Miltefosine is active against Sporothrix brasiliensis isolates with in vitro low susceptibility to amphotericin B or itraconazole

Abstract

Sporotrichosis is a common mycosis caused by dimorphic fungi from the Sporothrix schenckii complex. In recent years, sporotrichosis incidence rates have increased in the Brazilian state of Rio de Janeiro, where Sporothrix brasiliensis is the species more frequently isolated from patients. The standard antifungals itraconazole and amphotericin B are recommended as first-line therapy for cutaneous/lymphocutaneous and disseminated sporotrichosis, respectively, although decreased sensitivity to these drugs in vitro was reported for clinical isolates of S. brasiliensis. Here, we evaluated the activity of the phospholipid analogue miltefosine -already in clinical use against leishmaniasis -towards the pathogenic yeast form of S. brasiliensis isolates with low sensitivity to itraconazole or amphotericin B in vitro. Miltefosine had fungicidal activity, with minimum inhibitory concentration (MIC) values of 1-2 mg ml "1 . Miltefosine exposure led to loss of plasma membrane integrity, and transmission electron microscopy (TEM) analysis revealed a decrease in cytoplasmic electron density, alterations in the thickness of cell wall layers and accumulation of an electron-dense material in the cell wall. Flow cytometry analysis using an antimelanin antibody revealed an increase in cell wall melanin in yeasts treated with miltefosine, when compared with control cells. The cytotoxicity of miltefosine was comparable to those of amphotericin B, but miltefosine showed a higher selectivity index towards the fungus. Our results suggest that miltefosine could be an effective alternative for the treatment of S. brasiliensis sporotrichosis, when standard treatment fails. Nevertheless, in vivo studies are required to confirm the antifungal potential of miltefosine for the treatment of sporotrichosis. INTRODUCTIONSporotrichosis is the most frequent subcutaneous mycosis in Latin America, and has high incidence rates in Brazil, especially in the Rio de Janeiro state, where zoonotic transmission prevails (Barros et al., 2010). This disease is caused by dimorphic fungal species from the Sporothrix schenckii complex (Marimon et al., 2007;, including Sporothrix brasiliensis, the most virulent species (ArrillagaMoncrieff et al., 2009;Fernandes et al., 2013) and the most prevalent in the clinical cases from the Rio de Janeiro state (Oliveira et al., 2011;Rodrigues et al., 2013a;Borba-Santos et al., 2014). In zoonotic transmission, sporotrichosis is mainly acquired by scratches, bites or direct contact with lesion secretion from contaminated animals, where yeasts are the infective forms (Rodrigues et al., 2013b).The 'gold standard' treatment for cutaneous and lymphocutaneous forms of sporotrichosis is itraconazole, while amphotericin B is the first-line drug of choice for disseminated forms of the disease (Kauffman et al., 2007). However, recent reports demonstrated that these drugs are less potent against S. brasiliensis isolates, which have high minimum inhibitory concentration (MIC) values in vitro for these antifungals (Ottonelli Stopiglia et a...

In Vitro Activity of Miltefosine against Candida albicans under Planktonic and Biofilm Growth Conditions and In Vivo Efficacy in a Murine Model of Oral Candidiasis

“…These gastrointestinal side effects are probably related to oral ingestion of the drug and the detergent properties of miltefosine, which irritates the gastrointestinal mucosa directly, causing vomiting and diarrhea. In general, miltefosine has a good oral bioavailability (82 to 95%) and is distributed to all tissues with accumulation mainly in liver, lungs, kidneys, and spleen (25), and its cytotoxicity is not greater than that of the current gold standard drug, amphotericin B (29). The in vivo efficacy of oral treatment with miltefosine was initially demonstrated by Widmer et al (28) using models of disseminated cryptococcosis in mice, where doses of 3.6 and 7.2 mg/ kg/day increased survival of animals and reduced the fungal load in the brain and lungs.…”

“…Recently, some reports have attributed the development of resistance to miltefosine during the treatment of visceral leishmaniasis to the overexpression of an ABC transporter (Leishmania tropica MDR1 [LtrMDR1]) and to changes in membrane sterol composition (25,26). The broad-spectrum antifungal activity of miltefosine has been demonstrated in vitro against planktonic cells of several medically important fungi, including dermatophytes, Candida sp., Cryptococcus sp., Aspergillus sp., Fusarium sp., Scedosporium sp., Histoplasma capsulatum, Rhizopus sp., and Sporothrix schenckii (27)(28)(29)(30)(31)(32), and no reports about resistance development have been made so far.…”

Zoonotic Epidemic of Sporotrichosis: Cat to Human Transmission

“…Identifying these epidemiological trends associated with the emergence of drug resistance is important to adjust antifungal therapy and to encourage the development of new drugs to treat sporotrichosis. Currently, potential alternative therapies to impair Sporothrix development and tackle sporotrichosis include terpinen-4-ol and farnesol [23], miltefosine [24], TCAN26 (a structural analogue of miltefosine) [25], and H3 (a 24-sterol methyltransferase inhibitor) [26]. …”

Miltefosine Has a Postantifungal Effect and Induces Apoptosis in Cryptococcus Yeasts

“…The fungicidal effect of MFS on Saccharomyces cerevisiae relies on the disruption of the mitochondrial membrane potential, which results in cell death by apoptosis (15,16). On human fungal pathogens, the only alterations described after MFS treatment were abnormalities in plasma membrane morphology in Sporothrix brasiliensis (5) and Paracoccidioides spp. (10) and increased plasma membrane permeability and a reduction in total ergosterol in C. posadasii and H. capsulatum (7).…”