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Transcript
HOT TOPICS No:001 A Beginners Guide To Bacteria This hot topic will provide you with a basic understanding of Bacteria. It will serve as an introduction to the subject and take you through the key principles of what bacteria are, how they develop and what harm they can cause. Use this to brief your workers about bacteria and their effects. • What are bacteria? Bacteria are single cell micro-organisms that exist virtually everywhere. They can be found on humans, food, in the ground, in the air and in water. Most bacteria are harmless to humans, some are actually essential as they break down decaying matter in the body and others are helpful to us and are used in the food industry in the production of cheese and yoghurt. Some however can cause spoilage of food and others can cause illness including food poisoning. Definition • • • • Cell Wall – the rigid shell that gives the bacterium its shape Cell Membrane – controls the passage of waste and nutrients in and out of the bacterium Cytoplasm – the main body of each bacterium Nuclear Material – effectively the brain of the bacterium Flagella – attachments to the outside of the bacterium that allow it to move in liquids Below is a very simplified version of the structure of a bacterium Cytoplasm Nuclear Material Cell Wall Bacterium: One or a single eg: a bacterium is very small Bacteria: Multiple bacterium eg: bacteria are very small Cell Membrane Flagella se by the naked Bacteria are incredibly small, and cannot be seen eye. They vary in size from approximately 0.001mm to 0.003mm. Although you cannot see individual bacterium large numbers can cause visible effects on food such as discolouration, slime or odour What do bacteria look like? If you could see bacteria you would notice that they vary in shape considerably. There are four main shapes: How do bacteria multiply? Bacteria multiply by splitting into two. The time it takes for each bacterium to divide depends on the temperature and the food available to it. Food poisoning bacteria are generally thought to divide every 20 minutes in ideal conditions. However if o temperatures are kept low (below 10 C) division can take up to 10 hours. As a rough guide, if a food item is contaminated with 1000 bacteria per gram of food and the conditions are ideal for the bacterial to divide. You will have 1,000,000 bacteria within 2 hours. This number of bacteria is likely to cause food poisoning What makes bacteria multiply? Cocci: are spherical in shape Rods: are shaped like a sausage Bacteria responsible for food poisoning need the following conditions to enable them to grow and, in some cases, produce toxins. Definition Spirochaetes: are spiral in shape Vibrios: are shape like a comma Although shapes vary, all bacteria have a similar structure and all have 5 key features: Toxins: Food poisoning bacteria produce toxins, these are effectively poisions and can be produced in food or inside your body Copyright 2012 Stortfood Ltd. Registered Business Busine (07883802) A Beginners Guide To Bacteria Warmth: The best temperature for bacteria to multiply is around the o same temperature as the human body (about 37 C) although o o they will multiply quickly from 20 C to 50 C. To prevent growth o o of bacteria on food it must be kept below 5 C or above 63 C. This temperature range is often referred to as “The Danger Zone” Warm rooms are ideal for bacterial to multiply, but most won’t o o multiply in a refrigerator that runs between 1 C and 4 C and o none will multiply in a freezer (-18 C) although many will survive and start multiplying when the food thaws. Some bacteria are able to produce spores which protect them against adverse conditions such as high and low temperatures. Once the favourable temperature returns the spores release the bacteria which can then start to grow Food & Moisture: Bacteria prefer high protein food such as meat, poultry and dairy products. Food such as dried milk powder, gravy powder or even dried egg do not provide the conditions suitable for growth, that is whilst they remain a powder. Once liquid is added any bacteria present will begin to multiply. Other foods which do not support the multiplication of bacteria include products high in sugar, high in salt or high in preservatives or acids. Time: Given the right conditions of food, moisture and warmth, bacteria can divide into two every 10 minutes. If there is enough time a few bacteria can multiply to such as extent that there is enough to cause severe food poisoning. For this reason, high risk foods such as meats, fish, dairy products and poultry are o o not left in the danger zone (5 C to 63 C) for any longer than is absolutely necessary. Important It is often assumed that bacteria require oxygen to survive and to multiply. This is not always the case. Some bacteria thrive without the need for oxygen and some can survive with and without oxygen. Correct cooking is the only way to ensure bacteria are killed off. What Are High Risk Foods? High risk foods are generally ready to eat foods which by their nature support the multiplication of harmful bacteria and are intended to be consumed with no further preparation. Such foods include: • • • • • • Cooked meat and cooked poultry Cooked meat products including meat pies, gravy, stews, spreads and stock Milk, cream, artificial cream, custard and any dairy product Eggs and products made from raw egg such as mayonnaise and hollandaise sauce. Shellfish and other seafood including oysters, prawns and crabs Cooked rice What is food poisoning? Food poisoning is an acute illness which usually occurs within 1 to 36 hours of eating contaminated food. Symptoms can last from 1 to 7 days and can include: stomach cramps, diarrhoea, vomiting, nausea and fever. Food poisoning is caused by: • Bacteria and their toxins • Viruses • Chemicals such as insecticides & cleaning agents • Metals such as mercury, lead and copper • Poisonous plants such as toadstools Bacterial food poisoning is by far the most common and some instances can cause death. A large number of bacteria are usually involved and this normally requires them to multiply within food. What Are The Key Food Poisoning Bacteria? Salmonella: Source – Raw meat, milk, eggs, raw poultry, pets, rodents, flies, sewage/water Onset Period – 12 to 36 hours Symptoms – Abdominal pain, diarrhoea, vomiting and fever Clostridium Perfringens: Source – Animal and human excreta, soil, dust, insects and raw meat Onset Period – 12 to 18 hours Symptoms – Abdominal pain and diarrhoea. Vomiting is rare Staphylococcus Aureus: Source – Human nose, mouth, skin, boils and cuts. Raw milk from cows and goats Onset Period – 1 to 7 hours Symptoms – Abdominal pain, vomiting, prostration and subnormal temperatures Clostridium Botulinum: Source – Soil, fish, meat and vegetables Onset Period – 12 to 36 hours Symptoms – Difficulties in swallowing and breathing, double vision, paralysis. Fatalities are common and recovery of survivors takes many months Bacillus Cereus: Source – Cereals, especially rice Onset Period – 1 to 5 hours Symptoms – Vomiting, Abdominal pain, and some diarrhoea. Definition Onset Period: The time it takes before symptoms start to appear Copyright 2012 Stortfood Ltd. Registered Business (07883802) A Beginners Guide To Bacteria Food-bourne Diseases Bacteria in food is not just the cause of food poisoning. Other illness can be caused by bacteria in food. These are known as food-bourne diseases. Such illnesses include: • • • • • Typhoid Paratyphoid Tuberculosis Dysentry Brucellosis There are three specific types of bacteria known to cause foodbourne illness: Campylobactor: Source - Raw poultry, raw meat, raw milk, farm animals, sewage and birds. Onset Period – 2 to 5 days Symptoms – Fever, bloody diarrhoea, abdominal pains and nausea Unlike food poisoning, only small numbers of bacteria are required to cause these illnesses and multiplication within the food is not necessary. The bacteria responsible are found in the gut of man amongst other places and chain of infection is the same as that involved in food poisoning. This is known as the faecal – oral route. Note - More cases of illness are caused by this bacteria than by salmonella Listeria: Source - Animals, humans, sewage and raw milk. Onset Period – 1 to 70 days Symptoms – Flu like symptoms including fever and diarrhoea BACTERIA IN FAECES Note - Listeria is known to multiply at temperatures lower than o 3C E.coli O157: Source – Intestines of cattle, sheep and human, sewage, meat and raw milk. Onset Period – 3 to 4 days TRANSFERRED VIA HANDS/ SEWAGE Symptoms – Nausea, diarrhoea and severe abdominal cramps Note - NE.coli O157 is known to cause kidney failure in children and fatalities in the elderly. Remember BACTERIA GETS ON TO FOOD It is impossible to eliminate all food poisoning bacteria from food businesses and they will be present from time to time therefore it is vitally important that: • • • • FOOD IS CONSUMED • Bacteria are denied the chance to contaminate high risk food All food should be protected by storing at the correct temperatures at all times Work surfaces and equipment must be kept clean using appropriate cleaning and anti-bacterial agents Good hand washing and personal hygiene practices must be observed at all times Workers returning from foreign holidays should be assessed to ensure they are fit to work BACTERIA CAUSES ILLNESS IN MAN Copyright 2012 Stortfood Ltd. Registered Business (07883802)