Intestinal flora of animal models of human diseases as an environmental factor.

Genetically-engineered animals are known to be useful in clarifying the functions of many genes and as animal models for human diseases. However, it has been widely reported that pathophysiology is not expressed in these animals when they become germfree or SPF animals, i.e., the pathophysiology is not the result of genes alone and a combination of gene function and intestinal flora as an environmental factor are necessary. It is important to determine the roles of each of these two factors by pathophysiological analysis. Gnotobiotic mice were produced by establishment of specified bacterial species in germfree animals to form the intestinal flora of SPF animals and they were placed in barrier facilities. Measures have been taken against infections by bacteria such as Pseudomonas aeruginosa and Enterobacter cloacae. In addition, gnotobiotic mice with a highly normal physiology are required. Analysis of the effects of each bacterial species and combinations of bacteria on in vivo functions, i.e., the cross-talk between the host and intestinal flora, is essential in the creation of better laboratory animals. Monitoring of the intestinal flora, a key factor in the colonies produced, is a topic for future research.