Bacterial Food Poisoning or Intoxications

Staphylococcal Food intoxication • • • • • • Organisms: strains of staphylococcus aureus Type of toxin: enterotoxin Incubation period: 2 to 6 h Duration of illness: 6 to 24 h Symptom: Salivation, nausea, vomiting, abdominal cramps, diarrhea, sub-normal body temperatures, mortality is extremely low, in severe cases blood and mucus may be found in the stools 78 Foods commonly involved Staphylococcal Food intoxication • • • • • 1. protein- rich foods 2.cooked foods intended to be eaten cold 3.foods exposed to lukewarm temperatures for a few hours 4. foods insufficiently refrigerated due to large bulk or high refrigeration temperatures 5. leftover foods along with gravy which are not stored at adequately low temperatures 79 39 Mode of Transmission Staphylococcal Food intoxication • Sources from where microorganisms enter food are mostly human or animal and include droplet infection from nasal passages and direct contact with boils and infected wounds 80 Staphylococcal Food intoxication • • • • • • • • Prevention: 1. Use raw ingredients free from Staphylococcus aureus for example pasteurized milk. 2. Keep employees with any Staphylococcal infection like boils away from food. 3. Prevent cross contamination from raw meat to cooked meat and from contaminated equipment , utensils or hands to high risk foods. 4.Kill the organisms by heat treatment 5. Since the toxin is resistance to heat and hence is destroyed only when boiled gradually for at least 30 minutes, we can not rely on cooking to prevent the illness. 6. The growth of staphylococci can controlled by rapid cooking , chilling and prompt refrigeration 7. practice personal hygiene 81 40 Botulism • • • • • It is produced by anaerobic spore- forming bacteria which is found in the soil. Contaminated foods: vegetables, fish, canned , bottled and vacuum packed foods. The spores of this organisms can survive boiling for 6 h. Organism can not grow if the pH is below 4.5, so canned acidic foods are safe. Heating food to 80 0C for 15 min is sufficient to destroy the toxin. 82 Botulism • • • • Organism: Clostridium botulinum Toxin: neurotoxin Incubation period: 18 to 38 h Duration of illness: death in 24 h to 8 days, or slow , convalescence over 6 to 8 months. • Symptoms: nausea, vomiting, diarrhea, fatigue, dizziness, double vision, difficulty in swallowing and in speaking, vomiting, dryness of the mouth and constriction of the throat, paralysis of involuntary muscles which spread to the respiratory system and the heart. 83 41 Foods commonly involved Botulism • 1. Inadequately processed home-canned foods, including low and medium acid foods, acid foods lik canned tomatoes, peaches and pears in which other microorganisms are present. • 2. Smoked products that have been underprocessed. • 3. Damaged, leaky and rusty cans cans with broken seals. 84 Botulism • Prevention: 1. Use approved heat processes for canned food. 2. Reject gassy or spoiled canned food and refuse to taste doubtful food. 3. Avoid leftover cooked foods that not well reheated, or raw and precooked foods that have been frozen, thawed and held at room temperature. 4. smoked fish should be heated to at least 850C for 30 min and should be frozen immediately after packing. 5. Heat food to 100C for a few minutes to destroy toxin which is thermo labile. 85 42 Bacillus cereus food poisoning • • • Is found in soil, dust, water and on cereal grains The food usually affected is rice, especially boiled rice which is prepared and used on the following day. The spore survive boiling. They germinate, multiply and release a toxin in rice if it is not refrigerated. Outbreaks sometimes follow celebrations where rice was not washed pin clean water or boiled in advance and cooled slowly. 86 Bacillus cereus • • • • • • Organism: Bacillus cereus Toxin: an enterotoxin produced in food Incubation period: 1 to 16 h Duration of illness: 12 to 24 h Symptom: The onset of the symptoms is sudden and they include abdominal pain, acute vomiting and diarrhea, usually there is no fever. 87 43 Food commonly involved Bacillus cereus • Cereals like reheated boiled rice, corn flour sauce, Chinese fried rice, spice • Mode of transmission: contaminated cereals, grains especially rice, from the environment, as spores are present in soil. 88 Bacillus cereus • Prevention: • 1. cool cooked food rapidly and refrigerate promptly • 2. reheat food thoroughly and serve immediately • 3. keep the interval between cooking and eating as short as possible 89 44 Clostridium perfringens Food Poisoning • Is found in the human and animal intestinal tract, soil, dust, contaminated raw meat , poultry and some dried foods. • The spores can survive normal cooking temperatures and multiply rapidly in cooked meat which is cooled slowly or stored in a warm place. 90 Clostridium perfringens • Symptom: abdominal pain, diarrhea and nausea, vomiting rarely occurs, mild vertigo, mortality rate may be as high as 2 percent. • Foods commonly involved: • 1. meat dishes • 2. reheated dishes kept at warm temperatures for considerable periods of times. • 3. roasted meat and poultry • 4.sauces, salads, gravies 91 45 Clostridium perfringens • Prevention: • 1. thorough cooking of food, • 2.cool food rapidly to prevent multiplication of bacteria and reheat thoroughly just before serving • 3. handle raw and cooked food separately to prevent cross contamination. • 4.kitchen and personal hygiene • 5. wash all fruits and vegetables thoroughly. 92 Clostridium perfringens • • • • • Organism: Clostridium perfringens(welchii) Toxin: enterotoxin produced in intestine Incubation period: 8 to 24 h Duration of illness: 1 to 2 days Mode of transmission :from human faeces via hands to the food by direct contact, vector transmission by flies sitting on extra, cross contamination from raw to cooked meat, dusty kitchens and dirty card boards boxes placed on work tables. 93 46 Bacterial Food Infections • Salmonellosis • Organism: viable cells of salmonella chloraesuis or salmonella enteritidis, serotype typhymorium • Incubation period: 12 to 24 h • Duration of illness: 1 to 7 days • • • • • Mode of transmission: 1. contact transmission 2. cross contamination 3. vector transmission 4. use of cracked eggs or seafood from polluted waters 94 Salmonellosis • Symptom; diarrhea, abdominal pain, chills, fever, vomiting, dehydration, enteritis or local infection may also occur, watery, greenish, foul- smelling tools • • • • Foods commonly involved: 1. animal products 2. duck's eggs 3. high risk foods exposed to warm temperatures for long hours 4.seafood from polluted water 5. canned foods that are opened • • 95 47 Salmonellosis • Conditions necessary for an outbreak: • 1. the food must contain or get contaminated with the organism • 2. these bacteria should be present in considerable number • 3. live organisms should be ingested 96 Salmonellosis • • • • • • • • • Prevention: 1. purchase meat , poultry, eggs and fish that have been thoroughly inspected for wholesomeness. 2. wash hands often 3. the food handlers nails should be trimmed and clean 4. keep equipment clean and hygienic 5. to control rodents and insects in food preparation areas 6. to keep cool foods 7. thorough cooking at least 660C for at least 12 min 8. leftover food should be reheated quickly and thoroughly 97 48 Typhoid and paratyphoid (Enteric fever) • Typhoid fever is caused by S.typhi, whereas paratypoid fever is caused by S.enteritidis  • • • • • • • Typhoid fever: Organism: S.typhi Incubation period: 14 days Duration of illness: 1 to 8 weeks Mode of transmission: 1. vehicle transmission through contaminated milk and water 2. direct contact through hands that are contaminated 3. vector transmission by flies and other insects • Symptom: malaise, headache, high and continued fever, cough, anorexia, vomiting, diarrhea, bleeding from bowels 98 Foods commonly involved Typhoid fever • • • • • • • • Raw milk, vegetables grown on sewage farms, especially if eaten raw, and contaminated water Prevention: 1.ill persons or suspected carries should not be allowed in food preparation and service areas 2. use boiled cooled water 3. there should be proper sewage and disposal and non leaky sewer pipes 4. use pasteurized milk and other dairy products 5.Control the growth of rodents and insects 6. protect by immunization with vaccines 99 49 Paratyphoid • • • • • • • Organism: S. enteritidis, serotype Paratyphi A, B, and C Incubation period: 1 to 15 days Duration of illness: 1 to 3 weeks Mode of transmission: 1. vehicle transmission through contaminated foods like frozen foods, ice and ice creams 2. direct contact by infected carriers and persons who have not washed hands adequately, the source is the feces and urine of infected persons 3. vector transmission through houseflies 100 Paratyphoid • Foods commonly involved: • Contaminated foods, especially, confectionary, frozen foods and ice creams • Prevention: same as for typhoid 101 50 Prevention of food poisoning Food poisoning can be avoided by basic principles of food care: • Limiting contamination from source, hands, raw food, and environment • Purchasing • Storage • Refrigeration • Cooking • Personal hygiene • Clean up • Pest control 103 51 Sources Of Food Poisoning Bacteria Contaminated raw foods e.g. meat Food handlers Pests Pets Dirt and dust Refuse and waste 104 Transfer Of Food Poisoning Bacteria • Direct Contamination - when a raw food touches a high risk food • Indirect Contamination - when liquid or juices from raw food drips onto a high risk food • Cross Contamination - when bacteria are carried by hands or utensils, from a raw food to a high risk food. 105 52 Breaking Food Poisoning Chain • Protect food from contamination. • Prevent the multiplication of bacteria. • Destroy bacteria present in the food. 106 What is a High Risk Food? A HIGH RISK FOOD is one on which food poisoning bacteria are able to grow easily, and which is not cooked before eating to kill the bacteria. Cooked meat and poultry Cooked meat products e.g. gravy, stock, soup Meat or fish pates and spreads Cooked dairy products and rice 107 53 High risk foods • High risk foods are those which – easily support bacterial multiplication under favourable conditions – will not receive extra treatment, such as cooking, that would kill pathogens before the food is eaten • They usually – are ready-to-eat foods – are moist and high in protein – require refrigeration 108 Examples of high risk foods • • • • • • Cooked meat and cooked poultry Cooked meat products, such as stew, gravy and soup Meat and fish pastes, spreads and salads Milk and eggs and uncooked or lightly cooked products made from them Shellfish and seafood Cooked rice 109 54 Factor affecting growth of microbes • 1. Food and nutrients • • • 2. pH level Most bacteria prefer a neutral pH between 6.5 to 7.5 Moulds and yeast grow better in an acidic medium of pH 4 to 4.5 • • 3. Moisture: Bacteria need more moisture than yeasts and moulds and hence fungi grow faster on dry food material like bread and cereal grains • • 4. Temperature: At high temperatures ( above 65 C) , micro organisms are destroyed and at low temperatures, their growth is retard ( below 5 C) • • • A) Psychrophilic organisms: optimum temperature below 20 C B) Mesophilic organisms: optimum temperature between 20- 45 C C) Thermophilic organisms: optimum temperature above 45 C , For example, the spore – forming micro organisms like Clostridium and Bacillus Termopius 110 Factor affecting growth of microbes 5. Oxygen 6. Time 7. Osmotic pressure A Concentration of 3- 10 percent salt inhibits most micro organisms except the salt tolerant organisms 8 Sunlight or UV rays 111 55 Time and temperature control: general rules • • • • Keep hot food hot (at 63˚C or above) Keep cold food cold (at below 5˚C) Keep frozen food frozen (at -18˚C or below) Minimise the time high risk food is in the danger zone – – – – • Cook and serve food immediately if possible – – • • store deliveries immediately minimise preparation time heat quickly cool quickly avoid re-heating if food must be re-heated, do so only once Check the date codes Rotate foods in storage 112 Poor time and temperature control • Preparing food too soon before serving or selling it and leaving it at a danger zone temperature • Inadequate cooling – ‘warm’ for too long • Inadequate cooking – not hot enough for long enough all through the food • Holding hot food at a ‘warm’, instead of a hot, temperature • Inadequate re-heating – not hot enough for long enough all through the food 113 56 Temperature Control 1 • Freezer temperature -18 to -22’C (Daily checks required) • Refrigerator temperature 0 to 5’C (Minimum check is daily) • Hot food on display counter minimum of 63’C (Check frequently throughout display period) • Cooking & Re-heating Min core temp of 70’C for 2 minutes. (Check all products cooked or re-heated) 114 Temperature Control 2 • Cooling of food to less than 5’C must be completed in less than 90 minutes. • Optimum temperature for the growth of pathogenic bacteria is 37’C. 115 57 Date Coding USE BY: Applies to perishable foods. Is written as DAY, MONTH. Food is illegal beyond that date. BEST BEFORE: Applies to longer shelf life products. Is written as END MONTH, YEAR. Food is not illegal beyond that date. 116 Temperature control Stage of food handling When to check temperature Recommended safe temperatures DELIVERY Every time perishable food is delivered. 0˚C to 5˚C for refrigerated food. -22˚C to -18˚C for frozen food. Daily, at least. Daily, at least. 0˚C to 5˚C. 0˚C to 5˚C. Daily, at least. -18˚C or below. STORAGE Refrigerator or cold store Refrigerated storage counter or display Deep freezer THAWING Frozen meat and poultry Whenever food is thawed. 0˚C to 5˚C. COOKING eg. Joints of meat and poultry Whenever food is cooked. Minimum core temperature of 70˚C for 2 minutes. COOLING Whenever food is cooled. 10˚C or cooler (ideally 5˚C or below) within 90 minutes. RE-HEATING Whenever food is re-heated. Minimum core temperature of 70˚C for 2 minutes (82˚C in Scotland). HOT FOOD ON DISPLAY Frequently throughout the display period. Minimum core temperature of 63˚C. COLD FOOD ON DISPLAY Frequently throughout display period. By the Dr Aryaeian 0˚C to 5˚C. 117 58 Personal Hygiene 1 • ILLNESS You must not handle food, and must report immediately to your supervisor if you are suffering from any of the following…… COLD / SORE THROAT / SEPTIC CUT / SICKNESS / DIARRHOEA / ILLNESS FOLLOWING TRIP ABROAD. • FOOD POISONING CASE - Person suffering from illness. CARRIER - Infected person with no symptoms. 118 Food Preservation Methods (1) HIGH TEMPERATURE Sterilisation / UHT / Canning (2) LOW TEMPERATURE Refrigeration / Freezing (3) DEHYDRATION Drying / Salt / Sugar (4) PICKLING Acid / pH (5) VACUUM PACKING & CAP (6) CHEMICALS (7) IRRADIATION 119 59 Examples of food preservation methods • • • • • • • • • • • Refrigeration Freezing Pasteurisation Ultra heat treatment (UHT) Canning and bottling Sterilisation Concentrations of salt or sugar Pickling Modified atmosphere packaging (MAP) Smoking Dehydration 120 • • • • • • • • • • Control of Microbial Growth in foods A. Controlling temperature 1. Freezing 2. Heat: a) wet heat: 1. pasteurization LTH ( Low temperature holding) method at 62C for 30 minutes HTST( high temperature short time) or flash method at 72 C for 15 seconds UHTS ( Ultra high temperature sterilization) at temperatures above 135 C for 2 -3 seconds 2. Canning : > 100 C about 115 -125 C 121 60 Control of Microbial Growth in foods • • • • • • • 3. Cooking ( boiling , steaming , ..) At his method ( 100 C) most micro organisms are destroyed but spores survive. Foods cooked by these methods can not be stored for long. b) Dry heat: 1. sun drying, smoking and freeze drying: It destroys moulds , yeast and most bacteria and spores. 2. Cooking ( baking, roasting, grilling). The temperatures reached on the surface are approximately 115 C. Most bacteria are destroyed. 122 Control of Microbial Growth in foods • • B) Removing Oxygen C) Adding Chemical Preservatives • If these preservatives are used in foods, they should be mentioned on the label. They are used to preserve food in the following ways. 1. They may be added to food, for example, sodium benzoate in tomato sauce and potasium metabisulphite in lemon juice. 2. They may be applied on the surface of foods. Sulphur dioxide is used on dry fruits and borax is used to wash vegetables and whole fruit 3. Wrappers may be impregnated with sorbic acid to prevent surface spoilage of cheese. 4. the ice used to chilled food like fish may contain tetracycline. 5. They may be used as gases around food. Fruits and vegetables are stored in an atmosphere containing two to three percent carbon dioxide to retard the ripening process. • • • • • 123 61 Control of Microbial Growth in foods • D) Reducing the moisture content • The moisture content of food like milk is reduced by evaporation , dehydration of the food. Microorganisms survive in such foods, but they remain dormant. For example, Milk , eggs , fruits and vegetables • E) Exposure to Ultraviolet Rays • UV rays are lethal to bacteria. They have poor penetrating power and can be used only for surface sterilization or for sterilizing the air in a room. They are used to control mould growth on the surface of bakery products and to prevent spoilage of meat while tenderizing and aging. 124 THE WHO GOLDEN RULES FOR SAFE FOOD PREPARATION • • 1. Choose foods processed for safety • 2. Cook food thoroughly • 3. Eat cooked foods immediately • 4. Store cooked foods carefully • 5. Reheat cooked foods thoroughly • 6. Avoid contact between raw foods and cooked foods • 7. Wash hands repeatedly • 8. Keep all kitchen surfaces meticulously clean • 9. Protect foods from insects, rodents, and other animals • 10. Use pure water 125 62