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.. High-risk foods for STEC and their key controls: Food, Key control. Beef mince, burgers, sausages, meatballs, stuffed meats — Cook to 75 degrees C in the centre, checked with a probe. Whole intact cuts (steak, roast) — Searing the surface makes rare or medium safe. Leafy greens and salad — Wash under running water; buy from reputable suppliers; keep cold. Raw sprouts — High risk; best avoided by vulnerable people. Unpasteurised milk and raw-milk cheese — Best avoided by vulnerable people; buy from reputable suppliers. Unpasteurised juice — Best avoided by vulnerable people. 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 produce: the problem with no cook step Salad leaves, spinach, sprouts and other fresh produce are a growing source of STEC outbreaks worldwide because they are usually eaten raw. There is no cooking step to destroy any bacteria present, so contamination that occurs on the farm — from manure-based fertiliser, animals near growing areas, or contaminated irrigation and wash water — can carry all the way to the plate. Sprouts are especially high risk because the warm, moist conditions used to germinate seeds are ideal for bacterial growth. Businesses cannot rely on washing alone to make contaminated produce safe; washing reduces but does not eliminate bacteria. The practical controls are to buy from reputable, food-safe suppliers who manage water and growing risks, wash leafy greens thoroughly under running water (unless the pack is labelled ready-to-eat or pre-washed), keep produce refrigerated to slow any growth, and rigorously separate produce prep from raw meat prep. For vulnerable groups, avoiding raw sprouts and unpasteurised juices is a sensible added precaution. Produce can be contaminated before it reaches you; there is no cook step to fix it.. Sprouts and unpasteurised juices are high-risk and best avoided by vulnerable people.. Wash loose leafy greens under running water; pre-washed ready-to-eat packs do not need re-washing.. Buy from reputable suppliers, keep produce cold, and keep it well away from raw meat and its juices.. Stopping cross-contamination in the kitchen Even when incoming food is well managed, STEC can be spread inside a kitchen from raw meat to food that will not be cooked again. This is one of the most common and preventable causes of illness. The core defences are the familiar four: separate, clean, chill and cook. Keep raw meat and poultry physically separated from ready-to-eat foods in storage (raw below ready-to-eat in the fridge) and during preparation, using dedicated boards, knives and utensils, ideally colour-coded. Clean and then sanitise surfaces, equipment and hands between raw and ready-to-eat tasks — cleaning removes visible soil and sanitising reduces bacteria to safe levels, and both steps are needed. Wash hands thoroughly with soap and warm water after handling raw meat, using the toilet, or touching animals. Under Standard 3.2.2 of the Food Standards Code, food businesses have specific obligations for skills and knowledge, cleaning and sanitising, temperature control and handling of ready-to-eat food; requirements and any food safety supervisor or Standard 3.2.2A obligations vary by state and territory, so confirm what applies to you with your local council and state food regulator. Separate: raw meat below and away from ready-to-eat food; dedicated, colour-coded boards and utensils.. Clean then sanitise: two distinct steps on surfaces and equipment between raw and ready-to-eat tasks.. Wash hands with soap after raw meat, the toilet, and animal contact.. Chill: keep cold food at or below 5°C to slow any bacterial growth.. What to do if STEC is suspected STEC illness typically causes stomach cramps and diarrhoea that is often bloody, sometimes with vomiting but frequently little or no fever, usually starting a few days after exposure (commonly within about two to ten days). Because a proportion of cases progress to HUS, anyone with bloody diarrhoea — and especially a young child, older adult or vulnerable person — should seek medical advice promptly. Antibiotics and anti-diarrhoeal medicines are generally not recommended for suspected STEC because they may increase the risk of complications; medical assessment is important. For general health advice, healthdirect (1800 022 222) is a reliable Australian starting point. For food businesses, a suspected STEC link is a serious event. Preserve any implicated food and records, review your cooking and cross-contamination controls, and cooperate fully with investigators. Food businesses are generally required to notify the relevant authority of certain matters, and clusters of illness are followed up by public health units. If you become aware that food you have sold may be unsafe, contact your local council or state food regulator without delay — they can advise on recall, withdrawal and corrective actions. Watch for cramps and bloody diarrhoea, often with little fever, usually a few days (about 2-10) after exposure.. Seek medical advice for bloody diarrhoea, especially in children, older adults and vulnerable people.. Antibiotics and anti-diarrhoeals are generally not advised for suspected STEC — get medical assessment.. Businesses: preserve evidence, review controls, and notify your council or state food regulator promptly.. Worked examples: The medium-rare burger request: A customer asks for a medium-rare burger. Because mincing spreads surface bacteria throughout the patty, the centre must reach 75 degrees C, so the kitchen cooks it right through and checks with a probe rather than judging by colour. A seared whole steak could be served rare, but a burger cannot. Salad after raw chicken: A cook uses a board for raw chicken, then reaches for the same board to slice salad leaves. Because there is no cook step for salad, any STEC transferred goes straight to the customer. Washing and sanitising the board, or using a separate colour-coded one, breaks the chain. Checklist: Raw meat stored at or below 5°C, sealed, and below ready-to-eat food in the fridge or coldroom. Dedicated (ideally colour-coded) boards, knives and utensils for raw meat. Hands washed with soap and warm water after raw meat, the toilet and animal contact. Probe thermometer available, clean and checked for accuracy. Mince, burgers, sausages and stuffed meats cooked to 75°C in the centre. Leafy greens washed under running water (unless labelled pre-washed/ready-to-eat). Produce and salads prepared away from raw meat and its juices. Surfaces and equipment cleaned then sanitised between raw and ready-to-eat tasks. Hot food held at or above 60°C; cold food at or below 5°C. Reputable suppliers used for meat, produce and any raw-milk or juice products. Common mistakes: Judging mince doneness by colour instead of a probe thermometer — mince can brown before reaching 75°C, or stay pink after it is safe.. Treating a burger or sausage like a steak and serving it rare or medium — grinding spreads bacteria throughout, so the centre must be fully cooked.. Using the same board, knife or tongs for raw meat and then salad or cooked food without washing and sanitising in between.. Relying on washing alone to make contaminated leafy greens safe — washing reduces but does not eliminate STEC.. Serving raw sprouts, unpasteurised milk or unpasteurised juice to young children, older adults or other vulnerable people.. Storing raw meat above ready-to-eat food, allowing juices to drip and contaminate items that will not be cooked again.. Cleaning surfaces but skipping the sanitising step — removing soil is not the same as reducing bacteria to safe levels..