Salmonella
Salmonella biofilms make these varied and widespread threats to public health around the world even more of a problem.
Some animals (e.g. chickens, birds, snakes, frogs), can have Salmonella living in their gut without causing them any infection – but these bacteria could still infect you. That’s why you should always wash your hands after touching animals.
Salmonella can be split into subtypes including Salmonella Typhimurium (S. Typhimurium) and Salmonella Typhi (S. Typhi). S. Typhimurium causes food poisoning in humans and animals, when they eat contaminated meat or vegetables. For example, if S. Typhimurium from the gut of a chicken is transferred to the meat during processing it can be eaten accidentally and cause infection. This can result in diarrhoea, vomiting, fever and abdominal pain, but is usually cured by the immune system within a few days (Patel et al, 2014).
S. Typhi only infects humans. It passes between people via faeces when people have poor sanitation and no access to clean drinking water. S. Typhi causes a severe infection, known as typhoid fever, which can result in liver damage, heart problems, internal bleeding and even death. This is because S. Typhi producing a compound that destroys a protein involved in our immunity. Without this protein, S. Typhi is able to enter our cells and establish infection (Yale, 2012).
There is a vaccine available for S. Typhi. However, it is not widely available, resulting in localised outbreaks. As a result, S. Typhi is prevalent in India, Africa, Southeast Asia, and South America.
Many studies have shown that S. Typhi can grow as biofilms on living and non-living surfaces and that this is considered as an important survival strategy.
Salmonella bacteria can grow as biofilms on food and other common surfaces throughout the food chain. When Salmonella is growing in a biofilm it is also more resistant to disinfectants commonly used in food processing, which can result in people getting infected.
Further reading on Salmonella biofilms
Patel Samir, McCormick Beth A. Mucosal Inflammatory Response to Salmonella typhimurium Infection. Frontiers in Immunology, Vol 5, pp 311, 2014. https://doi.org/10.3389/fimmu.2014.00311
Yale researchers discover why typhoid fever pathogen targets only humans, 2012. https://news.yale.edu/2012/11/15/yale-researchers-discover-why-typhoid-fever-pathogen-targets-only-humans