9- Microbial causes of skin disease: fungal

Question 1

What is the most common mechanism that fungi causes disease

Answer 1

Tissue mycosis - invasion

Question 2

What is dermatophytosis

Answer 2

fungal infection of the skin- ringworm

Question 3

How is ringworm transmitted

Answer 3

direct contact, fomites (indirect)

Question 4

Describe the stages of infection by dermatophytosis

Answer 4

Skin microtrauma & moisture –> inoculation and germination of infective arthrospores
–> germ tubes penetrate stratum corneum –> growth of fungal hyphae –> lesions (foci within 5-7 days)

Question 5

Name the 2 fungus that causes dermatophytosis

Answer 5

Microsporum spp
Trichophyton spp

Question 6

T/F Dermatophytosis lesions are usually asymmetric

Answer 6

True

Question 7

What is fungal kerion

Answer 7

Nodular inflammatory mass due to inoculation of fungus into dermis
Especially occurs in hunting/working dogs

Question 8

Name 2 diagnostic tests for dermatophytosis

Answer 8

Direct examination of hair/ scales under the microscope
Woods lamp (only detects M. canis)
Fungal culture (McKenzie toothbrush technique)- can’t distinguish between carriage and disease
Fungal PCR - can’t distinguish between carriage and disease
Skin biopsy

Question 9

What is dysbiosis?

Answer 9

Imbalance of organism present in normal microbiome

Question 10

What is the disease caused by Malassezia called?

Answer 10

Malassezia dermatitis or otitis

Question 11

Name 3 clinical signs of malassezia disease

Answer 11

Pruritus - main sign
Skin:
Erythema, grease, sculpt, crust
Malodorous (bad smelling)
Well-demarcated

Ears: Red/waxy (erythrocytes-ceruminous otitis)

Question 12

How do you diagnose a malassezia infection

Answer 12

Cytology + response to therapy
stained acetate tape strip
Stained impressions smear
use x40-x100 objective