Prevalence of undetected tinea capitis in a school survey in Spain.

From October 1994 to November 1995, a prospective study aiming to detect dermatophytes on the scalp was undertaken in 5000 unselected school children aged between 3 and 16 years (mean age 8.34 years, SD +/- 3.83). Thirty-two (0.64%) had dermatophytes in the scalp, 22. (0.44%) had tinea capitis and 10 were asymptomatic scalp carriers. It is important to point out that 33% of the patients with tinea capitis and 60% of the asymptomatic scalp carriers also had ringworm in other body sites. There was a significantly higher proportion of cases of tinea capitis (P < 0.001)(particularly due to Trichophyton tonsurans, P < 0.001) and of cases of asymptomatic scalp carriers (P < 0.05) (particularly due to Trichophyton tonsurans, P < 0.001) in the immigrant population of African origin. In all the child index cases with positive scalp cultures (tinea capitis and carriers), the household members were studied clinically and mycologically. One child had a body ringworm caused by Microsporum canis. Twelve adults had positive cultures with dermatophytosis (one tinea capitis and eleven body ringworm). Three adult patients were also carriers of dermatophytes in other body sites. Our data indicate a change in the causative agents of tinea capitis seen in Madrid over a 12-month period, with cases due to antropophilic species (T. tonsurans, T. soudanense, M. audouinii and T. violaceum) occurring in the immigrant population from Africa; as a consequence, there is an emergence of T. tonsurans in the Spanish population.

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.

Chronic dermatophyte infection: evaluation of the Ig class-specific antibody response reactive with polysaccharide and peptide antigens derived from Trichophyton mentagrophytes.

An enzyme-linked immunosorbent assay was used to detect serum antibodies within Ig classes IgG, IgM, IgA, and IgE against two partially purified Trichophyton mentagrophytes-derived antigens: polysaccharide (SAC) and peptide (PEP). Sera from 27 chronically infected adults, 16 normal noninfected adults, and 17 noninfected children were evaluated. All sera were reactive, indicating that circulating antibody reactive to PEP and SAC is a feature common to most people, regardless of age and the presence of active infection. The reactivity to SAC was much greater than to PEP. Inhibition assays revealed that components of PEP are found in SAC. Chronically infected adults showed slightly elevated IgG and IgA reactivity to both SAC and PEP compared with noninfected normal adults. This elevated reactivity correlated with the extent (% surface affected) of cutaneous infection. IgE antibody reactivity was detected only against SAC and was somewhat elevated in chronically infected adults. There was no association between antibody reactivity and immunoglobulin level or between the individual subject's level of antibody reactivity to PEP and SAC.

The rise and fall of fluorescent tinea capitis.

The epidemiology of tinea capitis has had a remarkable change in the past 20 years. It is important for physicians to realize that most tinea capitis in the United States is caused by Trichophyton tonsurans and that these lesions cannot be diagnosed by the Wood's lamp. Trichophyton tonsurans tinea capitis is frequently misdiagnosed because the lesions mimic such common scalp conditions as dandruff and seborrhea. Further, this organism can cause chronic tinea capitis in women that may become a infectious reservoir for other family members. A negative potassium hydroxide preparation will not rule out infection with T tonsurans and cultures are necessary. Scalp lesions in children should be considered tinea capitis until culturally proved otherwise.

Cell mediated cross-reactivity in vivo and in vitro to purified dermatophyte antigen preparations in sensitized guinea pigs.

Guinea pigs were sensitized to either Trichophyton rubrum, Trichophyton mentagrophytes, or Epidermophyton floccosum. Cross-reactivity experiments were performed in vivo and in vitro with purified antigen preparations prepared from the respective dermatophyte according to the ethylene glycol method. All sensitized animals responded with delayed-type skin reactions to all three antigen preparations, although the strongest reactivity observed was to the homologous antigen. Spleen and blood lymphocytes from many (but not all) animals were stimulated by these antigens and the response to the homologous antigen was always more pronounced. The findings indicate the presence of a common group-specific dermatophyte antigen as well as the possibility of species-specific antigens in the experimental system studied.

Trichophytin extraction: biological comparison of trichophytin extracted from Trichophyton mentagrophytes grown in a complex medium and a defined medium.

The extraction of antigens (trichophytin) from Trichophyton mentagrophytes var. asteroides grown in both a complex medium and a defined medium proved to be reproducible and feasible. These extracts were first evaluated by skin testing in both infected and noninfected guinea pigs. Further evaluation and standardization was accomplished in selected humans by comparing these antigens to a trichophytin known to elicit allergic reactions to the dermatophytes. The trichophytins produced by this extraction procedure gave no false positive (or negative) skin test reactions. These antigens did, however, reliably elicit allergic sensitivity of both the immediate and delayed type. The potency of both complex and defined media antigen was shown to be equal to that of the standard trichophytin.