Molecular Identification and Antifungal Susceptibility of Clinical Isolates of Sporothrix schenckii Complex in Medellin, Colombia.

BACKGROUND: Sporotrichosis is a subcutaneous mycosis that affects humans and other animals. Infection prevails in tropical and subtropical countries. Until a few years ago, it was considered that two varieties of Sporothrix schenckii caused this mycosis, but by applying molecular taxonomic markers, it has been demonstrated that there are several cryptic species within S. schenckii complex which varies in susceptibility, virulence, and geographic distribution. OBJECTIVE: This study aimed to identify the clinical isolates of Sporothrix spp. from patients with sporotrichosis in Medellin, Colombia, using two markers and to evaluate the in vitro susceptibility to itraconazole. METHODS: Thirty-four clinical isolates of Sporothrix spp. from Colombia, three from Mexico, and one from Guatemala were identified through sequencing of the noncoding region ITS-1 + 5.8SDNAr + ITS-2 and of the fragment containing exons 3 and 4 of the ß-tubulin gene. Clinical isolate sequences were compared with GenBank reference sequences using the BLASTN tool, and then, phylogenetic analysis was performed. Besides, the in vitro susceptibility to itraconazole was evaluated by determining the minimum inhibitory concentrations according to the CLSI M38-A2 method. RESULTS: Clinical isolates were identified by morphology as Sporothrix spp. Using the molecular markers, ITS and ß-tubulin, isolates were identified as S. schenckii sensu stricto (25) and Sporothrix globosa (13). Susceptibility to itraconazole was variable among clinical isolates. CONCLUSION: This is the first scientific publication that identifies species that cause sporotrichosis in Colombia, along with the antifungal susceptibility to itraconazole.

Multicenter, International Study of MIC/MEC Distributions for Definition of Epidemiological Cutoff Values for Sporothrix Species Identified by Molecular Methods.

Clinical and Laboratory Standards Institute (CLSI) conditions for testing the susceptibilities of pathogenic Sporothrix species to antifungal agents are based on a collaborative study that evaluated five clinically relevant isolates of Sporothrixschenckii sensu lato and some antifungal agents. With the advent of molecular identification, there are two basic needs: to confirm the suitability of these testing conditions for all agents and Sporothrix species and to establish species-specific epidemiologic cutoff values (ECVs) or breakpoints (BPs) for the species. We collected available CLSI MICs/minimal effective concentrations (MECs) of amphotericin B, five triazoles, terbinafine, flucytosine, and caspofungin for 301 Sporothrix schenckii sensu stricto, 486 S. brasiliensis, 75 S. globosa, and 13 S. mexicana molecularly identified isolates. Data were obtained in 17 independent laboratories (Australia, Europe, India, South Africa, and South and North America) using conidial inoculum suspensions and 48 to 72 h of incubation at 35°C. Sufficient and suitable data (modal MICs within 2-fold concentrations) allowed the proposal of the following ECVs for S. schenckii and S. brasiliensis, respectively: amphotericin B, 4 and 4 µg/ml; itraconazole, 2 and 2 µg/ml; posaconazole, 2 and 2 µg/ml; and voriconazole, 64 and 32 µg/ml. Ketoconazole and terbinafine ECVs for S. brasiliensis were 2 and 0.12 µg/ml, respectively. Insufficient or unsuitable data precluded the calculation of ketoconazole and terbinafine (or any other antifungal agent) ECVs for S. schenckii, as well as ECVs for S. globosa and S. mexicana These ECVs could aid the clinician in identifying potentially resistant isolates (non-wild type) less likely to respond to therapy.

Candida tropicalis antifungal cross-resistance is related to different azole target (Erg11p) modifications.

Candida tropicalis ranks between third and fourth among Candida species most commonly isolated from clinical specimens. Invasive candidiasis and candidemia are treated with amphotericin B or echinocandins as first-line therapy, with extended-spectrum triazoles as acceptable alternatives. Candida tropicalis is usually susceptible to all antifungal agents, although several azole drug-resistant clinical isolates are being reported. However, C. tropicalis resistant to amphotericin B is uncommon, and only a few strains have reliably demonstrated a high level of resistance to this agent. The resistance mechanisms operating in C. tropicalis strains isolated from clinical samples showing resistance to azole drugs alone or with amphotericin B cross-resistance were elucidated. Antifungal drug resistance was related to mutations of the azole target (Erg11p) with or without alterations of the ergosterol biosynthesis pathway. The antifungal drug resistance shown in vitro correlated very well with the results obtained in vivo using the model host Galleria mellonella. Using this panel of strains, the G. mellonella model system was validated as a simple, nonmammalian minihost model that can be used to study in vitro-in vivo correlation of antifungals in C. tropicalis. The development in C. tropicalis of antifungal drug resistance with different mechanisms during antifungal treatment has potential clinical impact and deserves specific prospective studies.

Productos naturales con actividad antimicótica / Natural products with antimycotic activity

En las últimas décadas se ha observado no sólo un notable aumento de las infecciones causadas por hongos en todo el mundo sino un incremento de la resistencia farmacológica que han mostrado varias especies de hongos a los diferentes antimicóticos que se utilizan en la práctica médica. Esta situación ha llevado a la búsqueda de nuevos antifúngicos de origen natural. En recursos naturales, como plantas, insectos y organismos marinos y terrestres, se han identificado una serie de moléculas con actividad contra diferentes géneros y especies de hongos de importancia clínica para los humanos, convirtiéndose en alternativa para el desarrollo y la formulación de nuevos fármacos antimicóticos con menores efectos secundarios, mayor espectro de acción y menor costo que los disponibles actualmente para el tratamiento de las infecciones por hongos. En este artículo se presenta una revisión de las principales fuentes naturales de moléculas con actividad antimicótica (AU)

In the past few decades, a worldwide increase in the incidence of fungal infections has been observed and the resistance of some species of fungus to different fungicidals used in medical practice has also risen. This has led to the search for new antimycotics, particularly those obtained from natural sources such as plants, insects, and land and marine microorganisms. In these natural sources, a series of molecules with antifungal activity against different species of fungus of great clinical importance for humans has been found, and these substances have become an alternative for the development and formulation of new antifungals with fewer side effects, a greater spectrum of action and lower cost than those in current use. In this article, we review the main sources of molecules with antimycotic activity obtained from natural sources (AU)

[Natural products with antimycotic activity]. / Productos naturales con actividad antimicótica.

In the past few decades, a worldwide increase in the incidence of fungal infections has been observed and the resistance of some species of fungus to different fungicidals used in medical practice has also risen. This has led to the search for new antimycotics, particularly those obtained from natural sources such as plants, insects, and land and marine microorganisms. In these natural sources, a series of molecules with antifungal activity against different species of fungus of great clinical importance for humans has been found, and these substances have become an alternative for the development and formulation of new antifungals with fewer side effects, a greater spectrum of action and lower cost than those in current use. In this article, we review the main sources of molecules with antimycotic activity obtained from natural sources.

[Current knowledge on the strain typing of the pathogenic fungus Histoplasma capsulatum var. capsulatum: a review of the findings]. / Estado actual de la tipificación del hongo patógeno Histoplasma capsulatum var. capsulatum: una revisión de los hallazgos.

The classification of microbial strains is currently based on different typing methods, which must meet certain criteria in order to be widely used. Phenotypic and genotypic methods are being employed in the epidemiology of several fungal diseases. However, some problems associated to the phenotypic methods have fostered genotyping procedures, from DNA polymorphic diversity to gene sequencing studies, all aiming to differentiate and to relate fungal isolates or strains. Through these studies, it is possible to identify outbreaks, to detect nosocomial infection transmission, and to determine the source of infection, as well as to recognize virulent isolates. This paper is aimed at analyzing the methods recently used to type Histoplasma capsulatum, causative agent of the systemic mycosis known as histoplasmosis, in order to recommend those that yield reproducible and accurate results.