I am aware that dermatophytes in the environment will produce spores, but do they produce spores while on the patient?
Dear Jennifer,
Dermatophytes can produce asexual spores on the host. If you observe skin or nail samples from dermatophytosis, you often see hyphal cells disarticulating into (sub)cylindrical spores called "arthroconidia" (look at this: http://www.mycology.adelaide.edu.au/virtual/2009/ID2-May09.html). In some cases you can also see thick-walled subglobose resistance structures called "chlamydoconidia"
Cheers,
H
Note: these resistant structures are mostly referred to as "chlamydospores" in mycological literature, not as "chlamydoconidia", sorry :)
Whether it is bacteria or fungi they are usually known to produce spores when the conditions for survival are harsh (that is in the environment and not invivo or on the body).
However, spores are very important source of infection.
Dermatophytes usually form arthrospores (arthroconidia) on dermatophytes-infected patients. for example in white superficial onychomycosis (WSO).
Such spores can seen by direct microscopic examination of infected material.
Dermatophytes produce arthrospores by segmentation and fragmentation of the hyphae. These spores are highly resistant and adhere strongly to keratin also surviving in a dry environment for 12 months or longer. In a humid environment, however, arthrospores are short-lived. High temperatures (100°C) destroy them quickly.
Are these spores resistant for regular antifungal treatment,
Are these spores responsible for recurrent infections.
What medications are best suitable for eradication of spores
No dermatophyte resistance to antimycoticts has been reported.
Such spores function as a source of infection, infection by autoinoculation, and recurrent infections in case of incomplete treatment.
As for therapy:
Topical therapy
Topical therapy may be sufficient for dermatophytosis other than nail and scalp infections. For example, terbinafine topical formulations, tolnaftate, imidazole, amorolfine, cyclopiroxolamine, clotrimazole, miconazole, econazole, ketoconazole, bifonazole and tioconazole.
Terbinafine, which has the shortest treatment time of topical antifungals, takes about one week to kill the fungus but the skin will take about 2-4 weeks to return to normal.
Oral therapy
The oral agents against fungi have revolutionised the clinical management of severe and symptomatic infections. However, in onychomycosis, 'cure' is evidently not 100%.
In skin and nail infections, cure rates are now sufficiently good that failure of treatment suggests one should think that the fungal growth was not the prime cause.
If the affected nail is sufficiently dystrophic and thickened, then urea avulsion may be useful. This enables the affected nail to be removed. Urea paste (40%) is applied under occlusion for 1 week before cutting away the affected nail.
In symptomatic onychomycosis, tinea capitis and in systemic fungal infections associated with immunosuppression, oral therapy is the treatment of choice.
Example on oral therapy:
Oral therapy of Tinea capitis:
Griseofulvin 500 mg/day (not less than 10 mg/kg/day) until cured (up to 12 weeks)
Terbinafine 250 mg/day for 4 weeks
Itraconazole 100 mg/day for 4 weeks
Fluconazole 100 mg/day for 4 weeks
Dr Mohammed thank you for the answer.
Can I ask you what would be the MIC and contact time for an antifungal to be effective topically.
How does steroid when applied simultaneously affect the activity of topical antifungal.
Dear Satyaprasad, as you know, MIC is an indicator for in vitro activity of an antifungal, and this may be reflected on its in vivo activity. Several anti-dermatophytes are available, as well as several types of dermatophyte infections (ranging from superficial mycoses to tinea capitis and onychomycosis) in addition to the presence of some persistent types of dermatophytoses, therefore it would be very difficult to relate MIC and “contact time” for an antifungal, with its efficacy.
Topical therapy may be sufficient for dermatophytosis other than nail and scalp infections. For example, terbinafine topical formulations, tolnaftate, imidazole, amorolfine, cyclopiroxolamine, clotrimazole, miconazole, econazole, ketoconazole, bifonazole and tioconazole. Terbinafine, which has the shortest treatment time of topical antifungals, takes about one week to kill the fungus but the skin will take about 2-4 weeks to return to normal.
In cases of body ringworm and tinea cruris, local treatment with tolnaftate or imidazole derivatives is usually sufficient to achieve a cure within 2 to 4 weeks. Some cases with severe inflammation may be best treated with a preparation containing both an anti-fungal agent and a corticosteroid (e.g. 1 % econazole nitrate plus 0.1 % triamcinolone acetonide). This treatment results in rapid relief of the subjective symptoms, including pruritus and burning, as well as the inflammation. The oral administration of griseofulvin is justified only when the lesions persist after a month’s treatment.
In severe cases with extensive lesions, or in cases with lesions resistant to topical treatment, or in cases of frequent relapse, oral therapy is usually effective.
In symptomatic onychomycosis, tinea capitis and in systemic fungal infections associated with immunosuppression, oral therapy is the treatment of choice.
Thank you very much Dr Mohammed.
Very often there are mixed cases that present in clinics.
tenia being one of the most common and yet treated casually.
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