Acute Gastroenteritis or food poisoning - Types, risk factors and its clinical features ?

Acute Gastroenteritis is a severe inflammation of gastrointestinal tract resulting acute diarrhea and vomiting. It can be transmitted by contacts with contaminated food & drinks. The inflammation is caused by an infection by bacteria, their toxin, parasites or an adverse reaction to chemicals in the diet or medication.

Acute Bacterial Gastroenteritis or Bacterial Food Poisoning

Acute Gastroenteritis is a severe inflammation of the gastro intestinal tract affecting both the stomach and small intestine leads to acute diarrhoea and vomiting. It can be transmitted by contacts with contaminated food and water. The inflammation is caused mostly by an infection by viruses and less often by bacteria, their toxin, parasites or an adverse reaction to chemicals in the diet or medication.
Acute bacterial gastroenteritis may develop within 48 hours after consumption of unhealthy food or drinks.

Causes of acute gastroenteritis

Acute bacterial gastroenteritis is caused by different species of bacteria which are Salmonella, Shigella, Staphylococcus, Clostridium, E. coli, Compylobacter jejune, Vibrio cholera etc. Acute gastroenteritis (food poisoning) may occur due to ingestion of poisonous foods or contaminated with chemicals or pathogenic bacteria & their products.
Poisonous foods include fungi especially the 'death cap' fungus which may mistaken for the harmless edible mushroom and certain tropical fishes.
Chemical food poisoning may be due to injurious chemicals in the food Such cases are rare.

Types of bacterial food poisoning

Bacterial gastroenteritis (Bacterial food poisoning) is the most common type and is divided into two main types:
• The 'toxin' type
• The 'infection' type

Toxin type
Toxin type of food poisoning occur due to bacterial toxins, mostly caused by the exotoxin produced by Staphylococcus pyogenes in majority in majority of cases, is spread by a food handler having septic lesion of hands or arms or who is a carrier of the bacteria in his nose or throat. Exotoxin is heat resistant and not destroyed by cooking or even by boiling for a short time.

Infection type
Mainly Salmonella group of bacteria are responsible for infection type of food poisoning. It can also be caused by other bacteria too, like Shigella, Staphylococcus, Clostridium, E. coli, Campylobacter jejune, Vibrio cholera etc. The reservoir of infection is certain birds, mammals and reptiles. Food may be contaminated by infected excreta of rats or mice etc; or infection may be transferred by flies or by human carriers working in the handling of food.
The size of infecting quantity of bacteria is directally proportional to the speed of onset of symptoms & severity of illness. This shows the severity of bacterial multiplication when food is exposed to infection (bacteria) and thereafter remains at a hot temperature (in kitchen) for many hours or even days.

Risk Factors of acute gastroenteritis

Types of food which are likely to be infected are:
• Twice cooked meat dishes, stews, gravies, soups, custards, milk and synthetic cream.
• Tinned foods if not consumed just after the tin has been opened.
• Hen's eggs are rarely infected.
• Duck's eggs are quite easily infected because it is a carrier of Salmonella organisms in their oviduct and alimentary canal (track). So duck's eggs are not suitable for lightly cooked food like custards, milk puddings etc.

It has been observed that outbreaks of food poisoning are liable to occur when large amount of food is kept for future meals. The risk of infection is increases when food is kept at a high temperature instead of being stored in a refrigerator. Food poisoning more often reported, from canteens, restaurants, hospitals and other institutions than from private houses.

Pathology of Food Poisoning (Acute Gastroenteritis)

In all types of food poisoning the mucous membrane of stomach and small intestine shows different degrees of inflammation and even ulceration. In severe cases, the lesion may extend to the large intestine with accompanying septicemia.

Clinical Features or sign & symptoms of food poisoning

In food poisoning or acute gastroenteritis other members of households or institution are affected simultaneously which the diagnosis easier. Incubation period of disease is an important pointer for etiology.

• If vomiting starts within half an hour of the ingestion of a food, it is likely to be due to chemical poison;

• If it occurs within 6 hours, it is probably due to a bacterial toxin; whereas

• If it occurs 12 to 48 hours later, it is probably due to a Salmonella infection.

The symptoms vary in severity depending on the type of and amount of the poisonous substance ingested. The main symptoms are Nausea, Vomiting, Diarrhoea and Pain in abdomen due to colic of the small intestine.
In severe cases prostration, collapse and signs of dehydration are seen.
In case of 'chemical' and 'toxin' types of gastroenteritis

• Onset is sudden & severe

• Patient rapidly passes into a state of collapse with subnormal temperature

• Recovery often occurs within 24 hours.

In 'infection' type, of gastroenteritis
• Symptoms develop more slowly with rise of temperature.

• Patient may be ill for several days.

• Stools are watery and offensive with little blood & mucus
It is important to exclude, especially in children, certain surgical conditions like Appendicitis, Intestinal obstruction, Intussusceptions and Volvulus which may occur with acute pain in abdomen, vomiting and diarrhoea.

Laboratory Investigations for food poisoning

In case of acute gastroenteritis the lab tests performed are:
• Specimen of patient's vomit & faeces are collected and tested for blood and different types of infection
• Stool culture
• Complete blood count to exclude anaemia
• Electrolyte test
• Kidney function test

Treatment of Acute Bacterial Gastroenteritis or food poisoing

• Acute bacterial gastroenteritis mostly recovers within a day or two.
• The main goal of treatment is to make patient feel better and to avoid main complication of disease i.e. Dehydration secondary to acute diarrhoea.
• Patient is re-hydrated by ORS (Oral Rehydration Solution).
• Avoid milk and caffeinated liquid.
• Avoid solid food till diarrhoea subsides
• Avoid dairy products because it worsens the diarrhoea due to Temporary state of Lactose intolerance.
• If patient have diarrhoea with nausea and vomiting, hospitalisation is needed for I/V fluid infusion.
• Diuretics are contra-indicated in management of acute diarrhoea.
• Avoid antibiotics in acute bacterial gastroenteritis, unless the diarrhoea is severe.
Always seek advice of your doctor (Physician) for better management of diarrhoea & its complications especially in case of children suffering from acute gastroenteritis.

Other Names of food poisoning

• Acute Gastroenteritis
• Acute Bacterial Gastroenteritis
• Infectious Diarrhoea
• Bacterial food Poisoning

Complications of food poisoning

The main complications of disease are
• Dehydration
• Kidney Failure
• Anemia due to low blood count
• Systemic infection

Prognosis of Acute gastroenteritis

Mostly symptoms of bacterial gastroenteritis subside by fluid intake and electrolyte replacement within a week. Rarely kidney failure or death occurs in bacterial gastroenteritis. Prognosis of disease is poor in extreme of ages (in elderly or very young children).

Prevention of acute gastroenteritis

It can be prevented by:
• Improving the standards of personal hygiene in those handling food
• Proper handling, storage and preparation of food
• Good sanitation are main principle of prevention of disease.


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