Gnotobiotic animals in research: their uses and limitations

The gnotobiotic laboratory animal is potentially a very valuable tool for investigating any suspected interaction between the host and its associated microflora or between different components of that flora. However, like many other good ideas, the production of gnotobiotes is simple in concept but complicated in execution. In the early stages the greatest obstacles to the general use of germ-free animals were the expense and the restricted amount of space that could be maintained free from contaminants. Nowadays, with isolators made of plastic film and improved methods of chemical sterilization, gnotobiotic equipment has become available, even for large animals, at a relatively modest price. Further, colonies of germ-free rats and mice have been established in a number of breeding centres and their offspring can be easily transported to the research laboratory. Already the use of germ-free animals has contributed much to our knowledge of the host-microbe relationship but it has also focused attention on their limitations and on some characteristics that must be taken into account when interpreting the results of experiments with gnotobiotes.