Growth of the desulfomicrobium sp. strains, their sulfate ...
Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains
-
Upload
pantelis-stathopoulos -
Category
Documents
-
view
169 -
download
0
Transcript of Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains
![Page 1: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/1.jpg)
Development of a Growth/No Growth model using growth data of 10 different Listeria monocytogenes strains
Pantelis J. Stathopoulos Food Technologist
MSc
2011
![Page 2: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/2.jpg)
Presentation Structure
Introduction
The aim of the study
Methodology
Results and Discussion
Conclusions
1
2
3
4
5
![Page 3: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/3.jpg)
INTRODUCTION 1
![Page 4: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/4.jpg)
General
Listeria monocytogenes
1
Environmental Factors
Mathematical Modeling
![Page 5: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/5.jpg)
L. monocytogenes
• Gram+ bacterium,
• Potentially pathogenic,
• Resistant to severe values of pH/ aw
• Widespread in the environment.
• Temperature (Walker et al., 1990),
• pH (Farber et al., 1989; Buchanan et al., 1993)
• Water activity (Farber et al., 1992; Nolan et al., 1992)
Generally
Environmental Factors
1
![Page 6: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/6.jpg)
• pH: 4,0 – 8,0
• aw: 0,90 – 0,99
• Temperature: -2 – 45 oC
• Great variability of growth limits (Augustin and Carlier, 2000):
– Acid used for pH
– Humectants used for water activity
– Substrate used
– Experimental conditions
L. monocytogenes 1
Growth limits
![Page 7: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/7.jpg)
Statistical Growth Models
Predictive Microbiology (McMeekin et al., 1993)
L. monocytogenes
PATHOGENICITY WIDE DISTRIBUTION RESISTANCE
1
![Page 8: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/8.jpg)
Statistical Models
Primary Models • Mathematical description of growth kinetics (e.g. μmax, generation time)
Secondary Models • Mathematical description of the effect of several environmental factors (e.g.
temperature, pH, aw) on the growth limits of a microorganism
Tertiary Models • Combination of several secondary models for the production of a software
1
![Page 9: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/9.jpg)
Growth/ No Growth Models
Importance of Growth/No Growth models
• Study of the combined environmental factors that prevent microbial growth.
• Ability to retrieve data about the growth boundary of microorganisms on synthetic substrates, in order to reduce significantly the number of challenge tests necessary to determine the limits of growth in real food
1
![Page 10: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/10.jpg)
Tienungoon et al., 2000.
Growth/ No Growth Models
Growth
No - Growth
P < 10% P < 50% P < 90%
Growth
No - Growth
1
![Page 11: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/11.jpg)
Present State
G/NG models used for:
• Effect of antimicrobial substances on growth
(e.g. nisin, Boziaris and Nychas, 2006)
• Effect of the initial inoculum level on growth
(Vermeulen et al., 2009)
• Effect of novel methods of food processes on growth
(e.g. HHP, Bover-Cid et al. 2010, Pulse Light Hierro et al., 2011)
• Strain Variability
(Valero et al., 2010; Lianou and Koutsoumanis, 2011)
1
![Page 12: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/12.jpg)
Present State
Microbial Strains differ as
• For their origin of isolation (e.g. food, environment, clinical)
• For their serotype
• For their genotype
1
![Page 13: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/13.jpg)
Present State
Strain Variability and Statistical Modeling
• Escherichia coli
Modeling of five different strains of E. coli
(Valero et al., 2010)
• Salmonella spp.
A stochastic approach for integrating strain variability in modeling growth of Salmonella enterica
(Lianou and Koutsoumanis, 2011).
• Listeria monocytogenes
Two different strains of L. monocytogenes, produced two different statistical models (Tienungoon et al., 2000).
1
![Page 14: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/14.jpg)
Present State 1
Screening of Strains
• Screening of strains in order to choose the most resistant one
(Vermeulen et al., 2007).
• From a set of strains, the most resistant one is chosen
• In order to define the most resistant strain as for an environmental factor (e.g. pH), all the other factors (e.g. temperature, water activity) remain constant at their optimum value
![Page 15: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/15.jpg)
Present State 1
Screening of strains
pH
6.8
6.4
6.0
5.6
5.2
4.8
4.4
4.0
pH
6.8
6.4
6.0
5.6
5.2
4.8
4.4
4.0
aw
Simultaneously
Effect of pH/ aw/ Τ/ il
Successive
Effects of pH/ aw
aw
![Page 16: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/16.jpg)
AIM OF STUDY 2
![Page 17: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/17.jpg)
Aim of Study 2
General Perspective
• Data from different strains produce different statistical models?
• The uncertainty of the predictions of statistical models that are developed using data of one “representative” strain can be lifted with the development of a composite model using growth data of more than one strain?
![Page 18: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/18.jpg)
Aim of Study 2
In this study:
• For 10 different L. monocytogenes strains developed
10 different Growth/No Growth models
• Comparison of individual Growth/No Growth models
• Development of a composite Growth/No Growth model
3
SM-1 SM-2 SM-3 SM-4 SM-5 SM-6 SM-7 SM-8 SM-9 SM-10
Composite G/NG model
Individual G/NG models
10 9 8 7 6 5 4 2 1
![Page 19: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/19.jpg)
METHODOLOGY
3
![Page 20: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/20.jpg)
Methodology 3
10 L. monocytogenes strains
1
2
3
4
Clinical strains C
Food strains F
5
6
7
8
«Reference» strains
S-1
S-4
S-7
S-8
S-3
S-5
S-6
S-9
9 10
S-1 S-10
![Page 21: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/21.jpg)
Model Parameters 3
5760 combinations
aw
NaCl
NaCl – KCl
pH
CH3COOH
T
Inoculum Level
102 cfu/mL
103 cfu/mL
104 cfu/mL
Χ 10 strains
![Page 22: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/22.jpg)
aw / NaCl, NaCl - KCl 3
m (ΝaCl – KCl)/ (mol kg-1)
aw
Calculation of the appropriate quantities of NaCl and NaCl-KCl
KCl
NaCl
NaCl – KCl
0.91
1.36
1.36 mol (NaCl – KCl)
60% NaCl: 0.6 x 1.36 x MΜ = …. NaCl
40% KCl: 0.4 x 1.36 x MΜ = …. KCl
aw
![Page 23: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/23.jpg)
Methodology 3
SUBSTRATES
Inoculum
96 vials (ΒΗΙ broth)
102 cfu/mL
103 cfu/mL
104 cfu/mL
TIME
60 days
4οC
18οC
102 cfu/mL
103 cfu/mL
104 cfu/mL
Brain Heart Infusion
pH
aw
102 cfu/mL
103 cfu/mL
104 cfu/mL
![Page 24: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/24.jpg)
Statistical Analysis
Logistic Regression
• Statistical Treatment applied when the results we study are
binomial (0, 1) – e.g. Growth/ No Growth,
Toxin/ No Toxin,
• Expressed by the logarithm of the probability of occurrence or non-occurrence or
logit P
logit P = Ln P
1-P
3
![Page 25: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/25.jpg)
Methodology
Logistic Regression
DATA (Environmental Factors)
RESPONSE (0, 1)
Link Function
Logit P = Ln (P/1-P) = b0 + b1 x pH + b2 x aw + b3 x il + b4 x pH x aw + b5 x il x pH + b6 x il x aw
3
![Page 26: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/26.jpg)
Logit P =
Ln (P/1-P) = b0 +
b1 x pH +
b2 x aw +
b3 x il +
b4 x pH x aw +
b5 x il x pH +
b6 x il x aw
Methodology
Logistic Regression
Parameter il
Interaction pH x aw
Interaction il x pH
Interaction il x aw
Parameter aw
Parameter pH
3
![Page 27: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/27.jpg)
Methodology
• Logistic Regression process through Minitab Software
• Level if Significance α < 0.05
• Rejection of parameters (pH2, aw2, il2)
P – value > 0.800
Logistic Regression
3
![Page 28: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/28.jpg)
RESULTS AND DISCUSSION
4
![Page 29: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/29.jpg)
Results and Discussion
Effect of the initial inoculum level for all experimental conditions (aw, pH, T)
for all strains
4
![Page 30: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/30.jpg)
4
pH
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
aw
2 log
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
5 6
5
5
Growth Limits (4οC / NaCl)
aw
pH
3 log
4 log
1 -10 1 -10
5
6
1-10
5
6
![Page 31: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/31.jpg)
4
pH
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
aw
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
6 8
6 8
Growth Limits (4οC / NaCl - KCl)
pH
2 log 3 log
4 log
1 -10 1-10
6 8
1-10
5 6 8
1-10
4 6 8 10
6 8
6 8
6 8
6 8
6 8
![Page 32: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/32.jpg)
Growth Limits (18οC / NaCl)
4
pH
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
aw
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
1 5 6
1 3 8
1 7
1 2 6 9 10
1 5 7
1 6 7 9
1 3 7 8
1 9
1 4 5 6 7 8
1-10
1 5 7
1 6 7 9
1 3 7 8 9
1 9 1 -10
1 3 4 5 6 7 8 10
aw
1 7
1
1 7
1
1 7
1
1 7
1
1 7
1 7
1 7
1 7
1 7
4 5 7 8
1
2 log 3 log
4 log
7
![Page 33: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/33.jpg)
4
pH
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
aw
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
1
1 3-10
1 3-10
1 3-10
3-10
1
1-10
1-10
2-10
1-10
1 7 9
1-10
1 9
1-10
9 2-10
1 9
1 9
9
1 9
1 9
1 9
1 9
1
1 9
1 9
1 9
1
aw
Growth Limits (18οC/ NaCl – KCl)
1 9
9 9
2 log 3 log
4 log
pH
p
H
![Page 34: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/34.jpg)
Results and Discussion 4
Most Resistant Strains
2 log cfu/mL
3 log cfu/mL
4 log cfu/mL
1 - 10
2 log cfu/mL
3 log cfu/mL
4 log cfu/mL
4oC pH
18oC
2 log cfu/mL
3 log cfu/mL
4 log cfu/mL
2 log cfu/mL
3 log cfu/mL
4 log cfu/mL
4oC
18oC
NaCl
NaCl
NaCl/ KCl
NaCl/ KCl
1 - 10
5
1 - 10
aw
1 - 10
6
1 - 10
Comb
1 - 10
5, 6
7
pH
1, 7
1, 7
1, 7
aw
1, 7
1, 7
1, 7
Comb
1, 7
1, 7
1 - 10
pH
6, 8
6, 8
1 - 10
aw
1 - 10
6, 8
1 - 10
Comb
1 - 10
6, 8
1, 9
pH
1, 9
1, 9
1
aw
1
1, 9
1, 9
Comb
1, 9
9
T Π Ν
Ν Τ
![Page 35: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/35.jpg)
Results and Discussion 4
NOT FEASIBLE TO CHOOSE ONE AS THE MOST RESISTANT
Factors affecting the Growth Limits
Different Inoculum Levels
Different L. monocytogenes strains
Temperature
Ρυθμιστής aw
Probably Different Statistical
Models
EVERY STRAIN HAS DIFFERENT BEHAVIOUR AT DIFFERENT EXPERIMENTAL CONDITIONS
![Page 36: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/36.jpg)
Growth profiles and logistic regression
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
aw
0.8
7
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
0.8
7
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
1 3 2
aw aw
Logit P = -242,61 + 6,66 pH + 207,43 aw
Logit P = 1037,63 - 213,99 pH - 1134,44 aw + 0,83 il + 230,81 pH aw
4
![Page 37: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/37.jpg)
1. Growth profiles completed after 4 replications
2. Logistic Regression treats every replication as an individual situation
Growth profiles and logistic regression
Strains with the same Growth profile produce
different logistic regression equations
CAUSE
4
![Page 38: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/38.jpg)
Results and Discussion 4
Most Resistant Strains
2 log cfu/mL
3 log cfu/mL
4 log cfu/mL
1 - 10
2 log cfu/mL
3 log cfu/mL
4 log cfu/mL
4oC pH
18oC
NaCl
NaCl
1 - 10
5
1 - 10
aw
1 - 10
6
1 - 10
Comb
1 - 10
5, 6
7
pH
1, 7
1, 7
1, 7
aw
1, 7
1, 7
1, 7
Comb
1, 7
1, 7
• Considered Solution: Use of a mixed microbial culture
– Not expected results, the model of the mixed culture was almost the same with the individual model (Vermeulen et al., 2007)
![Page 39: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/39.jpg)
• Same procedure as for the individual models
• Use of growth data from 10 different strains
Composite Growth/No Growth Model 4
![Page 40: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/40.jpg)
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
6.8
6.4
6.0
5.6
5.2
1 2 n
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
C
0.8
7
0.8
9
0.9
1
0.9
3
0.9
5
0.9
7
0.9
9
Composite Growth/No Growth Model
Methodology for combining data aw aw aw
pH pH pH
4
![Page 41: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/41.jpg)
G/ NG Model (NaCl)
2 log
3 log
4 log
6
6
9
4oC
4oC
4oC
18oC
18oC
18oC
20
21
21
aw aw
![Page 42: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/42.jpg)
aw aw
G/ NG Model (NaCl - KCl)
4oC
4oC
4oC
18oC
18oC
18oC
6
7
10
18
18
20
2 log
3 log
4 log
![Page 43: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/43.jpg)
Used Probability 10% (P = 0.1)
Composite vs. Individual Models
Comparison of the
Composite Models with the
Individual Models of the more resistant strains
at each temperature and different water activity types
4
![Page 44: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/44.jpg)
4oC
4oC
4oC
18oC
18oC
18oC
composite
M 1
M 7
Composite vs. Individual Models M 1
M 1
M 5
NaCl Χ
Χ
Χ
composite
M 5
M 6
NaCl
4 log
2 log
3 log
![Page 45: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/45.jpg)
Composite vs. Individual Models
composite
M 1
M 9
M 9
M 9
M 1
Χ 4 log
2 log
3 log
Χ
Χ
NaCl- KCl NaCl- KCl
composite
M 6
M 8
![Page 46: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/46.jpg)
Composite vs. Individual Models
Observations
• At certain environmental conditions, the individual models fail to predict the growth of Listeria monocytogenes.
• At certain environmental conditions, the composite model has a smaller growth boundary than the individual models. Despite that, it safely predicts every condition where Listeria monocytogenes did grow.
– This means that in some cases the composite model gives less conservative observations
4
![Page 47: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/47.jpg)
CONCLUSIONS
5
![Page 48: Development of a GrowthNo Growth model based on growth data of 10 different L. monocytogenes strains](https://reader031.fdocuments.net/reader031/viewer/2022030213/589cea921a28abf86d8b6e8f/html5/thumbnails/48.jpg)
Conclusions
• Strain Variability as for their Growth Boundary
• Change of a single environmental condition (π.χ. pH) leads to a change of the Growth profile
• Even strains with the same Growth profile can produce different statistical models
• Development of a Growth/No Growth model using growth data of a single strain can lead to false estimations
• Development of a composite Growth/No Growth model using growth data of as many as possible strains under several environmental conditions and inoculum levels could lead to safer conclusions
5