Taxonomía de los hongos: un rompecabezas al que le faltan muchas piezas / Fungal taxonomy: A puzzle with many missing pieces

Los hongos son organismos polifacéticos presentes en casi todos los ecosistemas de la tierra, donde establecen diversos tipos de simbiosis con otros seres vivos. A pesar de ser reconocidos por los humanos desde la antigüedad -y de la cantidad de trabajos que han profundizado sobre su biología y ecología-, aún falta mucho por conocer sobre estos organismos. Algunos de los criterios que clásicamente se han utilizado para su estudio, hoy resultan limitados y hasta cierto punto permiten un agrupamiento de los aislamientos según algunas características, pero generan confusión en su clasificación y, más aún, cuando se pretende comprender sus relaciones genealógicas. Los caracteres fenotípicos no son suficientes para identificar una especie de hongos y, menos aún, para construir una filogenia amplia o de un grupo particular. Hay grandes vacíos que hacen que los árboles generados sean inestables y fácilmente debatidos. Para los profesionales de la salud, parece que la identificación de los hongos hasta niveles inferiores como género y especie es suficiente para elegir el tratamiento más adecuado para su control, comprender la epidemiología de los cuadros clínicos asociados y reconocer los brotes y los factores determinantes de la resistencia a los antimicrobianos. No obstante, la ubicación taxonómica dentro del reino permitiría establecer relaciones filogenéticas entre los taxones fúngicos, facilitando la comprensión de su biología, su distribución en la naturaleza y la evolución de su potencial patogénico. Los avances de las técnicas de biología molecular y las ciencias de la computación en los últimos 30 años han permitido cambios importantes dirigidos a establecer los criterios para definir una especie fúngica y alcanzar una construcción filogenética más o menos estable. Sin embargo, el camino por recorrer aún es largo, y supone un trabajo mancomunado de la comunidad científica a nivel global y el apoyo a la investigación básica.

Fungi are multifaceted organisms found in almost all ecosystems on Earth, where they establish various types of symbiosis with other living beings. Despite being recognized by humans since ancient times, and the high number of works delving into their biology and ecology, much is still unknown about these organisms. Some criteria classically used for their study are nowadays limited, generating confusion in categorizing them, and even more, when trying to understand their genealogical relationships. To identify species within Fungi, phenotypic characters to date are not sufficient, and to construct a broad phylogeny or a phylogeny of a particular group, there are still gaps affecting the generated trees, making them unstable and easily debated. For health professionals, fungal identification at lower levels such as genus and species, is enough to select the most appropriate therapy for their control, understand the epidemiology of clinical pictures associated, and recognize outbreaks and antimicrobial resistance. However, the taxonomic location within the kingdom, information with apparently little relevance, can allow phylogenetic relationships to be established between fungal taxa, facilitating the understanding of their biology, distribution in nature, and pathogenic potential evolution. Advances in molecular biology and computer science techniques from the last 30 years have led to crucial changes aiming to establish the criteria to define a fungal species, allowing us to reach a kind of stable phylogenetic construction. However, there is still a long way to go, and it requires the joint work of the scientific community at a global level and support for basic research.

Molecular identification of Trichophyton mentagrophytes complex strains in Hubei province / 中华皮肤科杂志

Objective To profile the intraspecific type of Trichophyton mentagrophytes clinically isolated from different anatomical sites of patients, and to compare the performance of different target sites for the identification of Trichophyton mentagrophytes complex strains. Methods A total of 48 Trichophyton mentagrophytes strains, which were clinically isolated from Department of Dermatology, Wuhan No. 1 Hospital in the latest 3 years, were included in this study. The phenotypes of these Trichophyton mentagrophytes isolates were primarily determined by morphological observation and the urease test. PCR was performed to amplify the nuclear ribosomal internal transcribed spacer(ITS) region and the D1?D2 domains of the large?subunit ribosomal DNA(28S rDNA)followed by DNA sequencing. Then, Clustal X2 software and MEGA 6.0 software were used to analyze the ITS and D1?D2 sequences and to build phylogenetic trees by the maximum?likelihood method (bootstrap = 2000). Results As the ITS sequence?based phylogenetic tree showed, the probability that the 48 isolates were grouped into the Trichophyton interdigitale clade reached 92%. However, Trichophyton interdigitale could not be effectively differentiated from Trichophyton quinckeanum by the D1?D2 sequence?based phylogenetic tree. In addition, Trichophyton interdigitale showed various appearances, including woolen type, downy type, cream type, powdery type and granular type. Conclusions Trichophyton mentagrophytes can be identified to the species level based on the sequence of ITS region, which shows higher efficiency in identifying Trichophyton mentagrophytes complex than the D1?D2 domains. Morphological characteristics can not serve as the basis for intraspecific typing of Trichophyton mentagrophytes.