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expert reaction to Müller recalling some Cadbury branded dessert products because of the possible presence of Listeria monocytogenes

An alert from The Food Standards Agency (FSA) states that Müller has taken the precautionary step of recalling some batches of various Cadbury branded dessert products because of the possible presence of Listeria monocytogenes.


Dr Matthew Gilmour, Group Leader in the Microbes in the Food Chain programme at the Quadram Institute Bioscience; and Director of the UK Food Safety Research Network, said:

“The food business has done the right thing by being cautious and acting quickly to recall these chocolate dessert products.  These food types are eaten broadly across the population, including by groups that are at higher risks for foodborne infections of Listeria such as young children, elderly, and those that are pregnant.

Listeria can find its way into foods either because it was already present in some of the ingredients or if it’s inadvertently introduced during production of food if present in the factory environment or equipment.  In this case, it seems one of the desserts not yet distributed to market was tested and found to be positive for Listeria, so the producer is being cautious by recalling the other products made in the same time frame on the same production line, on the chance that the Listeria has spread from the factory environment to the foods.  Chocolate products from a different producer were found to be contaminated with Salmonella last year, showing that this particular food type can be a risk for microbial contamination and merits that producers conduct testing and proactively recall foods, as done here, to keep food supplies safe.”


Food Standards Agency Head of Incidents, Tina Potter, said:

“This is a precautionary measure because although listeria has not been found in the product itself, it was found in a product manufactured in the same production environment, and it is therefore possible that the recalled products may be contaminated.

“Listeria generally causes only mild illness, but some people are at a higher risk of serious infection including those who are pregnant, over the age of 65, new-born babies and people with weakened immune systems.”

Further information:

– Based on what we know so far, there is no information to show a link to any other product recalls, however investigations are continuing.


Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:

“Listeria is a bacteria that can contaminate foodstuffs, most often those containing dairy.  People consuming contaminated foods are at risk of infection.  So, it isn’t out of the question that these types of products – chocolate pudding style desserts – could become contaminated.  However, food production is heavily regulated in the UK and all dairy products are screened for harmful micro-organisms.

“There are several methods of testing for Listeria, with some giving results quicker than others.  Typically, there is an initial test that gives an indicative result and hence we might say that there is a “possible presence” of Listeria.  Following this, a more detailed test can confirm Listeria and quantify the extent of the contamination.

“It is sensible to swiftly recall all the products that relate to the positive test sample, even before the presence of Listeria is completely confirmed.  Listeria can cause serious disease and disability so putting public health first is the only ethical approach to the problem.  If that is what has happened in this case, that is a good thing.

Listeria is often found in the environment, but cases of illness are fairly rare – each year there are perhaps 100-200 cases in the UK.  Generally, the classic food poisoning symptoms diarrhoea and/or vomiting are an indication of mild disease, but it can be much more serious than that.  The pathogen can use our guts as a gateway to our bloodstream where in people with weakened immune systems, like cancer patients, the elderly and very young, it can spread to our organs, including the brain, which can be fatal.  Unusually, it’s also one of the few bacteria that, when causing an infection, can cross the placenta and infect an unborn baby often causing lifelong disability if the infection is not fatal.”


Prof Catherine Rees, Professor of Microbiology, and Deputy Head of Division of Microbiology, Brewing & Biotechnology, University of Nottingham, said:

Is this a precautionary step or has contamination been found?

“The process of identifying Listeria in foods is quite technical difficult and requires several different stages before a definitive identification can be made, so it is also time consuming.  Hence manufacturers tend to err on the side of caution and issue recalls at the earliest point when there is an indication that there might be a problem, rather than waiting for the definitive results, and this is what seems to have happened here.

What does it mean that they have reportedly found “the possible presence of Listeria monocytogenes”?

“This just means that the process of identification is not yet complete – there are some closely related bacteria (such as Listeria innocua) that are completely harmless to humans, but it is difficult to tell these organisms apart until the end of the identification process.  So – on a precautionary principle – manufacturers would rather recall product if there is a chance that Listeria monocytogenes might be in the product rather than waiting until they are certain.

How harmful is listeria – is it dangerous to everyone or only to certain groups?

“Listeria monocytogenes does cause severe disease, but generally this only occurs in people who are immunocompromised; so young children, pregnant women, the elderly and other people with medical conditions that affect their immune system.  It can be found it a lot of environments, and healthy adults normally clear the infection quickly and don’t even realise they had an infection caused by this bacterium – generally symptoms would just be feeling fluey for a few days.  However in the immunocompromised it can lead to very severe infections, even resulting in death.  Fortunately, in the UK there are only about 150 cases confirmed cases every year and listeriosis remains a relatively rare food-borne infection (

Is it a good sign that this has been detected?

“Yes – it shows that the company is carrying out monitoring and is willing to recall products that might be a risk rather than not reporting their concerns early.  Given that we eat a large amount of ready to eat foods every year, many of which are high risk for Listeria, and yet conformed cases in the country are very low, then it shows that generally the monitoring system is working and keeping the public safe.

How unusual / worrying is this?

“Since the high risk foods for Listeria, also tend to be ones with short shelf lives, manufactures often can’t hold the product in the factory until all the tests are complete, so it is not unusual for recalls to be issued in relation to Listeria.  High volume products are seen as the biggest risk – the more widely products produced by one supplier are distributed, the more likely that someone who is vulnerable will eat that product and be affected.  Recently in the US there was a recall by a large manufacturer who sold a wide range of products – but the recall seems to have been successful and no cases have been reported associated with these contaminated goods (see  However in South Africa in 2018, widespread distribution of a contaminated product resulted in over 1000 cases and 200 deaths (see  This shows why the food industry remained vigilant, and sees avoiding Listeria contamination of product of one of its highest food safety priorities.  However the fact that this is a recall by a large volume manufacturer is a concern and the public should be strongly advised to follow the advice and not risk eating these products.”



Declared interests

Dr Simon Clarke: “No conflicts.”

Prof Catherine Rees: “None.”

For all other experts, no reply to our request for DOIs was received.

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