Contact: Samantha Martin
University of Liverpool
Study shows how Salmonella survives in environment
Scientists at the University of
Liverpool have demonstrated how a single-celled organism, living freely
in the environment, could be a source of
Salmonella transmission to animals and humans.
are microscopic living creatures that can contaminate almost any food
type, causing diarrhoea, abdominal pain and fever. Scientists know that
Salmonella – which can also cause typhoid fever – has evolved
unique mechanisms to prevent the body's immune system from functioning
effectively, but until now it was not understood how it survives so
successfully in the environment.
Scientists at Liverpool, in collaboration with the Institute for Animal Health, have shown that
use a secretion system to protect themselves inside amoeba – a
single-celled organism living on land and in the water. The research
suggests that amoeba may be a major source of
Salmonella within the environment and could play a significant role in transmission of infection to man and animals.
uses a system, called SP12 type III, which acts as a bacterial machine
inside organisms and causes disease in humans, animals and plants. The
system employs a 'syringe-like' mechanism to inject bacteria into cells
that would normally release compounds to rid the body of harmful
substances. This system changes the structure of the cell and prevents
these compounds from coming into contact with pathogens and destroying
Dr Paul Wigley, from the National Centre for Zoonosis Research, based at the University's Leahurst campus, explains: "
has managed to survive extremely successfully in the environment,
finding its way into our food and causing illness, despite the body's
best efforts to fight it off. We found that it uses a system which
operates in the human immune system as well as inside amoeba living in
the environment. This system essentially protects
Salmonella within cellular compartments, called phagosomes, where it can survive and multiply.
ability to survive in amoeba is a huge advantage to its continued
development as it may be more resistant to disinfectants and water
treatment. This means that we need to work to understand ways of
controlling amoeba in water supplied to animals and prevent it acting
as a 'Trojan Horse' for
Salmonella and other pathogens."
research, supported by the Society for Applied Microbiology, the
Department for Environment, Food and Rural Affairs (DEFRA), and the
Higher Education Funding Council for England (HEFCE), is published in
Applied and Environmental Microbiology.
Notes to editors:
The University of Liverpool is a member of the Russell Group of leading
research-intensive institutions in the UK. It attracts collaborative
and contract research commissions from a wide range of national and
international organisations valued at more than £93 million annually.
The Institute for Animal Health, supported by the Biotechnology and
Biological Sciences Research Council, is dedicated to the study of
infectious diseases in farm animals, with laboratories at Compton in
Berkshire and Pirbright in Surrey. www.iah.ac.uk
3. Research Paper reference: The
Salmonella Pathogenicity Island 2-Encoded Type III Secretion System Is Essential for the Survival of
Salmonella enterica Serovar Typhimurium in Free-Living Amoebae in
Applied and Environmental Microbiology
Vol. 75. Authors: Benjamin Bleasdale, Penelope J. Lott, Aparna
Jaganathan, Mark P. Stevens, Richard J. Birtles, and Paul Wigley.