E. coli: How It Spreads and How to Control It

Most E. coli is harmless, but Shiga toxin-producing E. coli (STEC) can cause severe illness and, in a minority of cases, life-threatening kidney failure (HUS). It spreads mainly through faecal contamination of beef mince, leafy greens, unpasteurised dairy and water. Control it by cooking mince right through to 75°C in the centre, washing produce, and stopping raw-to-ready cross-contamination through separation, cleaning and temperature control. Key takeaways: STEC (Shiga toxin-producing E. coli) is the dangerous form — it can cause bloody diarrhoea and, in a minority of cases, haemolytic uraemic syndrome (HUS), a serious condition that can cause acute kidney failure and most affects young children and older adults.. Beef mince is high risk because grinding spreads surface bacteria all the way through the meat, so it must be cooked to 75°C in the centre — a rare burger or sausage is not a safe choice, unlike a seared whole steak.. Leafy greens and sprouts can carry STEC from irrigation water, manure or soil, and there is no cook step for salad — so wash thoroughly, buy from reputable suppliers and keep produce cold.. Cross-contamination from raw meat and its juices to ready-to-eat food is a leading cause of illness — separate, clean and sanitise, and never let raw and ready-to-eat items share boards, tongs or surfaces.. A very low dose of STEC can make someone sick, so there is little margin for error; standard controls — cook, clean, chill, separate — must be applied consistently, not occasionally.. What E. coli and STEC actually are Escherichia coli (E. coli) is a group of bacteria that naturally lives in the gut of humans and animals. Most strains are harmless and are simply used as an indicator of faecal contamination in water and food. The strains that cause serious foodborne illness are the Shiga toxin-producing E. coli, known as STEC (also called VTEC or, for the best-known serotype, E. coli O157). These strains produce a toxin that damages the lining of the gut and, in severe cases, the small blood vessels of the kidneys. STEC matters out of proportion to how often it occurs. Food Standards Australia New Zealand notes that around 10% of STEC infections progress to haemolytic uraemic syndrome (HUS) — a condition that can cause acute kidney failure and is most dangerous for young children (particularly those under five) and older adults. Because the infectious dose is very low compared with many other foodborne bacteria, even small lapses in hygiene or cooking can be enough to cause illness. That is why STEC is treated as a priority hazard in meat processing and fresh-produce risk management. Most E. coli is harmless; STEC is the pathogenic form that produces Shiga toxin.. E. coli O157 is the most recognised serotype, but non-O157 STEC strains also cause illness.. A low infectious dose means there is little tolerance for undercooking or contamination.. Young children, older adults and people with weakened immune systems are most at risk of severe outcomes.. How STEC spreads to food STEC lives in the intestines of cattle, sheep and other ruminants, usually without making the animal sick. It reaches food through the faecal-oral route: contamination of the carcass at slaughter, manure or contaminated irrigation water on crops, animal contact, contaminated water, or person-to-person spread via unwashed hands. From there it can be moved around a kitchen on hands, boards, knives, cloths and surfaces. The foods most often linked to STEC in Australia and internationally are beef mince and other ground or comminuted meats, fermented and semi-dried sausages (such as some salamis and mettwurst), unpasteurised (raw) milk and raw-milk cheeses, unpasteurised juices, fresh leafy greens, and raw sprouted seeds. Water — drinking water from untreated sources, or water used to wash produce — is another recognised route. Understanding the route matters because it points to the control: a hazard introduced on the farm or at slaughter is managed differently from one spread by a dirty chopping board in your own kitchen. Primary reservoir: the gut of cattle, sheep and other ruminants.. Farm and processing routes: manure, contaminated irrigation or wash water, carcass contamination at slaughter.. Kitchen routes: raw meat juices, hands, boards, knives, tongs and cloths carrying bacteria to ready-to-eat food.. High-risk foods: beef mince, uncooked fermented sausages, raw milk and raw-milk products, unpasteurised juice, leafy greens and sprouts.. Why mince is different from a steak On a whole, intact cut of red meat, bacteria such as STEC are found almost entirely on the outer surface. Searing the outside of a steak or roast reaches those surfaces with lethal heat, which is why a rare or medium steak can be safe when the outside has been properly seared. Mincing changes everything. When meat is ground, rolled, needle-tenderised or stuffed, any surface bacteria are folded and distributed throughout the product. A burger patty or sausage is therefore contaminated in the centre as well as the surface, and the centre is exactly the part that stays coolest during cooking. For this reason, minced and comminuted red meat, burgers, meatballs, sausages and stuffed meats should be cooked until the centre reaches 75°C, verified with a clean probe thermometer rather than by colour. Meat colour is an unreliable guide — mince can brown before it is safe, or stay pink after it is safe. This is also why uncooked or lightly fermented spreadable sausages carry specific STEC risk and are not recommended for young children, pregnant women or other vulnerable people. Whole intact cuts: bacteria are on the surface, so searing the outside makes rare/medium safe.. Minced, rolled, tenderised or stuffed meat: bacteria are throughout, so the centre must be fully cooked.. Cook mince, burgers, sausages and meatballs to 75°C in the thickest part.. Use a probe thermometer — do not judge doneness by colour or juice run.. Leafy greens and pro