Superficial Mycology

Question 1

Considered as cosmetic infections where no pathologic changes are observed or living tissue is invaded or cellular host response to the fungi (Non-irritating/ asymptomatic infection)

Answer 1

Superficial mycoses

Question 2

Two varieties of superficial mycoses

Answer 2

→ White: Pityriasis Versicolor, White Piedra
→ Black: Tinea Nigra, Black Piedra

*piedra: hair

Question 3

Organism which causes tinea nigra

Answer 3

Exophiala werneckii

Question 4

Organism which causes WHITE piedra

Answer 4

Trichosporon beigelii

Question 5

Organism which causes black piedra

Answer 5

Piedraia hortae

Question 6

Also known as Pityriasis versicolor and “An-an”

Answer 6

Tinea versicolor

Question 7

species under genus Malasezzia which is not lipophilic

Answer 7

M. pachydermatis

Question 8

most common isolates under genus Malasezzia

Answer 8

M globosa and restricta

Question 9

other diseases caused by Genus Malassezia

Answer 9

dandruff (restricta)
Seborrheic dermatitis (restricta and sympodialis)
folliculitis
septicemia

Question 10

clinical features of tinea versicolor

Answer 10

FLAT macular and demarcated lesions (with thin chalky branny scales)

Question 11

T or F: Pigmentation of tinea versicolor lesions depend on patient’s skin color

Answer 11

true

Question 12

What makes oily body parts (FANTS) or sebum harbor tinea versicolor pathogens?

Answer 12

waxy esters, fatty acids, triglycerides

Question 13

Tinea versicolor should be differentially diagnosed from

Answer 13

tinea alba (does not affect extremities usually)
vitiligo

Question 14

color of tinea versicolor lesions under woodlamp

Answer 14

pale green

Question 15

specimen used for microscopic examination of tinea versicolor

Answer 15

skin scrapings

Question 16

smear used for diagnosing skin scrapings of tinea versicolor

Answer 16

KOH with Parker ink

*only edges of the fungi are seen with KOH only

Question 17

direct microscopic examination of tinea versicolor under KOH and PAS shows

Answer 17

spaghetti (blastospores) and meatballs (angular hyphal elements) appearance

*pathognomonic

Question 18

media used for culturing tinea versicolor

Answer 18

PDA with fatty acids

*circular convex creamy colonies

Question 19

it is a slow-growing saprophytic dematiaceous fungi found in soil, compost, humus and wood

Answer 19

exophiala werneckii

Question 20

tinea nigra is most commonly found where

Answer 20

palms

Question 21

clinical manifestation of tinea nigra

Answer 21

non-scaling and non-inflammatory well-demarcated gray to brown-black macular lesions

Question 22

tinea nigra must be differentially diagnosed from

Answer 22

chemical burns

skin cell carcinoma

Question 23

seen under light microscope for tinea nigra

Answer 23

Pigmented brown to dark olivaceous septate hyphal elements

Budding 2-cell yeast with melanized cell walls

Question 24

darkly pigmented septa between 2 cells part of the outer cell wall in tinea nigra

Answer 24

annelide

Question 25

aged tinea nigra on PDA is characterized by

Answer 25

abundant aerial mycelia and velvety, dark olive in color

Question 26

tinea nigra in LPCB

Answer 26

2- celled (cylindrical and spindle-shaped) pale brown yeast cells

Question 27

piedra meaning

Answer 27

small stone *due to firm irregular nodules

Question 28

the mass of fungus in piedra can be found in

Answer 28

hair shaft

Question 29

clinical features of black piedra

Answer 29

Discrete, hard, more compact, gritty, brown to black concretions or nodules

Question 30

commonness of black piedra

Answer 30

Scalp hair > Beard, mustache > Axilla and groin hairs – rare

Question 31

specimen collected for black piedra

Answer 31

hair with nodules *with 25% KOH or NaOH

Question 32

seen under direct microscopic examination for black piedra

Answer 32

→ Dark septate hyphae → Round to oval asci → Hyaline, curved to fusiform ascospore, a sexual spore

Question 33

media used to isolate black piedra

Answer 33

SDA with chloramphenicol SDA with cycloheximide *very slow growth and island colonies

Question 34

black piedra in isolated culture is characterized by

Answer 34

→ Dark brown to black colonies with greenish brown, short aerial mycelium

Question 35

etiologic agent of white piedra

Answer 35

Trichosporon beigelii or Trichosporon cutaneum

Question 36

t or F: white piedra commonly appears in scalp, eyebrows and lashes

Answer 36

false: face, axilla, genitals

Question 37

specimen used for diagnosis

Answer 37

hair with nodules (+ 10% KOH or 25%NaOH + 5% glycerin)

Question 38

isolation of white piedra (same as black but without cycloheximide)

Answer 38

SDA with chloramphenicol without cycloheximide (rapid) | LPCB (Hyaline hyphae, Arthroconidia, Blastoconidia)

Question 39

other characteristics of WHITE PIEDRA

Answer 39

``` → Non-carbohydrate fermenting → Assimilates dextrose, lactose, D-xylose and inositol → Negative KNO3 assimilation → Urease positive → Splits arbutin ```