Wednesday, February 10, 2016

What causes food poisoning and when should you consult a doctor

Eating contaminated food can cause food poisoning, leading to symptoms like nausea, vomiting, diarrhea, abdominal pain and fever within hours, sometimes days or even weeks, of eating contaminated food.

What are the causes of food poisoning?

Food poisoning is caused due to ingesting food contaminated by bacteria, viruses, parasites or toxins. Food can get contaminated during growing, processing, storage or preparation stage. Also, food that isn’t cooked thoroughly or cooked under unsanitary conditions can also cause food poisoning. Also, expired food products usually contain bacteria and toxins.

Bacteria that cause food poisoning are Salmonella, E. coli, Campylobacter, Clostridium perfringens, etc. Hepatitis A virus is present in the faeces of infected persons and is most often transmitted through consumption of contaminated water or food. Rotavirus is transmitted by the faecal-oral route and spread from person-to-person through contaminated hands. Foods that require no cooking like salads and fruits may be contaminated by infected food handlers.

What factors increase the risk of food poisoning?

Most often an inbuilt system within our stomach inhibits the growth of these organisms, but in some cases we end up ingesting such large quantities of them that it cause illness. Risk of infection depends on:

1. Age and health – Risk of infection increases in older adults and in people with chronic diseases as their immune response is weakened. Very young children are at risk too as their immune system is not fully developed.

2. Type of food – Eating raw foods like salads, etc. increase the risk of food poisoning as harmful bacteria and parasites are not destroyed before consumption. Vegetables that have not been washed well and undercooked meats can cause food poisoning.

3. Bad hygiene practices – Not washing hands, especially the nails, before and after handling food can increase the risk of food contamination. Nails are the first place dirt tends to accumulate, and become a haven for harmful bacteria to hide and breed. Preparing food using unclean cutting board and utensils can contaminate the food. Kitchen sponges that have been in use for long are known to be dirtier than a toilet seat as they are a breeding spot for different types of bacteria.

4. Type of organism contaminating the food – Most cases of food poisoning are from common bacteria such as Staphylococcus, Salmonella or E. coli and virus such as norovirus. Most strains of E.Coli are the natural gut bacteria. But food contamination by the strain E.Coli 0157:H7 can cause kidney problems and even death if not treated properly. Infection due to Listeria contamination can lead to inflammation of the brain membrane (meningitis). Clostridium botulinum causes severe illness affecting the nervous system (botulism).

5. Quantity of harmful toxin ingested – If you drink a little quantity or eat a mouthful or two of contaminated food, you are not likely to suffer from food poisoning. The inbuilt system within our stomach inhibits the growth of the bacteria. But ingesting large quantities of food contaminated by bacteria can causes illness.

When should one consult a doctor?

Food poisoning is mostly self-limiting and usually resolves without treatment within a few days in most people. Promptly replacing lost fluids by drinking lots of fluids or oral rehydration mixture and getting plenty of rest can help recover from food poisoning. Consult the doctor under following conditions:

Vomiting even liquid food
Severe or worsening diarrhea
Severe dehydration
Blood in stools
High fever
Vomiting for more than 12 hours in young children
What are the tests involved in the diagnosis of food poisoning?

Food poisoning is diagnosed from a detailed health history, physical examination and signs of the disease. Since most episodes of food poisoning are not severe and resolve within a few days without treatment, diagnostic tests are rarely pursued. Blood test and stool culture can help confirm the diagnosis and identify the causative organism. Blood tests can help diagnose bacterial or parasitic infection. For the stool analysis, a stool sample collected in a clean container is sent to the laboratory for microscopic examination and other tests.