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We have determined the in vitro activity of amphotericin B (AMB) and posaconazole (PSC) against Saksenaea vasiformis using broth microdilution and disk diffusion methods and determined the minimal fungicidal concentration (MFC). PSC was found to have the greatest in vitro activity in all cases and was the most efficacious in prolonging survival and reducing the fungal load in an immunocompetent murine model of disseminated infection caused by four strains of the fungus.

Saksenaea erythrospora is a filamentous fungus belonging to the order Mucorales. Cases of cutaneous mucormycosis caused by Saksenaea spp. have previously been reported in immunocompetent and immunosuppressed people. A premature, 1-day-old bull calf from Texas with numerous plaque-like and ulcerative lesions in the skin was found at necropsy to have multiple areas of mycotic dermatitis and abomasitis. Fungal culture of the skin followed by morphological characterization and genetic analysis identified the etiologic agent as S. erythrospora.

Objectives: We evaluated the in vitro activity of posaconazole and amphotericin B against several clinical strains of the mucoralean fungus Apophysomyces variabilis, and their efficacy in a murine model of disseminated infection caused by that fungus., Methods: The in vitro susceptibility of seven strains of A. variabilis to posaconazole and amphotericin B was determined by using a broth microdilution method. The in vivo efficacy of both drugs, posaconazole at 20 mg/kg twice daily orally by gavage and amphotericin B at 0.8 mg/kg once daily intravenously, was evaluated against six of the strains previously tested in vitro using immunocompetent mice., Results: In general, MICs of both drugs were within the range of susceptibility or intermediate susceptibility. Posaconazole and amphotericin B were able to significantly reduce the percentages of positive cultures in the affected tissues. However, in general, posaconazole significantly improved survival (median, 23 days; range, 7-30 days) compared with untreated controls (median, 6 days; range, 4-7 days) and, in some cases, with respect to the animals treated with amphotericin B (median, 15 days; range, 5-30 days)., Conclusions: Our results demonstrate the efficacy of posaconazole in the treatment of a disseminated murine infection caused by A. variabilis. However, further clinical studies are required to ascertain the potential use in human infections caused by this fungus.

The in vitro susceptibility of 17 strains of Mucor circinelloides to amphotericin B and posaconazole was ascertained by using broth microdilution and disk diffusion methods and by determining the minimal fungicidal concentration (MFC). We evaluated the efficacy of posaconazole at 40 mg/kg of body weight/day and amphotericin B at 0.8 mg/kg/day in a neutropenic murine model of disseminated infection by M. circinelloides by using 6 different strains tested previously in vitro. In general, most of the posaconazole MICs were within the range of susceptibility or intermediate susceptibility, while the small inhibition zone diameters (IZDs) were indicative of nonsusceptibility for all isolates tested. The MFCs were ≥ 3 dilutions higher than the corresponding MICs. In contrast, amphotericin B showed good activity against all of the strains tested regardless of the method used. The in vivo studies demonstrated that amphotericin B was effective in prolonging survival and reducing the fungal load. Posaconazole showed poor in vivo efficacy with no correlation with the MIC values. The results suggested that posaconazole should be used with caution in the treatment of infections caused by Mucor circinelloides or by strains of Mucor not identified to the species level.

Two new species in the order Mucorales, Mucor velutinosus and Mucor ellipsoideus, isolated from human clinical specimens in the USA, are described and illustrated. The former species is similar to Mucor ramosissimus, from which it can be differentiated by its ability to grow at 37°C and produce verrucose sporangiospores. Mucor ellipsoideus is also able to grow and sporulate at 37°C like M. indicus, the nearest phylogenetic species in this study, however, the former has narrow ellipsoidal sporangiospores in contrast to the subglobose to ellipsoidal sporangiospores of M. indicus. Analysis of the sequences of the ITS and the D1-D2 regions of the rRNA genes confirmed the novelty of these species. The in vitro antifungal susceptibility of the new species showed that amphotericin B was active against all isolates and posaconazole and itraconazole showed low activity.

Background: Apophysomyces is a monotypic genus belonging to the order Mucorales. The species Apophysomyces elegans has been reported to cause severe infections in immunocompromised and immunocompetent people. In a previous study of Alvarez et al.(3) [J Clin Microbiol 2009;47:1650-6], we demonstrated a high variability among the 5.8S rRNA gene sequences of clinical strains of A. elegans., Material and Methods: We performed a polyphasic study based on the analysis of the sequences of the histone 3 gene, the internal transcribed spacer region of the rDNA gene, and domains D1 and D2 of the 28S rRNA gene, as well as by evaluation of some relevant morphological and physiological characteristics of a set of clinical and environmental strains of A. elegans., Results and Conclusions: We have demonstrated that A. elegans is a complex of species. We propose as new species Apophysomyces ossiformis, characterised by bone-shaped sporangiospores, Apophysomyces trapeziformis, with trapezoid-shaped sporangiospores, and Apophysomyces variabilis, with variable-shaped sporangiospores. These species failed to assimilate esculin, whereas A. elegans was able to assimilate that glycoside. Amphotericin B and posaconazole are the most active in vitro drugs against Apophysomyces., (Copyright 2009 Revista Iberoamericana de Micología. Published by Elsevier Espana. All rights reserved.)