MALDI-TOF mass spectrometry - a rapid method for the identification of dermatophyte species.
ABSTRACT Altogether 285 dermatophyte isolates of 21 different species - including both Trichophyton rubrum and T. interdigitale, but also eight additional Trichophyton species, Microsporum canis and seven other Microsporum species, as well as Epidermophyton floccosum and Arthroderma spp. - were analyzed using Matrix Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and the AnagnosTec 'SARAMIS' (Spectral Archiving and Microbial Identification System) software. In addition, sequence analysis of the internal transcribed spacer (ITS) of the ribosomal DNA was performed for a high number of the tested strains. Sufficient agreement was found between the results obtained with standard identification methods and those with the MALDI-TOF MS for species identification of dermatophytes. A mass spectra database was constructed which contained the species identifications of all 285 isolates. The results were confirmed for 164 of the isolates by sequence analysis of the internal transcribed spacer (ITS) of the ribosomal DNA. Statistical analysis of all 285 dermatophyte strains showed that conventional identification matched the results of MALDI-TOF MS for 78.2% of the isolates tested. In the case of the 164 isolates for which the identifications were confirmed by PCR, the results of their conventional diagnosis and MALDI-TOF MS were in agreement for only 68.9 % (113 of 164 strains) of the test isolates. In contrast, there was agreement of 99.3 % or 98.8 % in the identifications obtained with PCR and MALDI-TOF MS techniques (283/285 or 162/164). The two exceptions were isolates that proved to be T. violaceum which could not be identified by the MALDI-TOF MS technique. In conclusion, the MALDI-TOF mass spectroscopy represents a fast and very specific method for species differentiation of dermatophytes grown in culture.
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ABSTRACT: Infections of the finger and the toe nails are most frequently caused by fungi, primarily dermatophytes. Causative agents of tinea unguium are mostly anthropophilic dermatophytes. Both in Germany, and worldwide, Trichophyton rubrum represents the main important causative agent of onychomycoses. Yeasts are isolated from fungal nail infections, both paronychia and onychomycosis far more often than generally expected. This can represent either saprophytic colonization as well as acute or chronic infection of the nail organ. The main yeasts causing nail infections are Candida parapsilosis, and Candida guilliermondii; Candida albicans is only in third place. Onychomycosis due to molds, or so called non-dermatophyte molds (NDM), are being increasingly detected. Molds as cause of an onychomycosis are considered as emerging pathogens. Fusarium species are the most common cause of NDM onychomycosis; however, rare molds like Onychocola canadensis may be found. Bacterial infections of the nails are caused by gram negative bacteria, usually Pseudomonas aeruginosa (recognizable because of green or black coloration of the nails) but also Klebsiella spp. and gram positive bacteria like Staphylococcus aureus. Treatment of onychomycosis includes application of topical antifungal agents (amorolfine, ciclopirox). If more than 50 % of the nail plate is affected or if more than three out of ten nails are affected by the fungal infection, oral treatment using terbinafine (in case of dermatophyte infection), fluconazole (for yeast infections), or alternatively itraconazole are recommended. Bacterial infections are treated topically with antiseptic agents (octenidine), and in some cases with topical antibiotics (nadifloxacin, gentamicin). Pseudomonas infections of the nail organ are treated by ciprofloxacin; other bacteria are treated according to the results of culture and sensitivity testing.Der Hautarzt 04/2014; 65(4):337-48. · 0.50 Impact Factor
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ABSTRACT: Dermatomycoses are caused most commonly by dermatophytes. The anthropophilic dermatophyte Trichophyton rubrum is still the most frequent causative agent worldwide. Keratinolytic enzymes, e.g. hydrolases and keratinases, are important virulence factors of T. rubrum. Recently, the cysteine dioxygenase was found as new virulence factor. Predisposing host factors play a similarly important role for the development of dermatophytosis of the skin and nails. Chronic venous insufficiency, diabetes mellitus, disorders of cellular immunity, and genetic predisposition should be considered as risk factors for onychomycosis. A new alarming trend is the increasing number of cases of onychomycosis - mostly due to T. rubrum - in infancy. In Germany, tinea capitis is mostly caused by zoophilic dermatophytes, in particular Microsporum canis. New zoophilic fungi, primarily Trichophyton species of Arthroderma benhamiae, should be taken into differential diagnostic considerations of tinea capitis, tinea faciei, and tinea corporis. Source of infection are small household pets, particularly rodents, like guinea pigs. Anthropophilic dermatophytes may be introduced by families which immigrate from Africa or Asia to Europe. The anthropophilic dermatophytes T. violaceum, T. tonsurans (infections occurring in fighting sports clubs as "tinea gladiatorum capitis et corporis") and M. audouinii are causing outbreaks of small epidemics of tinea corporis and tinea capitis in kindergartens and schools. Superficial infections of the skin and mucous membranes due to yeasts are caused by Candida species. Also common are infections due to the lipophilic yeast fungus Malassezia. Today, within the genus Malassezia more than 10 different species are known. Malassezia globosa seems to play the crucial role in pityriasis versicolor. Molds (also designated non-dermatophyte molds, NDM) are increasingly found as causative agents in onychomycosis. Besides Scopulariopsis brevicaulis, several species of Fusarium and Aspergillus are found.Journal der Deutschen Dermatologischen Gesellschaft 02/2014; · 1.40 Impact Factor
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ABSTRACT: A genomic in situ hybridization (GISH)-based method for dermatophyte identification has been developed. Using specific GISH probes, discrimination between Trichophyton interdigitale, Trichophyton rubrum and Microsporum canis has been conducted. Moreover, GISH has been found particularly helpful when proper dermatophyte identification was difficult due to ambiguous PCR-RFLP patterns.Journal of Microbiological Methods 02/2014; · 2.16 Impact Factor