Download A Non-Mammalian System to Study Bacterial Infections

AltexSupl-074-086
01.08.2007
13:56 Uhr
Seite 78
PROJECTS IN PROGRESS
A Non-Mammalian System to Study
Bacterial Infections
Pierre Cosson
Faculté de Médecine, Centre Médical Universitaire, Genève, Switzerland
Keywords: bacteria, protozoa, amoeba, infectious diseases, reduction, replacement, infectiosity
Background and aim
In the study of bacterial infectious diseases and in the development of new drugs, it is very often essential to test a bacteria’s capability to cause a disease. To initiate such a situation,
it is necessary to infect a host, typically a mouse, and allow the
disease to progress. We are working on a new system where
mice are replaced by a non-mammalian host: Dictyostelium
discoideum, a soil amoeba. Very similar results are obtained in
this system and in mammalian hosts. We now want to extend
these results to validate this system as an alternative to mammalian models.
Method and results
Dictyostelium discoideum is a powerful genetic system to
analyse the complex relationship between bacteria and phagocytic cells. Our initial work was focused on the mechanisms
controlling phagocytosis of bacteria by amoebae (Cornillon et
al., 2000). We have more recently focused on the interaction of
Dictyostelium amoebae with pathogenic bacteria (Fig. 1). We
have shown that Pseudomonas aeruginosa makes use of a
number of virulence factors to inhibit the growth of
Dictyostelium amoebae (Cosson et al., 2002). In particular virulence factors produced under the control of the quorum-sensing systems are crucial for Pseudomonas virulence against
amoebae, while in another Pseudomonas strain, the type III
secretion system was also important for virulence. Thus
virulence factors characterised previously in mammalian
systems, also play a role in Pseudomonas virulence against
Dictyostelium amoebae.
More recent results allowed us to extend our initial findings to
study many different bacterial pathogens, in particular
Klebsiella pneumoniae (Benghezal et al., 2006). Based on our
current results it is clear that, firstly this system can be adapted
to study many different bacterial pathogens (Charette et al.,
2005), secondly results obtained in this system are very similar
to results obtained in mammalian hosts and thirdly the system is
simple enough, to be easily used in non-specialised laboratories.
Conclusions and relevance for 3R
As is summarised above, our project is to establish, extend and
validate the Dictyostelium system as a relevant model in the
Fig. 1: A Dictyostelium amoeba eating bacteria.
Pathogenic bacteria often use the same mechanisms to defend
themselves against unicellular amoebae and to infect mammalian
animals. Consequently unicellular amoebae offer an alternative
system to study pathogenic bacteria. This system could reduce
significantly the need to use mammals to study pathogenic
bacteria.
study of bacterial infections. This would allow the replacement
of animal experiments using mammalian hosts (typically mice
or rats) with simple experiments, using Dictyostelium as a nonmammalian host. Experiments using animals to study infections usually require large numbers of animals. They inflict
significant suffering on the infected animals and the conclusion of the experiments is often animal death. Thus it will be
particularly useful to develop a credible alternative. Our project will allow the Dictyostelium system to be widely used by
many research laboratories in studying bacterial diseases. This
would make research in this field much easier and at the same
time reduce significantly the need for animal experiments in
mammalian species.
www.forschung3r.ch/en/projects/pr_90_03.html
78
ALTEX 24, Special Issue 2007
AltexSupl-074-086
01.08.2007
13:56 Uhr
Seite 79
PROJECTS IN PROGRESS
References
Alibaud, L., Köhler, T., Coudray, A. et al. (2007). Cellular
Microbiology (in preparation).
Benghezal, M., Fauvarque, M. O., Tournebize, R. et al. (2006).
Specific host genes required for the killing of Klebsiella bacteria by phagocytes. Cellular Microbiology 8, 139-148.
Charette, S., Cornillon, S., Cosson, P. (2005). Identification of
low frequency knockout mutants in Dictyostelium discoideum by single or double homologous recombination. J.
Biotechnology 122, 1-4.
Cornillon, S., Gebbie, L., Benghezal, M. et al. (2006). An
adhesion molecule in free-living Dictyostelium amoebae
with integrin beta features. EMBO Reports 7, 617-621.
Cornillon, S., Pech, E., Benghezal, M. et al. (2000). A member
of the 9TM superfamily involved in adhesion and phagocytosis in Dictyostelium. J. Biol. Chem. 275, 34287-34292.
Cosson, P., Zulianello, L., Joint-Lambert, O. et al. (2002).
Pseudomonas aeruginosa virulence analyzed in a
Dictyostelium discoideum host system. J. Bact. 184, 30273033.
Correspondence to
Prof. Dr. Pierre Cosson
Centre Médical Universitaire
Dpt de Morphologie
1 rue Michael Servet
1211 Geneva
Switzerland
e-mail: [email protected]
Fig. 2: To study infectious diseases, it is not always necessary
to infect animals.
Researchers in the NEMO Network use more simple hosts such as
amoebae, or drosophila flies. In this picture an amoeba (white)
eating up a yeast cell (red).
Development of QSAR-Models for Classification
and Prediction of Baseline Toxicity
and of Uncoupling of Energy Transduction
Beate Escher
EAWAG, Dept. of Environmental Toxicology, Dübendorf, Switzerland
Keywords: bacteria, QSAR, toxicology, in silico, reduction, replacement
Background and aim
The pending implementation of the European chemicals regulation REACH (Registration, Evaluation and Authorisation of
Chemicals) will have a significant impact on additional testing
needs. One approach to potentially reduce the cost and number
of animal tests required is the application of quantitative structure-activity relationships (QSAR) as a tool to prioritise further
testing. However, in the field of ecotoxicology there are still
www.forschung3r.ch/en/projects/pr_95_05.html
ALTEX 24, Special Issue 2007
large gaps for a full regulatory acceptance of QSARs, of which
some are difficult to assess in terms of predictive power and
often lack transparency.
Over the last years we developed an experimental in vitro
test, the Kinspec system (bacterial test), which allows the
determination of nonspecific toxic effects in membranes
(Escher and Schwarzenbach, 2002). Kinspec covers amongst
others the two nonspecific modes of action uncoupling (of
oxidative and photo-phosphorylation) and baseline toxicity.
One of the advantages of Kinspec is that it allowed new
insights into the mechanisms of uncoupling (Escher et al.,
79