Trichophyton Mentagrophytes Strains Research Articles

Soil dermatophytes in Madras, India, in relation to human ringworm.

A total of 269 soil samples collected from different habitats in Madras, India, were screened for the presence of dermatophytes by the hair-baiting technique. Three strains of Trichophyton mentagrophytes and 16 strains of Microsporum gypseum complex were isolated. These strains were subjected to the mating experiment. 2/3 soil isolates of Trichophyton mentagrophytes belonged to Arthroderma vanbreuseghemii (+) mating type, and 1/3 was Arthroderma vanbreuseghemii (-) mating type. Similarly 6/70 clinical strains of Trichophyton mentagrophytes isolated in our previous study also belonged to Arthroderma vanbreuseghemii (+) mating type. These 6 strains were isolated from severe cases of tinea capitis in children belonging to rural Madras. The teleomorphic and mating type homology between the clinical and soil isolates of T. mentagrophytes suggest that soil may act as reservoir for these organisms. The incompatible clinical strains of T. mentagrophytes var. interdigitale and A. vanbreuseghemii showed DNA homology, thereby establishing the epidemiologic link which supports the above findings.

Results of German multicenter study of antimicrobial susceptibilities of Trichophyton rubrum and Trichophyton mentagrophytes strains causing tinea unguium. German Collaborative Dermatophyte Drug Susceptibility Study Group.

Thirty-two strains of Trichophyton rubrum and 16 strains of Trichophyton mentagrophytes isolated from patients with tinea unguium in various parts of Germany were subjected to a microdilution test with six systemic or topical antimycotic agents. Apart from griseofulvin, there were no species-specific differences between the two species. Terbinafine was the most active antimycotic agent, with a MIC not exceeding 0.05 micrograms/ml.

Adherence of arthroconidia and germlings of anthropophilic and zoophilic varieties of Trichophyton mentagrophytes to human corneocytes as an early event in the pathogenesis of dermatophytosis

The association (adherence) between human corneocytes and arthroconidia of Trichophyton mentagrophytes strains 121 and 126, and T. interdigitale strain 4 was studied in vitro. Adherence of arthroconidia to corneocytes from either the palm and sole occurred and increased with time up to 6 h, by which time germination of arthroconidia had started. Significant differences were seen between the T. mentagrophytes strains and T. interdigitale in their adherence to corneocytes from the palm. When adherence values for plantar corneocytes were compared, significant differences were found between T. mentagrophytes and T. interdigitale. Not all corneocytes from either site had adherent arthroconidia, although there was a time-dependent increase in the numbers of corneocytes with adherent fungal cells. By scanning and transmission electron microscopy it was seen that there was a loose association between arthroconidia and corneocytes with no apparent damage to the corneocyte membrane. Adherence of germlings of T. interdigitale to corneocytes from the palm appeared to be mediated by germling outer cell wall fibrils. Hyphal branches and secondary germlings were observed to enhance the attachment of the parent hypha to adjacent corneocytes.

Purified trichophytin: lymphocyte reactivity in vitro and trichophytin-induced suppression

Three trichophytin preparations from different strains of Trichophyton mentagrophytes were produced according to the ethylene glycol method and assessed for their lymphocyte stimulation activity in vitro (LST). These trichophytin preparations showed significant variations in their effects on cord lymphocytes reactivity. The preparations also varied in their stimulation of lymphocytes from patients with dermatophytosis. Conclusions could be drawn about the immunological specificity, sensitivity and lymphocyte toxicity, which is important for the standardization of antigens. Furthermore, it was demonstrated that trichophytin-preincubated lymphocytes mediated a suppression of lymphocyte reactivity to this antigen.

Variability of biochemical characteristics in strains of Trichophyton mentagrophytes.

The characteristics of 23 strains of Trichophyton mentagrophytes isolated from clinical samples, were studied. Sabouraud agar was the most adequate medium to inhance at their utmost the different taxonomical features. Variability of enzymatic reactions in strains of T. mentagrophytes was observed.

High‐performance liquid chromatographic identification of beta‐lactam antibiotics produced by dermatophytes

Thirteen of 48 dermatophyte isolates were found by bioassay to produce beta-lactam antibiotics and seven produced other antibiotics. Estimation and detection of specific beta-lactams in culture broths by derivatization and HPLC was only possible following concentration and extraction procedures. Analysis of the concentrated broths demonstrated the production of penicillin X and penicillin G by two Trichophyton mentagrophytes strains and by one Microsporum canis strain; one further T. mentagrophytes strain produced only penicillin X. Additions of the beta-lactam side-chain precursors, phenylacetic acid and phenoxyacetic acid, to fermentation media failed to increase the antibiotic titres.

Production of a penicillin-like antibiotic by Trichophyton mentagrophytes on an agar-based medium containing skin keratin as the major nutrient.

A culture medium composed of powdered human plantar callus, synthetic sweat and agar, was used to study the synthesis of a penicillin‐like antibiotic by a strain of Trichophyton mentagrophytes grown in vitro. Series of 5 mm agar plug samples, taken radially across single colonies of the dermatophyte, were bioassayed for antibiotic, so that a profile of antibiotic concentration could be prepared. It was found that in colonies of 11 d and older, grown at 33°, antibiotic concentration was highest in the area of the colony edge.

Interactions of Trichophyton mentagrophytes and Micrococci on Skin Culture

Scanning electron microscopy was used to search for local or limited synthesis of antibiotics by a strain of Trichophyton mentagrophytes. Micrococcus luteus, which was susceptible to penicillin and to the dermatophyte when both were cultured on agar media, displayed morphological alterations of flattened walls, invagination, enlargement, and collapse in skin cultures with the fungus. Penicillinase did not neutralize these effects. A control strain of Staphylococcus spp with poor sensitivity to penicillin was resistant to the dermatophyte in all test systems. T. mentagrophytes showed positive tropism to the bacteria. Regional variation in fungal germination and antibiotic production, the limited yield of antibiotics, and the pattern of dermatophyte growth and alteration of bacterial morphology demonstrated the significant influence of microenvironment on antibiosis.

Single ascospore strains from the mating between Trichophyton mentagrophytes var. Erinacei and Arthroderma benhamiae

Eighteen single ascospore strains were isolated from the fertile mating of a strain of Trichophyton mentagrophytes (Robin) Blanchard var. erinacei ( Smith & Marples, 1963 ) with a strain of the African race of Arthroderma benhamiae ( Ajello & Cheng, 1967) . This mating gave birth to various types of conidial varieties. The morphology, the urease negative activity, the + mating type and the sexual degeneration that characterize T. mentagrophytes var. erinacei were transmitted to F 1 single ascospore strains and these characters are presumably genetically independent or only weakly linked. The hypothesis of sexual degeneration of T. mentagrophytes var. erinacei is reconfirmed. Though the variety erinacei is always of + mating type and has no urease activity, varieties ‘ erinacei ’ of + or — mating type and those with or without urease activity were artificially produced.

Experimental Human Trichophyton Mentagrophytes Infections

Inflammatory dermatophytosis was induced on the ankles, thighs, or forearms of 40 men using purified spore suspensions of a granular strain of Trichophyton mentagrophytes . Standard reproducible infections resulted from the application of a quantitated dose of spores to a measured skin area followed by continuous occlusion with a plastic patch for 4 days. Alternate methods of inducing infections included the use of infected skin scales as a source of spores and the substitution of damp clothing for the occlusive patch. The injections healed spontaneously within 90 days of onset. None spread to other body areas or to other persons. Details are provided on the methods of preparing purified spare preparations, quantifying inocula, and applying ucclusive patches.

Inhibition of pleomorphism by protein and ribonucleic acid inhibitors.

The granular strain of Trichophyton mentagrophytes (M12-4) was grown in the presence of specific inhibitors of protein, deoxyribonucleic acid (DNA), and ribonucleic acid (RNA) synthesis. Those inhibitors which block protein and RNA synthesis inhibit mutant pleomorphic patch formation. Inhibitors of DNA synthesis had no effect on the visible expression of the mutant patches. Data presented suggest that initiation of the pleomorphic patch is not inhibited, but rather that mycelial growth is blocked.

Tinea corporis caused by trichophyton mentagrophytes var. Granulosum

A small outbreak of human ringworm caused byTrichophyton mentagrophytes var.granulosum is described. The clinical morphology of some of the inflammatory lesions was more suggestive of nummular eczema or psoriasis than of tinea corporis. The isolation of a granular strain ofTrichophyton mentagrophytes indicated an animal source of these infections. The same organism was isolated from a pet white rat which apparently transmitted the disease.

EFFECT OF CARBON AND NITROGEN NUTRITION ON PLEOMORPHISM IN TRICHOPHYTON MENTAGROPHYTES

Pleomorphism in granular strains of Trichophyton mentagrophytes can be increased or decreased by modifying the nutritional environment. The presence of one of several carbohydrates is necessary and may be the controlling nutritional parameter determining whether or not mutant pleomorphic patches appear, although concentration of the nitrogen source is also important in the pleomorphic response. None of the non‐carbohydrate carbon‐containing compounds tested supported pleomorphism. The activity of any one compound, carbon or nitrogen, appears to be unrelated to the dry weight attainable in the presence of that compound; although a certain level of growth is necessary, it is not a sufficient requisite for pleomorphism. Data presented here give no clue as to the specific grouping or configuration of the carbohydrate which might be required for development of the pleomorphic patch. Some strains develop mutant patches readily when grown at 36 C on a medium containing a suitable source of carbohydrate and nitrogen. Other strains form patches on a more restricted range of these compounds; a few strains show no pleomorphic activity.

Effect of Carbon and Nitrogen Nutrition on Pleomorphism in Trichophyton mentagrophytes

Pleomorphism in granular strains of Trichophyton mentagrophytes can be increased or decreased by modifying the nutritional environment. The presence of one of several carbohydrates is necessary and may be the controlling nutritional parameter determining whether or not mutant pleomorphic patches appear, although concentration of the nitrogen source is also important in the pleomorphic response. None of the non-carbohydrate carbon-containing compounds tested supported pleomorphism. The activity of any one compound, carbon or nitrogen, appears to be unrelated to the dry weight attainable in the presence of that compound; although a certain level of growth is necessary, it is not a sufficient requisite for pleomorphism. Data presented here give no clue as to the specific grouping or configuration of the carbohydrate which might be required for development of the pleomorphic patch. Some strains develop mutant patches readily when grown at 36 C on a medium containing a suitable source of carbohydrate and nitrogen. Other strains form patches on a more restricted range of these compounds; a few strains show no pleomorphic activity.

Morphological response of Trichophyton mentagrophytes to keratin.

The protein keratin can induce a reversible change in morphology of some granular strains ofTrichophyton mentagrophytes leading to a gross appearance which is indistinguishable from the pleomorphic mutation. The only other chemical which induced the same morphological change was a low concentration of sodium acetate. Pleomorphic cultures ofT. mentagrophytes were unaffected.

Isolation ofTrichophyton mentagrophytesfrom a porcupine

Seven porcupines from different parts of Southern Africa were examined for dermatophytes One animal showed clinical signs of infection and a granular strain of Trichophyton mentagrophytes was isolated from it. A human contact developed ringworm lesions 3 weeks after handling the animal. A similar strain of T. mentagrophytes was isolated from the human contact. This appears to be the first record of dermatophyte infection in a member of the Hystricidae. Four isolates out of 6 obtained from the porcupine and human contact, produced yellow pigment in culture. Yellow strains of T. mentagrophytes are not infrequently isolated from cases of human and animal ringworm in Southern Africa. These strains are not identical with T. mentagrophytes var. erinacei.

NATURAL INFECTION IN LABORATORY ANIMALS DUE TO TRICHOPHYTON MENTAGROPHYTES IN INDIA.

Five strains ofTrichophyton mentagrophytes were isolated, four from guinea pigs and one from rabbit. The symptoms of the disease were studied. The morphological characters and the pathogenicity of the isolates were studied in detail. The significance of the findings is discussed.

Interrelation of pH, Temperature, and Growth in the Induction of Pleomorphism in Trichophyton mentagrophytes

There is a paucity of data on the effect of pH on the development of the pleomorphic mutant on the surface of granular strains of dermatophytic fungi, although some work has been reported on the interrelation of pH and growth of various species. Dermatophytic fungi exhibit the ability to grow at pH values of the medium between 4 and 10 (Stockdale, 1953a). An optimum pH for growth of around 6.0 has been reported for Trichophyton tonsurans (Swartz and Georg, 1955) and an optimum of slightly below 7.0 for T. persicolor (Stockdale, 1953b). Dermatophytic fungi also possess the ability to increase the alkalinity of the growth medium, apparently due to the release of ammonia (Georg, 1959). McVeigh and Campbell (1950) found that, when using casein hydrolysate, asparagine, or urea as the nitrogen source, three normal granular strains of T. mentagrophytes changed the pH from around 5.0 to 7.0 in 14 days while three mutant pleomorphic strains did not alter the pH of the growth media. Since the optimum experimental conditions of medium, temperature, and time of incubation required to promote the induction and growth of pleomorphic patches on the mycelium of certain granular strains of T. mentagrophytes are now known (Klein, 1964), the optimum pH for this phenomenon could be ascertained. It is of importance to determine whether there is a positive correlation between mycelial growth capacity and the appearance of pleomorphs. It seemed reasonable that manipulation of the hydrogen ion concentration of the medium might permit an evaluation of this basically important question. This paper, therefore, reports the results of a study on the effects of pH and of temperature on dry weight yield of a typical granular and two typical pleomorphic strains of Trichophyton mentagrophytes (Robin) Blanchard (Klein, 1963) and the relation of pH to the induction and development of the pleomorphic mutant.

TIME-TEMPERATURE INTERACTION IN THE INDUCTION OF PLEOMORPHISM IN TRICHOPHYTON MENTAGROPHYTES.

SUMMARY: The frequency of appearance of mutant pleomorphic patches on the surface growth of granular strains of Trichophyton mentagrophytes was markedly increased by incubation at 36° as compared to the number seen at 26°. A minimum of 8–9 days of incubation at the higher temperature was required to induce the higher frequency of pleomorphic mutants and, as the number of days at 36° increased, the number and relative size of the pleomorphic patches also increased. Typical mutants could be isolated whether the granular culture was incubated for 8–9 or 14 days at 36°. Visual scoring was relatively accurate since most of those patches visually scored as pleomorphic were found on isolation to be typical or atypical mutants. Three phenotypic characters were used here to define pleomorphism: type of surface mycelium, pigmentation on reverse side of colony, and effect of methionine. These characters could change independently of one another. Thus, pleomorphism may be the result of alterations in more than one closely linked chromosome-borne locus.

In vitro resistance studies with griseofulvin.

Successive generations of all forms of life tend to develop resistance to specific biologic antagonists which are constantly present in the environment. Griseofulvin is an antifungal antibiotic to which dermatophytes have not been previously exposed, and which has afforded strikingly beneficial results in clinical infections with these organisms. It was considered essential, therefore, to attempt to develop resistance in vitro, in an effort to prognosticate the future therapeutic effectiveness of the drug. Selected dermatophytes have been exposed to increasing concentrations of griseofulvin and, although only one phase of the study has been completed, the data which have been accumulated are of sufficient interest to justify a preliminary report. Method of Study The organisms selected for study were strains of Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton tonsurans, Trichophyton schoenleini, Epidermophyton floccosum, Microsporum audouini, and Microsporum canis, which had not been exposed to griseofulvin. The medium on which the organisms were grown was