Rare Lower Extremity Invasive Fungal Infection in an Immunosuppressed Patient: Exserohilum longirostratum

Multi-locus phylogeny and taxonomy of Exserohilum

Exserohilum includes a number of plant pathogenic, saprobic and clinically relevant fungi. Some of these species are of great importance in human activities, but the genus has never been revised in a phylogenetic framework. In this study, we revise Exserohilum based on available ex-type cultures from worldwide collections, observation of the holotypes and/or protologues, and additional isolates from diverse substrates and geographical origins. Based on nine nuclear loci, i.e., ITS, LSU, act, tub2, cam, gapdh, his, tef1 and rpb2, as well as phenotypic data, the genus and species boundaries are assessed for Exserohilum. Three species, i.e., E. novae-zelandiae, E. paspali and E. sorghicola, are excluded from the genus and reallocated in Sporidesmiella and Curvularia, respectively, whereas E. heteropogonicola and E. inaequale are confirmed as members of Curvularia. Exserohilum rostratum is revealed as conspecific with species previously described in Exserohilum such as E. antillanum, E. gedarefense, E. leptochloae, E. longirostratum, E. macginnisii and E. prolatum. Additionally, E. curvatum is revealed as synonym of E. holmii, and E. fusiforme of E. oryzicola. A total of 11 Exserohilum phylogenetic species are described, illustrated and discussed, including one novel taxon, E. corniculatum. The placements of 15 other doubtful species are discussed, and E. elongatum is validated.

Molecular identification and in vitro response to antifungal drugs of clinical isolates of Exserohilum

Exserohilum is an agent of human and animal mycoses. Although classification has been based on a few subtle morphological differences, three species of clinical interest have been traditionally accepted. In this study, by using a multigene sequence analysis, we have demonstrated that Exserohilum longirostratum and E. mcginnisii are probable synonyms of E. rostratum. The isolates tested were mainly from the nasal region. Antifungal susceptibility testing demonstrated high activity of the eight agents tested against this fungus.

Melanized fungi in human disease

Melanized or dematiaceous fungi are associated with a wide variety of infectious syndromes, including chromoblastomycosis, mycetoma, and phaeohyphomycosis. [corrected]. Many are soil organisms and are generally distributed worldwide, though certain species appear to have restricted geographic ranges. Though they are uncommon causes of disease, melanized fungi have been increasingly recognized as important pathogens, with most reports occurring in the past 20 years. The spectrum of diseases with which they are associated has also broadened and includes allergic disease, superficial and deep local infections, pneumonia, brain abscess, and disseminated infection. For some infections in immunocompetent individuals, such as allergic fungal sinusitis and brain abscess, they are among the most common etiologic fungi. Melanin is a likely virulence factor for these fungi. Diagnosis relies on careful microscopic and pathological examination, as well as clinical assessment of the patient, as these fungi are often considered contaminants. Therapy varies depending upon the clinical syndrome. Local infection may be cured with excision alone, while systemic disease is often refractory to therapy. Triazoles such as voriconazole, posaconazole, and itraconazole have the most consistent in vitro activity. Further studies are needed to better understand the pathogenesis and optimal treatment of these uncommon infections.