Fungal Infections Flashcards
how are fungal infections (mycoses) classified
by the degree of tissue involvement and the mode of entry into the host
the different classifications for fungal infections
– 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
what is white piedra
superficial infection caused by several species of trichosporon
trichosporon is a yeast genus with
arthroconidia which is spore forming
what other types of infection can trichosporon cause
systemic and can also infect cutaneous tissue
clinical presentation of white piedra
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
treatment of white piedra
shaving or local application antifungal such as amphotericin B, clotrimazole, ketoconazole, itraconazole
what is black piedra
asymptomatic superficial infection that is a visible colonization of the shaft of the hair
difference between the nodules of black and white piedra
nodules of black piedra cannot be pulled as compared to the ones that can be pulled off in white piedra
what causes black piedra
ascomycete genus piedraia
how do you treat black piedra
it is difficult to treat and antifungals have been used with different levels of successes
what is tinea nigra
superficial infection of the skin (stratum corneum) caused by hortae werneckii
where are the black to brown lesions of tinea nigra commonly seen
palms and soles of the feet
where are the pigmentation of tinea nigra more intense and what layers of the skin are affected
more intense near the borders
only dead layers affected – living tissue unaffected
what is seen on the colony of tinea nigra
colonies are smooth with an oily glistening olive-black color
what is seen on an aged colony of tinea nigra
aged colonies become velvety because of production of aerial hyphae – hyphae becomes darker with age
properties of pityriasis versicolor: melassezia
dimorphic
lipophilic
mesophilic
where does melassezia commonly affect?
sebum rich area like the chest and back
with higher incidences in areas with higher temp and humidity
layer of skin melassezia affect
stratum corneum
how does melassezia clinically present
macular rash or fine scaling of the upper trunk and shoulders
complication of melassezia
erythematous follicular papules
laboratory test to diagnose melassezia
skin scraping with KOH
what is seen on microscopy with melassezia
both filaments and yeast since it is dimorphic
melassezia furfur - spaghetti and meatballs
other infections involving melassezia
- 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
old name for melassezia
pityrosporum ovale
what does dermatophytes colonize
the keratinized tissue of stratum corneum
where do dermatophyte typically invade
skin, nail, hair
what does dermatophytes do to the skin, hair, nails
– 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
predisposing conditions to chronic infections by dermatophyte
– Normal persons with “minor immunological blind spots” – Old age – Collagen vascular disease – Diabetes mellitus – Hematological malignancy
how do you transmit dermatophytes
-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
what are the dermatophytic fungi
– Trichophyton (worse of the three)
– Microsporum
– Epidermophyton
what can the three dermatophytic fungi infect in terms of skin, hair, nails
- trichophyton: all three
- microsporum: only skin and hair
- epidermophton: only skin and nails
what is seen on microscopy of trichophyton
- macroconidia and microconidia being the most numerous
- macroconidia are smooth walled pencil shaped-fusiform
what does trichophyton secrete and what does that do
keratinases which allow dermatophyte to burrow deeper into the stratum corneum
what can inhibit cell mediated immunity and keratinocyte proliferation which sheds fungus
mannan from cell wall and lipophilic toxin
agar used for trichophyton and what is seen
sabourad agar/potato dextrose agar
on top is white looking powder while on reverse/bottom of agar is red looking powder
major cause of ringworm in skin
trichophyton tonsurans
what is tinea corporis
ringworm of upper part of covered body
what do the lesions of tinea corporis look like
well marginated with raised erythematous vesicular borders
more severe chronic tinea corporis is caused by
trichophyton rubrum
what is tinea cruris and what is another name for it
infection of inguinal area involving groin, perianal, and perineal areas
jock’s itch
what causes tinea cruris
trichophyton rubrum or epidermophyton floccosum
how does tinea cruris clinically present
- lesions are erythematous, scaly inflamed borders with vesicles
- bilaterally extends down the sides of inner thighs, waist area and buttocks
what is tinea capitis
infection of the scalp, eyebrows, eye lashes
common agents of tinea capitis
- ectothrix ringworm: microsporum (m. audouinni, m. canis, m. gypseum)
- endothrix ringworm: trichophyton tonsurans
difference between ectothrix and endothrix invasion
- 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
when does one see the “black dot” appearance
if endothrix invasion in tinea capitis – seen on scalp
common agent of tinea pedis aka athlete’s foot
t. rubrum, e. floccosum, t. mentagrophytes
what is tinea barbae and what are the causative agents
infection of the beard area caused by t. verrucosum (cattle) and t. mentagrophytes (mice, rodents)
what is tinea unguium and what causes it
infection of the nail plate by a dermatophyte
e. floccosum, t. rubrum, t. mentagrophytes
