Food

Lecture 3

FOODBORNE INTOXICATIONS
(Food poisoning)

Dr. Nadia Aziz

F.A.B.C.M. Lecturer
Department of community medicine
Medical college
Baghdad University

Foodborne diseases:

Including foodborne intoxications and foodborne infections, are terms applied
to illnesses acquired through consumption of contaminated food
also include those caused by chemical contaminants such as heavy metals and
organic compounds.
the more frequent causes of foodborne illnesses are:
1) toxins elaborated by bacterial growth in the food before consumption
Like : Clostridium botulinum, Staphylococcus aureus and Bacillus cereus
or in the intestines Clostridium perfringens
2) bacterial, viral, or parasitic infections (brucellosis, Escherichia coli, hepatitis A, salmonellosis and infection with vibrios etc…)
3) toxins produced by harmful algal species (ciguatera fish poisoning, paralytic, neurotoxic, diarrhoeic or amnesic shellfish poisoning).
Foodborne disease outbreaks are recognized by the occurrence of
illness within a variable but usually short time period (a few hours to a
few weeks) after a meal, among individuals who have consumed foods
in common.
Prompt and thorough laboratory evaluation of cases and
implicated foods is essential. Single cases of foodborne disease are
difficult to identify unless, as in botulism, there is a distinctive clinical
syndrome.
Ultimately, prevention depends on educating food handlers about proper practices in
cooking and storage of food and personal hygiene.
Toward this end, WHO has developed a document Five Keys to Safer Food, as follows:
1. Keep Clean.
2. Separate raw and cooked.
3. Cook thoroughly.
4. Keep food at safe temperatures.
5. Use safe water and raw materials.
I. STAPHYLOCOCCAL FOOD INTOXICATION ICD-10 A05.0
Identification
An intoxication (not an infection) of abrupt severe nausea, cramps,
vomiting and prostration, often accompanied by diarrhea and sometimes with subnormal
temperature and lowered blood pressure.
Deaths are rare; illness commonly lasts only a day or two

Diagnosis
In the outbreak setting, recovery of large numbers of staphylococci (105
organisms or more/gram of food) on routine culture media, or detection of
enterotoxin from an implicated food item confirms the diagnosis. Absence of staphylococci on culture from heated food does not rule out the diagnosis
A Gram stain of the food may disclose the organisms
that have been heat killed.
Isolation of organisms from stools or vomitus of 2 or more ill persons confirms the diagnosis.
Toxic agent
Several enterotoxins of Staphylococcus aureus, stable at boiling temperature. Staphylococci produce the toxins at levels of water activity too low for the growth of many bacteria.
Occurrence
About 25% of people are carriers of this pathogen.
Reservoir
Humans in most instances; occasionally cows with infected udders, as well as dogs and fowl.
Mode of transmission
Ingestion of a food product containing staphylococcal enterotoxin like salad dressings, sandwiches, meat products & inadequately processed cheese. When these foods remain at room temperature for several hours before being eaten, toxin-producing staphylococci
multiply and elaborate the heat-stable toxin.
Organisms may be of human origin from purulent discharges of an
infected finger or eye, abscesses, acneiform facial eruptions, nasopharyngeal
secretions; or of bovine origin, such as contaminated milk or milk products, especially cheese.
Incubation period
30 minutes to 8 hours, usually 2–4 hours.
Methods of control
A. Preventive measures:
1) Educate food handlers about: (a) strict food hygiene, sanitation
and cleanliness of kitchens, proper temperature control, handwashing, cleaning of fingernails; (b) the danger of working with exposed skin, nose or eye infections
and uncovered wounds.
2) Reduce food-handling time (from initial preparation to service) to a minimum, no more than 4 hours at ambient temperature.
(above 60°C/140°F) or cold (below 4°C/39°F) in shallow containers
and covered.
3) Temporarily exclude people with boils, abscesses and other
purulent lesions of hands, face or nose from food handling.
B. Control of patient, contacts and the immediate environment:
1) Report to local health authority: Class 4.
Control is of outbreaks; single cases are rarely identified.
2) Specific treatment: Fluid replacement when indicated.
C. Epidemic measures:
1) Conduct an epidemiological investigation including interviews
of ill and well persons to determine the association of
illness with consumption of a given food.
2) Inquire about the origin of incriminated food
3) Search for food handlers with skin infections, particularly of
the hands. Culture all purulent lesions and collect nasal
swabs from all foodhandlers.
II. CLOSTRIDIUM PERFRINGENS FOOD INTOXICATION ICD-10 A05.2
(C. welchii food poisoning, Enteritis necroticans, Pigbel)
Identification
An intestinal disorder characterized by sudden onset of colic followed by
diarrhea; nausea is common.
Generally a mild disease of short duration, 1 day or less,
rarely fatal in healthy people. Outbreaks of severe disease with high
case-fatality rates associated with a necrotizing enteritis have been documented
Diagnosis
In the outbreak setting, diagnosis is confirmed by demonstration of
Clostridium perfringens in anaerobic cultures of food (105/g or more) or patients’ stool
(106/g or more).
Detection of enterotoxin in patients’ stool also confirms the diagnosis.
Infectious agent
Type A strains of C. perfringens (C. welchii)
cause typical food poisoning outbreaks
type C strains cause necrotizing enteritis.
Occurrence
Widespread
Reservoir
GI tract of healthy people and animals (cattle, fish, pigs and poultry).
Mode of transmission
Ingestion of food containing soil or feces and then held under conditions that
permit multiplication of the organism.
Almost all outbreaks are associated with inadequately heated or reheated
Meats. Spores survive normal cooking temperatures
Incubation period
From 6 to 24 hours, usually 10–12 hours.
Susceptibility
Most people are susceptible.
Methods of control
Preventive measures:
1) Educate food handlers about the risks inherent in large-scale cooking.
2) Serve meat dishes hot, as soon as cooked, or cool them rapidly in a properly designed chiller and refrigerate until serving time.
III. BACILLUS CEREUS FOOD INTOXICATION ICD-10 A05.4
Identification
An intoxication characterized by
sudden onset of nausea and vomiting, and in others by colic and diarrhea.
Illness generally persists no longer than 24 hours and is rarely fatal.
Diagnosis
In outbreak, diagnosis is confirmed through cultures
of suspected food (more than 105 - 106 organisms per gram of
food).
Enterotoxin testing is valuable but may not be widely available.
Toxic agent
Bacillus cereus, an aerobic spore former. Two enterotoxins have been identified:
1-Heat stable causing vomiting, is produced in food when B. cereus levels reach
105 colony-forming units/gram of food.
2-Heat labile causing diarrhea, formed in the small intestine of the human host.
Occurrence Widespread
Reservoir
A ubiquitous organism in soil and environment
Mode of transmission
Ingestion of food kept at ambient temperatures after cooking. Outbreaks associated with vomiting have been most commonly associated with cooked rice.
mishandled foods have also been implicated in outbreaks.
Incubation period
From 0.5 to 6 hours in cases where vomiting is the predominant symptom; from 6 to 24 hours where diarrhea predominates.
9. Methods of control
A. Preventive measures: Foods should not remain at ambient
temperature after cooking


INTESTINAL BOTULISM FORMERLY INFANT BOTULISM ICD-10 A05.1
Identification
Human botulism is a serious but relatively rare intoxication caused by potent
preformed toxins produced by Clostridium botulinum.
There are 3 forms of botulism:
1- foodborne (the classic form)
2-wound
3-intestinal (infant and adult) botulism.
All share the flaccid paralysis that results from botulinum neurotoxin.
Foodborne botulism is a severe intoxication resulting from ingestion of
preformed toxin present in contaminated food.
The characteristic early symptoms and signs are marked fatigue, weakness and vertigo, usually followed by blurred vision, dry mouth, and difficulty in swallowing and
speaking.
Vomiting, diarrhea, constipation and abdominal swelling may
occur.
Neurological symptoms always descend through the body
Paralysis of breathing muscles can cause loss of breathing and death.
There is no fever and no loss of consciousness.
The case-fatality rate is 5%–10%.
Intestinal (infant) botulism is rare; it affects children below 1 and
(rarely) adults with altered GI anatomy and microflora. Ingested spores
germinate and produce bacteria that reproduce in the gut and release
toxin.
Infant botulism has in some cases been associated with ingestion
of honey contaminated with botulism spores
it may cause an estimated 5% of cases of sudden infant death syndrome (SIDS).
The case fatality rate of hospitalized cases is less than 1%
Diagnosis
Is made by demonstration of botulinum toxin in serum, stool, gastric aspirate or incriminated food; or through culture of C. botulinum from gastric aspirate or stool of the patients
Infectious agent
Clostridium botulinum, a spore-forming anaerobic bacillus, isolated from soil, seafood and meat from marine mammals.
Toxin is produced in improperly processed, canned, low acid or alkaline foods.
Toxin is destroyed by boiling
Occurrence
Worldwide
Reservoir
Spores, ubiquitous in soil, honey & in the intestinal tract of animals.


Incubation period
usually within 12–36 hours
Methods of control
A. Preventive measures: As other types of food intoxications.
B. Control of patient, contacts and the immediate environment:
1) Report to local health authority: Class 2
2) Specific treatment: Intravenous administration of 1 vial of polyvalent (AB or ABE) botulinum antitoxin as soon as possible,
Antibiotics do not improve the course of the disease.
C. Epidemic measures: Suspicion of a single case of botulism
should immediately raise the question of a group outbreak
involving a family or others who have shared a common food.

SALMONELLOSIS ICD-10 A02

Identification
A bacterial disease manifested by:
Acute enterocolitis, headache, abdominal pain, diarrhea, nausea and sometimes vomiting.
Dehydration, especially among infants or in the elderly, may be severe.
Fever is almost always present.
Infection may begin as acute enterocolitis and develop into septicemia or focal infection.
Deaths are uncommon, except in the very young, the very old, the debilitated and the
Immunosuppressed.
Diagnosis
Salmonella may be isolated from feces during acute stages of enterocolitis.
Infectious agents
In the recently proposed nomenclature for Salmonella the agent formerly
known as S. typhi is called S. enterica
Salmonella enterica serovar Typhimurium (commonly S. Typhimurium) and
Salmonella enterica serovar Enteritidis (S. Enteritidis) arethe most commonly reported.
Occurrence
Worldwide, contaminated food, mainly of animal origin, is the predominant mode of transmission.
The incidence rate of infection is highest in infants and young children.
person-to-person spread can also occur
Reservoir
Domestic and wild animals, including poultry, swine, cattle, rodents and pets such as iguanas, turtles, chicks, dogs and cats; also humans, i.e. patients, convalescent carriers
Chronic carriers are rare in humans but prevalent in animals and birds.
Mode of transmission
Ingestion of the organisms in food from infected animals or contaminated by feces of an infected animal or person. This includes eggs, raw milk, contaminated water, meat &
poultry.
Maternity units with infected (at times asymptomatic) infants,are sources of further spread.
Incubation period
From 6 to 72 hours, usually about 12–36 hours.
Period of communicability
Throughout the course of infection. A temporary carrier state occasionally continues for months, especially in infants.
Susceptibility
increased by achlorhydria, antacid treatment, gastrointestinal surgery,
broad-spectrum antibiotherapy, neoplastic disease, immunosuppressive
treatment and other debilitating conditions including malnutrition.
Methods of control
A. Preventive measures:
1) Educate all food handlers about the ways of proper preparation & handling of food.
2) Educate the public against consuming raw or incompletely cooked eggs and using
dirty or cracked eggs.
3) Exclude individuals with diarrhea from food handling and
from care of hospitalized patients, the elderly and children.
4) Establish the facilities for food irradiation for meats and eggs.
5) Inspect for sanitation and supervise abattoirs, food-processing plants.
B. Control of patient, contacts and the immediate environment:
1) Report to local health authority: Obligatory case report, Class2.
2) Isolation:
Enteric precautions, exclude symptomatic individuals from food handling.
3) Concurrent disinfection
4) Investigation of contacts and source of infection: Culture stools of household
contacts who are involved in food handling
5) Specific treatment:
rehydration and electrolyte replacement with oral rehydration solution
Antibiotics may not eliminate the carrier state
in adults, ciprofloxacin is highly effective but its use is not approved for
children; ampicillin or amoxicillin may also be used. Trimethoprim-
sulfamethoxazole and chloramphenicol are alternatives
Patients infected with HIV may require lifelong treatment to prevent Salmonella septicemia.
D. Disaster implications:
A danger in a situation with mass feeding and poor sanitation.


Organism
Incubation period
Signs & Symptoms
Duration
Food Sources
Staphylococcus aureus
30 min- 8 hrs
Sudden onset of severe nausea and vomiting.
24-48 hours
meats, egg, salads, cream pastries
Clostridiumperfringens
8–24 hours
Intense abdominal cramps, watery diarrhea
24hours
Meats, poultry
Bacillus cereus
6 -24 hrs
Abdominal cramps, watery diarrhea,
24-48 hours
Cooked rice
Clostridiumbotulinum
12-36 hours
Vomiting, diarrhea, blurred vision, muscle weakness, respiratory failure and death
Variable
Improperly canned foods, especially home-canned vegetables
Salmonella
6-72 hours
Diarrhea, fever, abdominal cramps, vomiting
4-7 days
Eggs, poultry, meat, unpasteurized milk or juice, cheese