Medically important fungi

Medically important fungi

1. Cocciodiodes immitis - biphasic life cycle

   • Valley fever (coccidiodomycosis) - self-limiting respiratory infection that occurs after inhalation of conidia of the fungi (spores). Endemic in south-west USA/Mexico/South America. Self-limiting but may spread to lungs, bones, meningis etc. African-Americans and Fillipinos more susceptible. Treatment with antifungal drugs.

2. Superficial mycoses - due to overgrowth of normal flora

   • Malassezia furfur - a benign fungal infection that grows slowly and causes irregular patches of hyperpigmentation (Pityriasis)

3. Cutaneous mycoses - overgrowth of normal flora, affects skin, nails and scalp (dermis + epidermis), chronic, diagnose with scrapings. Can cause tinea.

   • Microsporum canis - ringworm, can acquire from pets. Produces yellow pigment on agar.Spindle-shaped macroconidia and thick-walled microconidia.
   • Trichophyton rubrum - transmitted between humans. Wine-red pigment production. Only microconidias present.
   • Trichophyton mentagrophytes - can be from human or animals, 2 varieties. Yellow-brown pigment production on agar. Have spiral hyphae, dense micoconidia, multi-septate macroconidia.
   • TINEA- highly inflammatory dermatophyte infection
     • Tinea pedis - superficial inflammatory process, lacerations between toes
     • Tinea corporis = glaborous skin
     • Tinea cruris - see red circular lesions in groin area which increase in size
     • Tinea barbae - in the bearded region
     • Tinea capitis - hair and scalp
       • Ectrothrix - spores of fungi can grow in surface of the hair eg.T.mentagrophytes
       • Endothrix - spores are inside hair follicles eg.T.tonsurans
   • Onychomycosis - more severe, nails are discoloured/brittle, systemic treatment required

4. Yeasts - unicellular fungi, reproduce by budding/fusion, larger than bacteria

5. Moulds - multicelullular with hyphae, produce granular fluffy colonies

6. Opportunistic mycoses - can involve skin, mucosal surfaces, GI tract and systemic illness. Affects immunocompromised hosts.

   • Candidiasis (YEAST) - can be acute, subacute and chronic.
     • Interdigital
     • Chronic = Onychomycosis - growth in nail tissues . Oral - can happen in AIDS.
     • Invasive - eg. Urine - multiplying yeast cells and blastoconidia bursting from pseudohyphae.

7. Dimorphic - behaves as yeast in higher temps and as a mould in lower temps

   • Sporothrix schenkii - causes Sporotrichosis - ubiquitous in soil
     • which is a chronic infection in skin, subcutaneous tissue, lymphatics. get intradermal microabcesses. may spread to muscles/bones/lungs. can see discharging lymph nodes.

8. Endemic (systemic) mycoses: have 2 phases - environmental and tissue phase, inhalation of spores eg.C.immitis

   • YEAST = Cryptococcus (neoformans and gatii) - caused by inhalation
     • encapsulated yeast, will present as white mucoid colonies on solid media. Opportunistic, affects the lungs, can spread to CNS - can present at pneumoniae/meningitis. infection can disseminate.
       • Detection: capsules around yeast, PCR for DNA, culture, detect Ag
     • C.neoformans - pigeon droppings
     • C.gatii - red river gum tree. endemic in Australia, South California, Cenral Africa, Brazil