Foodborne illness, more commonly referred to as food poisoning, is the result of eating contaminated, spoiled, or toxic food. Human illnesses from the consumption of foods contaminated with biological factors are what is known as foodborne diseases. Every day, humans and animals consume food materials contaminated with microbes which adversely affect their health condition.
The Centers for Disease Control and Prevention (CDC), reports that one in every six people in the United States gets sick each year from eating contaminated food. This number is even higher in developing countries where there is poor hygiene level and more people handle food materials poorly. With this, it means that more people are affected as part of the more than 1,000 outbreaks that happen each year.
Foodborne illness is caused by unintentional contamination of food materials with microorganisms. Although biological hazards cause the majority of illnesses, some may be due to chemical contamination. We will be focusing more on the biological hazards in the course of our study.
A number of factors contribute to the outbreak of foodborne disease. While contamination can occur at any level of the food processing, it all affects the health of humans. Before consumption, foods are exposed to many different environments and conditions.
These dictate whether a pathogen present initially will survive or be killed, whether recontamination can occur, or whether a pathogen can multiply to reach a high population to cause disease.
Factors such as the presence of a pathogen in the raw materials with a potential of contaminating the finished products, the ability of a pathogen to grow optimally in a particular type of food, quality control failure during processing, and a higher possibility of contaminating the finished products by food handlers are all factors that cause food poisoning.
Generally, foodborne illness is favored by the following conditions:
- The microorganism or its toxin must be present in food.
- The food must be suitable for the microorganism to grow.
- The temperature must be suitable for the microorganism to grow.
- Enough time must be given for the microorganism to grow and to produce a toxin.
- The food must be eaten.
It is worthy of note that foods contaminated with pathogenic microorganisms usually do not look, taste or smell bad. Owing to this, it is impossible to determine whether a food is contaminated with pathogenic microorganisms without microbiological testing. To avoid potential problems in foods, it is very important to control or eliminate these microorganisms in food products.
Bacteria and viruses are the most common cause of food poisoning. The symptoms and severity of food poisoning vary, depending on which bacteria or virus has contaminated the food. Some parasites are also implicated in some incidences of food poisoning. The most common foodborne parasites are protozoa, roundworms, and tapeworms.
Molds, toxins, and contaminants: Most food poisoning is caused by bacteria, viruses, and parasites rather than toxic substances in the food. But some cases of food poisoning can be linked to either natural toxins or added chemical toxins.
Allergens: Food allergy is an abnormal response to a food triggered by the body’s immune system. Some foods, such as nuts, milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat or soybeans, can cause allergic reactions in people with food allergies.
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Symptoms of Food Poisoning: Common Signs and Severe Indicators
Symptoms can vary and the length of time for the symptoms to appear depends on the source of the infection, but it can range from as little as 1 hour to as long as 28 days.
Common cases of food poisoning will typically include at least three of the following symptoms:
- abdominal cramps
- loss of appetite
- diarrhea
- vomiting
- headaches
- mild fever
- weakness
- nausea
Symptoms of potentially life-threatening food poisoning include:
- diarrhea persisting for more than three days
- a fever higher than 101.5°F
- difficulty seeing or speaking
- symptoms of severe dehydration, which may include dry mouth, passing little to no urine, and difficulty keeping fluids down
- bloody urine
Causes and Management of Food Poisoning: Key Factors and Prevention Strategies
Direct or indirect contamination of food can cause infections in man. The transmission of these infections by food depends on the following conditions:
The presence of a food that supports the growth of the microorganism.
The inoculation of foods with sufficient number of microorganisms from a patient with clinical disease, or a carrier, or contaminated environment.
Contamination at suitable temperatures for a period long enough to permit the growth of the organism or the elaboration of the toxin.
The absence of suitable treatment or processing of the food to inactivate the organism or the toxin.
Ingestion of food by the host.
This series of events usually occurs in a setting where:
There is a reservoir of organism in man, animals, or the environment
Knowledge and practice of food hygiene and personal hygiene is inadequate to prevent transmission of the organism
Sanitation facilities are insufficient to prevent contamination of the environment with human excreta and its transfer to food.
Contamination of food leading to food poisoning can occur as a result of the way in which the food is handled and prepared. The major causes of food poisoning are:
1. Inadequate Cooking: Inadequate cooking of contaminated raw food and inadequate reheating of pre-cooked food will not produce heat sufficient enough to kill microorganisms on the food.
2. Food Storage Conditions: Cooked food should not be kept at temperatures that favor the growth of bacteria. Bacillus cereus forms spores that are relatively resistant to heat and these spores are commonly found on cereal grains. If cooked rice is kept warm, the spores germinate and the organisms grow and produce its toxin.
3. Cross-Contamination between Raw and Cooked Food: Cross-contamination is a problem in domestic food preparation, but may also occur, sometimes with dramatic effects, in industrial food processing.
4. Poor Personal Hygiene in Food Handlers: Personal hygiene begins at home, with the essential elements for good hygiene being a clean body, clean hair and clean clothing. Hair in food can be a source of both microbiological and physical contamination. Hairnets and beard covers should be worn to assure food product integrity. Long-sleeved smocks should be worn to cover arm hair.
Clean uniforms, aprons and other outer garments that are put on after the employee gets to work can help minimize contamination. While working, clothing should be kept reasonably clean and in good repair. Removal of smocks, laboratory coats or aprons should take place when leaving the work area to go to the employee break room, restroom or exiting the building.
Personal items such as meals and snacks should be stored in a locker or break room area that is located away from processing areas or areas where equipment and utensils are washed.
The only jewelry allowed in a food plant is a plain wedding band and/or one small post earring in each ear. No other jewelry is to be worn because it may fall into the product, it can present a safety hazard and it cannot be adequately sanitized against bacterial transmission.
It should be removed prior to entering the processing facility. Employees must wear different colored smocks when going from a raw processing part of the establishment to the cooked processing side. They should also step into a sanitizer footbath between the two processing areas to eliminate the bacteria on their shoes.
No employee who is affected with, has been exposed to, or is a carrier of a communicable disease, the flu or a respiratory problem, or any other potential source of microbiological contamination shall work in any area where there is a reasonable possibility that food or food ingredients can be contaminated.
The number one symptom of a foodborne illness is diarrhea. Other symptoms include fever, dizziness, vomiting, and sore throat with fever or jaundice. Any employee with these symptoms should not be allowed to work around food.
If an employee has been diagnosed with a foodborne illness, exclude them from the establishment, and contact the local health department. The health department must be notified if the employee has been diagnosed with one of the following foodborne illnesses: Salmonella typhi, Shigella species, shiga toxin producing E. coli, or hepatitis A virus.
1. Ingestion of Toxins
The ingestion of naturally occurring poisons present in mushrooms, toadstools, fish and shellfish and other contaminants causes food poisoning. Food poisoning from mushrooms such as Amanita phalloides or muscaria, results in sweating, cramps, diarrhea, confusion and sometimes convulsions. Patients usually recover within 24 hours if the infecting mushroom is Amanita phalloides, however, liver damage is common, leading to jaundice.
Remissions may occur, but the mortality rate is about 60 percent or higher. Fish poisoning can result from Pacific types such as sea bass, Caribbean types such as Cavallas, Scrombroid types such as Mackerel, and Tetraodon types such as Puffers. Symptoms include numbness of the limbs, joint aches, chills and fever. Muscle weakness and paralysis can also occur, and death may result within 24 hours.
2. Ingestion of Heavy Metals
Ingestion of heavy metals like lead and mercury can cause acute nausea, vomiting and diarrhea and may cause respiratory or nervous system damage over a long term. The severity of the symptoms depends on the metal and the dose, as well as the patient. Treatment includes bed rest, fluids and blood or plasma expanders in severe cases where shock is anticipated.
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Types of Food Poisoning Organisms: Classification Based on Disease Mechanisms
Food poisoning organisms can be classified into four groups, depending on the mechanism involved in causing disease:
i. Organisms that produce toxin in the food
ii. Organisms that multiply in the intestinal tract and produce toxins that cause the symptoms
iii. Organisms that invade the body but generally remain in the region of the intestinal tract or cause widespread systemic infection
iv. Other microbial infection
1. Organisms that Produce Toxin in the Food: Key Examples and Risks
The main examples of organisms that produce toxin in the food are Clostridium botulinum, Staphylococcus aureus and some strains of Bacillus cereus. The problem here is more of intoxication than infection and if the food contains a significant amount of the toxin, subsequent cooking will not reduce the risk of food poisoning.
i. Clostridium botulinum Food-Borne Poisoning: Types, Symptoms, and Treatment
Botulism is food poisoning caused by eating food containing a poisonous bacterium called Clostridium botulinum. There are three main types of botulism viz: food-borne botulism caused by eating foods that contain the botulism toxin.
Wound botulism caused by toxin produced from a wound infected with Clostridium botulinum and infant botulism caused by consuming the spores of the botulinum bacteria which then grow in the intestines and release toxin. The three forms of botulism are fatal and cause medical emergencies.
Food-borne botulism is particularly dangerous because eating a batch of Clostridium botulinum contaminated food can poison a large number of people. The Clostridium botulinum is found in the soil but grows in many meats and vegetables.
Clostridium botulinum spores are killed by boiling while the toxins may be destroyed by moist heat at 80° C for 30 minutes. The spores grow best in the absence of oxygen and this makes improperly processed foods in sealed containers a perfect environment for their growth.
If food contaminated by the bacterium Clostridium botulinum is not properly canned or bottled, the bacteria are able to produce a toxin called ‘botulin’, which produces the disease botulism.
Within 8 to 36 hours of ingestion of the contaminated food, the botulin toxin paralyzes nerves regulating muscle function, resulting in respiratory failure, as the muscles that control breathing weaken.
The toxin also affects the central nervous system and interrupts nerve impulses, but the mind continues to function normally. The symptoms of botulism usually appear 18 to 36 hours after ingestion of the contaminated food.
Disability progresses from difficulty in walking and swallowing, with impaired vision and speech, to occasional convulsions, and ultimately to paralysis of the respiratory muscles, suffocation, and death, all within a few hours or days, depending on the amount of toxin ingested.
The most direct way to confirm diagnosis is to demonstrate the presence botulin in the patient’s serum or stool by injecting serum or stool into mice and looking for signs of botulism. Botulism antitoxin may be effective if administered early.
Surgical opening of the trachea and use of a respirator may be lifesaving. Physicians may try to remove contaminated food still in the gut by inducing vomiting or by using enemas.
The respiratory failure and paralysis that occur with severe botulism may require a patient to be on a ventilator for weeks. Research into the use of botulism in biological warfare has produced a toxoid, an inactivated poison for use in a vaccine, to induce immunity.
ii. Staphylococcus Food-Borne Poisoning: Sources, Symptoms, and Prevention
The most common species of Staphylococcus is Staphylococcus aureus, which is found on the skin, mouth, external ear and in the nostrils of many healthy individuals. Another species of staphylococcus called Staphylococcus epidermidis is very widespread but is not normally pathogenic.
These bacteria can cause serious infections under the right conditions. They may infect wounds or give rise to endocarditis (inflammation of the heart membrane) if the host’s immune system is weak. They may also cause pneumonia and internal abscesses.
They do not form spores but can survive for several weeks in dry conditions. Some strains can withstand high temperatures; they do not often grow outside the body, but may do so in meat, milk or dirty water.
The various species of Staphylococcus multiply rapidly at room temperature and may directly infect the gastrointestinal tract. Due to careless food handling, workers may sneeze or cough on food or may have infected pimples or wounds on the hands or face and transmit the bacteria to the food. Staphylococcus aureus infections are characterized by the presence of pus and formation of abscesses.
Staphylococcus is responsible for skin pustules (pimple containing pus), boils and carbuncles (severe skin abscess), impetigo (contagious skin infection forming pimples and sores), infections of wounds and burns, breast abscesses, whitlow, osteomyelitis, bronchopneumonia, septicaemia, acute endocarditis, food poisoning and scalded skin syndrome.
The symptoms of Staphylococcal infection include nausea, vomiting and diarrhea which develop within 1 to 8 hours after exposure to the bacteria. Treatment is usually by combination of fluid and electrolyte replacement but deaths rarely occur.
2. Organisms that Multiply in the Intestinal Tract and Produce Toxins that Cause the Symptoms: Mechanisms and Examples
Organisms may multiply in the intestinal cavity (for example, Bacillus cereus and Clostridium perfringens) and produce relatively rapid symptoms after eating the contaminated food and the infection lasts for only a day or so.
Other organisms, including the various pathogenic strains of Escherichia coli, Aeromonas species and Vibrio cholerae invade and multiply inside the cells of the intestinal wall and secrete toxins. The onset of symptoms from such organisms is typically one to two days and the symptoms may last for several days.
i. Escherichia coli Food-Borne Poisoning: Strains, Risks, and Control Measures
E. coli infection is a potentially fatal form of food poisoning caused by certain strains of the bacterium Escherichia coli. About 5 million E. coli normally inhabit the human and animal intestinal tract, and are vital to processing vitamins in the diet. However, a number of strains are pathogenic and cause gastroenteritis.
Strains known as entero-pathogenic strains are associated with undercooked meat, and are a common cause of diarrhea in infants, but rarely produce gastroenteritis in adults. Other “entero-toxicogenic” strains are the main cause of “travellers’ diarrhea”.
A relatively large number of E. coli (100 million or more) are normally required to cause infections, which are generally associated with food and water contaminated by feces. Entero-invasive strains E. coli invade cells of the intestines, causing dysentery, with bloody diarrhea.
These are highly virulent strains, and ingestion of just a few organisms may cause infection. Outbreaks of such infection have been associated with undercooked hamburgers and unpasteurized milk. The entero-hemorrhagic strains are also highly virulent, causing both bloody diarrhea and possibly fatal systemic infection.
In particular, the strain E. coli 0157:H7, which also exists in animals and humans, is thought to be a virally infected, highly toxic strain of the E. coli. Ingestion of as few as 10 organisms may cause intestinal hemorrhaging and possible kidney failure.
The fatality rate from the infection is 50 percent in children and the elderly. The main source of infection is undercooked contaminated beef. Once infected, people in confined areas can transmit the pathogen.
Certain rare strains of the bacteria Escherichia coli cause food poisoning in young children, the elderly, and people with impaired immune systems. E. coli 0157:H7 normally found in the intestines and fecal matter of humans and animals can survive in meat if the meat is not cooked beyond 155°F.
Outbreaks are due mainly to contaminated cooked meats bought from local retail butchers. These incidences emphasize the need for improved food regulations, preparation and hygiene as bacteria from meat surfaces are incorporated during grinding and cutting, and subsequent insufficient cooking.
Symptoms of E. coli infection appear after four to nine days and include bloody diarrhea, cramping, pain, and fever. Complications of E. coli infection include septicemia, kidney failure and brain damage. Currently there is no cure for E. coli infection. Patients recover once the infection has run its course, although digestive and renal problems may persist.
Prevention of E. coli infection is by maintaining high standards of food hygiene. The standards food hygiene includes always washing the hands before handling food, scalding the utensils used to prepare meat and keeping raw meat separate from other foods and thoroughly cooking of food to 70° C.
ii. Vibrio cholerae Infection: Causes, Symptoms, and Prevention in Food and Water Contexts
Vibrio cholerae cause cholera – a severe infectious disease endemic to tropical countries and occasionally spreading to temperate climates. The major means of infection is through the use of contaminated water in the preparation of foods such as fruits and vegetables. Ready-to-eat foods may be contaminated by storage in contaminated containers or by sprinkling with contaminated water.
The symptoms of cholera are diarrhea and the loss of water and electrolytes in the stool. In severe cholera, the patient develops violent diarrhea, vomiting, thirst, muscle cramps and sometimes, circulatory collapse. Death can occur as quickly as a few hours after the onset of symptoms.
The mortality rate is greater than 50% in untreated cases, but falls to less than 1% with effective treatment. Prevention of the disease is a matter of sanitation and treatment consists mainly of intravenous or oral replacement of fluids and salts containing the correct mixture of sodium, potassium, chloride, bicarbonate and glucose.
A vaccine made from dead bacteria is commercially available and offers partial protection for a period of three to six months after immunization.
3. Organisms that Invade the Body but Generally Remain in the Region of the Intestinal Tract and/or Cause Widespread Systemic Infection: Overview and Impacts
Microorganisms like Campylobacter, Salmonella, Shigella and Yersinia remain in the intestinal tract. The onset of symptoms is relatively slow and the infection may persist for weeks. Organisms that invade and cause systemic infections in the body include Listeria monocytogenes, Salmonella typhi and Salmonella paratyphi. The onset of symptoms may occur many days after consuming the contaminated food and symptoms may persist for many weeks.
i. Salmonella Food-Borne Infection: Transmission, Types, and Control Methods
Salmonella is transmitted through contaminated poultry, eggs and other foods. Three species are recognized: Salmonella typhi, S. cholerasuis and S. enteritidis which have more than 1,400 antigenically distinct serotypes. S. typhi cause typhoid fever. S. typhimurium – a serotype of S. enteritidis causes salmonella gastroenteritis, a type of food poisoning characterized by abdominal pain, fever, nausea and vomiting, and diarrhea.
The incubation period is 8 to 48 hours, and an attack may last from three to seven days. Mild cases usually are treated with anti-diarrheal remedies while more severe cases require antibiotics. S. enteritidis occurs in most flocks of hens, thus undercooked chicken or eggs are the usual source of infection. Careful cleaning and thorough cooking of food prevent salmonella infections.
ii. Typhoid Fever: A Systemic Infection Linked to Food and Water Contamination
Typhoid fever is an acute infectious disease caused by the bacillus Salmonella typhi transmitted through milk, water, or solid food contaminated by feces of typhoid victims or of carriers. The incubation period of Salmonella typhi lasts one to three weeks. The bacteria collect in the small intestine, from where they enter the bloodstream and induce the first symptoms – chills followed by high fever.
Victims may also experience headache, cough, vomiting and diarrhea. The disease spontaneously subsides after several weeks in most instances, but in about 20 percent of untreated cases the disease progresses to pneumonia, intestinal hemorrhage and even death.
Control of typhoid includes pasteurization of milk, purification of water supplies, the recognition of carriers, improvement of sewerage facilities and inoculation of people exposed to the disease, such as hospital employees and travelers to areas with poor sanitary facilities.
4. Other Microbial Infections in Food Poisoning: Additional Organisms and Their Effects
Clostridium perfringens is found mainly in poultry products and it causes mild form of food poisoning. Symptoms last only a day and starts about 8 – 22 hours after ingestion and include abdominal pain, nausea, diarrhea and vomiting.
Shigella is found in chicken spread, fruit and fish salad. It is characterized by sudden appearance of abdominal pains, cramps, diarrhea, fever and vomiting with the presence of blood, pus and mucous in stools of about 35% of infected patients.
Frequently Asked Questions (FAQs)
- What are the main causes of foodborne illnesses?
Foodborne illnesses are primarily caused by unintentional contamination of food materials with microorganisms, such as bacteria, viruses, and parasites, though some cases result from chemical contamination or natural toxins. - How can cross-contamination between raw and cooked food be prevented?
Cross-contamination can be prevented by keeping raw and cooked foods separate, using different utensils and cutting boards for each, and maintaining proper hygiene during food preparation. - What are the common symptoms of food poisoning?
Common symptoms include abdominal cramps, loss of appetite, diarrhea, vomiting, headaches, mild fever, weakness, and nausea, typically appearing within 1 hour to 28 days after infection. - What are the types of botulism discussed in the article?
The three main types are food-borne botulism from eating foods containing the toxin, wound botulism from toxin in an infected wound, and infant botulism from spores growing in the intestines. - How does poor personal hygiene in food handlers contribute to food poisoning?
Poor personal hygiene can lead to transmission of bacteria through contaminated hands, hair, clothing, or jewelry, especially if handlers have infections, wounds, or fail to wash properly. - What are the key factors favoring the growth of microorganisms in food?
Key factors include the presence of the microorganism or toxin in food, suitable food for growth, appropriate temperature, sufficient time for multiplication, and eventual consumption of the food. - How is Escherichia coli food-borne poisoning typically transmitted?
It is transmitted through undercooked meat, unpasteurized milk, or food and water contaminated by feces, with strains like E. coli 0157:H7 being highly virulent and linked to contaminated beef. - What prevention measures are recommended for cholera caused by Vibrio cholerae?
Prevention involves sanitation, using clean water for food preparation, proper storage of ready-to-eat foods, and vaccination with a commercially available vaccine for partial protection.
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