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Faecal bacteria found in high street coffee chains’ iced drinks – here are the facts

Warning: may contain faecal bacteria. Ksw Photographer/Shutterstock

Ice from three high street coffee chains in the UK have been found to contain faecal bacteria following an investigation by BBC One’s Watchdog programme. Analysis that I carried out on behalf of the consumer series, found that ice used in drinks at Caffè Nero, Starbucks and Costa Coffee contained high levels of faecal coliform bacteria, with seven out of ten samples from Costa and three out of ten samples from the other two chains testing positive.

For the investigation, the Watchdog team took swabs and ice samples from ten coffee shops in each of the three chains – so, 30 coffee shops in total – before passing them on to us in the university laboratory to process. Swabs were taken from tables, trays and high chairs. We transferred each of the samples to a petri dish that contained a jelly to help the bacteria multiply.

We were interested in looking at the total number of bacteria, regardless of species (known as “total viable count”) and the number of bacteria that have the ability to grow in the human gut, called faecal coliforms. We found these two types (total viable count and faecal coliforms) in all of the 30 sites that we tested.

Our results were polarised. We either found none or very few bacteria, or we found what we consider to be too many to count (over 300), some of which were just total bacteria but sometimes from both total bacteria and coliform bacteria.

Faecal coliform in a petri dish. CA-SSIS/Shutterstock

The levels of bacteria that we found in the samples indicate that people’s health could be put at risk. Some of the bacteria we identified are “opportunistic pathogens”, which are bacteria that might not necessarily cause disease in healthy people, but could cause disease in people with reduced immunity, such as those who are already sick, the very young, elderly and people who have undergone an organ transplant or chemotherapy. Most of these pathogens will infect your gut, causing symptoms such as vomiting and diarrhoea. A few of them cause lung infections and skin and eye infections.

Better hygiene needed

Given our analysis it is most likely that ice we tested was contaminated by being touched by unclean hands, but it is also possible that ice buckets and machines may not have been cleaned to a high enough standard. Given the levels of bacteria allowed in tap water in the UK, we would not expect to find more than 10 bugs per millilitre. The results of the ice samples from the coffee shops, however, showed hundreds of coliforms per millilitre.

Although microbial levels in tap water are carefully controlled in the UK, ice often seems to be overlooked. When people travel abroad they often avoid drinking the local tap water but have no qualms about asking for ice with drinks. While bacteria can’t grow in ice, freezing water doesn’t actually kill the bacteria, it just stops them dividing.

In coffee shops there is probably an accumulation effect: if ice machines and equipment aren’t being regularly and thoroughly cleaned, then bacteria will collect to the high levels we discovered in the samples we tested. In light of our findings, I would urge businesses to review their ice handling and hygiene procedures.

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