Technical problems related to in vitro study of colon flora

The complexity of colon flora and the technical problems encountered in the sampling techniques and their processing limit the study of its composition and activities. First, we list the main limitations related to the sampling procedure-transport and storage. We show that (i) use of a cryoprotective medium is necessary for sample storage and (ii) that storage has to be at -40 degrees C. Second, bacterial analysis and enzymatic activities are examined. The lack of specificity of the culture media generally used means that systematic studies are difficult to carry out and that bacterial identification at species level requires genetic techniques. Third, we show that activities of procarcinogenic enzymes are significantly affected by any kind of storage. Finally, for statistics, the problem of the size and the nutritional habits of the studied population is examined.