A new study has revealed why we are at risk to salmonella. Research has revealed that the salmonella binds itself to the leaves using long stringy appendages usually found in the guts of livestock or egg-ducts of chickens.
There have been recent outbreaks of salmonella associated with salads and vegetables, with a greater contamination risk linked to pre-bagged salads and herbs. Contamination usually occurs during the slaughter process of meats, but of the 23% of food poisoning cases between 1996 and 2000 4% were related to prepared salads.
Scientists believe salmonella and E.coli 0157 contaminates salads and vegetables via one or more of three routes: if fertilised with contaminated manure; if irrigated with contaminated water; or if they come into contact with the bacteria during the preparation process. The new research however has revealed how the pathogens bind to leaves.
Professor Gadi Frankel from Imperial College London teamed up with Dr Rob Shaw et al. from the University of Birmingham to genetically engineer a specific type of salmonella without flagella (stringy appendages). When the flagella were absent, no bacteria was found on the leaves. This led the scientists to then discover that salmonella enterica serovar Senftenberg not only uses its flagella to move around, but it can also change form. Once ‘flattened, the bacteria are able to attach to leaves. The discovery is significant because it will lead to new developments in the prevention of this type of contamination.
Professor Frankel said: “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.” Additional research gains importance as there is a continuing drive for healthier eating, making salads and vegetables an increasingly preferred option. Professor Frankel adds: “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”.
Professor Frankel and the team have now moved on to researching which salad leaves and vegetables are more vulnerable to contamination, and if a resistance can be replicated. He explained: “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”.
The research is presented at this month’s 21st International ICFMH Symposium ‘Food Micro 2008′ conference in Aberdeen.
It's interesting...people buy organic food because it's healthier and supposed to be cleaner, now you should know that either ways you have to wash vegetables and fruits carefully if you wanna avoid salmonellosis as well as other infections.