Mycology-study

Fungal Infection
Mycosis

Dimorphic Fungi
Fungi that can have a nonmould (e.g. yeast) and a mould phase

Saprobe
Organism capable of living on decaying organic material

Hyphae
long, branching filaments that come together to form mycelium

Septate hyphae
hyphae with cellular separation and cross-walls.

Sparsely septate hyphae
AKA aseptate hyphae. Contain few separations

Pseudohyphae
Chains of cells formed by budding that resembles true hyphae.

Vegatative hyphae
The portion of hyphae that extend below the agar. Function as nutrient absorption.

Aerial hyphae
The portion of hyphae that extend above the agar. Function as support for reproductive structures – conidia.

Conidia
Asexual reproductive structures. Important for ID and morphological development.

Microconidia
Single-celled, small conidia

Macroconidia
Multi-cellular, large conidia

Arthroconidia
Conidia that result from fragmentation of hyphae into individual cells.

Perfect fungi
Fungi that undergo sexual reproduction

Imperfect fungi
Fungi that only indergos only asexual reproduction. The only fungal groups that produce conidia.

SDA
General purpose agar. Nutriet poor and selective for fungi.

SABHI
Brain Heart Infused agar. Nonselective for fungi. Contains dextrose, peptone, BHI. Make selective for dimorphs with the addition of cyclohexamide, chloramphenicol, gentamicin.

Inhibitory Mold Agar (IMA)
Selective agar for most fungal pathogens.

Dermatophyte Test Agar (DTA)
Used to isolate dermatophytes. Contains cyclohexamide, gent, and phenol red as pH indicator.

Mold/Yeast differential agars (4)
(1) potato dextrose agar (2) Bird seed and caffeine acid agars (3) cornmeal agar w/tween 80 (4) Rice, casein, and other nutrients.

PDA
Used to enhance conidia devt. pigment devt of T rubrum.

Birdseed agar
Selective and differential for C. neoformans. Brown to black colonies.

Cornmeal agar with Tween 80
Differentiate Candida spp.

Rice, casein agar
Differentiate Trichophyton spp.

Lactophenol cotton blue
ised to stain and preserve fungal elements.

Potassium hydroxide (KOH)
Used to dissolve nonfungal elements

India Ink
Reveal capsule surrounding C. neofomanans in CSF

Calcofluor white stain
A fluorochrome that stains chitin found in the cell wall of fungi. Viewed under UV light. Fungi appear white to blue.

Clinically significant yeasts (5)
(1) Candida albicans (2) Cryptococcus neoformans (3) Trichosporon (4) Rhodotorula (5) Geotrichum candidum

Opportunistic fungi (3)
(1) Aspergillus spp. (2) Zygomycetes (3) Fusarium

Blood (systemic) fungal pathogens (4)
(1) Candida spp (2) Blastomyces dermatitis (3) Histoplasma capsulatum (4) Cryptococcus neoformans

CSF fungal specimens (4)
(1) Cryptococcus neoformans (2) Candida (3) Histoplasma capsulatum (4) Coccidioides immitis

Hair fungal pathogens (2)
(1) Microsporum (2) Trichophyton

Nail fungal pathogens (3)
(1) Aspergillus (2) Epidermophyton (3) Trichophyton

Skin fungal pathogens (5)
(1) Candida – onychomycosis, paronychomycosis (2) Microsporum (3) Trichophyton (4) Epidermophyton (5) Blastomyces dermatitidis

Lung fungal pathogens (7)
(1) Candida albicans (2) Aspergillus (3) Rhizopus (4) Penicillum (5) Histoplasma capsulatum (6) Blastomyces dermatitidis (7) Coccidioides immitis

Throat fungal pathogens (2)
(1) C. albicans – thrush (2) Geotrichum candidum

Urine fungal pathogens (2)
(1) C. albicans – vulvovaginitis (2) C. glabrata

Genital tract pathogens (1)
C. albicans – vulvovaginitis

Urease Test and fungal specimens (2)
(1) Cryptococcus spp and positive (2) C. albicans in neg control

Candida albicans (5)
(1) Grows on fungal media, SBA, CHOC, EMB (2) Tween 80 = chlamydiospores (3) Urease neg (except C. krusei) (4) Unositol neg (5) color dif on CHROMagar

Cryptococcus neoformans (6)
(1) bat/pigeon droppings, contaminated veges/milk (2) Direct stain shows capsules in tissue with eosin/hematoxylin (3) Black/brown cultures on bird seed agar (4) positive urease (5) pos phenol oxidase (6) nitrate neg

Two Circular Fungi (2)
(1) C. neoformans (2) Cocci immitis

Tricosporon (3)
(1) White piedra on hair (2) urease pos (3) assimilate carbohydrate

Rhodotorula (3)
(1) moist environment (2) soil, dairy products (3) resemble Crypto but inositol neg

Aspergillus spp (2)
(1) fluffy growth at 2 days SABHI (2) conidiophores arise from foot cells to support a single vesicle

Aspergillus fumigatus (3)
(1) Most common cause of aspergillis (2) causes otomycosis (3) Conidiophores arise from foot cell. which support a single vesicle at their tip.

Aspergillus niger (1)
(1) On SABHI – grows black with a yellow reverse.

Zygomycetes (6)
(1) Absidia (2) Mucor (3) Rhizomucor (4) Rhizopus (5) Syncephalastrum (6) Generally opportunistic

Fusarium (2)
(1) Opportunistic mycetomas, keratitis, systemic infections (2) White, cottony colonies

Mycoses (3)
(1) skin and superficial tissue infections (2) superficial mycoses = epithelial, nail infections (3) Cutaneous mycoses = deeper layers of skin infections

Saprophytic fungi
Fungi that only live on organic matter

Dermatophytes (4)
(1) keratinophilic (2) Trichophyton (3) Epidermophyton (3) Microsporum

Keratinophilic
metabolize keratin

Trichophyton (3)
infect hair, nails, skin

Epidermophyton (2)
infect skin and, nails

Microsporum (2)
infect hair and skin

Tinea Pedis (3)
(1) athletes foot (2) Trichophyton, epidermophyton

Tinea corpus (3)
(1) ringworm – circular patches of skin (2) Microsporum, trichophyton

Tinea unguium (3)
(1) onychomycosis – nail destruction (2) epidermophyton, trichophyton

Tinea capitis (3)
(1) scalp infection (2) microsporum, trichophyton

Tinea barbae (3)
(1) beard infection (2) microsporum, trichophyton

Tinea cruris (3)
(1) jock itch (2) trichophyton, epidermophyton

ID of dermatophytes (3)
(1) colony morph (2) microscopic appearance (3) hair perforation test

Trichophyton characteristics (4)
(1) 7-10 days on SABHI (2) buff, granular and white colonies (3) many microconidia and few macroconidia – 3-7 cells (4) T. rubrum, T. mentagrophytes, T. verrucosum

Epidermophyton characteristics (4)
(1) 10 days on SABHI (2) yellow colonies with tan reverse (3) multiple macroconidia only (4) can have chlamydiospores and racquet hyphae

Microsporum (4)
(1) very slow growers (2) tan colonies with salmon reverse (3) microconidia and macroconidia – 4-15 cells (4) M. audouinii (arthro), M. canis (zoo), M. gypseum (geo)

Superficial mycoses (4)
(1) Tinea versicolor (2) Tinea nigra (3) Black pieda (4) White piedra

Cutaneous and superficial fungal infection
Caused by dermatophytes

Subcutaneous fungal infection
Caused by dematiaceous fungi

Subcutaneous infections associated with dematiaceous fungi (4)
(1) mycetoma (2) chromoblastomycosis (3) phaeophomycosis (4) sporotrichosis

Blastomyces dermatitides (4)
(1) Respiratory, systemic (2) Spore inhalation (3) Ohio/Mississippi river valley (4) Dimorph

Coccidioides immitis (5)
(1) Respiratory, systemic (2) Spore inhalation (3) Valley fever – central valley (4) arthroconidia (5) moist/white turn fluffy after a week

Histoplasma capsulatum (5)
(1) Respiratory, systemic (2) Spore inhalation, bat guano, bird droppings (3) Southern US, Midwest, Appalacia (4) Dimorph (5) macro/microconidia

Paracoccidioides brasiliensis (4)
(1) Respiratory, systemic (2) Spore inhalation, ingestion (3) South America (40) dimorph

Penicillum marneffei (2)
(1) Dimorph (2) Only penicillin that is true path

Pneumocystis jirovecii (3)
(1) LRT (2) immunocompromised (3) Cysts stain with methanamine silver, giemsa, calcofluro, acid-Schiff

A 38 yr old male from Ohio presents with chest infiltrates and has been cleaning up bird s*it. What could it be? (a) A. fumigatus (b) C. immitis (c) C. albicans (d) H. capsulatum
D – Ohio river valley fever

A man has been living in the San Joaquin Vally and presents with a fungal nodule. It is most likely: (a) A. fumigatus (b) B. dermititidis (c) C. immitis (d) H. capsulatum
C – central valley fever

After being pricked by a thorn, a patient developed subcutaneous fungal infection a necrotic ulcer. Dimorphic – yeast at 35 deg, mould at RT with delicate hyphae ad conidia. What disease? (a) blastomycosis (b) chromomycosis (c) mycetoma (d) sporotrichosis
D – Sporothrix schenckii is causative agent after deep implantation.

A yeastlike fungi was isolated from sputum. No hyphae seen on Tween 80, nitrate neg, inositol pos, urease at 37 deg. These are consistent with: (a) C. krusei (b) C. terreus (c) C. neoformans (d) T. bergelii
C – all are urease pos, A and D produce hyphae, B is nitrate pos and does not grow at 35 deg

Which of the following types of Candida albicans infection commonly acquired from an exogenous source? (a) Diaper rash (b) Neonatal thrush (c) perianal infection (d) UTI
B -oral Candidiasis generally acquired by mother with vaginal Candida.

In a direct exam of a KOH wet mount of a nail specimen, Epidermophyton floccosum could be detected as: (a) Arthrocondia (b) Blastoconidia (c) Macroconidia (d) Microconidia
A – Could be E. floccosum of Trichophyton. But A. floccosum produces arthroconidia

The mold phase of the systemic fungus Blastomyces dermatitis can be confused with: (a) Scedosporium apiospermum (b) Sporothrix schenckii (c) Aspergillus spp (d) Penicillium notatum
A

A fungal culture with hyaline, septate hyphae, and a young conidiophore with a foot cell, and a swollen vescicle and good clues to ID: (a) Acremonium (b) Aspergillus (c) Paecilomyces (d) Penicillium
B – conidiophore arising from a foot cell and terminating in a vescicle are good clues for aspergillus.

In clinical specimens, Zygomycetes are: (a) common, normal human microflora (b) contaminants only (c) Can have a dimorph tissue phase (d) Can cause a rapidly fatal infection
D – generally contanimants, but acan be fatal very quickly

T. rubrum and T. mentagrophytes may be differentiated by the: (a) colony morphology (b) Endothrix hair infection produced by T. rubrum (c) Flourescence of hair infected with T. rubrum (D) In vitro hair penetration by T. mentagrophytes
D – If Trichophyton is suspected, a hair perferation test should be requested.

Broad, coenocytic (nonseptate) hyphae found in tissue would be most typical of an infection with: (a) aspergillus (b) blastomyces (c) microsporum (d) rhizopus
D – all others have septate hyphae.

Fungus infecting the skin and nails typically produces in culture: (a) Spindle-shaped, hyaline, echinulate, macroconidia and microconidia (b) Cylindrical or club-shaped, smooth, thin-walled macroconida and microconidia (c) clusters of microconidia (d) large, thin-walled, club-shaped macroconidia w/o microconidia
D – skin and nails are effected by epidermophyton which do not produce microconidia

C. albicans is rapidl ID’d by: (a) failure to assimilate sucrose (b) “feathering” on EMB (c) chlamydiospores (d) germ tubes
D – chlamydiospores take 24-48 hours at RT

Which of the following stains greatly enhances the visibility of fungi to cell walls and causes fluorescence: (a) Rhodamine-auramine (b) Warthin-Starry (c) Calcofluor (d) Periodic acid-Schiff
C – binds chitin in cell wall

This fungi is dimorphic, has a tissue phase, mother cells with 12 narrow-necked buds, mycelium, chlamydiospores, and coiled hyphae: (a) Blastomyces dermititidis (b) Coccidiodes immitis (c) Histoplasma capsulatum (d) Paracoccidiodes brasiliensis
D

The formation of arthroconidia is not important in which fungi? (a) Coccidiodes (b) Geotrichum (c) Trichosporon (d) Sporothrix
D

A black pigment produced by colonies growing on bird seed agar is due to: (a) urease (b) phenol oxidase (c) sucrose assimilation (d) arthroconidia production
B – PO breaks down niger seeds to melanin. C neoformans.

Which is not opportunistic? (a) Absidia (b) Aspergillus (c) Coccidioides (d) Fusarium
C – cocci is a true pathogen

Which of the following contains species found as a dematiaceous contaminant? (a) alternaria (b) aspergillus (c) fusarium (d) penicillium
A – Dark hyphae and black bottom of plate

Which of the following is found as a common saprobe and as an agent of keratitis? (a) Exophiala (b) Phialophora (c) fusarium (d) wamggiella
C – ID’d by cornea scraping

The microscopic ID of Pneumocystis jirovecii is based in the detection of: (a) Arthroconidia in subcutaneous tissue (b) cysts and trophs in respiratory specimens (c) yeast in respiratory system (d) tuberulate macroconidia in ling tissue
B – silver or giemsa stain

Fungi that undergo asexual reproduction are termed: (a) imperfect (b) perfect (c) aseptate (d) septate
A

Hyaline septate hyphae, conidiophores, and multicellular banana-shaped conidia are characteristic of: (a) Fusarium (b) Curvularia (c) Acremonium (d) Trichophyton
A – microconidia also

What does not describe Rhodotorula rubra? (a) isolated from dairy, soil, water (b) most common cause of diaper rash (c) nosocomial pathogen (d) contaminant/commensal in urine, sputum, feces
C – C. albicans is diaper rash

What organism is likely to cause a light brown lesion on the upper back? (a) Candida albicans (b) Fusarium spp (c) Geotrichum candidum (d) Malassezia furfur
D – M. furfur is the major cause of tinea (pityriasis) versicolor. Tropical and subtropical regions.

Which is likely to be found in clinical specimens as normal microflora and as clinically significant isolates? (a) Aspergillus niger (b) Paracoccidioides brasiliensis (c) Penicillium marneffei (d) Candida albicans
D – endogenous opportunistic pathogen. A is a contaminant. B, C are not endogenous and cause systemic mycoses

A 4 year olds hair is falling out in patches and fluoresces when subjected to a Woods Lamp. The culture is white, cottony, growth at 25 deg on PDA. Microscopically there are rare microconidia, septate hyphae, terminal chlamydiospores, no macroconidia. Does not grow on rice grains. (a) Microsporidium audouinii (b) Microsporidium gypseum (c) Trichophyton mentagrophytes (d) Trichophyton rubrum
A – most commonly effects children. The only Microsporidium that does not grow on rice grains.

In tissue infected with Histoplasma capsulatum (a) the hyphae usually invade blood (b) encapsulated yeast are typical (c) tuberculate macroconidia are typical (d) The fungus is intracellular
D – found inside WBC’s. Halo may be mistaken for a capsule

Blastomycosis is likely found in which environment? (a) Lower Sonoran life zone (b) Mississipi and Ohio River valleys (c) Pigeon roosts (d) bat roosts
B – although rarely found in the environment

Coccidiomycosis is likely found in which environment? (a) Lower Sonoran life zone (b) Mississipi and Ohio River valleys (c) Pigeon roosts (d) bat roosts
A – dry, winters cold above freezing

Cryptococcus is likely found in which environment? (a) Lower Sonoran life zone (b) Mississipi and Ohio River valleys (c) Pigeon roosts (d) bat roosts
C – endemic to pigeon guts, not pathogenic to pigeons

Histoplasmosis is likely to be caused by contact with which environment? (a) Sphagnum moss (b) Starling roosts (c) Stagnent fresh water (d) colorado river valley
B – common in the Mississippi and Ohio River valleys

Sporotrichosis is likely to be caused by contact with which environment? (a) Sphagnum moss (b) Starling roosts (c) Stagnent fresh water (d) colorado river valley
A – caused by traumatic implantation

White piedra is caused by: (a) Hortaea werneckii (b) Trichosporon spp (c) Piedraia hortea (d) Fonsecaea compacta
B – white nodules in the hair shaft

Black piedra is caused by: (a) Hortaea werneckii (b) Trichosporon spp (c) Piedraia hortea (d) Fonsecaea compacta
C – black nodules on hair shaft

Tinea nigra is caused by: (a) Hortaea werneckii (b) Trichosporon spp (c) Piedraia hortea (d) Fonsecaea compacta
A – black/brown nodules on hands and forearms. Dematiaceous, septate hyphae.

The cause of tinea versicolor is (a) Aspergillus niger (b) Malassesia fufur (c) Microsporum gypseum (d) Geotrichum candida
B – chronic, mild, superficial skin infection

A keratinophilic saprophyte is (a) Aspergillus niger (b) Malassesia fufur (c) Microsporum gypseum (d) Geotrichum candida
C – dermatophyte

The cause of otomycosis is (a) Aspergillus niger (b) Malassesia fufur (c) Microsporum gypseum (d) Geotrichum candida
A – 90% of ear infectoions

On cornmeal agar with tween 80, the following displays true hyphae and arthroconidia only (a) Candida albicans (b) Geotrichum (c) Trichosporon (d) Aspergillus fumigatus
B – geotrichum displays arthroconidia only

On cornmeal agar with tween 80, the following displays true hyphae, arthroconidia, and blastoconidia (a) Candida albicans (b) Geotrichum (c) Trichosporon (d) Aspergillus fumigatus
C – differentiate via blastoconidia (rare)

On cornmeal agar with tween 80, the following displays pseudohyphae, blastoconidia, and chlamydospores (a) Candida albicans (b) Geotrichum (c) Trichosporon (d) Aspergillus fumigatus
A

On cornmeal agar with Tween 80, the following displays pseudohyphae and blastospores: (a) Mucor spp (b) Candida tropicalis (c) Cryptococcus neoformans (d) Candida albicans
B – long braching pseudohyphae. blue on CHROMagar

On cornmeal agar with Tween 80, the following displays blastospores only w/o hyphae or pseudohyphae: (a) Mucor spp (b) Candida tropicalis (c) Cryptococcus neoformans (d) Candida albicans
C – also urease pos, nitrate neg, brown pigment on birdseed agar.

Cryptococcus neoformans is most commonly isolated from: (a) Bone Marrow (b) CSF (c) chronic draining os sinus tract of foot (d) chronic interdigital lesion of foot
B

Histoplasmosis capsulatum is most commonly isolated from: (a) Bone Marrow (b) CSF (c) chronic draining os sinus tract of foot (d) chronic interdigital lesion of foot
A

Pseudallescheria boydii is most commonly isolated from: (a) Bone Marrow (b) CSF (c) chronic draining os sinus tract of foot (d) chronic interdigital lesion of foot
C – eumycotic mycetoma

Trichophyton mentagrophytes is most commonly isolated from: (a) Bone Marrow (b) CSF (c) chronic draining os sinus tract of foot (d) chronic interdigital lesion of foot
D – intertiginous tinea pedis. Usually between toes

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