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Micro Final (Lauren, Shelby, and Annie) > Dermatomycoses🍝 > Flashcards

Dermatomycoses🍝 Flashcards

1
Q

What makes dermatophytes different from other fungal species?

A

They are PATHOGENIC**

Require keratin for growth**

Do not infect mucosal surfaces

Secrete keratinase *

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2
Q

What are arthroconidia?

A

The infective stage of the fungi (a SPORE)

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3
Q

What is Trichophytin?

A

An antigen of dermatophytes that is a galactomannan peptide (sugar + protein)

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4
Q

Trichophytin is the name of an antigen that is unique to dermatophytes. It is made of galactomannan peptide, which is a sugar and a protein.
Which part of Trichophytin elicits an immediate vs delayed immune response?

A

Sugar component-immediate response (but sugars dont make much of an immune response)

Peptide component-delayed response (allows for long lasting immunity)

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5
Q

If you look at dead keratinized tissue under a microscope, what will you see if it is infected with dermatophytes?

A

Hyphae (hair like)

Arthroconidia (spores)

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6
Q

If a patient has onychomycosis, where do you get the culture material from?

A

Under the nails

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7
Q

What kind of medium will detect dermatophytes?

A

Dermatophyte Test Medium (DTM)

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8
Q

What is Dermatophyte Test Medium (DTM)?

A

Is a Selective and Differential medium that will ONLY grow fungi (no bacteria). And if a dermatophyte is present, it will turn Red.

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9
Q

How is dermatophyte test medium selective?

A

It has cyclohexamide and antibiotics to stop bacterial growth
(Selects for fungal growth)

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10
Q

How is dermatophyte test medium differential?

A

It contains nitrogenous compounds that ONLY dermatophytes can eat, so it will turn Red within 3 days if the organism eats them and turns the pH more alkaline.**

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11
Q

What does 10% KOH do to help you visualize fungi under a microscope?

A

Digests human tissue, leaves fungal components intact

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12
Q

What are the 3 classifications of dermatophytes?

A

Zoophilic- animal pathogens that may be transmitted to people

Antrophilic- Human to human transmission

Geophilic- transmitted through soil to people

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13
Q

What will a dermatophytic skin lesion look like?

A

Inflamed at edges (most organisms here)

Central clearing zone

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14
Q

What parts of the world have more dermatophytic infections?

A

Tropics

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15
Q

What are some factors that put you more at risk of contracting a dermatophyte?

A

Communal bathing facilities

Contact sports 🤼‍♀️

Immunocompromised

Cushing Syndrome

Diabetes

Nail trauma

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16
Q

What are the 3 elements of fungi that may be seen under a microscope?

A

Arthrospores/arthroconidia INFECTIOUS PART

Microconidia- asexual spore

Macroconidia- asexual spore

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17
Q

What is an “Id reaction” to dermatophytes?

A

An ALLERGIC skin reaction to fungi, but occurring in areas DEVOID of fungi!** sometimes caused by excessive treatments or itching

Ex: rash on the foot, but the fungi is up on the leg

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18
Q

What kind of dermatophytic infection most commonly has an Id reaction?

A

Tinea pedis (Athletes foot)

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19
Q

How do you treat Id reactions?

A

Treat them as an allergy: corticosteroids, antihistamines, wet compresses

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20
Q

Are spores susceptible to common disinfectants, bleach, and detergents?

A

Yes

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21
Q

Are Trichophyton species fluorescent

A

Not usually**

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22
Q

What will you see under microscope if you’re looking at a Trichophyton species?

A

Spindle-shaped hyphae***

Pencil-shaped macroconidia with thin walls ✏️

Microconidia

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23
Q

What is the most common cause of tinea capitis and ringworm?

A

Microsporum species

24
Q

Do microsporum species fluoresce?

A

YES***💡💡💡

25
Q

What kind of macroconidia will you see under the microscope if you’re looking at a microsporum species?

A

Large, spindle shaped

Multicellular

Thick walled

26
Q

What is the difference between endothrix and ectothrix when it comes to tinea capitis?

A

Endothrix- caused by Trichophyton. INSIDE hair follicle, alopecia more likely

Ectothrix- caused by microsporum. On outer surface of hair

27
Q

Can you get tinea capitis from puppies?

A

Yes

28
Q

What causes “black dot” ringworm?

A

Broken hair follicles

29
Q

What is the most common dermatophytosis?

A

Tinea pedis (athletes foot)

30
Q

What disease can Tinea Unguium (onychomycosis) mimic?

A

Psoriasis

31
Q

When someone’s nails are infected with a dermatophyte, what else is usually present?

A

Candida.

You must treat both the candida and the dermatophyte

32
Q

Why don’t topical treatments work for onychomycosis?

A

The infection is in the nail BED.

33
Q

What are the most commonly encountered **opportunistic* mycoses

A

Candidiases

Normal flora of skin

34
Q

Which form of candida is part of your normal flora: yeast or mold

A

Yeast

Mold form is when it causes problems

35
Q

What are the causes of candidiasis?

A

Absence of competing normal flora

Broad spectrum antibiotics***

Immunocompromised ***

Introduction to abnormal site

Pathologic change in micro environment

36
Q

What kind of virulence factors does Candida albicans exhibit?

A

Attachment only. THATS IT

37
Q

Which is the more adhesive form of Candida albicans: germ tube or yeast cell

A

Germ tube********

38
Q

How do you diagnose Candida?

A

Direct microscopic examination. Will stain purple with a gram stain (but it’s not really gram positive), and it will be HUGE

39
Q

What will you see under the microscope when you look at candidia?

A

Yeast cells

Pseudohyphae

Hyphae

40
Q

Which form of candida produces enzymes that will chew away at your tissue matrix?

A

Germ tubes

41
Q

Which two species of candida produce germ tubes?

A

C albicans

C dubliniensis

42
Q

What kind of agar should you culture candida on?

A

Chromagar

43
Q

What does Chromagar do?

A

It is selective for candida (no bacteria), and differentiates between the species based on what color they turn

selective and differential

44
Q

What is a really fast test you can do to figure out what species of candida you have?

A

Germ tube test**

Put sample in serum, incubate at 37* for 3 hours, and then look for germ tubes.

If germ tubes form, you know its C albicans or C dubliniensis

45
Q

Why is it difficult to do serology to diagnose candidiasis?

A

Candida is normal flora = false positives

Many have had prior exposure

Low titers of antibody

46
Q

What fungus causes tinea versicolor?

A

Malassezia furfur

47
Q

What will malassezia furfur look like under a microscope?

A

SPAGHETTI AND MEATBALLS🍝

Short, unbranched hyphae and spherical cells

48
Q

What is required for malassezia furfur to grow?

A

Fat

49
Q

Where in your body does malassezia furfur like to live?

A

Sebaceous glands

50
Q

What does tinea versicolor/malassezia furfur look like on the skin?

A

Patches of depigmented or hyperpigmented skin ***

51
Q

How do you diagnose tinea versicolor/malassezia furfur?

A

Microscopic KOH exam of skin scrapings 🍝

52
Q

What fungi causes tinea negra?

A

Hortaea werneckii

53
Q

Does tinea negra/ hortaea werneckii grow as a yeast or a mold?

A

Both

54
Q

How does salt affect tinea negra/hortaea werneckii?

A

NO AMOUNT OF SALT BOTHERS IT

Extreme halotolerant 🧂🧂🧂🧂🧂

55
Q

What does tinea nigra/hortaea werneckii look like on the skin?

A

Brown lesion often on palms and soles

56
Q

Why is tinea nigra/hortaea werneckii brown on the skin?

A

It produces melanin

57
Q

How do you diagnose tinea nigra?

A

KOH and microscopy

Micro Final (Lauren, Shelby, and Annie) (4 decks)

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