Fungal Infections

Question 1

how are fungal infections (mycoses) classified

Answer 1

by the degree of tissue involvement and the mode of entry into the host

Question 2

the different classifications for fungal infections

Answer 2

– Superficial
• Localized to the skin, the hair, and the nails.
– Relatively common in normal population. – Subcutaneous
– Systemic
• Deep infections of the internal organs.
– Relatively uncommon in normal population. – Opportunistic
• Infection only in the immuno compromised

Question 3

what is white piedra

Answer 3

superficial infection caused by several species of trichosporon

Question 4

trichosporon is a yeast genus with

Answer 4

arthroconidia which is spore forming

Question 5

what other types of infection can trichosporon cause

Answer 5

systemic and can also infect cutaneous tissue

Question 6

clinical presentation of white piedra

Answer 6

asymptomatic hair growth on outside of hair shaft – white, greenish, or yellowish soft nodules that can affect hair on scalp, eyebrows, beard, eyelashes, axilla, and groin

Question 7

treatment of white piedra

Answer 7

shaving or local application antifungal such as amphotericin B, clotrimazole, ketoconazole, itraconazole

Question 8

what is black piedra

Answer 8

asymptomatic superficial infection that is a visible colonization of the shaft of the hair

Question 9

difference between the nodules of black and white piedra

Answer 9

nodules of black piedra cannot be pulled as compared to the ones that can be pulled off in white piedra

Question 10

what causes black piedra

Answer 10

ascomycete genus piedraia

Question 11

how do you treat black piedra

Answer 11

it is difficult to treat and antifungals have been used with different levels of successes

Question 12

what is tinea nigra

Answer 12

superficial infection of the skin (stratum corneum) caused by hortae werneckii

Question 13

where are the black to brown lesions of tinea nigra commonly seen

Answer 13

palms and soles of the feet

Question 14

where are the pigmentation of tinea nigra more intense and what layers of the skin are affected

Answer 14

more intense near the borders

only dead layers affected – living tissue unaffected

Question 15

what is seen on the colony of tinea nigra

Answer 15

colonies are smooth with an oily glistening olive-black color

Question 16

what is seen on an aged colony of tinea nigra

Answer 16

aged colonies become velvety because of production of aerial hyphae – hyphae becomes darker with age

Question 17

properties of pityriasis versicolor: melassezia

Answer 17

dimorphic
lipophilic
mesophilic

Question 18

where does melassezia commonly affect?

Answer 18

sebum rich area like the chest and back

with higher incidences in areas with higher temp and humidity

Question 19

layer of skin melassezia affect

Answer 19

stratum corneum

Question 20

how does melassezia clinically present

Answer 20

macular rash or fine scaling of the upper trunk and shoulders

Question 21

complication of melassezia

Answer 21

erythematous follicular papules

Question 22

laboratory test to diagnose melassezia

Answer 22

skin scraping with KOH

Question 23

what is seen on microscopy with melassezia

Answer 23

both filaments and yeast since it is dimorphic

melassezia furfur - spaghetti and meatballs

Question 24

other infections involving melassezia

Answer 24

• pts receiving lipid nutrients through central venous catheter
• deep line catheter associated sepsis in neonates
• nurse who had a dog got the m. pachydermatis
• seborrheic dermatitis and dandruff

Question 25

old name for melassezia

Answer 25

pityrosporum ovale

Question 26

what does dermatophytes colonize

Answer 26

the keratinized tissue of stratum corneum

Question 27

where do dermatophyte typically invade

Answer 27

skin, nail, hair

Question 28

what does dermatophytes do to the skin, hair, nails

Answer 28

– Typical skin lesion • Annular (ring), scaly patch with a raised margin • Commonly called ring worm and jock itch. – Infection of hair • Causes hair loss leaving a dry scaly patch of skin – Nail infection • Nails become yellow, thickened, and crack

Question 29

predisposing conditions to chronic infections by dermatophyte

Answer 29

``` – Normal persons with “minor immunological blind spots” – Old age – Collagen vascular disease – Diabetes mellitus – Hematological malignancy ```

Question 30

how do you transmit dermatophytes

Answer 30

-contact with infected skin scales from humans or animals -scales can be carried to the next host by way of: • Dirty moist shower mats • Shared nail and hair clippers • Shared combs • Used shoes

Question 31

what are the dermatophytic fungi

Answer 31

– Trichophyton (worse of the three) – Microsporum – Epidermophyton

Question 32

what can the three dermatophytic fungi infect in terms of skin, hair, nails

Answer 32

- trichophyton: all three - microsporum: only skin and hair - epidermophton: only skin and nails

Question 33

what is seen on microscopy of trichophyton

Answer 33

- macroconidia and microconidia being the most numerous | - macroconidia are smooth walled pencil shaped-fusiform

Question 34

what does trichophyton secrete and what does that do

Answer 34

keratinases which allow dermatophyte to burrow deeper into the stratum corneum

Question 35

what can inhibit cell mediated immunity and keratinocyte proliferation which sheds fungus

Answer 35

mannan from cell wall and lipophilic toxin

Question 36

agar used for trichophyton and what is seen

Answer 36

sabourad agar/potato dextrose agar | on top is white looking powder while on reverse/bottom of agar is red looking powder

Question 37

major cause of ringworm in skin

Answer 37

trichophyton tonsurans

Question 38

what is tinea corporis

Answer 38

ringworm of upper part of covered body

Question 39

what do the lesions of tinea corporis look like

Answer 39

well marginated with raised erythematous vesicular borders

Question 40

more severe chronic tinea corporis is caused by

Answer 40

trichophyton rubrum

Question 41

what is tinea cruris and what is another name for it

Answer 41

infection of inguinal area involving groin, perianal, and perineal areas jock's itch

Question 42

what causes tinea cruris

Answer 42

trichophyton rubrum or epidermophyton floccosum

Question 43

how does tinea cruris clinically present

Answer 43

- lesions are erythematous, scaly inflamed borders with vesicles - bilaterally extends down the sides of inner thighs, waist area and buttocks

Question 44

what is tinea capitis

Answer 44

infection of the scalp, eyebrows, eye lashes

Question 45

common agents of tinea capitis

Answer 45

- ectothrix ringworm: microsporum (m. audouinni, m. canis, m. gypseum) - endothrix ringworm: trichophyton tonsurans

Question 46

difference between ectothrix and endothrix invasion

Answer 46

- ectothrix: fungus form sheath of hyphae and arthroconidia around shafts of hair - endothrix: hyphae invades the hair follicles and shaft and form many spores within the hair shaft

Question 47

when does one see the "black dot" appearance

Answer 47

if endothrix invasion in tinea capitis -- seen on scalp

Question 48

common agent of tinea pedis aka athlete's foot

Answer 48

t. rubrum, e. floccosum, t. mentagrophytes

Question 49

what is tinea barbae and what are the causative agents

Answer 49

infection of the beard area caused by t. verrucosum (cattle) and t. mentagrophytes (mice, rodents)

Question 50

what is tinea unguium and what causes it

Answer 50

infection of the nail plate by a dermatophyte | e. floccosum, t. rubrum, t. mentagrophytes