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Title: Colonization and penetration of the stratum corneum by dermatophyte fungi
Author: Al-Jabre, Salih Hamad Mohamad
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1990
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Abstract:
The colonization and penetration of stratum corneum by dermatophyte fungi were investigated employing arthrospores of three strains, two of Trichophyton mentagrophytes and one of Trichophyton interdigitale. The adherence of arthrospores to corneocytes from palm and sole and germination in suspensions of corneocytes from the same body areas were determined. The growth of arthrospores on stripped sheets of stratum corneum from different body areas, namely, sole, leg, groin, abdomen, back, cheek, forearm, and palm, was also studied. The ultrastructure of corneocyte and stratum corneum - dermatophyte relationship was investigated by scanning and transmission electronmicroscopy. Scale from cases of tinea pedis was also investigated ultrastructurally. The resistance of arthrospores to ordinary environmental and desiccated conditions in the presence and absence of corneocytes was studied and the type of dormancy expressed by arthrospores was investigated. The effect of exposing arthrospores to distilled water for 24 hr on their germination in corneocyte suspensions and on stratum corneum was studied. The possibility of using corneocytes as a model for assessing antifungal activity of drugs against dermatophytes was explored. Two phases of investigation were conducted; phase I consisted of arthrospore germination in corneocyte suspensions in the presence of antifungal drugs and phase II consisted of firstly inducing arthrospore germination in corneocyte suspensions then adding antifungal drugs. Arthrospore formation was studied under various cultural conditions; temperature of 37°C, elimination of glucose from growth media, presence of amphotericin-B in growth media and increased tension of carbon dioxide. With the exception of amphotericin-B arthrospore formation occurred and was especially abundant with carbon dioxide. Ultrastucturally, the arthrospores appeared mainly round and were surrounded by a thick wall of which the outer aspect appeared fibrillar. Disarticulated arthrospores were seen connected by fibrils likely to be remnants of the original hyphal wall. Adherence of arthrospores to corneocytes occurred and showed a time dependent increase up to 6 hr by which time arthrospores had started to germinate. The adherence of arthrospores to corneocytes was verified by scanning and transmission electronmicroscopy. A floccular material bridged the closely opposed walls of arthrospores and corneocytes. The surface of corneocytes appeared convoluted and arthrospores adhered to more than a convolution of the surface thereby conferring a firmer attachment. Germination of arthrospores in corneocyte suspensions occurred and showed also a time dependent increase up to 16 hr by which time long branched germ tubes had developed. Both corneocyte-adherent and nonadherent arthrospores had germinated and sometimes the arthrospores had multigerminated. Germ tubes adhered to corneocytes and penetrated them. Corneocytes penetrated by germ tubes appeared ragged. Growth of arthrospores on stratum corneum started by germination at 4 hr which increased with time up to 16 hr by which time long branched germ tubes had developed. By 24 hr distinct fungal microcolonies, consisting of arthrospores which had multigerminated and germ tubes which had multibranched, developed. Germ tubes penetrated transversely and through the thickness of the stratum corneum. By 7 days masses of hyphae had broken down into arthrospores but some hyphal branches and terminal segments remained aseptate. Ultrastructurally, small germ tubes were either appossed to the surface of corneocytes, attached to the margin of corneocytes, insinuated between corneocytes or appeared to be inserted in them. Growing germ tubes either extended over the surfaces of corneocytes, penetrated or appeared buried in them producing ridges. By 7 days the corneocytes appeared disintegrated. In the scale from cases of tinea pedis, fungal elements were located within the keratin and surrounded by electronlucent zones. Germination of arthrospores had not occurred on the stratum corneum in the absence of moisture or oxygen or at 45°C and 4°C. On the outer layers of stratum corneum arthrospore germination was statistically not different from inner layers. In the absence of stratum corneum arthrospore germination was minimal, 0.00-3.441.1.06 after 16 hr, and the germ tubes were short, thin and only faintly stained with Periodic acid-Schiff. Exposing the arthrospores to distilled water at 28°C for 24 hr prior to their inclusion in corneocyte suspensions or inoculation onto stratum corneum increased germination. Under conditions not suitable for germination the arthrospores expressed an exogenous type of dormancy provided that these conditions were not lethal. Conditions under which the arthrospores expressed an exogenous type of dormancy were found to be: absence of moisture or nutrient and 4°C. A condition found to be lethal was 45°C.Survival of arthrospores exposed for 6 days to ordinary environmental and desiccated conditions was greater in the presence of corneocytes than in their absence, the difference reached significant levels under environmental conditions, P values were less than 0.05 and 0.01.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.796414  DOI: Not available
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