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Micro Post Midterm > Fungal Infections > Flashcards

Fungal Infections Flashcards

1
Q

how are fungal infections (mycoses) classified

A

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

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2
Q

the different classifications for fungal infections

A

– 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

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3
Q

what is white piedra

A

superficial infection caused by several species of trichosporon

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4
Q

trichosporon is a yeast genus with

A

arthroconidia which is spore forming

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5
Q

what other types of infection can trichosporon cause

A

systemic and can also infect cutaneous tissue

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6
Q

clinical presentation of white piedra

A

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

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7
Q

treatment of white piedra

A

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

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8
Q

what is black piedra

A

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

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9
Q

difference between the nodules of black and white piedra

A

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

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10
Q

what causes black piedra

A

ascomycete genus piedraia

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11
Q

how do you treat black piedra

A

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

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12
Q

what is tinea nigra

A

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

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13
Q

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

A

palms and soles of the feet

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14
Q

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

A

more intense near the borders

only dead layers affected – living tissue unaffected

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15
Q

what is seen on the colony of tinea nigra

A

colonies are smooth with an oily glistening olive-black color

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16
Q

what is seen on an aged colony of tinea nigra

A

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

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17
Q

properties of pityriasis versicolor: melassezia

A

dimorphic
lipophilic
mesophilic

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18
Q

where does melassezia commonly affect?

A

sebum rich area like the chest and back

with higher incidences in areas with higher temp and humidity

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19
Q

layer of skin melassezia affect

A

stratum corneum

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20
Q

how does melassezia clinically present

A

macular rash or fine scaling of the upper trunk and shoulders

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21
Q

complication of melassezia

A

erythematous follicular papules

22
Q

laboratory test to diagnose melassezia

A

skin scraping with KOH

23
Q

what is seen on microscopy with melassezia

A

both filaments and yeast since it is dimorphic

melassezia furfur - spaghetti and meatballs

24
Q

other infections involving melassezia

A
  • 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
25
Q

old name for melassezia

A

pityrosporum ovale

26
Q

what does dermatophytes colonize

A

the keratinized tissue of stratum corneum

27
Q

where do dermatophyte typically invade

A

skin, nail, hair

28
Q

what does dermatophytes do to the skin, hair, nails

A

– 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

29
Q

predisposing conditions to chronic infections by dermatophyte

A 
– Normal persons with “minor immunological blind spots” 
– Old age
– Collagen vascular disease
– Diabetes mellitus
– Hematological malignancy
30
Q

how do you transmit dermatophytes

A

-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

31
Q

what are the dermatophytic fungi

A

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

32
Q

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

A
  • trichophyton: all three
  • microsporum: only skin and hair
  • epidermophton: only skin and nails
33
Q

what is seen on microscopy of trichophyton

A
  • macroconidia and microconidia being the most numerous

- macroconidia are smooth walled pencil shaped-fusiform

34
Q

what does trichophyton secrete and what does that do

A

keratinases which allow dermatophyte to burrow deeper into the stratum corneum

35
Q

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

A

mannan from cell wall and lipophilic toxin

36
Q

agar used for trichophyton and what is seen

A

sabourad agar/potato dextrose agar

on top is white looking powder while on reverse/bottom of agar is red looking powder

37
Q

major cause of ringworm in skin

A

trichophyton tonsurans

38
Q

what is tinea corporis

A

ringworm of upper part of covered body

39
Q

what do the lesions of tinea corporis look like

A

well marginated with raised erythematous vesicular borders

40
Q

more severe chronic tinea corporis is caused by

A

trichophyton rubrum

41
Q

what is tinea cruris and what is another name for it

A

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

42
Q

what causes tinea cruris

A

trichophyton rubrum or epidermophyton floccosum

43
Q

how does tinea cruris clinically present

A
  • lesions are erythematous, scaly inflamed borders with vesicles
  • bilaterally extends down the sides of inner thighs, waist area and buttocks
44
Q

what is tinea capitis

A

infection of the scalp, eyebrows, eye lashes

45
Q

common agents of tinea capitis

A
  • ectothrix ringworm: microsporum (m. audouinni, m. canis, m. gypseum)
  • endothrix ringworm: trichophyton tonsurans
46
Q

difference between ectothrix and endothrix invasion

A
  • 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
47
Q

when does one see the “black dot” appearance

A

if endothrix invasion in tinea capitis – seen on scalp

48
Q

common agent of tinea pedis aka athlete’s foot

A

t. rubrum, e. floccosum, t. mentagrophytes

49
Q

what is tinea barbae and what are the causative agents

A

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

50
Q

what is tinea unguium and what causes it

A

infection of the nail plate by a dermatophyte

e. floccosum, t. rubrum, t. mentagrophytes

Micro Post Midterm (31 decks)

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