ABSTRACT
Phaeohyphomycosis is the term used to denote the infections caused by more than 100 species in 60 genera belonging to dematiaceous fungal pathogens (including the common and closely related genera Bipolaris, Drechslera, and Exserohilum). The genus Exserohilum was established1 for species having distinctly protruding hila.2 This eliminated the inconsistency and permitted a more logical grouping of species into three anamorphic genera, Bipolaris, Drechslera, and Exserohilum. Alcorn et al.3 described in detail the concept and justi–cation for grouping them into three genera. Exserohilum species are ubiquitous but rarely pathogenic for human beings. They are encountered in grass or rotting wood and thrive in warm and humid climates. The genus is characterized by its conidia, which are ellipsoidal, distoseptate, and have a protruding and truncate hilum. Three species of Exserohilum have been recognized as human pathogens: Exserohilum rostratum, Exserohilum longirostratum, and Exserohilum mcginnisii. The most common infections caused by Exserohilum species are sinusitis and
skin infections, although a few cases of cerebral abscesses, keratitis, osteomyelitis, prosthetic valve endocarditis, and disseminated infection have been described.4-7
9.1.1.1 Classification The taxonomic classi–cation is as follows: Kingdom Fungi, Phylum Ascomycota, Class Euascomycetes, Order Pleosporales, Family Pleosporaceae, Genus Exserohilum. The distinct telemorphic state of Exserohilum is Setosphaeria. Exserohilum is a terrestrial plant pathogen and is differentiated from the closely related genera based on the conidial formation from a protruding exserted hilum. The dark pigmentation is caused by deposition of dihydroxynaphthalene melanin.4 The hilum is present as a scar on a conidium, at the point of attachment to the conidiophore. It is distinguished on the basis of conidial shape and size, hilar morphology, location and sequence of the conidial septa, and the origin of the germ tubes from the conidial cells. The conidium of
9.1 Introduction ....................................................................................................................................................................... 83 9.1.1 Classi–cation, Morphology, and Biology .............................................................................................................. 83
9.1.1.1 Classi–cation ........................................................................................................................................... 83 9.1.1.2 Description and Natural Habitats ........................................................................................................... 84
9.1.2 Epidemiology ......................................................................................................................................................... 84 9.1.3 Pathogenesis and Clinical Features ....................................................................................................................... 85
9.1.3.1 Invasive and Noninvasive Infections ...................................................................................................... 85 9.1.3.2 Signs and Symptoms ............................................................................................................................... 85
9.1.4 Immune Response ................................................................................................................................................. 86 9.1.5 Diagnosis ............................................................................................................................................................... 86
9.1.5.1 Phenotypic Identi–cation ........................................................................................................................ 86 9.1.5.2 Genotypic Identi–cation.......................................................................................................................... 86
9.1.6 Treatment and Outcome ........................................................................................................................................ 87 9.2 Methods ............................................................................................................................................................................. 88
9.2.1 Sample Preparation ................................................................................................................................................ 88 9.2.2 Detection Procedures ............................................................................................................................................. 88
9.2.2.1 Phenotypical Criteria for Identi–cation of Molds ................................................................................... 88 9.2.2.2 Slide Culture ........................................................................................................................................... 88 9.2.2.3 Lactophenol Cotton Blue Mount ............................................................................................................. 89 9.2.2.4 Lactophenol Mounts with Tease Mount Procedure ................................................................................ 89 9.2.2.5 Scotch Tape Lactophenol Mount ............................................................................................................ 89 9.2.2.6 Molecular Detection Method .................................................................................................................. 90
9.3 Conclusion and Future Perspectives .................................................................................................................................. 90 References ................................................................................................................................................................................... 91
Exserohilum species is ellipsoidal to fusiod and germinates by germ tubes originating from either one or both of the end cells or other intermediate cells.
