Colin K. Campbell

Analysis of the dermatophyte species isolated in the British Isles between 1980 and 2005 and review of worldwide dermatophyte trends over the last three decades

Infections of the skin, hair and nails by dermatophyte fungi are common in developed and developing countries alike. However, the species involved and the resulting clinical entities vary both geographically and with time. We have surveyed 15,333 dermatophytes obtained from primary isolations at the Mycology Reference Laboratory, Bristol, UK from 1980 through 2005. Several striking trends in dermatophyte prevalence were apparent over this period. The relative frequencies of isolations of Microsporum canis (cat and dog ringworm), Trichophyton verrucosum (cattle ringworm), T. mentagrophytes var. mentagrophytes (rodent ringworm) and Epidermophyton floccosum (a cause of human groin and foot infections) all decreased by 90%. Conversely, the contributions of T. tonsurans and T. violaceum (two anthropophilic scalp-infecting species) to total dermatophyte isolations increased by 1000% over the same period. Finally, T. rubrum and T. mentagrophytes var. interdigitale, the two common causes of foot infection comprised 80% of all dermatophytes isolated in 1980 and 90% of isolations in 2005. Similar trends in dermatophyte prevalence were evidenced throughout the British Isles, based on the voluntary reporting of isolations from a large number of British laboratories at 5-yearly intervals over the same period. The implications of these changing patterns of dermatophyte species, and the clinical entities they produce are discussed in the context of a review of worldwide dermatophyte isolations over the last three decades, with emphasis on the causal agents of tinea capitis.

Ultra-rapid preparation of total genomic DNA from isolates of yeast and mould using Whatman FTA filter paper technology – a reusable DNA archiving system

Conventional methods for purifying PCR-grade fungal genomic DNA typically require cell disruption (either physical or enzymatic) coupled with laborious organic extraction and precipitation stages, or expensive column-based technologies. Here we present an easy and extremely rapid method of preparing yeast and mould genomic DNAs from living cultures using Whatman FTA filter matrix technology. Aqueous suspensions of yeast cells or hyphal fragments and conidia (in the case of moulds) are applied directly (or after freeze-thawing) to dry FTA filters. Inoculated filters are then subjected to brief microwave treatment, to dry the filters and inactivate the organisms. Filter punches are removed, washed rapidly, dried and placed directly into PCR reactions. We show that this procedure inactivated all of the 38 yeast and 75 mould species tested, and generated PCR-grade DNA preparations in around 15 minutes. A total of 218 out of 226 fungal isolates tested liberated amplifiable DNA after application to FTA filters. Detection limits with yeast cultures were approximately 10 colony-forming units per punch. Moreover, we demonstrate that filter punches can be recovered after PCR, washed and used in fresh PCR reactions without detectable cross-contamination. Whatman FTA technology thus represents a cheap, ultra-rapid method of fungal genomic DNA preparation, and also potentially represents a powerful fungal DNA archiving and storage system.

Polycytella Hominis is a mutated form of Scedosporium Apiospermum

PCR amplification and sequencing of two separate regions of the nuclear ribosomal repeat region revealed that Polycytella hominis, a hyphomycete isolated from a human case of mycetoma, was genetically indistinguishable from Scedosporium apiospermum (the anamorph of Pseudallescheria boydii). These organisms also exhibited remarkably similar susceptibility profiles to common antifungal agents. P. hominis is thus likely to be a mutant of S. apiospermum showing abnormalities of sporulation, for which a possible mechanism is discussed. Polycytella hominis should thus be regarded as a synonym of Scedosporium apiospermum.

Arthroderma olidum, sp. nov. A new addition to the Trichophyton terrestre complex

In 1981, four fungal isolates from hair of the European badger (Meles meles) were examined by Dr Phyllis Stockdale at the Commonwealth Mycological Institute, Kew, and deposited in the UK National Collection of Pathogenic Fungi as an undescribed member of the Trichophyton terrestre complex. The present paper formalizes the complete description of a new ascomycete taxon, Arthroderma olidum following successful recent attempts to re-isolate the same fungus from the soil of Badger holes in South West England. Furthermore, using ribosomal RNA gene sequencing, we show that the asexual form of A. olidum is conspecific with the recently described Trichophyton eboreum1 isolated from a human skin specimen in Germany.