Stool
Sampling protocol
- Faecal specimen should be collected in the early stages of the disease when pathogens are usually present in the stool in large numbers, and preferably before antibiotic/ antiparasitic treatment is begun
- The specimen should be collected in the morning to reach the laboratory before noon, so that it can be processed the same day
- Cysts of Giardia duodenalis and Entamoeba histolytica, larvae of Strongyloides stercoralis tend to be excreted in “showers” and it is generally accepted that 3 to 5 serial stools must be examined before an individual is considered free from these infections
- For helminths more that one specimen is seldom necessary for a correct diagnosis
- For the diagnosis of pinworm (Enterobius vermicularis) infection, the cellophane tape method is recommended
- If enteropathogenic bacteria is suspected, formed stool should be rejected for examination
- Instruct the patient on how the specimen should be collected and transferred to the container
- Provide him/her with sticks and containers
- The stool should be collected on a piece of toilet tissue or old newspaper
- A sample is transferred with the sticks to the container
- The specimen should contain at least 5g of faeces and, if present, those parts that contain blood and/or mucopus should be selected
- The specimen should not be contaminated with urine
- Close the lid
- The specimen should be transported to the laboratory and processed within a few hours
- If a delay in shipment of the specimen to the laboratory is anticipated, stool specimen should be placed in a container with transport medium (Cary-Blair, Stuart or Amies) or glycerol-phosphate buffer
- For cholera or other Vibrio spp. alkaline peptone is an excellent transport (and enrichment) medium
- For trophozoites of Entamoeba histolytica the specimen should be kept warm and examinated within one hour after defecation without prior refrigeration
- Suitable specimen container provided with a lid: a clean glass cup, a plastic or a waxed cardboard box or a special container with a spoon attached to the lid or stopper
- 2 sticks to transfer the specimen to the container
- Urine or toilet water must never be mixed with the specimen