Fungi

Fungi Table

Cutaneous and Subcutaneous Mycoses
Fungi	Disease	Treatment
Malassezia furfur	Tinea versicolor	MiconazoleSelenium sulfide
Trichophyton, Microsporum, and Epidermophyton	Tineas (ringworm, jock itch, and athlete’s foot)	Imidazoles
Sporothrix schenckii	Sporotrichosis (rose gardner’s disease)	Itraconazole
Systemic Mycoses
Histoplasma capsulatum	Histoplasmosis (pneumonia)	FluconazoleAmphotericin B
Coccidioides immitis	Coccidioidomycosis (pneumonia, meningitis, and skin/bone infection)	FluconazoleAmphotericin B
Blastomyces dermatitidis	Blastomycosis (chronic inflammatory lung disease and skin/bone infection)	FluconazoleAmphotericin B
Paracoccidioides brasiliensis	Paracoccidioidomycosis (pneumonia)	FluconazoleAmphotericin B
Opportunistic Mycoses
Candida albicans	Oral thrushCandida intertrigoVaginitisDisseminated disease in immunocompromised (neutropenia)	NystatinAmphotericin B
Cryptococcus neoformans	Cryptococcosis (meningitis, pneumonia, and skin/bone infections)	Amphotericin BFlucytosine
Aspergillus	Allergic bronchopulmonary aspergillosisAspergillomaInvasive aspergillosis	ItraconazoleAmphotericin B
Mucor and Rhizopus	Mucormycosis (rhinocerebral infection)	Amphotericin B
Pneumocystis jiroveci	PCP (diffuse interstitial pneumonia)	TMP-SMX

Fungi Introduction

Fungi is a large group of eukaryotic organisms including yeasts, molds, and mushrooms
Yeast
- unicellular fungi
- reproduce by budding
  - reproduce more slowly than bacteria
- cells are spherical to ellipsoidal in shape
- buds that do not separate form long chains of yeast cells called pseudohyphae
  - Candida albicans forms pseudohyphae
Molds
- multicellular colonies
  - composed of clumps of intertwined branching hyphae
- grow by longitudinal extension
- produce spores
Dimorphic fungi
- can grow as either yeast or mold depending on the environmental conditions
  - usually grows as a yeast at body temperatures
  - “mold in the cold”
- examples
  - Histoplasma
  - Blastomyces
  - Coccidioides
Sporothrix

Fungal Morphology

Spores
- the reproductive structure of molds
  - adapted for dispersal
- conidia are asexual fungal spores (Greek: “konia” = “dust”)
  - most fungal spores are asexual
  - types of conidia include blastoconidia and arthroconidia
  - coccidioidomycosis and histoplasmosis are transmitted by inhalation of asexual species
Hyphae
- long, threadlike, branching, filamentous, tubular structure of a fungus
- composed of fungal cells attached end to end
- grow by extending from the ends of the tubules
Cell membrane
- innermost layer around fungal cytoplasm
- contains ergosterol
  - analogous to cholesterol in humans
  - amphotericin B and nystatin bind to ergosterol
  - ketoconazole inhibits ergosterol synthesis
Cell wall
- surrounds cell membrane
- contains mostly complex carbohydrates
  - explains calcification in chronic infection
- fungal cell walls are potent antigens
Capsule
- polysaccharide coating surrounding the cell wall
- visualized with India ink stain
- can be an antiphagocytic virulence factor
  - used by Cryptococcus neoformans