract Background Food industry led reformulation efforts have attempted to address the prevalence of obesity by modifying nutrient compositions in food products. This study explored progress in nutrient composition alterations in products in Irish supermarkets by comparing the nutrient labels of products sold in 2014 and 2017. Methods We conducted two supermarket audits in 2014 and 2017 to examine the changes in the nutrient profile of cereals, breads, spreads, unflavoured milks, yogurts and juices. Information on the nutrients of interest to the study (energy, protein, fat, carbohydrate, saturated fat, salt, sugar and some micronutrients) were extracted and stored in Microsoft Excel. The nutrient profile of each product was compared across the two timepoints. Our study shows that the mean level of sugars in cereals remains high and that the mean level of salt remains high in cereals, breads, and spreads. Results In total, 143 products were directly compared (86 cereals, 26 breads, 17 spreads and 14 milks). Our study shows that the composition of salt and sugar in cereal, bread, spreads and milk has declined by 12 and 7%, respectively. Saturated fat has declined in cereals (7%), but has increased in breads (12%), spreads (1%), and milks (5%). Manufacturers increased the serving sizes in nine cereals and one milk. Conclusions From a population health perspective, the results are encouraging but care should be exercised by the food industry not to allow total fat and saturated fat levels to creep upwards. Further research and engagement of public health specialists and the food industry are needed.

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