In vitro Nail Infection Through Several Kinds of Fungi

Park, Hyun Jeong; Cho, Baik Kee

Abstract

BACKGROUND: The techniques that are currently used to diagnose nail infections, KOH and culture, can only provide indirect evidence of a fungal cause because false-negative and falsepositive results are high. The use of histologic examination can be of help for a more accurate and specific diagnosis.
OBJECTIVE
This study was undertaken to investigate the characteristics of nail invasion and morphology in nail sections by 5 species of fungi including Trichophyton mentagrophutes var mentagrophytes, Trichophyton, rubrum, Candida albicans, Scopulariopsis brevicaulis, and Fusarium oxysporum.
METHODS
Two in vitro methods for the study of nail invasion were used. In one method, those cultured fungi were inoculated on the ventral surface of the human nail clippings (direct nail inoculation method). In the other method, invasion of nail clippings by those fungi was induced in the continuous shaking liquid media (continuous shaking liquid culture method).
RESULTS
1. In direct nail inoculation method, the gross findings are similar to those obtained in routine culture media. By 1 week, the nail fragments were totally covered by a white fungal mycelium on gross examination. 2. Non-dermatophytes were slower invader of nail tissue than dermatohytes. Invasion was quicker and more extensive in the dystrophic nail. Full thickness invasion of the normal nail fragment was observed in 46.8+/-9.8 days. But it took 13.3+/-2.6 days to invade the dystrophic nail fragment (p<0.05). 3. This model showed the morphologic differences of three groups of fungi. Deramtolphytes gernerally showed regular, straight, septate and branched hyphae, which run parallel to the nail surface; C. albicans appeared as pseudofilaments running haphazardly within the nail; S. brevicaulis and F. oxysporum appeared as irregular, thicker hyphae without any spores. 4. By using the continuous shaking liqyid culture method, T. Mentagrophytes var mentagrophytes was only successful in nail invasion.
CONCLUSION
The direct nail inoculation method is a simple method showing the dynamics of the nail invasion in vitro. Unlike to dermatolphytes, NDFF(non-dermatolphytic filamentous fungi) and Candida sp. could invade only dystrophic abnormal nail. Dermatophytes, Candida sp., and NDFF showed some differences in shape and arrangement fo the hyphae on the histopathologic sections. But they are not diagnostic to the species.