Influence of Soil and Its Micropopulation on Pathogenic Dermatophytes in Parasitized Hair

Abstract

Researches and experiments v/ere made designed to test the influence of soil and its micro population on pathogenic dermatophytes in pathological material. For these tests mostly were used hairs infected by Trichophyton violaceum.

The results have shown that parasitized hairs deposited in moistened soil, under laboratory and natural conditions, retain their shape rather a long time, while the fungal elements in the hairs gradually lose their shape and refract light less intense until, in the end, they completely break up into a homogenous granular mass. The keratin substance of the hair' remains unaffected, the cuticle retaining its primary structure for a longer time.

The process of degradation of fungous elements does not always run its course within the same period, for it sometimes may occur that during the first few days of their stay in the soil the parasitized fungi in the hair tend to show signs of a rudimentary germination of spores without, however, reaching full saprophytic growth owing to the antagonistic action of the micro population present in the soil.

The lysis of the parasitized fungi of T. violaceum in the hair occurs on an average within 6—8 days, sometimes even sooner; the process seldom takes longer unless the temperature is low. However, the vitality of the fungus in a parasitized hair as a rule tends to disappear before the appearance of morphological changes, as shown by tests which proved negative cultures on Sabouraud’s maltose agar \with an addition of antibiotics.

Eighteen specimens of soil were used in these tests, and the results were more of less identical.

Further tests were made with the object of establishing the factors responsible for the lysis of the fungus in pathological material when brought into contact with soil. For this reason, experiments “were made to isolate the micro-organisms in parasitized hairs that were kept in soil for some time and in which the decomposition of fungi had already taken place. One series of experiments was concerned with the isolation of micro-organisms that decompose cellulose as the basic biological manifestation in soil. On a culture-medium with filter-paper (after Imšenecki) several different colonies of microorganisms were isolated, which were found to decompose the cellulose of the filter-paper fairly intensively. In their appearance and microscopic morphology, these correspond to the cellulose bacteria that have been classified by Winogradsky as belonging to the genus of cell-fascicules or cellvibrions.

Another series of tests was concerned with microorganisms that were isolated on conventional culture-media. Eight different (as yet undetermined) strains were isolated, five of which revealed a lysing action on the dermatophytes in infected hairs (one of the strains showing clear signs of symbiosis stimulating germination of the spores). The action of these isolated microorganisms was more intense in their primal substratum, viz. in soil.

The action of pure cultures of isolated microorganisms proved more intense in non-sterile than in sterilized soils, presumably due to the symbiotic action of several species of microorganisms on decomposition of fungous elements in nature.

Of considerable interest are the observations relative to control tests in sterilized soil. In the beginning, the spores remain well conserved in parasitized hairs of T. violaceum, deposited into sterilized soil (moistened with sterile water), a few days later, however, they begin to show signs of decomposition. In these instances, around the hair there appeared clusters of microorganisms which must have originated in the autochthonous saprophytic flora that was present in the pathological material before being deposited into sterilized soil.

To this effect, further tests were made in order to ascertain whether it was the chemico-physical properties of the subtratum itself that were concerned, with the latter having an effect on the decomposing of pathogenic dermatophytes in the parasitized hair in soil, or whether it was a direct biochemical function of certain microorganisms that digest the organic material of dermatophytes.

In extracts of non-sterile soil in distilled water or a physiological solution of NaCl, the dermatophytes in parasitized hairs shoved changes analogous to those in non-sterile soil alone, but such action was absent when the extract had passed through a Seitz filter. Nor were there any changes to be observed in alcohol or ether extracts.

The results of these experiments are characteristic and definite enough for the assumption to be made that the decomposing of fungal parasites is brought about under the influence of direct contact with microorganisms which, through their metabolism, are responsible for the fungilitic action on pathologic material, and that therefore we are concerned here with one of fundamental phenomena in the nature.

This is confirmed by the fact concerning the fungilitic action of the autochthonous saprophytic banal flora that is present in the pathologic material itself (on parasitized hair). For when the saprophytic flora has been destroyed by sterilization and the pathological material deposited into sterilized soil, the fungal elements in the hair remain morphologically intact, while the substratum retains to be sterile. In non-sterile soils the sterilized hairs of T. violaceum behave in the same way as fresh parasitized hairs do when deposited into soil; the decomposition of the fungus occurs a few days later.

Of a different kind is the mechanism of action on a parasitized hair of the keratinophillic saprophytic micro population of soil (e. g. M. gypseum) which by means of proteolytic enzymes decomposes not the parasites in the hair but only the keratinous substance — a matter which will be dealt with in another article.

As regards the question of saprophytic life of pathogenic dermatophytes in nature, i. e. in soil, it can hardly be assumed, according to the results recorded, that pathogenic dermatophytes like T. Violaceum — which have reached almost full parasitic and genetically determined specificity for the keratinous substrate of human organism might also possess the ability of independent saprophytic life in soil.

The results recorded above, which clearly show that the micro-population of soil and the microorganisms of saprophytic flora in pathological material are able to decompose the dermatophytes, may well serve as a basis for the solution of a number of problems relating to epidemiology and pathogenesis of human and animal infection with pathogenic dermatophytes.