CSIM 1.40 Fungal Infections Flashcards by K W

What are the three main types of fungus? Name the most common form of each

Moulds
• Aspergillus
• Zygomycetes (mucor)

Yeasts
• Candida
• Cryptococcus neoformans

Dimorphic fungi (yeast at 37º, moulds at 25º) IMG 106

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What are the main types of opportunistic fungi?

Candida albicans

* Cryptococcus neoformans

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What are the types of fungal infection

Superficial
- Subcutaneous
- Systemic

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What are the three names for the clinical manifestation of fungal infection of the skin

Ringworm
- Dermatophytosis
- Tinea

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What fungi grow on the skin superficially - name the main genera

Dermatophytes - require keratin for growth, genera include:
• Trichophyton
• Microsporum
• Epidermaphyton

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What are the ways that fungal infections can be transmitted?

Anthropophilic
• Man to man

Zoophilic
• Animal to man

Geophilic
• Soil to man

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Tinea (dematophytosis/ringworm) affecting the following is called what?

1) Body
2) Groin
3) Pedis
4) Nail
5) Scalp

1) Tinea corporis
2) Tinea cruris
3) Tinea pedis (athlete’s foot)
4) Tinea unguium
5) Tinea capitis

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Describe tinea corporis lesions

Dry scaling
- Annular spreading with central clearing
- Raised and inflamed border
- ITCHY

IMG 107

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What complication can arise from Tenia Pedis near to the toenails?

Secondary invasive bacterial infection
• Staphylococcus
• Streptococcus

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Describe tinea capitis lesions

“Kerion” lesions
• Circular scaling
• Hair loss
• Hair loss is permanent if untreated due to scarring

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How is tinea capitis usually transmitted

Zoophilic

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What are the types of tinea capitis under the microscope?

Endothrix
• dermatophyte infections of the hair that invade the hair shaft and internalize into the hair cell

Exothrix
• Dermatophyte infections of the hair that infect the hair surface but do not invade the cell

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How is a diagnosis made for tinea/ringworm/dermatophytosis?

Specimen taken
• Hair
• Nail scraping
• Skin scraping

Place this under KOH and observe under calcoflour microscopy

The dye fluoresces under UV light and should reveal fungi

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How is tinea unguium treated?

Terbinafine

Toenail
• 12 weeks

Fingernail
• 6 weeks

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What is the most common cause of fungal infection?

Where is this found

Candida (genus of yeast)

Part of commensal flora

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How is tinea capitis treated?

Ketoconazole shampoo

What are the main risk factors for candidiasis?

Use of antibiotics
- Intravenous catheters
- GI tract surgery
- Immune suppression (steroids/HIV)

What is the most common form of yeast infection

Superficial candidiasis

Why is yeast infection common in babies?

Because they have a weakened immune system

Where is candidiasis usually found and what is it often referred to in this case?

What are the symptoms of this?

When might this occur chronically or reoccur? What is this called?

Oropharyngeal - thrush
• Sore throat
• White patches
• Difficulty swallowing

Chronic mucocutaneous candidiasis (CMC)

What makes lesions from candidiasis different to tenia?

They are found only in moist areas, and are disemminated rather than round

What formulary antifungal is used to treat candidiasis?

What else is used where possible

Nystatin with fluconazole

Reducing moisture
Treating underlying disorders

Which bug is responsible for mild chronic infection of the striatum corneum causing pathchy discolouration of skin and dandruff?

What is the name of the condition this causes?

Malassezia yeast

Pityriasis versicolor

What are the subcutaneous mycoses?

Mycotoma

* Sporotrichosis

which population is the most likely to sustain a cryptococcus infection?

HIV/AIDS

What are the main source of cryptococcus? Where is infection most commonly seen? What is this called?

Pigeon droppings Lungs - Pulmonary cryptococcosis

What prevents aspergillus spores growing when breathed in?

Neutrophils

Who is most susceptible to INVASIVE aspergillosis?

Immunocompromised - no neutrophils

What is otomycosis and which fungus usually causes this?

Fungal outer ear canal infection caused by aspergillus

What does non-invasive aspergillosis of the immunocompetent usually effect? What does invasive aspergillosis of the immunocompromised usually effect?

Immunocompetent: • Otomycosis • Keratitis ``` Immunocompromised: • Pulmonary • Tracheobronchitis • Sinusitis • Endocarditis ```

What are the dimorphic fungi called?

* Histoplasmosis * Blastomyces * Coccidiodes immitis * Paracoccidiodes

How do polyenes such as amphotericin work?

By binding to ergosterol on the fungal cell membrane - forming pores and making the membrane leaky

How do azoles such as fluconazole work?

Inhibits ergosteol synthesis - affects membrane integrity of fungus • Binds to cytochrome p450 enzymes • Therefore inhibits C-14α demethyltion of lanosterol • C14α methyl sterols accumulate and ergosterol concentrations decrease

What is nystatin used for? Name a more general antifungal we need to know

CANDIDA Fluconazole - an azole

Why do the azoles have a lot of drug-drug interactions? What effect does this have on their commonly used route of administration

Because they act on the cytochome P450 enzymes Usually used topically