The medical treatment for the microbial infectious disease is one of the great tasks even in these days in which a large number of antimicrobial drugs have appeared. One of the causes of such a situation is the fact that the sensitivity of the microorganism to the antimicrobial agent always changes due to some affairs such as the acquisition of resistance. Another cause is the fact that certain microorganisms, which are not exterminated by the antimicrobial agent, still exist. As for the causes as described above, the representative cases of the latter involve fungi which cause the dermatophytosis. In the case of the latter, the cause of the almost unsuccessful extermination resides in the fact that there is no evaluation system which makes it possible to screen an agent that is effective upon actual administration to a living body.
The reason, why there is no effective screening system for the antifungal agent as described above, includes the following fact. Usually, the screening for the antifungal agent involves the in vitro screening in which the influence exerted on the growth of fungi is observed on a medium, and the in vivo screening in which an agent is administered to an animal to be infected in vivo, a segment or fragment of a biological tissue therefrom is transplanted to a medium, and the viable cell number of fungi proliferated thereby is counted to estimate the number of fungi surviving in the biological tissue. It is assumed that the in vitro screening is indicative of the antifungal activity of the agent, while the in vivo screening is representative of the effect based on those ranging to the absorption and metabolism characteristics of the living body. However, in the case of the in vivo screening for the antifungal agent or the like, the agent remains at the administration site, and the growth of fungi is inhibited thereby. As a result, the number is counted as if the viable cell number is decreased, in which no appropriate screening is performed for the agent. Any means, which inactivates the agent remaining as described above, has not been known yet until the present time. That is, although it is demanded to realize a means for inactivating the agent remaining in the tissue in order to measure a correct viable cell number in the tissue, such a means has not been obtained yet. Therefore, it is affirmed that this fact impedes the development of effective antifungal agents for the skin.