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Immunological studies on dermatophytes. 3. Further analyses of the reactivities of neutral polysaccharides with rabbit antisera to Microsporum quinckeanum, Trichophyton schoenleinii, Trichophyton rubrum, Trichophyton interdigitale, and Trichophyton granulosum.

The serological reactivities of polysaccharides isolated from five species of dermatophytes, Microsporum quinckeanum, Trichophyton granulosum, T. interdigitale, T. rubrum, and T. schoenleinii, with rabbit antisera to these species were studied qualitatively by precipitation in gel and quantitatively by complement-fixation analyses. Significant differences in the serological reactivities of the galactomannans I were detected with antisera to T. schoenleinii and T. interdigitale. The differences appeared to be related to the specificity of these antisera for the galactofuranose residues in the polysaccharides. Antisera to M. quinckeanum, T. granulosum, or T. rubrum did not detect differences between the galactomannans I. The serological reactivities of the galactomannans II were different with each of the five antisera. The reactivities of the glucans could be correlated with the amount of alpha 1 --> 6 linked glucopyranose residues when antisera to T. schoenleinii and M. quinckeanum were used.

Animals↗

Immunological studies on dermatophytes. IV. Chemical structures and serological reactivities of polysaccharides from Microsporum praecox, Trichophyton ferrugineum, Trichophyton sabouraudii, and Trichophyton tonsurans.

The chemical structures and serological specificities of polysaccharides isolated from four species of dermatophytes, Microsporum praecox, Trichophyton ferrugineum, T. sabouraudii, and T. tonsurans, were investigated. Each of these species yielded a mixture of crude polysaccharides which could be separated into three water-soluble, neutral polysaccharides free of nitrogen. These were grouped as galactomannan I, galactomannan II, and glucan. The galactomannans I were quite similar in chemical structure. When measured by complement fixation, their serological cross-reactivities were similar with rabbit antisera to each of these species except T. sabouraudii. The differences in their relative reactivities with this antiserum could be correlated with differences in structure and specificity of this antiserum for galactofuranose end groups. The galactomannans II differed both in chemical structure and in their serological reactivities with antisera to each of these species. The galactomannan II from T. ferrugineum differed most in chemical structure and was the least reactive serologically. The glucans also differed in both structure and serological reactivities.

Antigens↗

Isoelectric focusing applied to taxonomic differentiation of the Trichophyton mentagrophytes complex and the related Trichophyton interdigitale.

Somatic extracts from dermatophytes of the Trichophyton mentagrophytes complex and of Trichophyton interdigitale grown on trypticase soy broth were prepared for analytical isoelectric focusing in thin layer polyacrylamide gels over the pH range 4-6.5. A total of 44 strains were studied: 8 Arthroderma benhamiae (4 Americano-European and 4 African races), 4 Arthroderma vanbreuseghemii, 6 Trichophyton mentagrophytes and 26 Trichophyton interdigitale. Laser densitometric analysis revealed two outstanding clusters of profiles. The first one matched with the Arthroderma vanbreuseghemii profile and gathered all the Trichophyton interdigitale strains studied and 4 Trichophyton mentagrophytes. The second one corresponded to the Arthroderma benhamiae profile and gathered 2 Trichophyton mentagrophytes. This isoelectric focusing analysis suggests on one hand that Trichophyton interdigitale might be the anamorph species corresponding to the teleomorph Arthroderma vanbreuseghemii, and on the other hand that Trichophyton mentagrophytes might correspond to two teleomorph species, either Arthroderma vanbreuseghemii or Arthroderma benhamiae.

Animals↗

Evaluation of trichophyton agars for identification of Trichophyton soudanense.

Studies of three monoconidial subcultures of each of 10 isolates of Trichophyton soudanense on seven trichophyton agars revealed variations in growth among the subcultures of each isolate and among the isolates themselves on six agars. In contrast, greater consistency and generally good to excellent growth were noted with all isolates on trichophyton agar 1 (basal medium). These results are contrary to those found with other Trichophyton species and suggest that growth on the trichophyton agars is not a suitable test for the identification of T. soudanense.

Agar↗

Establishing a method of inoculum preparation for susceptibility testing of Trichophyton rubrum and Trichophyton mentagrophytes.

A total of 92 clinical isolates of dermatophytes (52 of Trichophyton rubrum and 40 of Trichophyton mentagrophytes) were selected for testing with six antifungal drugs (terbinafine, griseofulvin, clotrimazole, miconazole, isoconazole, and fluconazole) and two pairs of drug combinations (ketoconazole-cyclopiroxolamine and itraconazole-cyclopiroxolamine). Two methods of inoculum preparation for susceptibility testing were evaluated that used (i) inocula consisting only of microconidia of dermatophytes filtered in Whatman filter model 40 and (ii) unfiltered inocula consisting of hyphae and microconidia. We followed the recommendations of approved document M38-A of CLSI (formerly NCCLS) with some adaptations, including an incubation period of 7 days and an incubation temperature of 28 degrees C. Reference strains of Candida parapsilosis, Candida krusei, Trichophyton rubrum, and Trichophyton mentagrophytes were included as quality-control strains. MICs were consistently higher (usually 1 to 2 dilutions for drugs tested individually) when nonfiltered inocula were tested (P < 0.01) except for terbinafine. Larger MICs were seen when testing drugs with nonfiltered inocula. The curves of drug interaction were used to analyze the reproducibility of the test, and it was shown that high levels of reproducibility were achieved using the methodology that included the filtration step. The standardization of methodologies is the first step to yield reliability of susceptibility testing and to proceed with clinical laboratory studies to correlate MICs with clinical outcomes.

Antifungal Agents↗

Antigenic relationship between downy and granular forms of Trichophyton mentagrophytes and Trichophyton rubrum.

One strain each of granular and downy varieties of Trichophyton mentagrophytes and two strains each of granular and floccose colonial types Trichophyton rubrum were used for preparation of antigens. The antigens were analyzed by double diffusion against homologous and heterologous antisera raised in rabbits. A total of 17 distinct antigens were recognized, seven of which were common to two dermatophytes. Granular and downy varieties of the Trichophyton species produced on additional line of nonidentity. Cross reactions failed to establish any relationship between similar morphologic forms of different dermatophytes. One isolate of T. rubrum, which was originally the floccose culture type but changed into the granular form after artificial infection, showed an antigenic relationship to the floccose culture.

Antigens, Fungal↗

Morphological evidences for onion-induced growth inhibition of Trichophyton rubrum and Trichophyton mentagrophytes.

The antifungal activity of onion (Allium cepa L.) on two important dermatophytes, Trichophyton rubrum and Trichophyton mentagrophytes, with special reference to morphological aspects was studied. Growth of both fungi was found to be strongly inhibited by aqueous onion extract (AOE) as a dose-dependent manner. The extract showed fungicidal effect for both fungi at concentrations >3.12% (v/v). The fungus T. mentagrophytes was more affected by the onion as compared to T. rubrum at all concentrations used. Morphological effects of onion exposure were examined in correlation with fungal growth. Corresponding to the growth inhibition, light and electron microscopy observations revealed morphological anomalies in hyphal compartments. The results demonstrated that AOE targets the cell membrane of the fungi as breaking down of both inner and outer membranes with consequent extrution of materials into the surrounding medium. Cytoplasmic membranes and other membranous structures of organelles, such as nuclei and mitochondria, were also disrupted. In correlation to the fungal growth, morphological alterations occurred to a less content for T. rubrum compared with T. mentagrophytes. The hyphae of T. rubrum were found to be mainly affected by converting to resistant forms, i.e., chlamidospores as a consequence of phenotype switching response to AOE. Plasmolysis accompanied by an almost complete depletion and disorganization of cytoplasmic structures were found to be the final event which led to cell death. Ultrastructural evidences obtained from this study strongly support that morphological changes of T. rubrum and T. mentagrophytes caused by AOE are associated with its fungistatic and fungicidal activities. With respect to the morphological results and the preliminary data on fungal biochemistry, a mechanism of action by interacting of AOE with thiol (-SH) groups present in essential compartments of the fungal cells was postulated.

Antifungal Agents↗

NMR study of the galactomannans of Trichophyton mentagrophytes and Trichophyton rubrum.

Around 90% of chronic dermatophyte infections are caused by the fungi Trichophyton mentagrophytes and Trichophyton rubrum. One of the causes of the chronic infection resides in the immunosuppressive effects of the cell-wall components of these organisms. Therefore we have attempted to identify the chemical structure of galactomannan, one of the major cell-wall components. The cell-wall polysaccharides secreted by T. mentagrophytes and T. rubrum were isolated from the culture medium and fractionated into three subfractions by DEAE-Sephadex chromatography. Analysis of each subfraction by NMR indicated that there are two kinds of polysaccharides present, i.e. mannan and galactomannan. The mannan has a linear backbone consisting of alpha1,6-linked mannose units, with alpha1,2-linked mannose units as side chains. The core mannan moiety of the galactomannan was analysed by a sequential NMR assignment method after removing the galactofuranose units by acid treatment. The result indicates that the mannan moiety has a linear repeating structure of alpha1,2-linked mannotetraose units connected by an alpha1,6 linkage. The H-1 signals of the two intermediary alpha1, 2-linked mannoses of the tetraose unit showed a significant upfield shift (Deltadelta=0.05-0.08 p.p.m.), due to the steric effect of an alpha1,6-linked mannose unit. The attachment point of the galactofuranose units was determined at C-3 of the core mannan by the assignment of the downfield-shifted 13C signals of the galactomannan compared with those of the acid-modified product. In these galactomannans there were no polygalactofuranosyl chains which have been found in Penicillium charlesii and Aspergillus fumigatus.

Carbohydrate Conformation↗

Case Reports. Tinea capitis due to Trichophyton soudanense and Trichophyton schoenleinii.

Four cases of tinea capitis, two due to Trichophyton soudanense in Italian children who had had contact with Africans, and two due to Trichophyton schoenleinii in an African and an Italian child, respectively, are reported. Infections caused by anthropophilic dermatophytes are rare in Italy and are related to immigration. The most frequent agents of tinea capitis in Italy are zoophilic dermatophytes.

Child↗

Tinea due to Trichophyton violaceum and Trichophyton soudanense in Hamilton, New Zealand.

Between 1994 and 2000, 63 isolates of Trichophyton violaceum and five isolates of Trichophyton soudanense were recorded in both private and public laboratories in Hamilton, New Zealand. A retrospective analysis of medical records of these patients was performed. From these 68 isolates, 58 were recovered from scalp specimens and 10 were recovered from other body sites. There were 51 patients with tinea capitis and nine patients in the tinea corporis group. Six patients had more than one isolate reported at different laboratories. As expected, the vast majority of scalp infections (46/51 patients) were children, with an overall median age of 6 years (range 8 months to 66 years). All patients in the tinea capitis group, except one, were refugee immigrants from East Africa. Of nine patients in the tinea corporis group, six were refugees from the same area. For tinea capitis, 31 patients received systemic antifungal therapy for at least 4 weeks, with either terbinafine (21 patients), griseofulvin (four patients) or itraconazole (six patients). Five patients received topical antifungal creams or shampoo as monotherapy only. The remainder (15 patients) received either no therapy or no record was available. The emergence of these two pathogens as causes of tinea capitis in Hamilton closely correlates with the increasing number of refugees from endemic areas. There is a high rate of person-to-person transmission with these anthropophilic organisms in children as well as adults in the family. Transmission of infection to the local population has been observed, but there is no evidence to date to suggest that these organisms have become endemic in the local population.

Adolescent↗