Melanins Protect Sporothrix brasiliensis and Sporothrix schenckii from the Antifungal Effects of Terbinafine

Immunopathogenesis of Human Sporotrichosis: What We Already Know

Sporotrichosis is a subacute/chronic mycosis caused by dimorphic fungus of the genus Sporothrix. This mycosis may affect both human and domestic animals and in the last few years, the geographic dispersion and increase of sporotrichosis worldwide has been observed. The occurrence of cases related to scratching/bites of domestic felines have increased, characterizing the disease as predominantly a zoonosis. In humans, sporotrichosis mainly involves the cutaneous tegument of infected patients, but other tissues may also present the infection. The main forms of clinical presentation are lymphocutanous sporotrichosis (LC) and fixed sporotrichosis (F). Although less common, mucosal, cutaneous disseminated, and extracutaneous forms have also been described. Multiple factors from the fungus and host can play a role in driving the clinical evolution of sporotrichosis to benign or severe disease. In this review, we discuss the immunopathological aspects involved in human sporotrichosis. Putting together the two branches of knowledge—host immune response and fungal evading mechanisms—we may perceive new possibilities in understanding the fungus–host interaction in order to be in a position to go further in the control of sporotrichosis.

Refractory sporotrichosis due to Sporothrix brasiliensis in humans appears to be unrelated to in vivo resistance

Sporotrichosis is a subacute to chronic infection caused by members of the Sporothrix schenckii complex. Itraconazole is the first choice antifungal drug for treating this infection, with terbinafine and potassium iodide as alternatives and amphotericin B used in cases of severe infections. Correlation of antifungal susceptibility data with the clinical outcome of the patients is scarce. The aim of this study was to correlate clinical and mycological data in patients with refractory sporotrichosis. In this work, antifungal susceptibilities, determined according to the reference M38-A2 CLSI protocol, of 25 Sporothrix strains, isolated from seven human cases of sporotrichosis with adversities in the treatment, are presented. Tested drugs included itraconazole, ketoconazole, posaconazole, voriconazole, terbinafine, and amphotericin B. Fungi were identified using the T3B PCR fingerprinting. This method identified all strains as Sporothrix brasiliensis and also demonstrated a high degree of similarity between the strains. In general, voriconazole was ineffective against all strains, and elevated minimal inhibitory concentrations (MICs) were observed for amphotericin B. High itraconazole and terbinafine MICs were not observed in S. brasiliensis isolates from patients of this study. Moreover, a significant increase in itraconazole and terbinafine MIC values from strains isolated from the same patient in different periods was not observed. The results suggest that the antifungal susceptibility to terbinafine and itraconazole determined by the reference method does not play an important role in therapeutic failure of sporotrichosis and that acquisition of resistance during prolonged antifungal treatment is not likely to occur in S. brasiliensis.

Successful Treatment of Canine Sporotrichosis with Terbinafine: Case Reports and Literature Review

Sporotrichosis occurs worldwide, and the metropolitan region of Rio de Janeiro, Brazil, is a main endemic area, with a large number of human and animal cases in the last 19 years. This mycosis is more frequently described in cats rather than in dogs. There are a limited number of oral antifungal agents for the treatment of sporotrichosis in animals. In this context, the effectiveness of terbinafine in the treatment of sporotrichosis in humans, as well as the promising results of in vitro susceptibility tests, inspired us to use this drug in the therapy of this mycosis in dogs. We reported for the first time the use of terbinafine in the treatment of two dogs with sporotrichosis caused by Sporothrix brasiliensis. Moreover, we provided an overview of therapeutic features of canine sporotrichosis cases reported since the 1960s. One of the dogs presented the fixed cutaneous form of the disease, while the other patient presented hyperemia of the nasal mucosa and respiratory signs only. Terbinafine showed high antifungal activity in vitro against the canine Sporothrix isolates. The dogs were successfully treated with terbinafine, with remission of all clinical signs initially presented. The current reports indicate that this drug can emerge as a therapeutic option for canine sporotrichosis.

Sporotrichosis: an update on epidemiology, etiopathogenesis, laboratory and clinical therapeutics

In the late 90's there was a change in both the route of transmission and the people at risk for sporotrichosis. This zoonotic cat-man alternative transmission route elicited changes in strategies to control the epidemic. There was a progressive increase in the number of cases involving especially children and the elderly. In addition to becoming hyperendemic, uncommon clinical pictures like immunoreactive clinical presentations or severe systemic cases have emerged. New species were identified and classified through molecular tools using more virulent clinical isolates, like S. brasiliensis, compared to the environmental isolates. Likewise, different species of Sporothrix have been associated with different geographic regions. The serological and molecular techniques are used as an auxiliary tool for the diagnosis and/or for species identification, although the isolation and the identification of Sporothrix spp. in clinical specimen is still the gold standard. Currently sporotrichosis epidemics requires the knowledge of the epidemiological-molecular profile to control the disease and the specific treatment. Itraconazole, potassium iodide, terfinafine, and amphotericin B are the available drugs in Brazil to treat sporotrichosis. The drug of choice, its posology, and treatment duration vary according to the clinical presentation, the Sporothrix species, and host immune status. New treatment choices, including a vaccine, are being developed; nevertheless, more clinical trials are required to confirm its efficacy.

The Transcriptome of Exophiala dermatitidis during Ex-vivo Skin Model Infection

The black yeast Exophiala dermatitidis is a widespread polyextremophile and human pathogen, that is found in extreme natural habitats and man-made environments such as dishwashers. It can cause various diseases ranging from phaeohyphomycosis and systemic infections, with fatality rates reaching 40%. While the number of cases in immunocompromised patients are increasing, knowledge of the infections, virulence factors and host response is still scarce. In this study, for the first time, an artificial infection of an ex-vivo skin model with Exophiala dermatitidis was monitored microscopically and transcriptomically. Results show that Exophiala dermatitidis is able to actively grow and penetrate the skin. The analysis of the genomic and RNA-sequencing data delivers a rich and complex transcriptome where circular RNAs, fusion transcripts, long non-coding RNAs and antisense transcripts are found. Changes in transcription strongly affect pathways related to nutrients acquisition, energy metabolism, cell wall, morphological switch, and known virulence factors. The L-Tyrosine melanin pathway is specifically upregulated during infection. Moreover the production of secondary metabolites, especially alkaloids, is increased. Our study is the first that gives an insight into the complexity of the transcriptome of Exophiala dermatitidis during artificial skin infections and reveals new virulence factors.