Examine the stool specimen visually without delay for:
- consistency (e.g. formed, liquid),
- colour (white, yellow, brown, black),
- atypical components (mucus, blood, parasites).
Examine microscopically for:
- atypical components (blood, mucus, fat).
Specimens should also be cultured for the identification of enteric pathogens. The specimens should be inoculated as soon as possible after arrival in the laboratory. Immediate inoculation is particularly helpful for the identification of Shigella and Campylobacter spp. If immediate inoculation is not possible, the specimens should be stored at 4 °C.
There are several suitable media of varying selectivity for primary plating, which allow certain enteric pathogenic bacteria to grow, while inhibiting growth of Gram-positive and some Gram-negative bacteria. These media also permit morphological differentiation of species of bacteria.
The plates can be inoculated directly from the rectal or faecal swabs, care being taken to apply a light or heavy inoculum to the medium, as appropriate. However, when more than three plates are to be inoculated, it is helpful to make a faecal suspension in saline. The inoculation of plates with the saline faecal suspension, using an inoculation loop, helps ensure that only small amounts of organic matter are transferred on to the plates, which might otherwise distort the appearance of the colonies.