Pityrosporum: microscopía en lactantes menores / Pityrospora: microscopy in infant smalles

Se practicó microscopía de improntas sobre cinta adhesiva del vértex de 80 niños y de la frente de 20 niños-200 días de vida, para contaje de Pityrospora. Cuarenta y cuatro muestras del vértex resultaron incontables por lo numeroso de la población, 2 negativas para P.orbiculares, 57 negativas para P.ovales. Tres veces se vio germinación de P.ovale. Historia de atopia o presencia de asma no influyó sobre población de Pityrospora. El vértex resultó más poblado que la frente. En opinión de los autores, la microscopía es mucho más informativa que el cultivo. aparentemente, durante la cuarta semana de vida ocurre una explosión en la población de Pityrospora

Ensayo del método de Wikler en pacientes con pitiriasis versicolor / Assay of Wikler's method in patients with versicolor pityriasis

El pityrosporum es un hongo saprófito normal de la piel sana que se ha asociado etiológicamente a ciertas dermatosis como son la pitiriasis versicolor y la dermatitis seborreica, estableciéndose un paralelismo entre su densidad poblacional y la severidad clínica de las lesiones. En el siguiente estudio se ensaya el método de Wikler, utilizando cinta adhesiva transparente para tomar muestras de piel sana y afecta, en veinte pacientes con diagnóstico de pitiriasis versicolor. Las muestras fueron cultivadas y se determinó el número de colonias en cada caso, encontrándose una diferencia significativa a favor de la piel afectada. Se considera que el método de Wikler es adecuado para cultivar el Pityrosporum en aquellas dermatosis en las que interese cuantificar la población del hongo

Scanning electron microscopy of Malassezia furfur attachment to Broviac catheters.

Malassezia furfur has been increasingly associated with Broviac-catheter-related sepsis in infants receiving fat emulsions for parenteral alimentation. We examined by scanning electron microscopy the appearance of M. furfur attached to Broviac catheter segments mock-infected in vitro and to Broviac catheters removed from two infants with catheter-related sepsis. In vitro attachment occurred equally on external and internal surfaces of the catheters. Although some organisms were attached next to surface defects in the catheters, we could not determine if such defects were preferential sites of attachment. In the patient catheters, a dense coating of yeast cells was found adhering to the luminal surface, most abundantly near the tip. No organisms were seen on the external surface of the catheters. These findings show the need to examine the mechanisms of intraluminal catheter colonization in order to understand better the pathogenesis of M. furfur infections.

New diagnostic methods in dermatological mycology.

In dermatological mycology, direct microscopy and culture are the main diagnostic procedures. Microscopic examination of a wet KOH preparation is usually satisfactory for the detection of the infecting organism based on the morphological characteristics of the fungal elements. However, examination of the KOH mount requires skill and experience. In order to help the unskilled personnel to recognize fungal elements by microscopic examination, a number of differential strains have been described. Great strides have been made to improve the sensitivity and specificity of direct microscopy for the detection of fungi also on chemical properties of the fungal cell wall. Thus fluorescence microscopy using fluorescent brighteners, e.g. Blancophor BA holds great promise for its wide application in dermatologic mycology. Culture media enjoy considerable application in the isolation and identification of dermatophytes and Candida species from clinical specimens. Some novel media have been formulated recently to assist in the early detection and identification of some fastidious dermatophytes e.g. Trichophyton verrucosum. In dermatological mycology the predictive diagnostic value of the diagnostic tests has to be delineated for each disease state. As an example, direct microscopy is a useful diagnostic procedure for the detection of dermatophytes and Pityrosporum-yeasts in clinical materials, but less valuable for the detection of Candida. Furthermore, considerable attention needs to be focused on the utilization of new and old diagnostic tests from a series of viewpoints including necessity, usefulness, clinical relevance and cost-benefit analysis.

Identification of tyrosinase inhibitors in cultures of Pityrosporum.

Lipid fractions capable of inhibiting the dopa-tyrosinase reaction in vitro were isolated by thin-layer chromatography from submerged cultures of Pityrosporum supplemented with oleic acid or vaccenic acid. Analysis of these fractions by gas chromatography-mass spectrometry revealed the presence mainly of C(9) and C(11) dicarboxylic acids. Standard dicarboxylic acids from C(8) to C(13) were capable of inhibiting tyrosinase in vitro to varying extents. Enzymatic kinetic studies showed that they act as competitive inhibitors of tyrosinase. These observations suggest that dicarboxylic acids could be used in the treatment of people with hyperpigmentary disorders.