Food poisoning

Prepared bySamira fattah

Assis. Lec.College of health sciences-HMU

Lecture 5&6

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

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.

Classification of food borne diseases

Food borne diseases are classified into:

1. Food borne infections 2. Food borne intoxications

Foodborne infection

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

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.

Foodborne infection

These can either be• bacterial• viral • Parasitic

• Food borne infections tend to have long incubation periods and are usually characterized by fever.

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)

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.

- 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.

• 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.

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.

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.

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.

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.

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).

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.

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.

Prevention: • Cook raw meats properly.• Do not use raw (unpasteurized) milk. • Thoroughly clean food contact surfaces (cutting

boards) and hands after handling raw foods.

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.

• 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).

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.

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

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.

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.

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.

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.

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 .

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.

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.

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.

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 foodsPeople 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.

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.

Giardia lamblia

Description This microorganism is important because it is

common cause of non-bacterial diarrhea in the United States.

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.

PreventionHandle and cook foods properly.

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.

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.

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.

Anisakis spp.

DescriptionAnisakis spp. are nematodes (or roundworms)

that have been associated with foodborne infection

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.

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.

PreventionHandle and cook seafood properly.

Trichinella spiralis DescriptionTrichinella 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.

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.

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.

• 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 TaeniasisCook all raw beef and pork steaks, chops, and roasts to a minimum internal temperature of 145 °F(63° C).

Food borne intoxicationsFood 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 intoxicationsb. Fungal intoxicationsc. Chemical intoxicationd. Plant toxicantse. Poisonous animals.

BACTERIAL FOOD BORNE INTOXICATIONS

1. Staphylococcus aureus 2. Bacillus cereus 3. Clostridium perfringens 4. Clostridium botulinum

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.

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.

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.

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.

Bacillus cereus food borne intoxication • The organism produces the following

enterotoxins which are involved in a food borne intoxicationa. Two diarrhoeal enterotoxins: -hemolysin enterotoxin -non-hemolytic enterotoxinb. Emetic toxin

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.

Symptoms of disease in man1-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.

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.

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.

• 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.

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.

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.

Prevention1. 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

Clostridium botulinum foodborne Intoxication

• The strains are divided into proteolytic and

non-proteolytic types according to whether they hydrolyze proteins or not.

• 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.

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.

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.

Symptoms of the disease in manAdult 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.

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

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.

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.

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

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.

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.