Different inocula of Trichoderma longibrachiatum were tested in a murine model, and only the highest one (1 ؋ 10 7 CFU/animal) killed all of the mice at day 15 postinfection, with spleen and liver the most affected organs. The efficacies of amphotericin B deoxycholate, liposomal amphotericin B, voriconazole, and micafungin were evaluated in the same model, with very poor results. Our study demonstrated the low virulence but high resistance to antifungal compounds of this fungus.T richoderma, a saprobic filamentous fungus widely distributed in nature (1), has recently emerged as human pathogen. Trichoderma spp. produce a wide variety of clinical manifestations (2-12), mostly attributed to T. longibrachiatum. In general, clinical cases have poor prognosis due to their intrinsic resistance to antifungals (13). Antifungal susceptibility data are scarce, and appropriate treatment does not exist. Although amphotericin B shows poor in vitro activity, it is the most used drug, while voriconazole and echinocandins show better in vitro activities (14). Our aim was to evaluate the virulence of T. longibrachiatum in a murine model and the efficacies of amphotericin B, liposomal amphotericin B, micafungin, and voriconazole.Two clinical strains of T. longibrachiatum (FMR 12626 and FMR 12643), identified by multilocus sequence analysis (14), were used. Antifungal activity was determined following the CLSI guidelines (14, 15). For FMR 12626, the MICs of amphotericin B and voriconazole were 0.13 and 0.5 g/ml, respectively, and for FMR 12643, the MICs were 2 and 4 g/ml, respectively. The minimum effective concentrations (MECs) of micafungin for FMR 12626 and FMR 12643 (determined with a stereoscopic microscope) were 0.25 and 0.03 g/ml, respectively.Isolates were cultured on potato-dextrose agar at 35°C for 4 days. Suspensions were adjusted by hemocytometer counts, and viability was confirmed by culturing onto dichloran Rose Bengala chloramphenicol (DRBC) agar, which restricts the fast and invasive growth of Trichoderma (16).For virulence studies, male OF-1 mice weighing 30 g were immunosuppressed with 200 mg/kg of cyclophosphamide, producing neutrophil counts of Ͻ100 cells/mm 3 (17). Groups of 16 animals (8 for survival and 8 for fungal burden and histopathology studies) were established. Groups were infected intravenously (i.v.) in the lateral tail vein with 1 ϫ 10 4 , 1 ϫ 10 5 , 1 ϫ 10 6 , or 1 ϫ 10 7 CFU of each strain per mouse in 0.2 ml. On day 6 postinfection, mice from the tissue burden groups were euthanized by CO 2 inhalation. Lungs, kidneys, livers, spleens, and brains were removed, homogenized, 10-fold diluted, and placed onto DRBC agar for calculation of CFU per gram. All care procedures were supervised and approved by L. Loriente Sanz (ID 39671243) of the Veterinary and Animal Welfare Advisory of the Universitat Rovira i Virgili Animal Welfare and Ethics Committee.Treatments were evaluated in mice challenged with 1 ϫ 10 7 CFU, which produced an acute infection with all mice dying within 15 days. Treatments consisted...