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