Dr. Mark Fielder, from Kingston University, London, has been keeping a close watch on how the European E. Coli outbreak has developed. Below, he answers some key question about the situation.

Why has it taken so long for German authorities to locate the source of the outbreak?

“It’s important to remember that microbiology is quite a slow science – it takes time to grow the organisms implicated in any given situation. The authorities and health professionals also have the problem of establishing links between the evidence they have from the outbreak and common aspects that tie the infection and the potential source together.

With all the possible factors that might cause the infection to spread, it takes time to get a definitive answer to identify an exact source of infection. In some circumstances this can be quite quick but in others, such as the current one, the situation can be more complicated.”

How have health authorities been trying to isolate the cause?

“Where possible, all affected patients will have been interviewed to try to establish any potential links they may have in terms of food they have eaten, locations they have been to, recent travel and potential exposure to risk factors. The authorities will have drawn up a case definition, which sets out the inclusion and exclusion criteria for a person to be examined for an infection in an outbreak situation. This is a routine procedure in such instances.

Samples will have been taken from all patients potentially involved in the outbreak to determine exactly what organism they are carrying. The isolated organisms all have to be identical for the patient to be included in the outbreak and they have to satisfy the case definition. Samples will also be taken from the suspected sources of the outbreak to try to establish the presence or absence of the organism. This means the authorities will be able to link or exclude possible source materials.”

Why have so many vegetables been seen as possible culprits?

“It’s not completely clear why, in this case, apparently incorrect suggestions of the source of the infection have been made, so it is difficult to speculate. One thing we do know is that vegetables of all types are potential sources of infection, which is why we are encouraged to thoroughly wash and clean them before we eat them.

Peeling vegetables, where appropriate, is also important as this can help remove contamination. Also people should always remember to clean their hands properly after handling unwashed vegetables to help break any cycle of infection.”

Do you think the infection could have spread beyond the source in the food chain?

“As yet, we don’t have any evidence that this has actually happened. However, it’s not impossible that, if infection control measures are breached, there may be other cases due to cross-contamination. But this has not been seen to date in this outbreak.”

We usually link meat products with E. Coli infections. Are vegetables also common sources?

“It’s well known that certain organisms such as E. coli have been associated with poor processing and cooking of meat and meat products, but there is also a large body of work noting similar problems in relation to vegetables and fruit. This is enhanced by the fact that many fruits and vegetables are not cooked at all prior to consumption so the potential risk might, in certain cases, be increased. With this is mind, it’s extremely important that people should thoroughly wash and clean fruit and vegetables before they eat them.

Peeling fruit and vegetables, where appropriate, is also helpful as it can help remove contamination. Also people should always clean their hands properly after handling unwashed vegetables to help break any cycle of infection.”

Once compelling proof is shown regarding this new E. Coli strain, will it be possible to eradicate it completely?

“It’s difficult to say that we will be able to eradicate this particular strain of E. coli O104 completely but what we will be able to do is better understand the way it works. We are now aware of this strain, its toxin-producing capability, its virulence factors and its antibiotic resistance profile.

A greater understanding of the organism will provide us with valuable information to improve our detection and control mechanisms and so try and stay one step ahead of the organism in future.”

Source: Kingston University, River House, 53-57 High Street, Kingston upon Thames, Surrey, KT1 1LQ. United Kingdom

Written by Christian Nordqvist