Transcript Microbial Foodborne Diseases

Human Gastrointestinal Disorders
Causes
• From consumption of food and water containing
viable pathogenic microorganisms or their
preformed toxins.
• From ingestion of pathogenic algae or parasites and
their preformed toxins .
From Other reasons Which include:
• Ingestion of toxins naturally present in many foods
such as certain mushrooms, some sea foods.
• Toxins formed in some foods e.g. biological amines
(histamine) in fish, cheeses, fermented meat
products
The presence of toxic chemicals in contaminated
food and water (heavy metals and pesticides).
Allergy to some normal components of a
food(allergy to gluten in cereal).
Genetic inability to metabolize normal food
components9lactase enzyme deficiency).
Nutritional disorders(rickets due Ca deficiency).
Indigestion from overeating.
**The incidence of foodborne diseases of
microbial origin is higher than that for all other
causes combined.
Types of Microbial Foodborne Diseases
Foodborne diseases in humans result from the
consumption of either food and water contaminated
with viable pathogenic bacterial cells(or spores in case
of infant botulism) or food containing toxins produced
by toxigenic bacteria and molds. On the basis of mode
of illness, these are divided into three groups:
Intoxication or poisoning
Infection
Toxicoinfection
Intoxication
Illness occurs as a consequence of ingesting a preformed
bacterial or mold toxin, a toxin has to be present in the
contaminated food. Staphyloccocus aureus food poisoning is
an example of this type.
Infection
Illness occurs as a result of the consumption of food and
water contaminated with enteropathogenic bacteria or
viruses. Viable Microorganisms have the potential to establish
and multiply in the digestive tract to cause the illness.
Salmonellosis and hepatitis A are examlpes.
Toxicoinfection
Illness occurs after ingesting large number of viable
pathogenic bacteria, the bacterial cells either sporulate or die
and release toxins. Clostridium perfringens gastroenteritis is
an example.
Predominant Bacterial and Viral pathogens
Associated with Foodborne Diseases
Staphylococcus aureus •
Clostridium botulinum
Salmonells Spp.
Shigella Spp.
Escherichia coli
Campylobacter Spp.
Clostridium perfringens
Bacillus cereus
Hepatitis A virus
Norwalk-like virus
Predominant Food Types Associated with
Foodborne Diseases of Bacterial and Viral Origin
*Meat Products
*Fish Products
*egg Products
*Dairy Products
*Salads
*Baked Food
*Fruits and vegetables
*Mushrooms
*Ethnic Food
*Multiple Foods
*Unknown Foods
Predominant Contributing Factors Associated
with Foodborne Disease Outbreaks
• Improper Holding Temperature (temperature
abuse)
• Poor Personal hygiene
• Inadequate Cooking
• Contaminated Equipment
• Food From Unsafe Sources
• Others
Human Factors In foodborne Disease Symptoms
When a group of people consumes food contaminated with
live cells of pathogens or their toxins, all the members might
not develop disease symptoms.
Not all infected people show the same symptoms or severity
of a symptom. This is probably due to the difference in
resistance among individuals.
Infants and old, sick, and immunodeficient people are more
susceptible than healthy ones.
The chance of developing disease symptoms is directly
related to the amount of a contaminated food consumed,
number of viable cells, amount of toxin and virulence.
Consumption of 10 viable cells of E. coli 0157:H7 can cause
disease, while one million cells of Yersinia enterocolitica are
needed to cause disease.
Foodborne Intoxication
Foodborne intoxication or food poisoning of microbial origin
occurs by ingesting a food containing a preformed toxin.
General characteristics of food poisoning
The toxin is produced by a pathogen while growing in a food.
A toxin can be heat labile or heat stable.
Ingestion of a food containing active toxin is necessary for
poisoning(except for infant botulism, in which viable spores
need to be ingested).
Symptoms generally occur quickly(in about 30 min).
Symptoms differ with type of toxin(enterotoxins produce
gastric symptoms and neurotoxins produce neurological
symptoms).
Staphylococcal Intoxication
S. aureus along with many other staphylococci, are
naturally present in nose, throat, skin, and
hair(feathers) of healthy humans, animals, and
birds.
S. aureus can be present in infections, such as cuts
in skin and abscesses in humans, animals and birds,
and cuts in hands and facial-erupted acne in
humans.
Food contamination generally occurs from these
sources.
Toxins and toxin Production
Enterotoxigenic strains of S.aureus produce seven
different enterotoxins; A, B, C1, C2, C3, D, E
They are serologically distinct heat stable proteins
of molecular weight 26-30kDa and differ in toxicity.
Normal temperature and time used to process or
cook foods do not destroy the potency of the
toxins.
Under optimum conditions of growth, toxins can be
detected when a population has reached over a few
million per gram or milliliter of food and within four
hours.
Disease and Symptoms
A healthy adult has to consume 30 g or ml of a food
containing 100-200 ng toxins produced by 1-2 million
cells/g or ml; infants and old and sick individuals need
lesser amounts.
The symptoms occur within 2-4 hours and are directly
related to the potency and amounts of toxin ingested
and an individual resistance.
The disease lasts for 1-2 days and is rarely fatal.
The primary symptoms , from stimulation of the
autonomic nervous system by the toxins, are salivation,
nausea, vomiting, abdominal cramps and diarrhea.
Secondary symptoms are sweating, chills, headache
and dehydration.
Food Association
Food types involved in Staphylococcal food
poisoning:
Pork
Bakery products
Turkey
Chicken
Eggs
Fish
Dairy products
Fruits
Ethnic foods
Identification Methods
Food or vomit samples are analyzed for the presence
of enterotoxigenic S. aureus cells and enterotoxins.
Biological testing for enterotoxin
Animals(cat, monkeys, dogs) are given the enterotoxin
preparation orally or it is injected intraperitoneally or
intravenously. Vomiting symptoms by the test animals
is a positive indication of the presence of
staphylococcal enterotoxin.
Serological Methods
The enterotoxin are purified and examined by one of
the several immunological methods e.g ELISA.
Botulism
Botulism results following consumption of food
containing the potent toxin botulin of the
anaerobic bacteria Clostridium botulinum.
It is a neurotoxin and produces neurological
symptoms along with some gastric symptoms.
Unless prompt treatment is administered, it is quit
fatal.
Infant botulism occurs when an infant ingests
C.botulinum spores, which germinate, grow and
produce toxins in the GIT and cause specific
symptoms.
Toxin
Spores of C. botulinum are widely distributed in soil,
sediments of lakes, plants, intestinal contents of
animals and fishes.
Fruits and vegetables can be contaminated with
spores from soil, fishes from water and sediments.
The toxins are neurotoxic proteins, only small amount
of toxin is required to produce the symptoms and
cause death.
The toxin is absorbed from intestine and spread via
blood to the peripheral nerves.
The toxin blocks signal transfers, irreversibly causing
paralysis of all involuntary muscles
Disease and Symptoms
Botulism is caused by ingestion of the neurotoxin botulin
formed in food.
Neurological symptoms develop within a short time,
especially if the amount of botulin consumed is high.
A very small amount(1ng/kg body weight) is necessary for
severe symptoms and even death.
Neurological symptoms include blurred or double vision,
difficulty in swallowing, breathing and speaking, dryness of
the mouth and paralysis of different involuntary muscles.
Death usually results from respiratory failure.
The toxins are antigenic; thus antitoxins are available.
Soon after symptoms antitoxin should be administered, it
should not be delayed.
Food Association
Food types involved in botulism outbreaks
Beef stew
Chicken
Dairy products
Fish Fruits and vegetables
Mushrooms
Pork
Turkey
Prevention of Botulism
Use of proper temperature and time in home
canning of low acid products.
Strict regulations for commercial canning.
Some foods (e.g fish) should be properly and
uniformly cooked at high temperatures.
Suspected foods should be properly heated before
consumption, but it is better not to eat them.
The presence of toxin in food is tested by injecting a
food extract intraperitoneally into mice,
development of neurological symptoms and death
in 92 hours suggest the presence of toxin.
Mycotoxicosis
Many strains of molds, while growing in a suitable
environment(including foods), produce metabolites
that are toxic to humans, animals and birds, and are
grouped as mycotoxins.
Consumption of foods containing mycotoxins causes
mycotoxicosis.
They are secondary metabolites and not proteins or
enteric toxins.
Many are carcinogens.
Recently, thousands of turkeys died from liver necrosis
in England following feeding peanut meal in which
Aspergillus flavus grew and produced the toxin
aflatoxin.
Organisms
Toxigenic species and strains of molds from many
genera are known to produce mycotoxins.
Aspergillus flavus……………..aflatoxin
Aspergillus nodulans……………sterigmatocystin
Penicillium viridicatum……….ochratoxin
Penicillium patulum………….patulin
Penicellium roquefortii………..roquefortin
Claviceps purpurea…………………….ergotoxin
Molds grow best in humid ,warm environment, they
are aerobic, they can grow at low temperature and
low pH.
Spores are present in soil, dust and the environment.
Food Association
The growth of toxigenic mold strains and the presence
of specific mycotoxins have been detected in many
foods:
Corn, Wheat, rice, beans, peanuts, bread, cheeses,
spices, cotton seeds and spaghetti.
Prevention of human mycotoxicosis is by reduction of
food contamination by molds.
Anaerobic packaging, reducing Aw, freezing and the use
of specific preservatives.
Mycotoxins can be detected by solvent extraction of
foods then applying thin layer chromatography for the
extract. Mass spectral methods are also used to
identify specific mycotoxin.