Acquistion and selection of virulence traits of Salmonella enterica serovar Typhimurium in the organs of infected mice

Lead Research Organisation: University of Cambridge
Department Name: Veterinary Medicine

Abstract

Salmonella enterica is a pathogen capable of causing a spectrum of diseases in humans and animals. S. enterica serovar Typhi causes approximately 22 million cases of typhoid fever and over 200,000 deaths annually; serovar Paratyphi causes about 5.5 million annual cases in humans. Other non-typhoidal Salmonella serotypes (NTS) cause gastroenteritis in humans and animals and can spread from animals to humans via contaminated food (e.g. meat and eggs). NTS are a common cause of bacteraemia and sepsis in immuno-compromised individuals (e.g. HIV and malaria patients) and in children, especially in developing countries (e.g. Africa), where they constitute a major cause of death. Current measures in the treatment of S. enterica infections have been revealed as insufficiently effective, and there is a need to develop novel vaccines and therapeutics. The interaction between S. enterica with the host immune system is complex and the outcome of the infection is the result of a fine balance between a continuous escalation of the immune response and the expression of bacterial immunoevasion mechanisms. Consequently, in order to continue growing in the tissues, S. enterica is likely to require the coordinated and sequential regulation of genes. Bacterial gene regulation has so far been investigated largely using exposure to artificial environmental conditions or to in vitro cultured cells and little information is available on how S. enterica adapts in vivo to sustain cell division and survival. Currently, it is impossible to mimic in vitro the many, possibly unknown, inflammatory events that occur during infection. Understanding how gene regulation affects virulence traits of bacterial pathogens in vivo is one of the major challenges of the post-genomic era. Using microbiology, microscopy and sensitive molecular techniques we aim to develop an understanding of the dynamic interactions between host and bacterial mechanisms that determine net growth rates of S. enterica within the host. These experiments will help us to develop an understanding of the influence of passage in a host on the fitness and virulence of S. enterica, which will directly inform the development of novel vaccines and strategies to control and treat a major global health problem.

Technical Summary

Bacteria of the species Salmonella enterica are a threat to public health; S. Typhi causes ~22 million cases of typhoid fever and over 200,000 deaths annually. The emergence of multi-drug resistant Salmonella strains and the insufficient efficacy of some of the currently available Salmonella vaccines highlight the urgent need for improved prevention strategies to combat salmonellosis in humans and animals. The design of novel vaccines and antimicrobials would benefit from a more sophisticated evaluation of how S. enterica coordinates the sequential regulation of genes to enable the bacteria to maintain their growth/survival throughout the infection in the face of the continuous escalation of the host immune responses. In vitro approaches have been used to explore the interaction between pathogens and individual host cells, but these strategies lack the anatomical and functional complexity of whole-body systems. The mechanisms underlying the spatiotemporal and genetic basis of in vivo bacterial adaptation and expression of virulent traits remain largely unresolved. The hypothesis behind the proposed research is that the increase in bacterial numbers observed during the early stages of a systemic S. enterica infection is due to a fine and dynamic balance between bacterial adaptation and increasing activation of the host antimicrobial response. To address this hypothesis the work will have a number of objectives, which will collectively 1) determine the spatial and temporal dynamics of S. enterica adaptation to the in vivo environment; and 2) determine the traits that are at the basis of S. enterica adaptation to the in vivo environment. The basic in vivo model for these studies will be the mouse model of invasive S. enterica infection. We will use bacteriological counts from tissue homogenates, fluorescence microscopy and quantitative PCR to determine the spread, localization and distribution of S. enterica in the tissues. In addition, we will use microarrays and proteomics to identifying bacterial gene and protein regulation mechanisms in vivo within the whole animal. The work will develop an understanding of the influence of growth and passage in a host on the fitness and virulence of S. enterica and determine the mechanistic and temporal elements involved in S. enterica in vivo adaptation. This will provide knowledge and technological basis for targeting individual bacterial components in vivo with novel drugs and vaccines and for eliciting immune responses against individual bacterial virulence determinants directed at the sites of infection where these are maximally expressed by the microorganisms.

Publications

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Chaudhuri RR (2011) Quantitative RNA-seq analysis of the Campylobacter jejuni transcriptome. in Microbiology (Reading, England)

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Dybowski R (2015) Single passage in mouse organs enhances the survival and spread of Salmonella enterica. in Journal of the Royal Society, Interface

 
Title Generation of Salmonella mutants 
Description Generation of Salmonella mutants 
Type Of Material Technology assay or reagent 
Provided To Others? No  
Impact Too early to measure any outputs 
 
Description Investigations into Copper homeostasis in Salmonella 
Organisation University of Manchester
Department Faculty of Life Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution In vivo studies of Salmonella copper mutants
Collaborator Contribution Data has been written up and published: J.B.C. 2010, 285:25259-25268
Impact Data has been written up and published: J.B.C. 2010, 285:25259-25268
Start Year 2009
 
Description Salmonella with Wolf 
Organisation ETH Zurich
Country Switzerland 
Sector Academic/University 
PI Contribution Sharing of research materials, and collaboration on several research projects leading
Collaborator Contribution Collaboration on several research projects leading
Impact Several publications in print and more in submission
Start Year 2010
 
Description Studies into the involvement of Salmonella pathogenicity island 2 in in vivo infection 
Organisation Imperial College London
Department Section of Microbiology
Country United Kingdom 
Sector Academic/University 
PI Contribution Me and my group have used a number of Salmonella mutants that we obtained from our collaborators to look at the effect of SPI-2 in intracellular growth and bacterial spread
Collaborator Contribution Generation of scientific data which has been written up and is just about to be submitted to Nature
Impact Generation of scientific data which has been written up and is just about to be submitted to Nature
Start Year 2010
 
Description The application of Wet STEM to bacterial systems 
Organisation University of Cambridge
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution Provision of Salmonella strains and mutants, training into bacterial culture and preparation techniques
Collaborator Contribution Submission of a manuscript (decision pending) to Journal of Microscopy
Impact Submission of a manuscript (decision pending) to Journal of Microscopy. This collaboration is multi-disciplinary and involves microbiologists and physicists
Start Year 2009
 
Description Article for Genetic Engineering News 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Interview for Genetic Engineering News concerning our research.

Difficult to assess the article appeared in print, on-line, facebook and twitter
Year(s) Of Engagement Activity 2011
 
Description Foreign Office vist to Thailand 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Discussion of the research to members of the Thailand Government. acadmeia and industry in Thailand

Ongoing discussions concerning possible collaborative projects
Year(s) Of Engagement Activity 2011
 
Description Keynote speaker at the 2nd World Congress on Antibiotics and Antibiotic Resistance, Manchester, UK, 13-15 October 2016. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Keynote speaker at the 2nd World Congress on Antibiotics and Antibiotic Resistance, Manchester, UK, 13-15 October 2016. Title of the presentation: Relationships between pathogen behavior, immunity and efficacy of antimicrobial drugs within a mammalian host. The talk generated interest in the relationships between in vivo behaviour of bacteria and out use of vaccines and antimicrobials. The talk increased awareness that we must take care of the characteristics of the infection before designing treatment and prevention strategies
Year(s) Of Engagement Activity 2016
 
Description Primary School Visit 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Talk about infectious diseases (including work related to this grant) to a local primary school.

Difficult to assess, but hopefully inspitring young children (the scientists of tomorrow) to be interested in infectious diseases
Year(s) Of Engagement Activity 2010,2011