General fungal question

Question 1

Structure of fungi

Answer 1

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

Question 2

Fungi environmental preferences

Answer 2

Almost all are aerobic
Some are facultative anaerobic

Need moist environment

Prefer a slightly acidic pH.

Question 3

How do human pathogenic fungi reproduce?

What is asexual and sexual reproduction called in fungi?

Answer 3

Most human pathogenic fungi reproduce asexually.

This is called Anamorph reproduction

Sexual reproduction is called Telomorph.

Question 4

what are the types of asexual spores formed by fungi?

5

Answer 4

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.

Question 5

How are fungi classified.

Answer 5

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.

Question 6

What are the 7 fungal phyla?

Answer 6

Microsporidia

Chytridiomycota

Blastocladiomycota

Neocallimastigomycota

Glomeromyctoa

Ascomycota

Basidiomycota

Question 7

How are the mycoses classified medically?

Answer 7

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.

Question 8

What are the mycoses?

Answer 8

Dermatomycoses, aka Cutaneous mycoses

Subcutaneous mycoses

Systemic mycoses

Question 9

What are the major groups of dermatomycoses?

4

Answer 9

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

Question 10

What are the risk factors for dermatomycosis?

Answer 10

Heat and moisture. Athletes, Wrestlers, barefoot swimmers.

Lipids. Lipid TPN is a risk factor for disseminated form.

Question 11

What is mallassezia furfur and its disease/risk factors

Answer 11

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.

Question 12

What is the genus of the tinea species?

Answer 12

Trichophyton

Question 13

What are the clinical characteristics of subcutaneous mycoses?

Answer 13

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

Question 14

What are the Tinea species?

Answer 14

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

Question 15

What species are the subcutaneous mycoses?

Answer 15

Sporothrix schenckii - causes sporotrichosis.

Phialophora verrucosa
Fonsecaea pedrosoi
Cladosproium carrioni
- all cause chromomycoses aka chromoblastomycoses.

Question 16

Sprotrichosis, clinical symptoms and treatment?

Answer 16

Granulomatous ulcer forms at the implantation site.

Draining sinus tract and secondary ulcers along the lymphatic route.

Question 17

Chromoblastomycosis, causative agents, clinical symptoms and treatment.

Answer 17

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

Question 18

How are dematomycoses diagnosed and treated

Answer 18

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.

Question 19

What is the risk factor for subcutaneous mycoses?

Answer 19

Traumatic implantation with dirt or thorns of plants.

Question 20

What are the sytstemic mycoses?

Answer 20

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.

Question 21

What are the Opportunistic Mycoses?

6 groups

Answer 21

Cryptococcus neoformans
Cryptococcus gattii

Candida species: albicans, krusei, glabrata, tropicalis, parapsilosis.

Aspergillus

Pneumocystis jirovecii

Mucorales order: Rhizopus, Rhizomucor, Absidia, Mucor species.

Question 22

Risk factor for the opportunistic mycoses

Answer 22

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.