Spatiotemporal replication dynamics of Salmonella during systemic disease
Author(s)
Watson, Kathryn Geraldine
Type
Thesis
Abstract
Salmonella enterica serovar Typhimurium (S. Typhimurium) causes a
systemic disease in susceptible mouse strains that is widely used as a model
of human typhoid fever. I developed a reporter system based on fluorescence
dilution that measures bacterial replication directly at both the population and
single cell level. To understand how S. Typhimurium colonises host tissues
during disease, I applied fluorescence dilution to study S. Typhimurium
replication during acute murine typhoid, following oral inoculation. Bacteria
that had not replicated were found in the Peyer’s patches (PP), mesenteric
lymph nodes (MLN) and spleen. Hence, replication is not a prerequisite for S.
Typhimurium to traverse the intestinal wall and reach deeper tissues.
Furthermore, non-replicating bacteria were found to persist for long periods of
time within the intestine and, to a smaller extent, in the spleen, suggesting
that these bacteria may represent dormant reservoirs that cause chronic
infections. Bacteria replicated rapidly upon invasion of the PP, while the MLN
represented a more restrictive niche for bacterial replication. In addition, the
spleen was seeded preferentially by bacteria that had already replicated
elsewhere. Further analysis of bacterial replication in the spleen provided
insights into the contribution of the Salmonella-encoded pathogenicity island-2
type III secretion system to replication in this organ. Experiments also showed
that S. Typhimurium preferentially colonised and replicated within
macrophages within the spleen. Therefore, the use of fluorescence dilution
has provided detailed insights into the relationship between the replication of
S. Typhimurium and its colonisation of host tissues, and has revealed the
existence and localisation of non-replicating bacteria that could persist during
chronic infections.
systemic disease in susceptible mouse strains that is widely used as a model
of human typhoid fever. I developed a reporter system based on fluorescence
dilution that measures bacterial replication directly at both the population and
single cell level. To understand how S. Typhimurium colonises host tissues
during disease, I applied fluorescence dilution to study S. Typhimurium
replication during acute murine typhoid, following oral inoculation. Bacteria
that had not replicated were found in the Peyer’s patches (PP), mesenteric
lymph nodes (MLN) and spleen. Hence, replication is not a prerequisite for S.
Typhimurium to traverse the intestinal wall and reach deeper tissues.
Furthermore, non-replicating bacteria were found to persist for long periods of
time within the intestine and, to a smaller extent, in the spleen, suggesting
that these bacteria may represent dormant reservoirs that cause chronic
infections. Bacteria replicated rapidly upon invasion of the PP, while the MLN
represented a more restrictive niche for bacterial replication. In addition, the
spleen was seeded preferentially by bacteria that had already replicated
elsewhere. Further analysis of bacterial replication in the spleen provided
insights into the contribution of the Salmonella-encoded pathogenicity island-2
type III secretion system to replication in this organ. Experiments also showed
that S. Typhimurium preferentially colonised and replicated within
macrophages within the spleen. Therefore, the use of fluorescence dilution
has provided detailed insights into the relationship between the replication of
S. Typhimurium and its colonisation of host tissues, and has revealed the
existence and localisation of non-replicating bacteria that could persist during
chronic infections.
Date Issued
2011
Date Awarded
2011-11
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Holden, David
Creator
Watson, Kathryn Geraldine
Publisher Department
Medicine
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)