Dermatomycoses🍝 Flashcards by Lauren F

What makes dermatophytes different from other fungal species?

They are PATHOGENIC**

Require keratin for growth**

Do not infect mucosal surfaces

Secrete keratinase *

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What are arthroconidia?

The infective stage of the fungi (a SPORE)

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What is Trichophytin?

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

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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?

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

Hyphae (hair like)

Arthroconidia (spores)

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

Under the nails

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What kind of medium will detect dermatophytes?

Dermatophyte Test Medium (DTM)

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What is Dermatophyte Test Medium (DTM)?

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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How is dermatophyte test medium selective?

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

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How is dermatophyte test medium differential?

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

Digests human tissue, leaves fungal components intact

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What are the 3 classifications of dermatophytes?

Zoophilic- animal pathogens that may be transmitted to people

Antrophilic- Human to human transmission

Geophilic- transmitted through soil to people

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What will a dermatophytic skin lesion look like?

Inflamed at edges (most organisms here)

Central clearing zone

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What parts of the world have more dermatophytic infections?

Tropics

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

Communal bathing facilities

Contact sports 🤼‍♀️

Immunocompromised

Cushing Syndrome

Diabetes

Nail trauma

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

Arthrospores/arthroconidia INFECTIOUS PART

Microconidia- asexual spore

Macroconidia- asexual spore

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What is an “Id reaction” to dermatophytes?

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

Tinea pedis (Athletes foot)

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How do you treat Id reactions?

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

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

Yes

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Are Trichophyton species fluorescent

Not usually**

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

Spindle-shaped hyphae***

Pencil-shaped macroconidia with thin walls ✏️

Microconidia

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

Microsporum species

Do microsporum species fluoresce?

YES***💡💡💡

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

Large, spindle shaped Multicellular Thick walled

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

Endothrix- caused by Trichophyton. INSIDE hair follicle, alopecia more likely Ectothrix- caused by microsporum. On outer surface of hair

Can you get tinea capitis from puppies?

Yes

What causes “black dot” ringworm?

Broken hair follicles

What is the most common dermatophytosis?

Tinea pedis (athletes foot)

What disease can Tinea Unguium (onychomycosis) mimic?

Psoriasis

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

Candida. You must treat both the candida and the dermatophyte

Why don’t topical treatments work for onychomycosis?

The infection is in the nail BED.

What are the most commonly encountered **opportunistic* mycoses

Candidiases | Normal flora of skin

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

Yeast | Mold form is when it causes problems

What are the causes of candidiasis?

Absence of competing normal flora Broad spectrum antibiotics*** Immunocompromised *** Introduction to abnormal site Pathologic change in micro environment

What kind of virulence factors does Candida albicans exhibit?

Attachment only. THATS IT

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

Germ tube**************************

How do you diagnose Candida?

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

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

Yeast cells Pseudohyphae Hyphae

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

Germ tubes

Which two species of candida produce germ tubes?

C albicans C dubliniensis

What kind of agar should you culture candida on?

Chromagar

What does Chromagar do?

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

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

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

Why is it difficult to do serology to diagnose candidiasis?

Candida is normal flora = false positives Many have had prior exposure Low titers of antibody

What fungus causes tinea versicolor?

Malassezia furfur

What will malassezia furfur look like under a microscope?

**SPAGHETTI AND MEATBALLS**🍝 Short, unbranched hyphae and spherical cells

What is required for malassezia furfur to grow?

Fat

Where in your body does malassezia furfur like to live?

Sebaceous glands

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

Patches of depigmented or hyperpigmented skin *******

How do you diagnose tinea versicolor/malassezia furfur?

Microscopic KOH exam of skin scrapings 🍝

What fungi causes tinea negra?

Hortaea werneckii

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

Both

How does salt affect tinea negra/hortaea werneckii?

NO AMOUNT OF SALT BOTHERS IT Extreme halotolerant 🧂🧂🧂🧂🧂

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

Brown lesion often on palms and soles

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

It produces melanin

How do you diagnose tinea nigra?

KOH and microscopy