Food poisoning

Food poisoning is the name for the range of illnesses caused by eating or drinking contaminated food or drink.

It is also sometimes called foodborne illness.

Types

Most food poisoning is caused by harmful bugs (pathogens) getting into food.

The most common types of food poisoning are:

1 bacterial eg. Salmonella, Campylobacter, E.coli and Listeria2 viral eg. Norovirus, Rotavirus and Hepatitis A3 intoxication caused by the toxins produced by some bugs such as Staphylococcus aureus, Bacillus cereus andClostridium perfringens.

Some of these bugs can also be transferred from person-to-person with or without symptoms, or via contaminated surfaces. The symptoms they cause are the same even if food is not involved.

Some people have allergies and intolerances to specific foods or ingredients. These are not considered food poisoning, although they can also be very serious and even life threatening: see allergies and intolerances.

Symptoms

Symptoms of food poisoning range from mild to very severe.

Symptoms usually take between a few hours to a few days to begin and may last for a few days, depending on the type of pathogen.

Symptoms often include one or more of:

nauseastomach crampsdiarrhoeavomitingfeverheadaches

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Causes

Some foods accommodate harmful bugs or toxins more than others.

The bugs or toxins may be present on foods at the time of purchase, get on to food by cross contamination and poor hygiene or grow to harmful levels as a result of poor temperature control.

Harmful bugs can be:

carried on the bodies of people handling food

frequently present in the throat, nose, skin, hair and faeces

transferred to food after touching the nose, mouth or hair or smoking without washing hands before handling food. Sneezing or coughing around or near food can also lead to contamination.

Food poisoning can be caused by:

not cooking food thoroughly

not storing food that needs to be chilled below 5°C

someone who is ill or has poor hand hygiene handling the food

eating food after a ‘use-by’ date

cross contamination, where bacteria is spread between food, surfaces, utensils and equipment

Higher risk foods include:

meat, especially undercooked mince and rolled, formed or tenderised meats

raw or undercooked poultry such as chicken, duck and turkey

raw or lightly cooked eggs including foods made from raw egg such as unpasteurised mayonnaise

smallgoods such as salami and hams

seafood

cooked rice not kept at correct temperatures

cooked pasta not kept at correct temperatures

prepared salads such as coleslaw, pasta salads and rice salads

prepared fruit salads

unpasteurised dairy products

Diagnosing correctly that illness is caused by food poisoning and identifying the particular cause can be difficult. Identifying the cause is not always possible.

Foodborne illness pathogens

Most foodborne illness is caused by pathogenic bacteria or viruses in food.

Other less common foodborne illness occurs from accidental chemical poisoning and natural contaminants.

The most common types of foodborne illness are:

4 bacterial eg Salmonella, Campylobacter, E.coli and Listeria;5 viral eg Norovirus, Rotavirus and Hepatitis A;6 intoxication caused by toxins produced by pathogens such as Staphylococcus aureus, Bacillus cereus andClostridium perfringens.

Symptoms and the most frequent food vehicle will vary depending on the type of pathogen.

(Wide table: scroll/swipe sideways if not all columns are displayed.)

Pathogen Microscopicimage of pathogen **

Typical incubation period (time between eating and onset of symptoms)

Typical symptoms

Typical food vehicles *

Bacillus cereus toxin (vomiting and diarrhoea)

1 - 6 hours

6 - 24 hours

Sudden onset of severe nausea and vomiting

Abdominal cramps, nausea and watery diarrhoea

Improperly refrigerated cooked rice and pasta, and fresh noodles

Meats , stews, gravy

Campylobacter

2 - 5 days Fever, nausea, abdominal cramps and diarrhoea

Raw and undercooked poultry, unpasteurised milk and

(sometimes bloody)

contaminated water

Clostridium perfringens toxin

6 - 24 hours Abdominal cramps, watery diarrhoea and nausea

Meats, poultry, gravy, dried or precooked foods

Escherichia coli including (STEC)

2 - 10 days more commonly 3 - 4 days

Diarrhoea (often bloody), abdominal cramps

Improperly cooked beef, unpasteurised milk and juice, sprouts and contaminated water

Hepatitis A

2 - 7 weeks Jaundice, fatigue, loss of appetite, nausea

Raw or poorly cooked seafood harvested from contaminated waters, ready-to-eat foods handled by an infected food handler

Listeria monocytogenes

3 days - 10 weeks

Meningitis, sepsis, fever

Soft cheeses, unpasteurised milk, ready-to-eat deli meats

Norovirus

24 - 48 hours

Fever, nausea, vomiting, abdominal cramps, diarrhoea and headache

Poorly cooked shellfish, ready-to-eat foods touched by an infected worker

Salmonella

6 – 72 hours,usually 12-36 hours

Headache, fever, abdominal cramps, diarrhoea, vomiting and nausea

Undercooked poultry, raw egg desserts and mayonnaise, sprouts, tahini

Staphylococcus aureus toxin

0.5 – 8 hours Sudden onset of vomiting and abdominal cramps

Cream desserts and pastries, potato salad

Vibrio parahaemolyticus

4–30 hours, usually 12-24 hours

Nausea, vomiting, abdominal cramps and watery diarrhoea

Undercooked or raw seafood.

Some people are more at risk

Some people can be more vulnerable to, or are affected more by the symptoms of food poisoning.

These include:

children younger than 5 years old

pregnant women

people older than 70 years of age with certain underlying conditions, and

people with compromised immune systems through chronic or acute ill health and some conditions and treatments

In rare cases, food poisoning can result in long-term health problems and even death.

ood Poisoning

Counselor,

Food poisoning refers to an acute illness caused by ingestion of food contaminated by bacteria, bacterial toxins, viruses, natural poisons, or harmful chemical substances. It is characterized by a short incubation period (1 wk or less). The symptoms, varying in degree and combination, include abdominal pain, vomiting, diarrhea, headache, and prostration; more serious cases can result in life- threatening neurologic, hepatic, and renal syndromes leading to permanent disability or death. Most of the illnesses are mild and improve without any specific treatment. Some patients have severe disease and require hospitalization, aggressive hydration, and antibiotic treatment.

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Pathophysiology:

The pathogenesis of diarrhea in food poisoning is classified broadly into either noninflammatory or inflammatory types. Noninflammatory diarrhea is caused by the action of enterotoxins on the secretory mechanisms of the mucosa of the small intestine, without invasion. This leads to watery diarrhea without the presence of

leukocytes (white blood cells). The enterotoxins may be either preformed before ingestion or produced in the gut after ingestion. Examples of organisms causing noninflammatory diarrhea include Vibrio cholerae, enterotoxicEscherichia coli, Clostridium perfringens, Bacillus cereus, Staphylococcusorganisms, Giardia lamblia, Cryptosporidium, rotavirus, Norwalk virus, and adenovirus.

Inflammatory diarrhea is caused by the action of cytotoxin on the mucosa, leading to its invasion and destruction. The colon or the distal small bowel commonly is involved. The diarrhea usually is bloody, with the presence pus comprised of leukocytes. Sometimes, the organisms penetrate the mucosa and proliferate in the local lymphatic tissue, followed by systemic dissemination and sepsis. Examples include Campylobacter jejuni, Vibrio parahaemolyticus, enterohemorrhagic and enteroinvasive E coli, Yersinia enterocolitica, Clostridium difficile, Entamoeba histolytica, and Salmonella and Shigella species.

In some types of food poisoning (e.g., staphylococci, B cereus), vomiting is caused by a toxin acting on the central nervous system. For example, the clinical syndrome of botulism results from the inhibition of acetylcholine release in nerve endings by the botulinum.

The pathophysiological mechanisms that result in acute gastrointestinal symptoms produced by some of the noninfectious causes of food poisoning (naturally occurring substances [e.g., mushrooms, toadstools] and heavy metals [e.g., arsenic, mercury, lead]) are not well known.

Frequency:

A recent study from the US Centers for Disease Control and Prevention (CDC)

reports that food-borne diseases cause approximately 76 million illnesses, 325,000

hospitalizations, and 5,000 deaths in the United States each year. Identified

pathogens account for an estimated 14 million illnesses, 60,000 hospitalizations,

and 1,800 deaths. Salmonella, Listeria, and Toxoplasmaorganisms are responsible

for 1,500 deaths. Unidentified pathogens account for the remaining 62 million

illnesses, 265,000 hospitalizations, and 3,200 deaths.

History:

A detailed history, including the duration of the disease, characteristics and

frequency of bowel movements, and associated abdominal and systemic

symptoms, may provide a clue to the underlying cause. The presence of a common

source, types of specific food, travel history, and use of antibiotics always should

be investigated. The presenting complaints, typical features and pathogenesis of

various causative agents, and diagnosis and treatment information is complex and

beyond the scope of this overview.

The following are some of the salient features of food poisoning: Diarrhea in food

poisoning usually lasts less than 2 weeks. If it persists longer than 2 weeks, it is

considered chronic and food poisoning is a less likely cause; the presence of fever

suggests an invasive disease. However, sometimes fever and diarrhea may result

from infection outside the gastrointestinal tract, as in malaria; a stool with blood or

mucus indicates ulceration of the large bowel. Bloody stool without fecal

leukocytes should raise the suspicion of enterohemorrhagic E coli infection; a

bulky whitish stool suggests the involvement of the small intestine, causing

malabsorption; a profuse rice-water stool indicates cholera or a similar process;

abdominal pain is most severe in inflammatory processes. Painful abdominal

muscle cramps suggest underlying electrolyte loss, as in severe cholera; a history

of bloating and malodorous gas should raise the suspicion of giardiasis;

Yersiniaenterocolitis often mimics the symptoms of appendicitis; tenesmus (i.e.,

cramps in the rectum felt after a bowel movement), a feature suggesting the

inflammation of rectum, is present in cases of shigellosis.

Physical:

The physical examination should focus on assessing the severity of dehydration. A

dry mouth, decreased axillary sweat, and decreased urine output indicate mild

dehydration. An orthostatic fall in blood pressure, skin tenting, and sunken eyes

indicate moderate dehydration. Severe dehydration manifests as hypotension with

tachycardia, confusion, and frank shock. A rectal examination always should be

performed to directly visualize the stool, test occult blood, and palpate the rectal

mucosa for any lesions. Orthostatic changes, fever, and signs of peritoneal

irritation indicate a malignant course secondary to invasive disease.

Causes:

The CDC (Centers for Disease Control) estimates that 97% of all cases of food

poisoning result from improper food handling; 79% of cases result from food

prepared in commercial or institutional establishments and 21% of cases result

from food prepared at home.

The most common causes are (1) leaving prepared food at temperatures that allow

bacterial growth, (2) inadequate cooking or reheating, (3) cross-contamination, and

(4) infection in food handlers. Cross-contamination may occur when raw

contaminated food comes in contact with other foods, especially cooked foods,

through direct contact or indirect contact on food preparation surfaces.

Bacteria are responsible for approximately two thirds of the outbreaks of food

poisoning with a known cause in the United States. As many as 1 in 10 Americans

has diarrhea due to food-borne infection each year.

Lab Studies:

Gram staining and Loeffler methylene blue staining of the stool for WBCs helps to

differentiate invasive disease from noninvasive disease. Microscopic examination

of the stool for ova and parasites are an essential study. Bacterial culture for enteric

pathogens such as Salmonella, Shigella, and Campylobacter organisms becomes

mandatory if a stool sample shows positive results for WBCs or blood or if patients

have fever or symptoms persisting for longer than 3-4 days. If the patient is notably

febrile, then blood cultures should be obtained to rule out bacteremia and sepsis.

Other labs including CBC count with differential, serum electrolyte assessment,

and BUN and creatinine levels help to assess the inflammatory response and the

degree of dehydration. Assay for C difficile should be done to help rule out

antibiotic-associated diarrhea in patients receiving antibiotics or those with a

history of recent antibiotic use.

Imaging and Other Studies:

Flat and upright abdominal radiographs should be obtained if the patient

experiences bloating, severe pain, or obstructive symptoms or if perforation is

suggested.

Sigmoidoscopy should be considered in patients with bloody diarrhea. It can be

useful in diagnosing inflammatory bowel disease, antibiotic-associated diarrhea,

shigellosis, and amebic dysentery.

Treatment:

Because most cases of acute gastroenteritis are self-limited, specific treatment is

not necessary. The main objective is adequate rehydration and electrolyte

supplementation. This can be achieved with either an oral rehydration solution

(ORS) or intravenous solutions (eg, isotonic sodium chloride solution, lactated

Ringer solution). Strict personal hygiene should be practiced during the illness.

Some practical tips: At home oral rehydration is achieved by administering clear

liquids and sodium-containing and glucose-containing solutions. A simple solution

(ORS) may be composed of 1 level teaspoon of salt and 4 heaping teaspoons of

sugar added to 1 liter of water. The use of ORS has reduced the mortality rate

associated with cholera from higher than 50% to less than 1%. ORS also is

indicated in other dehydrating diarrheal diseases. The World Health Organization

(WHO) recommends a solution (under medical care) containing 3.5 g of sodium

chloride, 2.5 g of sodium bicarbonate, 1.5 g of potassium chloride, and 20 g of

glucose per liter of water. Intravenous solutions are indicated in patients who are

severely dehydrated or who have intractable vomiting.

Absorbents (eg, Kaopectate, aluminum hydroxide) help patients have more control

over the timing of defecation. However, they do not alter the course of the disease

or reduce fluid loss. An interval of at least 1-2 hours should elapse when using

other medications with absorbents. Antisecretory agents such as bismuth

subsalicylate (Pepto- Bismol) may be useful. The dose is 30 mL every 30 minutes,

not to exceed 8-10 doses a day. Antiperistaltics (opiate derivatives like Lomotil and

Imodium) should not be used in patients with fever, systemic toxicity, or bloody

diarrhea or in patients whose condition either shows no improvement or

deteriorates.

If symptoms persist beyond 3-4 days, the specific etiology should be determined

by performing stool cultures. If symptoms persist and the pathogen is isolated,

specific treatment should be initiated. Once cultures are performed, empiric

treatment with an agent that covers Shigella and Campylobacter organisms is

reasonable in those with severe diarrhea with systemic signs. A 3-day course of a

fluoroquinolone (eg, ciprofloxacin 500 mg twice a day, norfloxacin 400 mg twice a

day) is the first-line therapy. TMP/SMX (Bactrim DS 1 tab once a day) is an

alternative therapy, but resistant organisms are common in the tropics. Infection

with either V cholerae or V parahaemolyticus can be treated with either a

fluoroquinolone or with doxycycline (100 mg twice a day).