Food Poisoning

 

                            Food Poisoning

                            PKGhatak, MD

Food and drinks can be contaminated with microorganisms if not handled properly. Certain bacteria grow in the leftover food kept outside the refrigerator and produce toxins. When people eat leftover food, these toxins produce an illness which is called food poisoning.

In general, such a definition of food poisoning is not universally followed. Viral gastroenteritis, cholera, amebiasis, typhoid fever and others are also included in food poisoning. It is better to address those illnesses as food borne illnesses rather than food poisoning.

Bacterial Toxin.

Bacteria can grow over a wide range of temperatures, from 4 degrees C to 60 degrees C,  provided moisture and nutrients are present. A growing bacterial colony produces toxins.

Toxins produced by bacteria are in two groups-

A. Exotoxin. Endotoxins are secreted by bacteria in the food. Exotoxins can be heat resistant or destroyed by heating.

B. Endotoxin. Endotoxins are present in the bacterial bodies and released in food when the bacteria die or are killed by antibiotics.

Preformed toxins in food produce symptoms in 1 to 6 hrs. after ingestion, whereas, bacterial infection and toxin generation take over 8 hrs. and then symptoms develop. Bacteria commonly responsible for food poisoning are Staphylococcus, Bacillus, Clostridium, E.coli and Vibrio species.

Staphylococcus aureus food poisoning.

S. aureus readily grows when food is left on the kitchen countertop. Symptoms start within 1 to 6 hrs. after eating food. Reheating food before eating does not destroy the bacterial toxin. Nausea and vomiting are common symptoms and start abruptly. Campy abdominal pain and diarrhea follow. The illness is self limited and patients recover in 24 hrs.

Bacillus cereus.

Reheated fried rice is often the source of poisoning. Intense nausea and vomiting start within 1 to 8hrs after eating food. The toxin can be detected in stool and leftover food.

Symptoms last for 12 hrs. It is also a self limited illness.

Clostridium botulinum.

Clostridium botulinum is a soil bacteria. Canned vegetables not properly washed and low oxygen environment in a sealed can are ideal for the production of toxins. Another source is natural honey. The ingested toxin produces nerve paralysis and the illness is known as Botulism. Though the symptoms start days after ingestion of the poison, botulism is due to the toxin present in food and not a bacterial infection.

Botulism. The sudden onset of fluctuant and intermittent but severe muscle paralysis in a healthy person should alert the physicians of botulism. Botulism toxin prevents the release of a neurotransmitter, Acetylcholine, at the neuromuscular junctions.

Symptoms generally develop 3 days after ingestion of the toxin and continue to progress further for another 3- 4 days. Paralysis of eye muscles produces double vision, and eyelid paralysis causes drooping eyelids. Muscles of swallowing and speech muscles are also paralyzed producing difficulty in eating and drinking, and nasal voice. In severe cases, the muscles of limbs may be paralyzed. Identifying the toxin in unused portions of food and serum helps in the diagnosis. An electroencephalogram(EEG) is also useful.

Ant-toxins are available to reverse the effects of toxins. Hospitalization and close monitoring of respiration and blood oxygen and CO2 are essential parts of the management of botulism. Public health authorities must be informed.

Clostridium perfringens.

This spore-forming Clostridium is found in soil and feces. Uncooked beef, poorly cooked poultry and fish are the source of toxins. Between 6 to 24 hours after eating symptoms of severe diarrhea and abdominal cramps develop. The illness can last one to several days. The initial onset may be from preformed toxin but subsequently, the bacteria multiply in gut epithelium and continue to generate enterotoxin and produce symptoms.

Enterotoxin producing E. coli.

This entity falls in between preformed toxin and bacterial infection and perhaps, both are operative.

Animals and humans harbor E. coli in their large guts. When food and drinks are contaminated with feces, severe watery diarrhea and abdominal cramps develop within a day or two after ingestion. It is a common cause of food poison among international travelers. Antibiotic fluoroquinolones are effective therapy.

Vibrio parahaemolyticus.

This vibrio usually contaminates shrimps, carbs and shellfish. Eating raw oysters or lightly cooked seafood produces a sudden onset of abdominal pain and diarrhea within 2 to 48 hrs. Nausea, vomiting and diarrhea last for 2 to 5 days.

Proper hydration is required to prevent dehydration.

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