Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How Salmonella bacteria contaminate salad leaves – it’s not rocket science

03.09.2008
How Salmonella bacteria can cause food poisoning by attaching to salad leaves is revealed in new research presented today (3 September) at the 21st International ICFMH Symposium ‘Food Micro 2008’ conference in Aberdeen.

The new study shows how some Salmonella bacteria use the long stringy appendages they normally use to help them ‘swim’ and move about to attach themselves to salad leaves and other vegetables, causing contamination and a health risk.

Food poisoning from Salmonella and E. coli is commonly associated with eating contaminated bovine or chicken products, as the pathogens live in the guts of cows and the guts and egg-ducts of chickens, and contamination of meat can occur during the slaughtering process.

However, some recent outbreaks of food poisoning have been associated with contaminated salad or vegetable products, and more specifically, pre-bagged salads. For example, in 2007 a Salmonella outbreak in the UK was traced back to imported basil, and an E. coli outbreak in the USA in 2006 was traced to contaminated pre-packed baby spinach.

Between 1996 – 2000, 23% of the UK’s infectious intestinal disease outbreaks like salmonella and E. coli were caused by contaminated food, and of these, 4% were linked to prepared salad.

The new research, led by Professor Gadi Frankel from Imperial College London and carried out with Dr Rob Shaw and colleagues at the University of Birmingham, has uncovered the mechanism used by one particular form of Salmonella called Salmonella enterica serovar Senftenberg, to infect salad leaves, causing a health risk to people who eat them.

Understanding the mechanism that pathogens such as salmonella use to bind themselves to salad leaves is important if scientists are to develop new methods of preventing this kind of contamination and the sickness it causes.

Scientists know that Salmonella and E. coli O157 – a strain of E. coli that can cause serious sickness in humans - can spread to salads and vegetables if they are fertilised with contaminated manure, irrigated with contaminated water, or if they come into contact with contaminated products during cutting, washing, packing and preparation processes. However, until now, scientists did not understand how the pathogens managed to bind to the leaves.

Professor Frankel and his colleagues at the University of Birmingham found that Salmonella enterica serovar Senftenberg bacteria have a secondary use for their flagella - the long stringy ‘propellers’ they use to move around. The flagella flatten out beneath the bacteria and cling onto salad leaves and vegetables like long thin fingers. To test this observation the scientists genetically engineered salmonella without flagella in the lab and found that they could not attach themselves to the leaves, and the salad remained uncontaminated.

Professor Frankel says: “Discovering that the flagella play a key role in Salmonella’s ability to contaminate salad leaves gives us a better understanding then ever before of how this contamination process occurs. Once we understand it, we can begin to work on ways of fighting it.”

The team’s next steps will involve looking at the extent to which different types of salad leaves are affected by salmonella. Professor Frankel explains that some types of leaves are less susceptible to salmonella contamination that others: “If we can find out what factors affect susceptibility, we may be able to develop new technologies to harness the ‘immunity’ found in some salad leaves to protect others from contamination,” he says.

However, Professor Frankel says that even though such a small minority of cases are currently linked to salads, the numbers are likely to increase in coming years. “In their efforts to eat healthily, people are eating more salad products, choosing to buy organic brands, and preferring the ease of ‘pre-washed’ bagged salads from supermarkets, then ever before. All of these factors, together with the globalisation of the food market, mean that cases of Salmonella and E. coli poisoning caused by salads are likely to rise in the future. This is why it’s important to get a head start with understanding how contamination occurs now,” he said.

In a previous study, Professor Frankel and his colleagues discovered the mechanism by which E. coli 0157 binds to salad leaves. They have shown that E. coli O157 bacteria use short needle-like filaments, which are normally used to inject bacterial proteins into human cells, to attach them to salad leaves, causing contamination and a risk of transmission via the food chain to humans.

Danielle Reeves | alfa
Further information:
http://www.imperial.ac.uk

More articles from Life Sciences:

nachricht New photocatalyst speeds up the conversion of carbon dioxide into chemical resources
29.05.2017 | DGIST (Daegu Gyeongbuk Institute of Science and Technology)

nachricht Copper hydroxide nanoparticles provide protection against toxic oxygen radicals in cigarette smoke
29.05.2017 | Johannes Gutenberg-Universität Mainz

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Strathclyde-led research develops world's highest gain high-power laser amplifier

The world's highest gain high power laser amplifier - by many orders of magnitude - has been developed in research led at the University of Strathclyde.

The researchers demonstrated the feasibility of using plasma to amplify short laser pulses of picojoule-level energy up to 100 millijoules, which is a 'gain'...

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

New insights into the ancestors of all complex life

29.05.2017 | Earth Sciences

New photocatalyst speeds up the conversion of carbon dioxide into chemical resources

29.05.2017 | Life Sciences

NASA's SDO sees partial eclipse in space

29.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>