This document discusses various causes of food poisoning, including bacteria, viruses, parasites, toxins, and chemicals. It covers common foodborne pathogens like Salmonella, E. coli, C. perfringens, and Norovirus. Symptoms, transmission routes, and prevention methods are described for each. Bacterial pathogens are classified as causing infection or intoxication. Intoxications have shorter incubation periods than infections and lack fever. The document also discusses foodborne parasites, mycotoxins, and chemical/plant toxicants as causes of illness.

1. Food poisoning
Prepared by
Samira fattah
Assis. Lec.
College of health sciences-HMU
Lecture
5&6

2. Food poisoning
General definition
Illness caused by the infection with
microorganisms and ingestion of toxins
produced, and chemical poisoning.
Causes
• Bacteria and their toxins
• Viruses
• Chemicals
• Vegetable poisoning

3. Food poisoning
(or food borne illness)
• Foods contaminated with pathogenic
microorganisms usually do not look bad, taste bad,
or smell bad.
• It is impossible to determine whether a food is
contaminated with pathogenic microorganisms
without microbiological testing.

4. Classification of food borne
diseases
Food borne diseases are classified into:
1. Food borne infections
2. Food borne intoxications

5. Foodborne infection
• is caused by the ingestion of food containing
live bacteria which grow and establish
themselves in the human intestinal tract.

6. Foodborne intoxication
• is caused by ingesting food containing toxins
formed by bacteria which resulted from the
bacterial growth in the food item.
• The live microorganism does not have to be
consumed.

7. Foodborne infection
These can either be
• bacterial
• viral
• Parasitic
• Food borne infections tend to have long
incubation periods and are usually characterized
by fever.

8. Bacterial food borne infections
• Bacteria are the most troublesome and important
biological foodborne hazard for the foodservice and
food retail Establishment.
• Bacterial cells can exist in two different states:
- the vegetative state.
- the spore state.
• Spores are produced when the bacterial cell is in an
environment where it cannot grow (frozen foods, dried
foods)

9. Escherichia coli
The Escherichia coli (or E. coli) group of bacteria
includes four strains of foodborne pathogens:
• enterotoxigenic E. coli
• enteropathogenic E. coli
• enterohemorragic E. coli
• and enteroinvasive E. coli.

10. - The most important of the group is a particular
type of enterohemorrhagic E. coli called
E. coli O157:H7
- Illness can be due to an infection and a toxico-
infection.
- Illness due to E. coli 0157:H7 is particularly
serious in infants because it can cause kidney
failure and bloody diarrhea.

11. • Common foods:
This microorganism has been isolated from raw milk
and raw ground beef.
• Transmission in foods:
E. coli is usually transferred to foods like beef by
contact with the intestines of animals.
Transmission can also occur if employees are carriers
and do not wash their hands properly after going to
the bathroom.

12. Prevention:
• Cook hamburger patties until well done or until all
the juices run clear.
• Do not use raw milk products.
• Make sure that employees practice good personal
hygiene.

13. Salmonella spp.
Description:
• Salmonella is a facultative anaerobic bacterium that
frequently causes a foodborne infection.
• Like E. coli, the source for Salmonella is the intestinal tracts
of warm blooded animals.
Common foods:
• This microorganism exists in many foods, especially raw
meat and poultry products, eggs, milk, dairy products, pork,
milk chocolate, and cream- filled desserts.

14. Transmission in foods:
-Transmission to foods is very common
by cross contamination from raw
foods (especially poultry).
- From food contact surfaces (cutting
boards), or from food handlers.
Prevention:
• Cook foods thoroughly.
• Practice good personal hygiene.
• clean and sanitize food contact
surfaces after use with raw foods.

15. Shigella spp.
Description:
• Shigella is a facultative anaerobic bacterium that
causes about 10% of foodborne illnesses in the U.S.
• The microorganism is frequently found in the
intestines of humans and warm blooded animals.
• The microorganisms can cause an infection or toxico
infection.
• A common illness caused by Shigella is bacillary
dysentery.

16. Common foods:
• This microorganism is common in ready-to-eat salads
(i.e. potato, chicken), milk and dairy products,
poultry, and raw vegetables.
Transmission in foods:
• Water that is contaminated by fecal material and
unsanitary handling by food workers are common
transmission routes.
Prevention:
Practice good personal hygiene and wash foods with
potable water supply (suitable for drinking).

17. Campylobacter jejuni
Description:
• Campylobacter jejuni is considered by many food scientists as
the number one agent that causes foodborne illness.
• The microorganism, which causes infection, is unique
compared to most other foodborne pathogens because it has
a very strict gaseous requirement for growth.
• It is classified as a microaerophile because it can tolerate only
3-6% oxygen for growth.

18. Common foods:
This microorganism is commonly found in raw milk and in
raw chicken.
Some scientists estimate that Campylobacter jejuni may be
present in nearly 100% of retail chickens.
Transmission in foods:
Campylobacter jejuni is often transferred from raw meats
to other foods by cross-contamination. This is typically
done by transfer from a food contact surface (such as a
cutting board) or from food worker’s hands.

19. Prevention:
• Cook raw meats properly.
• Do not use raw (unpasteurized) milk.
• Thoroughly clean food contact surfaces (cutting
boards) and hands after handling raw foods.

20. Listeria monocytogenes
Description
• Listeria monocytogenes is a facultative
anaerobic bacterium that causes foodborne
infection.
• Listeriosis, the illness caused by Listeria
monocytogenes, usually causes gastro-
intestinal symptoms for the healthy adult.

21. • However, disease complications can be life
threatening (septicemia, meningitis, encephalitis)
for people with weakened immune systems.
• It is important to food retail operations because
it can survive under many conditions such as high
salt foods.
• Unlike many other foodborne pathogens, it can
grow at refrigerated temperatures below 41°F
(=5°C).

22. Common foods:
This microorganism has been isolated from many foods
and is most common in raw meats, raw poultry, dairy
products (cheeses, ice cream, raw milk), raw
vegetables, and seafood.
Transmission in foods
• Transmission to foods can occur by cross-
contamination.
• Also, foods that are not cooked properly can contain
live cells.

23. Prevention
• Cook foods thoroughly.
• Practice good personal hygiene.

24. Vibrio spp.
Description:
• There are three species within the Vibrio group of bacteria
that cause been implicated in foodborne infections.
• They include
-Vibrio cholera
- Vibrio parahaemolyticus
- Vibrio vulnificus.
• All are important since they are very resistant to salt and
are common in seafood.

25. Common foods
Vibrio spp. are commonly found in raw, under-
processed, improperly handled, contaminated fish
and shellfish.
These bacteria are generally found more in the summer
months and from warmer waters.

26. Transmission in foods
• Since the microorganism exists in many raw seafood,
transmission to other foods by cross contamination is a
concern.
• Most illnesses are caused due to eating raw or
undercooked seafood, especially oysters.
Prevention
• Cook seafood properly.
• Avoid consumption of raw seafood.
• Practice good personal hygiene.

27. Viral foodborne infections
• Foodborne viruses differ from foodborne bacteria. They
are the smallest and simplest form of life known.
• Unlike bacteria, they do not reproduce or grow in foods.
• They are usually transferred from one food to another,
from a food handler to a food, or from a water supply to
a food.

28. Hepatitis A
Description
• Hepatitis A is a foodborne virus that is associated with
many foodborne infections.
• It is a particularly important hazard to retail food
establishments because it has an incubation period of 10-45
days.
• This means that a food worker can harbor the
microorganism for up to 6 weeks and not show symptoms of
illness.
• However, during this time, the food worker can contaminate
foods and other workers in the food retail establishment .

29. Common foods
• Ready-to-eat foods that are washed with a non-
potable water supply or foods that are handled
excessively can be contaminated with Hepatitis A.
• Examples include raw vegetables and raw seafood.
• Due to the long incubation period, it is very difficult to
identify the food source of a Hepatitis A infection.

30. Transmission in foods
The virus is primarily transmitted from person-to
person contact, by cross contamination, and by fecal
contamination.
Prevention
• Handle and cook foods properly.
• Avoid consumption of raw seafood.
• Practice good personal hygiene.

31. Norwalk virus
Description:
The Norwalk virus is other common foodborne
virus that associated with many foodborne
infections, with some outbreaks involving up
to 3000 people.

32. Common foods
Raw seafood. Raw fruits and vegetables that are washed with a
contaminated water supply. Non-heated foods that are handled by
people who are shedding the virus.
Transmission in foods
People who are infected can spread it directly to other people, or can
contaminate food or drinks they prepare for other people.
Prevention
• Handle and cook foods properly.
• Avoid consumption of raw seafood.
• Practice good personal hygiene.

33. Foodborne Parasites
• Parasitic infection is far less common than
bacterial or viral foodborne illness.
• There are many examples of parasites that can
enter the food system and cause foodborne
illness.

34. Giardia lamblia
Description
This microorganism is important because it is
common cause of non-bacterial diarrhea in
the United States.

35. Common foods
These parasites are most commonly associated with the consumption
of contaminated water. Raw foods that are in contact with
contaminated water, especially raw vegetables, can also be
contaminated.
Transmission in foods
These parasites are transmitted from a contaminated water supply,
person-to-person contact and by fecal contamination.
Prevention
Handle and cook foods properly.

36. Toxoplasma gondii
• It is the third leading cause of death from
foodborne disease.
• The infective stage (oocyst) develops in the
gut of the cat. The oocysts are then shed into
the environment with cat feces.

37. How do people get toxoplasmosis?
• By consuming foods (such as raw or undercooked
meats, especially pork, lamb, or wild game).
• When will symptoms appear?
The time that symptoms appear varies, but generally
symptoms will appear 1 week to 1 month after
consuming the parasite.

38. How to prevent toxoplasmosis
• Wear clean latex gloves when handling raw meats.
• Cook all raw beef, pork, lamb and veal steaks to a minimum
internal temperature of 145 °F (63° C).
• Wash hands thoroughly with warm water and soap after
handling cats, especially before you handle or eat food.

39. Anisakis spp.
Description
Anisakis spp. are nematodes (or roundworms)
that have been associated with foodborne
infection

40. Common foods
• They generally cause foodborne disease through
consumption of raw or undercooked seafood.
• The most common foods include seafood such as cod,
haddock, fluke, salmon, herring, flounder and monkfish.

41. Transmission in foods
• This parasite is transferred in the water in which the marine
animal lives.
• This parasite may also be transferred to other foods by
improper food handling.
Prevention
Handle and cook seafood properly.

42. Trichinella spiralis
Description
Trichinella spiralis is a foodborne roundworm that can
cause parasitic infection.
Common foods
People get trichinellosis by consuming raw or
undercooked meats such as pork, bear, cougar, fox, wolf
or dog infected with Trichinella larvae.

43. Transmission in foods
This parasite is inherently carried by animals. It
is generally thought that a possible route to
the animal is through consumption from
eating infected tissues from other animals.
Prevention
Cook pork until there are no signs of pink and
always cook meats properly.

44. Taenia saginata/Taenia solium
(Tapeworms)
• humans are the definitive hosts of both
organisms.
• This means that the reproductive cycle,
and thus egg production by the
organisms, occurs only within humans.
• Eggs are passed in human feces and
they may be shed into the environment
for as long as the worms remain in the
intestines (for as long as 30 years).
• In addition, the eggs may remain viable
in the environment for many months.

45. • How do people get Taeniasis?
People get Taeniasis by consuming raw or undercooked
infected beef or pork.
• When will symptoms appear?
T. saginata (beef tapeworm) infections appear within 10 to 14
weeks.
• T. solium (pork tapeworm) infections appear within 8 to 12
weeks.
• How to prevent Taeniasis
Cook all raw beef and pork steaks, chops, and roasts to a
minimum internal temperature of 145 °F(63° C).

46. Food borne intoxications
Food borne intoxications have short incubation periods
(minutes to hours) and are characterized by lack of
fever.
Food borne intoxications can be classified into:
a. Bacterial intoxications
b. Fungal intoxications
c. Chemical intoxication
d. Plant toxicants
e. Poisonous animals.

47. BACTERIAL FOOD BORNE INTOXICATIONS
1. Staphylococcus aureus
2. Bacillus cereus
3. Clostridium perfringens
4. Clostridium botulinum

48. Staphylococcus aureus food borne
intoxication
This is a type of food borne intoxication is
caused by consumption of food contaminated
with staphylococcal enterotoxins produced by
certain strains of Staphylococcus aureus while
growing in food.

49. The organism produces the following five serologically
different enterotoxins that are involved in food borne
intoxication.
1. Staphylococcal enterotoxin A(SEA),
2. Staphylococcal enterotoxin B (SEB),
3. Staphylococcal enterotoxin C (SEC),
4. Staphylococcal enterotoxin D (SED),
5. Staphylococcal enterotoxin E (SEE)
-Individual strains of S. aureus may produce one or more of
enterotoxin types while growing in food.

50. Toxin production
• Toxin production occurs at growth temperature 12-
44oC, pH 4.2 and salt concentration of ≤10%.
• No toxin production occurs at temperatures below
12oC, pH < 4.2 and > 10 % salt.

51. Vehicle foods
• Milk and milk products (including pasteurized milk, yoghurt,
chocolate milk, fermented milk, cream filled pastries), poultry,
fish, shellfish, meat and meat products, non meat salads, egg
and egg products, vegetables and cereal products have been
involved.
Disease symptoms in man
• Incubation period is 1-6 hrs after consumption of food
contaminated with at least 1.0 µg of enterotoxin.
• Clinical signs include salvation, nausea, vomiting, abdominal
cramps, sometimes diarrhea .
• Duration of illness is 24-72 hrs.

52. Bacillus cereus food borne intoxication
• The organism produces the following
enterotoxins which are involved in a food
borne intoxication
a. Two diarrhoeal enterotoxins:
-hemolysin enterotoxin
-non-hemolytic enterotoxin
b. Emetic toxin

53. Vehicle foods
• Bacillus cereus is a common soil saprophyte and is easily
spread to many types of foods, especially of plant origin.
• It is frequently isolated from meat, eggs and dairy products.
• Cereal dishes (e.g. rice), spice, mashed potatoes, herbs,
vegetables, minced meat, cream and milk pudding have been
involved in B. cereus poisoning.

54. Symptoms of disease in man
1-Emetic syndrome
The syndrome is characterized by nausea, vomiting, abdominal
cramps and sometimes diarrhea that occur 1-6 hrs after
consumption of contaminated food.
The syndrome is associated with ingestion of rice and pasta
based foods.

55. 2. Diarrhoea syndrome
In the diarrhea syndrome, patients experience profuse
diarrhoea (watery stool), abdominal cramps and tenesmus
(rarely vomiting) beginning 8 to 16 hours after ingestion of
contaminated food.
Fever is absent and symptoms resolve within approximately 12
hours.

56. Clostridium perfringens intoxication
• intoxication caused by Clostridium perfringens
enterotoxin (CPE) produced in the gastrointestinal
tract.
• The organism is found in the soil, dust, water, sewage
marine sediments, decaying materials, intestinal
tracts of humans and other animals.

57. • If the spores are present as contaminants on raw
meat they may resist boiling or steaming for 4 or
more hours, and on slow cooling the spores will
germinate into rapidly multiplying bacterial cells,
which produce large amounts of toxin.

58. Vehicle foods
• The food involved are those that are prepared one day and
served the next day.
• Foods that have been involved include red meats, chickens,
fish, pork, fruits, vegetables, etc.
• Foods poisoning occurs when the level reaches 107-108 cells/g
of food.
• Growth is enhanced by anaerobic conditions achieved after
removal of oxygen by cooking.

59. Symptoms of disease in man
• Symptoms appear 6-24 hours after ingestion of a large
number of viable vegetative cells up to 5x108/g food, but not
after ingestion of spores.
• Symptoms include nausea, intestinal cramps, pronounced
diarrhea,
• Vomiting is rare and the illness takes a duration of 1-2 days.

60. Prevention
1. Proper cooking of food and eating freshly prepared foods.
2. Fast cooling of cooked food. Storing food in small quantities
will enhance cooling.
3. Storage of leftovers or unused foods in freezers

61. Clostridium botulinum foodborne Intoxication
• The strains are divided into proteolytic and
non-proteolytic types according to whether
they hydrolyze proteins or not.

62. • The intoxication is caused by botulinal toxins A, B, E,
F and G, produced by C. botulinum type A, B, E, F and
G, while the organism grows in food.
• C. botulinum types C and D produce toxins C and D
that cause disease in animals
• Type E strains are non-proteolytic while the rest are
proteolytic.
• Spores of C. botulinum type A can survive
temperatures of 120oC.

63. Growth characteristics
• Proteolytic strains grow at temperature range
between 10-50oC, while non-proteolytic grow at 3.3-
45oC (optimum 35-37oC).
• Toxin production occurs at temperature range
between 25-30oC.
• Botulinus toxin is one of the most lethal poisons
known. The calculated lethal dose for an adult
person is 10 µg.

64. Types of foods implicated
• Foods associated with anaerobic conditions such as spoiled
canned meat, or hams and bacon stacked without air access,
are particularly liable to be infective.
• Home made fermented foods have been incriminated,
together with smoked, pickled and canned foods that are
allowed to stand and then eaten without adequate cooking.
• Uncooked fresh foods are safe because they are eaten before
the toxin has had time to develop.

65. Symptoms of the disease in man
Adult botulism
• The period of incubation in man is usually (12-72 hrs).
• Symptoms include nausea, vomiting, fatigue, dizziness,
headache, dryness of skin, mouth and throat, constipation,
lack of fever, nerve paralysis and great muscular weakness,
double vision, respiratory failure and death.
• Duration of illness 1-10 days and mortality is high up to 60-
100% of affected persons.

66. Infant botulism
• Occurs in infants less than 1 year of age following ingestion of
spores in honey and syrup.
• The spores germinate in the gastrointestinal tract with toxin
production.
• Symptoms are similar to adult botulism

67. Preventive measures
• proper manufacturing practices e.g. ensure proper
sterilization and preservation of canned meat.
• Preserved foods possessing rancid or other odors
should be rejected.

68. Fungal intoxications
• These are caused by consumption of metabolites produced by
fungi, when growing in food.
• These metabolites are called mycotoxins.
• Grains, oilseeds, fruits and vegetables are mostly involved if
they are stored at high humidity or if they are not properly
dried before storage.
• Of significance to public health is aflatoxicosis.

69. Aflatoxicosis
• Aflatoxicosis is caused by aflatoxins produced by the
fungi, e.g. Aspergillus flavus.
• Four types of aflatoxins have been described i.e.
aflatoxin B1, B2, G1 and G2.
• Animals consuming feeds contaminated with
aflatoxin B1 leads to secretion in the milk of aflatoxin
M1 and M2

70. Effects of aflatoxins
• When consumed in large doses, they are
lethal in causing acute hemorrhagic
syndromes
• Sub-lethal doses cause histotoxic changes
• Long term consumption of small doses cause
liver tumors as these are potent carcinogens.

71. Prevention of aflatoxicosis
• Proper drying and storage of grains and other
affected foods
• Quality control of potentially hazardous foods by use
of appropriate analytical tests.
• Use of fungicides as seed dressings to protect stored
cereals and other foods like pulses and potatoes
against fungal invasion.