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FOOD POISONING Foodborne Diseases Apply to illnesses acquired by consumption of contaminated food. Sometimes incorrectly referred to as food poisoning. Includes : Foodborne intoxications Foodborne infections. Foodborne intoxication By toxins, whether biological or chemical e.g. Staphylococcus Fish poisons Heavy metals. Foodborne infection e.g. Salmonella Vulnerable Groups Food poisoning is more likely to affect people with lowered resistance to disease than healthy people who might show mild symptoms or none at all. The following are particularly vulnerable to food poisoning: • Elderly or sick people • Babies • Young children •Pregnant women Symptoms of Microbiological Food Poisoning Vomiting Abdominal pain Diarrhea Fever Others e.g. neurological; Botulism Causes of Foodborne Diseases A- Infective Bacterial Viral Protozoa B. Non infective (intoxication) Non Biological a. Chemical Poisons b. Heavy metals c. Other organic Cpds Food Poisoning (contd.) Physical contamination:objects falling in to food – metal, glass, packaging materials etc. Chemical contamination:Bleach, cleaning chemicals getting in to food Natural contamination: Poisonous plants and berries, undercooked red kidney beans Causes of Foodborne Diseases (Continued) Biological From: a- Mushrooms b- Harmful algal species c- Fish e.g. Ciguatera Fish poisoning Scombroid Fish poisoning associated with raised Histamine levels. Paralytic shell Fish poisoning [In Japan]. Causes Food Borne Disease Bacteria Salmonella species Campylobacter jejuni Staphylococcus aureus Clostridium perfringens Clostridium botulinum Bacillus and other sporing bacilli Shigella species. E.coli Yersinia enterocolitica Vibrio parahaemolyticus, Aeromonas hydrophilia, Streptococcus species Group C, E and G . The other e.g. Listeria monocytogens Causes Of Foodborne Viruses Unlike bacteria viruses do not multiply in Foods. Acquired by: a- Primary contamination From shell Fish From Oysters From Mussels From Vegetables e.g Hepatitis A From Vegetables irrigated by untreated water. b- Secondary contamination. From Food handlers e.g. Hepatitis A Foodborne Viruses (Continued) Viruses: a- Hepatitis A b- Hepatitis E c- Small rounded structured viruses(SRSV) e.g. Norovirus Caliciviruses Astroviruses Rotaviruses Causes of Foodborne Disease Protozoae 1- Giardiasis. 2- Amoebiasis 3- Cryptosporiosis 4- Isospora 5- Balantidum 6- Blastocytosis hominis 7- Microsporidia 8- Toxoplasmosis (?) Some Diseases Which Are Transmitted By Food But Not Considered As Food Poisoning: 12345- Bovine tuberculosis (milk) Brucellosis (milk) Toxoplasmosis (meat) Listerosis (milk products) Mad cow diseases etc. Selected Clinical and Epidemiologic Characteristics of Typical Illness Caused By Common Foodborne Pathogens* Pathogen Typical Incubation Period Duration Typical Clinical Presentation Assorted Foods Salmonella species 1-3 Days 4-7 Days Gastroenteritis Undercooked eggs or poultry, produce Campylobacter jejuni 2-5 Days 2-10 Days Gastroenteritis Undercooked poultry, unpasteurized Bacterial dairy products E. coli, Enterotoxigenic 1-3 Days 3-7 Days Gastroenteritis Many foods Shigella species 1-2 Days 4-7 Days Gastroenteritis Produce, egg salad Listeria monocytogenes 2-6 weeks Variable Gastroenteritis, meningitis abortion Deli meat, hotdogs, unpasteurized dairy products Bacillus cereus 1-6 hour <24 hour Vomiting, Gastroenteritis Fried rice, meats Clostridium botulinum 12-72 hour Days-months Blurred vision, paralysis Home-canned foods, fermented fish Staphylococcus aureus 1-6 hour 1-2 Days Gastroenteritis, particularly nausea Meats, potato & pork, unpasteurized dairy products. Yersinia enterocolitica 1-2 Days 1-3 weeks Gastroenteritis, Undercooked appendicitis-like pork, syndrome unpasteurized dairy products. Viral Typical incubation period Duration Typical clinical presentation Norovirus 1-2 Days 12-60 Hr Gastroenteritis Under cooked shellfish Hepatitis A virus 15-50 Days Weeksmonths Hepatitis Assorted foods Produce, undercooked shellfish Parasitic Typical incubation Duration Typical clinical presentation Assorted foods Cryptos poridium parvum 2-10 Days Weeks Gastroenteritis Produce, water Cyclospora cayetanesis 1-11 Days Weeks Gastroenteritis Produce, water Toxoplasma gondii 5-23 Days Months Influenza-like illness, Food contaminated by cat feces, undercooked lymphadenopathy meat Giardia lamblia 1-4 Wk Weeks Gastroenteritis Water Taenia solium Variable Variable Asymptomatic, cysticercosis Raw pork Types of bacteria Spoilage: Not particularly harmful bacteria which cause food to go off Beneficial: “Good Bacteria” which are used to make yoghurt and cheese Pathogenic: Illness causing bacteria In order to grow and multiply germs need: Time Moisture Food Warmth Flies Waiting Remember it like this Too Many In ideal conditions where there is Moisture, Food and Warmth (37degrees centigrade is ideal), bacteria can double every 10 to 20 minutes. They do this by dividing in to two. This is called Binary Fission These cells are beginning to divide into two After 10 minutes After 20 minutes After 30 minutes After 40 minutes cooking chicken to a core temperature of 75°C should kill most of the bacteria Time : 9.30 Bacteria : 0 Time : 9.40 Bacteria : 12,000 Time : 9.50 Bacteria : 24,000 Time : 10.00 Bacteria : 48,000 Time : 10.10 Bacteria : 96,000 Time : 10.20 Bacteria : 192,000 Time : 10.30 Bacteria : 384,000 Time : 10.40 Bacteria : 768,000 Time : 10.50 Bacteria : 1.5 million From 0 to 1,536,000 in only 80 minutes !!!!!! Knife contaminated by blood Bacterial Growth Curve Numbers Of Bacteria rapid multiplication no multiplication Lag Phase Stationary Phase Numbers of bacteria remain constant as the number produced is equal to the number dying Time (hours) Numbers of bacteria decrease Spore A resting resistant phase of some bacteria (including Clostridium Perfingens and Botulinum and Bacillus Cereus). The bacterium produces a protective coat which helps it to survive high temperatures (up to 120°C) and lack of water. When favourable conditions return, the spores split open and release the bacteria which are then able to grow and multiply Bacterial cell Spore forming inside cell Spore Formation This is what happens ………….. Cell Spore forms in cell Cell disintegrates Spore is released Spore starts to germinate Spore continues to germinate Now see as, in suitable conditions, the cell begins to divide (binary fission)…………………………. Staphylococcus Aureus Found in human nose and throat (also skin) Salmonella Found in animals, raw poultry and birds Bacillus Cereus Found in soil, vegetation, cereals and spices Clostridium Perfingens Found in animals and birds Clostridium Botulinum Found in the soil and associated with vegetables and meats Important Microbial Causes of Food Poisoning Toxin related A. Staphylococcus aureus Short incubation period < 6 hours An intoxication Not infection Important Microbial Causes of Food Poisoning (Continued) Clinical Features: Abrupt, violent Nausea, vomiting, cramps (abdominal pain) Prostration Diarrhea, sub normal temperature Source infected human & food handlers Food contaminated enterotoxin produced Toxin is heat stable Diagnosis: 1- Epidemiologically 2- Isolation of organism from suspected food. 3- Toxin detection in faeces of patients (rarely done) B- Bacillus cereus (from rice meals) Bacillus caereus is an spore forming aerobic bacillus produces two types of enterotoxins. a- Heat stable causing: emetic type of food poisoning incubation period < 6 hours vomiting, nausea b- Heat labile causing: diarrheal type incubation period 6-24 hours “BOTH TOXINS ARE PREFORMED IN FOOD” Clostridium Perfringens Causative agent: type A strains of C. perfringens (C. Welchii) Gram positive anaerobic rod spore forming characterized by sudden: Onset of colic Diarrhea Nausea Pathogenesis Incubation period 10-16 hours Spore-vegetate in food, when swollen they sporulate in the intestine and Produce toxin Diagnosis: Detection of spores in food >105 spores Detection of spore in faeces >106 spores Botulism: Causative agent Clostridium Botulinum Gram positive anaerobic spore forming It produces a powerful toxin The most lethal (killing toxin) 3 Kg can kill the whole population of the world. Food sources: Canned food e.g. fish under anaerobic conditions. Pathogenesis (Continued) Incubation period 12-24 hours under anaerobic condition the spores germinate in the foods to produce the toxin. Classified into A – G strains they produce the responsible toxins A, B, E and F Toxin is heat labile Toxin inhibits release of acetylcholine at neurone muscular junction leading to flaccid paralysis. Symptoms: Neurological (no gastrointestinal) As abnormal eye movements Listeriosis Causative agent Listeria monocytogenes Gram positive rod aerobic Resembles dipththeroids Can multiply at lower temperature 4°C Sources Wide spread in dust, soil, water, sewage, vegetation, animals feeds, poultry, meat fish, vegetable Diseases In pregnant women = febrile illness Neonates – meningitis Immunocompromised patients – febrile illness Food Poisoning Outbreaks: 1.Illness in a period of time - few hours, few weeks. 2.In individuals who consumed common food. 3.Many acute cases can happen 4.Proper evaluation of cases and implicated food is essential 5.Single cases are difficult to recognized unless they have a distinctive clinical syndrome e.g. Botulism LABORATORY DIAGNOSIS OF FOOD POISONING OUTBREAKS 1- Type of Food 2- Incubation period 3-Isolation of the causative agent from a- Patient faeces, Vomit b- From incriminated food and related articles. 4- Investigation of Food Handlers in the same way. LABORATORY INVESTIGATIONS OF FOOD HANDLERS 1-Most Important to explain the procedure 2-Don’t frightened the food handlers 3-Look for Salmonellae, Giardia, Amebae 4-Stop work until three specimens are negative Salmonellosis Caused by No typhoid causing Salmonellas. Called Food poisoning gastro intestinal Salmonellas. Cause about 85% of cases of Food poisoning or Food borne diseases (Shawrma) They are Gram –ve rods belonging to Enterobactericaee group There are more then 2500 species of Salmonellas enterica. Salmonellasis (Continued) Pathogenesis: Incubation period 12-72 hours may be more depends on the dose of Bacteria Swollen. CAMPYLOBACTER JEJUNI A common cause of infectious diarrhea. Affect children. Sources: Chicken (Shwarma) Milk Person to person spread. Diarrhea extends 1- 3 days. Gram stain of faces spiral organisms Culture on selective medium at 42°C. 10 Golden Rules For The Food Preparation 12345- Choose foods processed for safety Cook food thoroughly Eat cooked foods immediately Store cooked foods carefully Reheat cooked foods thoroughly 10 Golden Rules For The Food Preparation (Continued) 6- Avoid contact between raw food and cooked food. 7- Wash hands repeatedly. 8- Keep all kitchen surfaces meticulously clean. 9- Protect food from insects, rodents and other animals. 10-Use safe water. Are you safe? © British Nutrition Foundation 2003 What should you do before you cook? What clothing should your wear? Why should you wash your hands? When is it important to wash your hands? How would you know if the ingredients are safe to use? Why should you tie back long hair? © British Nutrition Foundation 2003 Washing hands Always wash hands before cooking and after: • going to the toilet; • handling raw food, e.g. meat; • touching hair, the mouth, spots or cuts; • coughing or sneezing into your hands; • blowing your nose; • going out of the kitchen, e.g. to put the rubbish out. © British Nutrition Foundation 2003 How would you know how long these foods last? All packaged food has a date mark. A date mark: • tells us by when a food is safe to eat; • is in 2 formats: • ‘use by’ or • ‘best before’ © British Nutrition Foundation 2003 Is it safe to eat? ‘Use by’ dates are used for perishable foods, e.g. cheese, milk ‘Best before’ dates are used for less perishable foods, e.g. canned baked beans, jar of jam and frozen fish fingers. © British Nutrition Foundation 2003 Where should these foods be stored? Different foods are stored in a variety of ways to keep them safe to eat for longer. Dry cupboard © British Nutrition Foundation 2003 Refrigerator Freezer Raw and cooked foods Raw meat and poultry should be stored on the bottom shelf of the fridge to prevent crosscontamination. © British Nutrition Foundation 2003 Fruit and vegetables Always wash fruit and vegetables before you eat or use them to cook. This removes dirt and other and other particles. © British Nutrition Foundation 2003 Campylobacter enteritis Escherichia Coli 0157 Listeriosis That’s the end of lesson 1! Coming next lesson: Foodborne diseases Typhoid and paratyphoid fever Dysentery Enjoy your food! © British Nutrition Foundation 2003 Shigellosis Epidemiology Endemic in developing countries Poor sanitation, crowding and flies 10 to 20 percent of enteric disease 50% of the bloody diarrhea or dysentery of young children Developed countries, single-source, food or waterborne outbreaks occur sporadically under cooked food and contaminated water) Substandard sanitary facilities. Homosexual men Shigella Family Enterobacteriaceae G-ve,facultatively anaerobic, non-sporeforming rods. Four serogroups (species) • • • • Serogroup A — S. dysenteriae Serogroup B — S flexneri Serogroup C — S. boydji Serogroup D — S sonne • Developing countries (most virulant); S. dysenteriae S flexneri • Developed conteries S sonne Differentiated from the closely related Escherichia coli Pathogenicity Physiology (failure to ferment lactose or decarboxylate lysine) and serology Clinical Manifestations - Shigella Person-to-person spread Also food/water vectors IP 24-48 hrs, disease 7 days & carried for 30 D Vomiting and mild to moderate dehydration Bloody diarrhea or dysentery Nonbloody diarrhea Fever, abdominal pain tenesmus with watery diarrhea or scant stools with pus, blood, mucus Complications Bacteremia uncommon Convulsions 25% of Shigella infections involving children under the age of 4 years Ekiri syndrome, an extremely rare, fatal encephalopathy has also been described in Japanese children with S sonnei or S flexneri infections Reactive arthritis (Reiter’s) 2% HLA-B27 S flexneri Hemolytic-uremic syndrome S dysenteriae serotype 1 Protein loss Pathogenesis — Shigella Fecal-oral Infectious dose very low (< 200 bugs) 10-100 Invades mucosa with subsequent multiplication and mucosal destruction Invasiness property encoded on large 140 Mda IPA plasmid InterCellular Spread (IcsA) Shiga-toxin ( I& II) • Exotoxin is an enterotoxin and cytotoxin Diagnosis Shigellosis on the basis of fresh blood in the stool. Neutrophils in fecal smears is also a strongly suggestive sign. Watery, mucoid diarrhea may be the only symptom of many S sonnei infections DDx EIEC, Salmonella enteritidis, Yersinia enterocolitica, Campylobacter species, and Entamoeba histolytica Isolation Procedures - Shigella Enrichment media Plate media GN broth & Selenite broth Low selectivity —MAC Med selectivity — XLD High selectivity — DCA, HEK Caution — some Shigella strains are inhibited by SS agar Screening Procedures - Shigella Lactose or xylose NON-fermenting colonies Screen suspect colonies biochemically TSI — K/A I no gas / no H25 Some sonnei and fiexneri produce gas Nonmotile, urease negative Screen typical biochemically ID colonies with grouping antisera Antimicrobial Susceptibility Testing Shigella Susceptibility testing should be done Empiric treatment when susceptibility is not known is TMP-SMX Use Quinolone if resistance to TMP-SMX is suspected Control Prevention of fecal-oral transmission Vaccines are not currently available, but some promising candidates are being developed