Here we discuss a major issue in food safety – E.coli outbreaks – including possible causes to look out for and effective prevention strategies to have in place.
Tragic Death of Three Year Old Girl Due to E.coli 0157 Bacteria
Eighteen people (16 in Scotland, 2 in England) fell ill with the deadly E.coli 0157 strain in July this year. In terrible recent news, a three year old girl from Dunbartonshire has died from the infection. Health Protection Scotland has carried out investigations, and has identified Errington Cheese, a gourmet cheese made with unpasteurised milk, as the probable cause of the infection.
Batch G14 of Lanark White Ewe Milk Cheese, made by Errington, has been withdrawn by Food Standards Scotland.
Humphery Errington, owner of the cheese business, has stated that he is extremely upset at the accusation and is facing financial ruin. The company is conducting its own tests.
There are many types of E.coli. Some are harmless, causing few symptoms in infected individuals. However, as has been proven over the years, E.coli 0157 is a particularly virulent strain and can be fatal. The most vulnerable are those with undeveloped immune systems, such as babies and children, those with compromised systems, such as those who are sick, and older people whose systems are weaker.
Causes of E.coli
E.coli (the 0157 strain and others) is found naturally in the stomach and gut of all mammals, including humans where it exists without causing problems. The bacteria are excreted, falling onto the earth, growing plants, or into natural water courses, infecting crops and streams. When animals are killed, the faeces of the animals can also contaminate their flesh, often through poor hygiene and health & safety practices.
In the recent outbreak, if the source is found to be Errington cheese, the infection has most probably been caused by raw or unpasteurised milk.
In unpasteurised milk products there can be a risk from pathogens, for example Salmonella and Listeria, as well as E.coli. When in the cows udder, the milk is sterile. It can become contaminated in a variety of ways that include exposure to faeces during or after milking, an infection of the glands (mastitis) or by poor hygiene and storage.
Examining the problems associated with E.coli has also highlighted the larger problem of the mass production of meat.
It has also been discussed by experts, and has recently been highlighted by the Food Standards Agency, that the widespread use of antibiotics in animal husbandry has given rise to super-bug strains of E.coli which have become resistant to antibiotics due to their over-use.
The FSA recently stated an investigation showed 24% of 92 chickens samples from Tesco, Asda, Sainsbury’s, Morrisons, Waitrose, the Co-op and Aldi all had antibiotic resistant E.coli strains on their surfaces. This is also true of compylobacter and salmonella – other common sources of food poisoning.
Although dangerous, E.coli 0157, is still a bacterium, and can be killed by heat. For this reason, safety recommendations advise thorough cooking to a core temperature of 72 °C. Pasteurisation of milk requires a sliding scale of temperatures dependent on a heat/time ratio. The lowest is 63 °C for 30 minutes, rising to 138 °C for 2 seconds for ultra pasteurisation (UP). Pasteurisation would have made a safe the cheese in question, but would it have altered the nature of the product?
There is always another side to the discussion. Worrying new research as recently emerged from The UDSA’s Eastern Research Centre in America in Wyndmoor.
Scientists have discovered that E.coli previously subjected to heat treatments that did not kill them, may then become more heat resistant. In experiments, scientists contaminated gravy samples with E.coli 0157 bacteria. These samples were then heated to 114.8 °F for between 15 – 30 minutes. This did not kill the bacteria, and the bacteria became more resistant to heat and when subsequently re-heated to 140 °F. An increased resistance and tolerance was noted which lasted for 48 hours. This is concerning, and may make us re-think how ready prepared food is re-heated.
Although most E.coli infections are short term and at worst, unpleasant, as we have seen, in vulnerable individuals death can result. The usual symptoms of E.coli are a raised temperature, abdominal cramps pain and diarrhoea. Severe symptoms can lead to bloody diarrhoea and can cause kidney failure.
Infections by E.coli, and other pathogenic bacteria, can be prevented if we understand the potential dangers and take care when preparing and handling foods. Food must be cooked and re-heated to the recommended temperatures for the appropriate length of time.
All utensils and equipment must be clean and disinfected to avoid cross contamination. All raw vegetables, fruits and salads must be properly washed before use.
Care must be taken when using raw foods such as unpasteurised milk and seafood products. Food handlers must washed their hands carefully before preparing foods, after handling raw foods, and going to the toilet. It is important that all staff in food preparation and serving situations must know the dangers posed by E.coli and other pathogens and understand how to handle food safely.