interactions of the food-borne pathogen listeria
TRANSCRIPT
Interactions of the food-borne pathogen Listeria monocytogenes with the food and host environment
Dr. med. vet. Claudia Guldimann, PhD
Institute for Food Safety and Hygiene, University of Zürich
Imag
e: C
DC
Aim
• Follow L. monocytogenes along the food chain
• Explore interactions
• Discuss why L. monocytogenes is a successful pathogen
In order to cause disease, a food-borne pathogen must:
Hurdles against L. monocytogenes
Food / food processing environment Host
Food processing- Good manufacturing process- Cleaning and disinfection- HACCP
Food preservation / Food preparation- Aw value: salt, sugar, drying- Acid- Temperature- Protective cultures- Packaging
- Digestive enzymes- Stomach acid- Immune system
Listeria monocytogenes – lifestyle
Listeria monocytogenes – lifestyle
Figure 1
Clonal complex from 7-gene MLST
Listeria monocytogenes
Stoller A, Stevens M.J.A., Stephan R., Guldimann C.Pathogens 2019, 8(1), 32;
CC from 7-gene MLST
Disinfection agents
Some L. monocytogenes are resistant to high concentrations of peraceticacid
Stoller A, Stephens M, Stephan R, Guldimann C, Pathogens 2019, 8(1), 32
Impact of the matrix
The food matrix is a significant factor
Ziegler M, Kent D, Stephan R and Guldimann C, Int J Food Microbiol. 2019 May 2;296:83-92
8 °C5 °C
Listeria monocytogenes
CFU
/ml,
log
red
uct
ion
Horlbog J., Kent D., Stephan R., Guldimann C. Nature Scientific Reports, 8, Article number: 12931 (2018)
Listeria monocytogenes
Horlbog J., Stephens MJA, Stephan R., Guldimann C.Microorganisms, 2019 Oct 16;7(10). pii: E455.
RNAseq data of transcriptome
Metabolic map of up- and downregulated pathways
Bile (deutsch: Galle)
Upregulated under bile stress
Genes involved in cell wall modification
Genes involved in motility
Positive regulators of virulence
NOT: bile response genes
Acid: I’m in the stomach!- Upregulate virulence genes- Upregulate bile resistance genes
Bile: I’m near cells to invade!- Upregulate virulence genes- Upregulate motility
Guariglia-Oropeza V., Orsi R., Guldimann C., Wiedmann M., Boor KJ.,Front Microbiol. 2018 Feb 6;9:120
Hurdles against food borne pathogens
Food / food processing environment Host
Food processing- Good manufacturing process- Cleaning and disinfection- HACCP
Food preservation / Food preparation- Aw value: salt, sugar, drying- Acid- Temperature- Protective cultures- Packaging
- Digestive enzymes- Stomach acid- Immune system
Conclusion
L. monocytogenes is exquisitely adapted to the niches it inhabits
This adaptation is governed by intricate regulatory processes that are interdependent.
A better understanding of these adaptive processes will lead to evidence-based, targeted control measures to increase food safety.
Integrated risk analyses needed.
Thank you!
Simone Buess
Andrea Stoller
Matthias Ziegler
Corinne EicherJule Horlbog
Prof. Roger StephanInstitute for Food Safety and Hygiene, University of Zürich
Food environment
• Mild food preservation methods increase SEA production from prophage
Listeria monocytogenes
Listeria monocytogenes = Listeria monocytogenes?
Figure 1
Clonal complex from 7-gene MLST
Horlbog et al., Nature Scientific Reports, 2019
Horlbog et al., MDPI Microorganisms, 2019
Stoller et al., MDPI Pathogens 2019
Figure 1
Clonal complex from 7-gene MLST
L. monocytogenes in general - barriers
19
Contaminated food
Bacteriaemia
CNS infection
Abortion
Strain differences – growth in rich medium & salt
4
5
6
7
8
9
CC1 CC6 CC121 CC9 CC207 CC224 CC31 CC4 CC415 CC54 ST226 ST739
clonal.complex
BH
I.V
ma
x
BHI Vmax
0.8
1.0
1.2
1.4
1.6
I II
lineage
rel.la
gtim
e
Relative lagtime
Horlbog JA, Kent D, Stephan R, Guldimann C, Nature Scientific reports, 2018 Aug 28;8(1):12931
Strains that often affect humans grow faster in rich medium and recover faster under high salt conditions
Single cell differences
Single cell difference – virulence gene regulation
There is a stable population of single cells that express high levels of PrfA
This trait is passed on to daughter cells
S. Peterhans, Dissertation 2017
Conclusions
Strain differences
Understanding the mechanisms of how strains differ might allow new defense mechanismsRisk assessment
Food
Food matrix and production environment
Understanding which foods inhibit growth may yield safer productsUnderstanding which disinfectants work is crucial.
Single cell level
Understanding gene regulation at the single cell level may yield new avenues for preventive / therapeutic measures