20161023 food poisoning
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This document discusses food poisoning, including its definition, types, common bacterial and non-bacterial causes, pathogenesis, and differential diagnosis. Food poisoning is acute gastroenteritis caused by ingestion of contaminated food or drink. The most common bacterial causes are Salmonella, Staphylococcus, Clostridium botulinum, Clostridium perfringens, and Bacillus cereus. Non-bacterial causes include viruses, protozoa, natural toxins, chemicals, and radiation. Laboratory investigations include microbiological analyses of clinical samples and implicated foods to identify the causative agent and control ongoing outbreaks.
20161023 food poisoning
- 1. FOOD POISONING Dr. Sushrit A. Neelopant Assistant Professor, Department of Community Medicine RIMS, Raichur
- 2. Definition • Acute gastro-enteritis caused by ingestion of food or drink contaminated with o living bacteria or o their toxins or o inorganic chemical substances or o poisons from plants and animals
- 3. Types of food poisoning • Bacterial • Non bacterial
- 4. Most common Bacterial causes • Salmonella non-typhi species • Staphylococcus aureus • Clostridium botulinum • Clostridium perfringens • Bacillus cereus
- 5. Less common Bacterial causes • Escherichia coli • Campylobacter • Yersinia enterocolitica • Vibrio parahemolyticus • Aeromonas • Listeria monocytogenes • Streptococcus
- 6. Non bacterial causes • Viruses Hepatitis A and E, Norovirus Poliovirus, Rotavirus • Protozoa Cryptosporidium species, Entamoeba histolytica Giardia lamblia, Toxoplasma gondii
- 7. Contd.. • Natural toxins Marine biotoxins- Shellfish toxins, Scombroid poisoning, Tetrodotoxin Mushroom toxins Mycotoxins (e.g. aflatoxins) Plant toxicants Pyrrolizidine alk. Phytohaemagglutinin- red kidney bean poisoning Grayanotoxin (honey intoxication)
- 8. Contd.. Chemicals Pesticides (organophosphates, antimony) Toxic metals (Cd, Cu, Pb, Hg, Sn) Zn Polychlorinated biphenyls Radionuclides Fluoride Nitrites (food preservatives) Sodium hydroxide Monosodium glutamate
- 9. Salmonella food poisoning Most common form. 1. Increase – communal feeding 2. Increase – international trade in human food 3. Higher incidence in farm animals 4. Household detergents interfering in sewage treatment 5. Wide distribution of prepared food
- 10. Contd.. • Agent - S. typhimurium S. choleraesuis S. enteritidis • Killed - >550C. • Incidence highest – rainy season – tropical climate and warmer months – temperate climate.
- 11. Contd.. • Source – Zoonosis Farm animals and poultry Rats and mice- urine and faeces contaminate food Temporary human carriers Contaminated meat, milk and milk products, sausages, custards, egg and egg products
- 12. Pathogenesis • Infectious dose- 103 to 106 CFU • Increased susceptibility- Decreased gastric acidity- infants, antacids, achlorhydria Loss of intestinal integrity- IBD, GI surgery, Antibiotics
- 13. Contd.. • Penetrate mucous layer of the gut • Traverse through phagocytic microfold (M) cells within Peyers patches • Increase IL-8 secretion • Increase PMN cells • Degranulation and release of toxic substances • Damage to mucosa • Inflammatory diarrhea
- 14. Contd.. • Incubation period – 12 to 24 hours • Signs and symptoms - Abdominal cramps, fever (38 – 390C), diarrhoea Diarrhoea – watery and non bloody Last for 2 to 3 days • Mortality – 1%, high in elderly, infants and immunocompromised. • Convalescent carrier state – several weeks
- 15. Staphylococcal food poisoning • As common as salmonella • Agent – Enterotoxin of coagulase positive Staph. aureus G+ve, non sporing, non motile Aerobic and facultatively anaerobic. Blood agar - golden β-hemolytic colonies Survives - long period on environmental surfaces
- 16. Contd.. • Killed - >550C. • 8 antigenic types of enterotoxins – A, B, C1-3, D, E and H • Formed at 35 to 370C • Heat resistant, destroyed by boiling for 30 minutes or more • Pyrogenic, mitogenic, hypotensive, thrombocytopenic and cytotoxic effect
- 17. Contd.. • Source – ubiqitous Present on skin, nose and throat Man and animal – Boils and other pyogenic infections Cows – mastitis Salads, custards, milk and milk products
- 18. Contd.. • Pathogenesis – Ingestion of preformed toxin in food Stimulates vagus nerve, vomiting centre and intestinal peristalsis
- 19. Contd.. • Incubation period – 1 to 6 hrs • Signs and symptoms – Nausea and vomiting, resolves in 8 – 10 hours • Death - uncommon
- 20. Botulism • Most serious but rare • Derived from latin botulus – sausage • Agent– Exotoxin- C. botulinum type A, B or E – neurotoxins Widely distributed saprophyte- soil, vegetable, hay, silage, animal manure, sea mud. G+ve bacillus, Strict anaerobe Motile- peritrichate flagella, subterminal, oval, bulging spores
- 21. Contd.. • Source – organism widely distributed in soil, dust and intestine of animals Enters food as spores Home preserved foods- home-canned vegetables, smoked or pickled fish, home- made cheese Type E – fish products
- 22. Contd.. • Pathogenesis – preformed toxin in food acts on parasympathetic nervous system Infant botulism – infection of the gut with the bacteria and subsequent formation of the toxin
- 23. Contd.. • Incubation period – 12 to 36 hours Signs and symptoms – symmetric descending paralysis Cranial nerve involvement marks onset of symptoms Diplopia, dysarthria, dysphonia, dysphagia. Dizziness, blurred vision, dry mouth, sore throat
- 24. Contd.. Nausea, vomiting and abdominal pain – precede or follow onset of paralysis. Alert and oriented Gag reflex suppressed Deep tendon reflexes normal or decreased Paralytic ileus, severe constipation and urinary retention.
- 25. Clostridium perfringens food poisoning • 2nd or 3rd most common cause. • More severe form of food poisoning. • More common in elderly and those who are on long term antibiotics. • Agent – Also known as Clostridium welchii Type A G+ve bacillus, spore bearing Motile by peritrichate flagella Strict anaerobe
- 26. Contd.. • Source – present in faeces of humans and animals Soil, water and air Meat, meat dishes and poultry Food cooked 24 hours or more, allowed to cool slowly to room temperature, heated prior to serving.
- 27. Contd.. • Pathogenesis – spores survive cooking not cooled enough germinate produce toxin (alpha, theta etc) Toxin binds to receptor on small bowel brush border, induces calcium ion dependent alteration in permeability Ion loss leads to cell death
- 28. Bacillus cereus food poisoning • Agent – G+ve, Spore bearing, Motile, Aerobic • Source – Ubiquitous soil, raw, dried and processed food. Fried rice Spores survive cooking, germinate and multiply under favourable temperature.
- 29. Contd.. • Pathogenesis – 2 enterotoxins – 2 forms of food poisoning • Emetic form – Staphlococcal type of enterotoxin • Diarrheal form – E coli LT type
- 30. Escherichia coli food poisoning • Agent – G-ve, nonsporing Motile- peritrichate flagella Aerobe and facultative anaerobe Killed - >550C. • Pathogenesis – 5 groups -- Enteropathogenic – Invades intestinal mucosa -- Enterotoxigenic – Labile toxin and Stable toxin
- 31. Contd.. -- Enteroinvasive – Invades intestinal mucosa -- Enterohaemorrhagic – Verotoxin -- Enteroaggregative – adhere to mucosal cells • Source – commensal in GIT, present in faeces • Incubation period – 12 hours to 3 days • Symptoms – diarrhoea, dysentery • Milk and milk products
- 32. Campylobacter food poisoning • Agent – Gram negative, spirally curved, non sporing Motile- polar flagella Micro aerophilic • Source – animals – poultry, meat and milk Milk and milk products • Symptoms – Fever, abdominal pain and watery diarrhoea
- 33. Yersinia enterocolitica food poisoning • Agent – Gram negative, non sporing Motile at 220C • Source – zoonosis Milk and milk products and meat • Symptoms – mild diarrhoea, abdominal pain, fever and vomiting
- 34. Vibrio parahemolyticus food poisoning • Agent – G-ve, non sporing Motile by peritrichate flagella Capsulated, pleomorphic • Source – Marine organisms Sea foods • Symptoms – Abdominal pain, diarrhoea, vomiting and fever
- 35. Aeromonas food poisoning • Widely distributed in nature • Sea foods, meat, diary products and poultry • Symptoms – rice water diarrhoea or dysentery
- 36. Listeria monocytogenes food poisoning • Agent – Gram positive, Motile- peritrichate flagella at 220C- slow, tumbling Aerobic and micro aerophilic • Milk and milk products Meat, poultry, vegetables, salads and sea foods • Common in pregnant, alcoholics, drug abusers, immuno-suppressed or immuno- compromised
- 37. Streptococcal food poisoning • Agent – Gram positive, non sporing and non motile Aerobe and facultative anaerobe • Source – raw milk, custard, boiled eggs in salad, ham • Symptoms – abdominal pain, vomiting and diarrhoea
- 38. Differential diagnosis Less than 1 hour Unusual taste, burning in mouth Metallic salts 1 to 2 hours Cyanosis, headache, giddiness Nitrites 2 to 4 hours Retching, diarrhoea and abdominal pain Staphylococcus aureus and enterotoxins • Upper GI symptoms appear first or predominate – nausea and vomiting
- 39. Contd.. 8 to 16 hours Abdominal cramps, diarrhoea Bacillus cereus 6 to 24 hours Diarrhoea, thirst, dilatation of pupils Mycotoxin 12 to 48 hours Diarrhoea Norovirus
- 40. Contd.. 2 to 36 hours Nausea, vomiting Clostridium perfringens, bacillus cereus 1 to 3 days Abdominal cramps, vomiting Salmonella • Lower gastrointestinal symptoms
- 41. Contd.. Less than 1 hour Gastrointestinal symptoms Shellfish toxin Chest pain, convulsions, cyanosis Organo- phosphate Excessive salivation, perspiration, constricted pupils Muscaria-type mushrooms • Neurological symptoms – visual disturbance, vertigo, tingling, paralysis
- 42. Contd.. 12 to 36 hours Vertigo, blurred vision, loss of light reflex, difficulty in swallowing, speaking and breathing, dry mouth, paralysis. Descending, bilateral flaccid paralysis starting with cranial nerves, preserved sensorium Clostridium botulinum More than 72 hours Numbness, weakness in legs, spastic paralysis and coma Organic mercury
- 43. Laboratory investigations 1. Microbiological analyses • Clinical samples Faecal samples- most commonly collected specimens; Vomitus, urine, blood, swabs from rectum, nostrils, skin and nasopharynx Taken as soon as possible, preferably before antibiotic treatment Also from exposed but not ill persons
- 44. All containers labelled - waterproof marking pen before or immediately after collection - patient’s name, identification, date and time of collection, and any other information required by the laboratory. • Molecular typing PCR, PFGE, genetic sequencing technology
- 46. Investigation of a food poisoning outbreak Specific objectives Control – ongoing outbreaks Detection, removal – implicated foods; Identification- specific risk factors – host, agent and environment Identification – factors that contributed to the contamination, growth, survival and dissemination of the suspected agent;
- 47. Contd.. Prevention – future outbreaks Strengthening of food safety policies; Acquisition of epidemiological data – risk assessment Stimulation of research – prevention of similar outbreaks.
- 48. Contd.. • Epidemiological investigation • Environmental and food investigation • Laboratory investigation
- 49. Epidemiological investigations • Verification of the diagnosis 1. checking the validity – information 2. identifying cases 3. reports of laboratory tests 4. ensuring the collection of appropriate clinical specimens and food samples. 5. demographic details 6. clinical details, 7. contact with other ill persons 8. food consumption history
- 50. Contd.. • Form preliminary hypotheses and plan further action Describe the event in simple epidemiological terms General control and precautionary measures may be implemented
- 51. Contd.. • Descriptive epidemiological investigations 1. direct immediate control measures, 2. generate more specific hypotheses about the source and mode of transmission, 3. suggest the need for further clinical, food or environmental samples, and 4. guide the development of further studies.
- 52. Contd.. • establishing a case definition; • identifying cases and obtaining information from them; • analysing the data by time, place and person characteristics; • determining who is at risk of becoming ill;
- 53. Contd.. • developing hypotheses about the exposure/vehicle that caused the disease; • comparing the hypotheses with the established facts; • deciding whether analytical studies are needed to test the hypotheses.
- 54. Contd.. Establishing a case definition • A case definition - set of criteria for determining whether a person should be classified as being affected by the disease under investigation. • Simple and practical • Sensitive and specific
- 55. Contd.. • a person with three or more loose stools in a 24-hour period • a person with three or more loose stools in a 24-hour period with lab confirmed salmonella infection
- 56. Contd.. Identifying cases and collecting information • Determine the full extent of the problem and the population at risk of illness. • Active search for additional cases. • Use a standard questionnaire. • Identification, demographic, clinical and risk factor information
- 57. Contd.. Collating data • Provide insight into the distribution of clinical symptoms and other factors among cases. • The data can be summarized in a line listing
- 58. Contd.. Analysing data • Percentage of cases with a particular symptom or sign should be calculated and arranged in a table in decreasing order
- 59. Contd.. Time • Epidemic curve – histogram with the number of cases on the y-axis and the date of onset of illness on the x-axis. • The shape of an epidemic curve is determined by: - the epidemic pattern (point source, common source or person-to-person spread); - the period of time over which persons are exposed; - the incubation period for the disease.
- 61. Contd.. Place • Assessment by “place” provides information on the geographical extent of the outbreak, reveal clusters or patterns that provide important clues about its cause. • Spot maps and area maps
- 62. Contd.. Person • Identify features that are common to cases as a clue to etiology or sources of infection. • Age, sex, ethnicity and occupation. • Find out the population at risk to calculate attack rate
- 63. Contd.. Developing explanatory hypotheses • Address the source of the agent, mode and vehicle of transmission, the specific exposure • Plausible • Supported by the facts • Able to explain most of the cases. • Analytical epidemiological investigations - if needed
- 64. Environmental and food investigations • Identify – source, mode and extent of the food contamination; • Assess – how pathogens survived processes designed to kill them or to reduce their numbers; • Assess – potential for growth of pathogens during food processing, handling and storage; • Identify implement corrective interventions.
- 65. Contd.. Investigation of food establishments- • interviewing managers; • interviewing any employees • a review of employee records- a review of the overall operations and hygiene; • specific assessment of procedures undergone by a suspect food; • food and environmental sampling • a review of food worker health and hygiene • assessment of the water system and supply;
- 66. Investigation of a suspect food Product description • All raw materials and ingredients used • Sources of the ingredients; • Physical and chemical characteristics, • Use of returned, reworked or leftover foods in processing; Observation of procedures from receipt to finish
- 67. Contd.. Food samples - ingredients used to prepare implicated foods; - leftover foods from a suspect meal; - foods from a menu that has been implicated epidemiologically; - foods known to be associated with the pathogen in question;
- 68. Contd.. Environmental samples Sources of and the extent of contamination • Work surfaces, food contact surfaces of equipment, containers, refrigerators, door handles etc • Meat scraps, drippings on refrigerator floors and deposits on saws or other equipment • Tables, cutting boards, grinders, slicing machines and other utensils
- 69. Contd.. Food-handlers • Stool specimens or rectal swabs • Swabs from nasopharynx • Swabs from skin lesions
- 70. Control measures • Control of source - removing implicated foods from the market; - modifying a food production or preparation process; - closing food premises or prohibiting the sale or use of foods.
- 71. Contd.. • Control of transmission - Boiling of microbiologically contaminated water or avoidance of chemically contaminated water; - Advice on proper preparation of foods - Advice to dispose of foods; - Exclusion of infected persons from work and school
- 72. Contd.. - Emphasizing personal hygiene measures Avoid preparing food until free from diarrhoea or vomiting. Wash hands after defecation, urination and before meals. Use separate towels, liquid soaps and disposable towels or hand-dryers. Clean toilet seats, flush handles, hand-basin taps and toilet door handles