General fungal question Flashcards
Structure of fungi
Cell walls with Chitin. N-glucosamine polymer
Ergosterol in the cell membrane
eukaryotes so 80S rRNA
yeasts, unicellular 3-15 uM
molds, multicellular forming branching hyphae and a mat called a mycelium
dimorphic, can be either
Fungi environmental preferences
Almost all are aerobic
Some are facultative anaerobic
Need moist environment
Prefer a slightly acidic pH.
How do human pathogenic fungi reproduce?
What is asexual and sexual reproduction called in fungi?
Most human pathogenic fungi reproduce asexually.
This is called Anamorph reproduction
Sexual reproduction is called Telomorph.
what are the types of asexual spores formed by fungi?
5
Chlamydospores:
thick walled spores that are heat and dessicant resistant.
form inside hyphae or pseudohyphae
Candida albicans
Arthrospores, arthroconidia
Formed by fragmentation of a hyphae
Coccidioides immitis
Sporangiospores
made in a sporangium, sac like structure on the end of a sporangiophore of a pseudohyphae
Rhisopus, Mucor species.
Conidia, Conidiospores
Many special phialide cells extend off of a conidiophore like fingers, and they produce condiospores.
Aspergillus, Penicillium, Dermatophytes
Blastospores, Blastoconidia
Conidia form by budding, typcially off of yeasts.
Cladosporium.
How are fungi classified.
It has changed a lot,
They are classified based on their sexual spores and sexual reproductive structures.
They are eukaryotic and more closely related to animals than plants.
Kingdom fungi
Currently 7 phyla.
What are the 7 fungal phyla?
Microsporidia
Chytridiomycota
Blastocladiomycota
Neocallimastigomycota
Glomeromyctoa
Ascomycota
Basidiomycota
How are the mycoses classified medically?
Based on the site/type of infection:
Superficial, cutaneous, subcutaneous, or systemic mycoeses.
Based on their exogenous or endogenous acquisition infection by a normal flora
Based on type of virulence,
Primary pathogens, always pathogenic causing defined infections, in well defined geographic ranges
or
Opportunistic pathogens, cause infections in immunocompromised, not confined geographically.
What are the mycoses?
Dermatomycoses, aka Cutaneous mycoses
Subcutaneous mycoses
Systemic mycoses
What are the major groups of dermatomycoses?
4
Cause cutanous infections that do not pass the skin/epidermis layer.
Malassezia furfur
Microsporum species
Epidermophyton floccosum
Trichophyton
Black and White Piedra, infect hair shafts.
Piedraia hortae and Trichosporon species
What are the risk factors for dermatomycosis?
Heat and moisture. Athletes, Wrestlers, barefoot swimmers.
Lipids. Lipid TPN is a risk factor for disseminated form.
What is mallassezia furfur and its disease/risk factors
Malassezia furfur –> causes pityriasis versicolor
A normal skin flora that is an opportunistic pathogen.
Patches of hypo or hyperpigmented skin, no other symptoms in healthy people. Acids made by the fungus damages melanocytes causing depigmentation
In IC’d,
Risk for malasseia fungemia, especially in Neonates recieving total parenteral nutrition, because the fungus is lipophillic.
Causes: Sepsis and thrombocytopenia.
What is the genus of the tinea species?
Trichophyton
What are the clinical characteristics of subcutaneous mycoses?
They infect the subcutaneous layer, and infections start due to Traumatic Implantation.
They survive by degrading local tissue with their exozymes, and creating a MicroAerophilic enviroment
They don’t spread systemically,
Some spread via lymphatics to local lymph nodes.
At wound site:
Abscesses and ulcers
Draining sinus tracts
What are the Tinea species?
Dermal mycoses, superficial mycoses, cause rash and local skin inflammation. Tinea means worm, they are the ringworms.
pedis - foot corporis - ring worm, anywhere cruris - crotch capitis - head, scalp ringworm barbae - bearded area of the face and neck onychomycosis - nail faciei - face. nigra - causes black pigmented spots.
Tinea species named based on the part of the body the typically colonize.
Tineas cause itching and epidermis inflammation
What species are the subcutaneous mycoses?
Sporothrix schenckii - causes sporotrichosis.
Phialophora verrucosa
Fonsecaea pedrosoi
Cladosproium carrioni
- all cause chromomycoses aka chromoblastomycoses.
Sprotrichosis, clinical symptoms and treatment?
Granulomatous ulcer forms at the implantation site.
Draining sinus tract and secondary ulcers along the lymphatic route.
Chromoblastomycosis, causative agents, clinical symptoms and treatment.
Chromoblastomycosis, aka cladosporiosis.
Cladosporium carrionii
Fonsecaea pedrosoi
Phialophora verrucosa
Very slow growing subcutaneous infection, causing wart-like, papilloma/verrucous lesions. that are red and inflamed along the lymphatic line.
Can rarely spread via lymphatics “metastasize” to new sites, or cause lymphedema, elephantiasis.
Though it is slow growing it is tough to treat and very resistant.
Oral terbinafine
Oral Itraconazole
Cryosurgery with liquid nitrogen
How are dematomycoses diagnosed and treated
Skin scrapings with KOH prep.
Wood’s lamp illuminates microsporum and malassezia
Rx: topical Azoles, Iconazole
Onychomycoses, nail infections need to be treated systemically.
Oral Terbinafine
or
Oral Griseofulvin.
What is the risk factor for subcutaneous mycoses?
Traumatic implantation with dirt or thorns of plants.
What are the sytstemic mycoses?
Histoplasma capsulatum
Blastomyces dermatitidis
Paracoccidioides brasiliensis
Coccidioides immits
(from smallest to largest)
All are dimorphic.
They are all primary pathogens, cause infection in healthy people and are not opportunistic.
Risk factor is inhalation of fungi-laden dust or spores.
All of them cause as primary lung infection that then disseminates hematogenously.
What are the Opportunistic Mycoses?
6 groups
Cryptococcus neoformans
Cryptococcus gattii
Candida species: albicans, krusei, glabrata, tropicalis, parapsilosis.
Aspergillus
Pneumocystis jirovecii
Mucorales order: Rhizopus, Rhizomucor, Absidia, Mucor species.
Risk factor for the opportunistic mycoses
Immunocompromised patients
HIV, Leukemias, neutropenias Diabetics, Diabetic keotacidosis Transplant patients Corticosteroid therapy Radiotherapy Burns Wounds Immunodeficiencies
Lung disorders, Granulomatous lesions
Pregnancy
Oral contraceptives
Diabetes
Old age.
