Species identification and strain differentiation of dermatophyte fungi by analysis of ribosomal-DNA intergenic spacer regions.
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Restriction fragment length polymorphisms (RFLPs) identified in the ribosomal-DNA (rDNA) repeat were used for molecular strain differentiation of the dermatophyte fungus Trichophyton rubrum. The polymorphisms were detected by hybridization of EcoRI-digested T. rubrum genomic DNAs with a probe amplified from the small-subunit (18S) rDNA and adjacent internal transcribed spacer (ITS) regions. The rDNA RFLPs mapped to the nontranscribed spacer (NTS) region of the rDNA repeat and appeared similar to those caused by short repetitive sequences in the intergenic spacers of other fungi. Fourteen individual RFLP patterns (DNA types A to N) were recognized among 50 random clinical isolates of T. rubrum. A majority of strains (19 of 50 [38%]) were characterized by one RFLP pattern (DNA type A), and four types (DNA types A to D) accounted for 78% (39 of 50) of all strains. The remaining types (DNA types E to N) were represented by one or two isolates only. A rapid and simple method was also developed for molecular species identification of dermatophyte fungi. The contiguous ITS and 5.8S rDNA regions were amplified from 17 common dermatophyte species by using the universal primers ITS 1 and ITS 4. Digestion of the amplified ITS products with the restriction endonuclease MvaI produced unique and easily identifiable fragment patterns for a majority of species. However, some closely related taxon pairs, such as T. rubrum-T. soudanense and T. quinkeanum-T. schoenlenii could not be distinguished. We conclude that RFLP analysis of the NTS and ITS intergenic regions of the rDNA repeat is a valuable technique both for molecular strain differentiation of T. rubrum and for species identification of common dermatophyte fungi. (+info)
The antifungal activity of mupirocin.
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The antibacterial agent mupirocin (pseudomonic acid A) is used as a topical agent in the treatment of superficial infections by Gram-positive bacteria, particularly Staphylococcus aureus. However, we demonstrate here that the compound also inhibits the growth of a number of pathogenic fungi in vitro, including a range of dermatophytes and Pityrosporum spp. It inhibited the incorporation of amino acids and precursors of RNA, but not that of acetate, by Trichophyton mentagrophytes. It also inhibited the isoleucyl-tRNA synthetase from Candida albicans, indicating a mechanism of action similar to that in bacteria. When administered topically, mupirocin was efficacious in a T. mentagrophytes ringworm model in guinea pigs. These results suggest that mupirocin could have clinical utility for superficial infections caused by dermatophytes. (+info)
Molecular markers reveal exclusively clonal reproduction in Trichophyton rubrum.
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Genotypic variability among 96 Trichophyton rubrum strains which displayed different colony morphologies and were collected from four continents was investigated. Twelve markers representing 57 loci were analyzed by PCR fingerprinting, amplified fragment length polymorphism, and random amplified monomorphic DNA markers. Interestingly, none of the methods used revealed any DNA polymorphism, indicating a strictly clonal mode of reproduction and a strong adaptation to human skin. (+info)
Dermatophytosis: association between ABO blood groups and reactivity to the trichophytin.
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The authors investigated the relationship between dermatophytosis and ABO blood groups through blood typing, identification of isolated dermatophytes and specific cellular immune response of 40 individuals carriers of this mycosis. They verified that the fungus Trichophyton rubrum, isolated from 54.5% of the patients, was more frequent in individuals belonging to blood group A. The cellular immune response, evaluated through the trichophytin antigen, was positive in 25% of the studied patients; the presence of immediate reactions (30 minutes) was verified in 35%. The blood group distribution among patients with dermatophytosis and control groups was, respectively: 47.5% X 36% in group A, 40% X 50% in group O, 12. 5% X 11% in group B. Even though the authors have found a higher number of patients belonging to blood group A infected by T. rubrum, these results suggest that there is no statistical evidence that these individuals are more susceptible to dermatophytosis. (+info)
Dermatophytosis caused by Trichophyton raubitschekii. Report of the first case in Sao Paulo, Brazil.
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The authors report the first case of dermatophytosis caused by Trichophyton raubitschekii in a patient from the State of Sao Paulo with Tinea corporis lesions localized on the buttocks. Culture on Sabouraud-agar with cycloheximide permitted the isolation and identification of the fungus, and the diagnosis was confirmed by Dr. Lynne Sigler, University of Alberta, Canada. Systemic treatment with fluconazole, 150 mg/week for 4 weeks, in combination with topical treatment with isoconazole initially yielded favorable results, with recurrence of the lesions after the medication was discontinued. This is the fifth case of this dermatophytosis published in the Brazilian medical literature. (+info)
Diagnosing dermatomycosis in general practice.
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BACKGROUND: Diagnosing dermatomycosis from a clinical image is not always easy. Microscopy of a potassium hydroxide preparation (KOH-test) and culturing are seldomly used in general practice. Cyanoacrylate surface skin scraping (CSSS) is a new diagnostic tool that may be useful and simple. OBJECTIVES: We aimed to investigate the diagnostic value of signs and symptoms, the KOH-test and the CSSS, in patients with erythematosquamous skin lesions, using the culture as the gold standard. Our goal is to formulate an optimal algorithm for the diagnosis of mycosis, based on one or more of these tests and including both optimal accuracy and costs. METHODS: Scales from 148 consecutive general practice patients were tested using a KOH-test, CSSS and culture. Clinical data were collected using a questionnaire. RESULTS: Twenty-six (18%) positive fungal cultures were identified. The sensitivity of the clinical diagnosis was 81% and its specificity 45%; for the KOH-test, these figures were 12 and 93% respectively; and for the CSSS, 62 and 88%, respectively. The positive predictive value of the clinical diagnosis was 24% and the negative predictive value 92%; for the KOH-test these figures were 25 and 83%, respectively, and for the CSSS, 52 and 92%, respectively. Determining CSSS in all patients proved to be the most accurate policy (accuracy = 83%). The likelihood ratio of CSSS in all patients was 5.17 for a positive test result and 0.43 for a negative test result. An approach in which CSSS is obtained in only those patients whom the physician considers by clinical examination to have dermatomycosis, with no testing in other patients, results in positive and negative likelihood ratios of 4.69 and 0.56, respectively. Such a policy would result in an overall sensitivity of 50%, a specificity of 89%, a positive predictive value of 50% and a negative predictive value of 89%. DISCUSSION: The clinical picture of dermatomycosis is not very reliable. The combination of a clinical judgement if this is negative and an additional CSSS in the case of a positive clinical judgement provides us with the best cost-benefit ratio, if both diagnostic accuracy and logistic considerations are taken into consideration. (+info)
Fluorometric assessment of In vitro antidermatophytic activities of antimycotics based on their keratin-penetrating power.
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Keratin particles impregnated with amorolfine or clotrimazole in serial doubling dilutions (64 to 0.125 microg/ml) were used to evaluate the activities of these agents against 20 isolates each of Trichophyton mentagrophytes and Trichophyton rubrum in a yeast carbon broth medium incorporating Alamar Blue dye. The proposed MIC with keratin impregnation (MIC(K)) is defined as the lowest concentration of an agent used to impregnate keratin particles that effects a fluorescence-based fungal growth quotient of 0.05 or less. The conventional colorimetric and visual MICs of amorolfine for the dermatophytes, 64 microg/ml] and 64 microg/ml [range, 16 to >64 microg], respectively) may indicate the strong in vivo antidermatophytic activity of amorolfine as a topical agent. The new antidermatophytic susceptibility testing procedure has potential clinical utility for the in vitro screening of agents for use in the topical treatment of superficial mycoses. (+info)
Molecular taxonomy of the Trichophyton rubrum complex.
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The validity of taxa around Trichophyton rubrum was evaluated by a combination of phenetic and molecular methods. Morphological and physiological features were compared to results of sequencing of the internal transcribed spacer region of the ribosomal operon, PCR fingerprinting, and amplified fragment length polymorphism analysis. The 15 species and varieties investigated (Trichophyton circonvolutum, Trichophyton fischeri, Trichophyton fluviomuniense, Trichophyton glabrum, Trichophyton gourvilii, Trichophyton kanei, Trichophyton kuryangei, Trichophyton megninii, Trichophyton pedis, Trichophyton raubitschekii, Trichophyton rodhaini, Trichophyton rubrum var. nigricans, Trichophyton soudanense, Trichophyton violaceum var. indicum, and Trichophyton yaoundei) were reclassified or synonymized as T. rubrum or T. violaceum. (+info)