CSIM 1.40 Fungal Infections

Question 1

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

Answer 1

Moulds
• Aspergillus
• Zygomycetes (mucor)

Yeasts
• Candida
• Cryptococcus neoformans

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

Question 2

What are the main types of opportunistic fungi?

Answer 2

• Candida albicans

* Cryptococcus neoformans

Question 3

What are the types of fungal infection

Answer 3

• Superficial
  
  • Subcutaneous
  • Systemic

Question 4

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

Answer 4

• Ringworm
  
  • Dermatophytosis
  • Tinea

Question 5

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

Answer 5

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

Question 6

What are the ways that fungal infections can be transmitted?

Answer 6

Anthropophilic
• Man to man

Zoophilic
• Animal to man

Geophilic
• Soil to man

Question 7

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

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

Answer 7

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

Question 8

Describe tinea corporis lesions

Answer 8

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

IMG 107

Question 9

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

Answer 9

Secondary invasive bacterial infection
• Staphylococcus
• Streptococcus

Question 10

Describe tinea capitis lesions

Answer 10

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

Question 11

How is tinea capitis usually transmitted

Answer 11

Zoophilic

Question 12

What are the types of tinea capitis under the microscope?

Answer 12

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

Question 13

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

Answer 13

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

Question 14

How is tinea unguium treated?

Answer 14

Terbinafine

Toenail
• 12 weeks

Fingernail
• 6 weeks

Question 15

What is the most common cause of fungal infection?

Where is this found

Answer 15

Candida (genus of yeast)

Part of commensal flora

Question 16

How is tinea capitis treated?

Answer 16

Ketoconazole shampoo

Question 17

What are the main risk factors for candidiasis?

Answer 17

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

Question 18

What is the most common form of yeast infection

Answer 18

Superficial candidiasis

Question 19

Why is yeast infection common in babies?

Answer 19

Because they have a weakened immune system

Question 20

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?

Answer 20

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

Chronic mucocutaneous candidiasis (CMC)

Question 21

What makes lesions from candidiasis different to tenia?

Answer 21

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

Question 22

What formulary antifungal is used to treat candidiasis?

What else is used where possible

Answer 22

Nystatin with fluconazole

• Reducing moisture
• Treating underlying disorders

Question 23

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?

Answer 23

Malassezia yeast

Pityriasis versicolor

Question 24

What are the subcutaneous mycoses?

Answer 24

• Mycotoma

* Sporotrichosis

Question 25

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

Answer 25

HIV/AIDS

Question 26

What are the main source of cryptococcus?

Where is infection most commonly seen? What is this called?

Answer 26

Pigeon droppings

Lungs - Pulmonary cryptococcosis

Question 27

What prevents aspergillus spores growing when breathed in?

Answer 27

Neutrophils

Question 28

Who is most susceptible to INVASIVE aspergillosis?

Answer 28

Immunocompromised - no neutrophils

Question 29

What is otomycosis and which fungus usually causes this?

Answer 29

Fungal outer ear canal infection caused by aspergillus

Question 30

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

What does invasive aspergillosis of the immunocompromised usually effect?

Answer 30

Immunocompetent:
• Otomycosis
• Keratitis

Immunocompromised:
  •  Pulmonary
  •  Tracheobronchitis
  •  Sinusitis
  •  Endocarditis

Question 31

What are the dimorphic fungi called?

Answer 31

• Histoplasmosis
  
  • Blastomyces
  • Coccidiodes immitis
  • Paracoccidiodes

Question 32

How do polyenes such as amphotericin work?

Answer 32

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

Question 33

How do azoles such as fluconazole work?

Answer 33

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

Question 34

What is nystatin used for?

Name a more general antifungal we need to know

Answer 34

CANDIDA

Fluconazole - an azole

Question 35

Why do the azoles have a lot of drug-drug interactions?

What effect does this have on their commonly used route of administration

Answer 35

Because they act on the cytochome P450 enzymes

Usually used topically