Lecture 17 dimorphic fungi

Question 1

General properties of Sporothrix schenckii and what diseases it causes

Answer 1

Common environmental mould, found in hay, rose thorns.
As a fungi enters through wounds (uses proteases as virulence factor) and causes chronic disease that produces pyogranulomatous nodules in skin and lymphatic vessels

Question 2

How to sample, culture and diagnose Sporothrix schenckii

Answer 2

Sample - biopsy of tissue
Culture - SDA or brain heart infusion agar at 25 and 36 degrees
Diagnosis - Biopsy gram stain or immunofluorescence at 36 degrees look for budding yeast.

Question 3

General properties of Blastomyces dermatitidii and what diseases it causes

Answer 3

Exotic in NZ usually seen in USA, found in faecally contaiminated soil and decaying matter. Causes pulmonary infections (inhalation of conidia), can cause granulomatas pneumonia. Also can cause disseminated usually in immunocompromised patients

Question 4

How to sample, culture and diagnose blastomyces dermatitidii

Answer 4

Sample - swabs from lesion or biopsy
Culture - SDA + cyclohexamide at 25-30 degrees
Diagnosis - Stain with calcufluor white, budding yeast at 36, or pear shaped conidia at 25

Question 5

General properties of Histoplasmosis capsulatum and what diseases it causes

Answer 5

Many countries, found in soil/decaying vegetation particularly soil enriched by bird/bat faeces (high N). Inhaled microconidia yeast replicate inside macrophages - can result in pulmonary infection, GIT disease and disseminated disease in immunosuppresion

Question 6

How to sample, culture and diagnose Histoplasmosis capsulatum

Answer 6

Sample - blood smear or biopsy
Culture - SDA at 25 degrees, blood agar at 37
Diagnosis - hard to microscopy as in macrophages, can use Serology (latex agglunitation)

Question 7

General properties of Coccidiodes immitis and what disease it causes

Answer 7

Affects dogs, humans and horses. Found in soil of deserts. Inhaled arthrospores results in granulomas in lungs, can spread to bone, liver brain and kidney. Can cause transient pulmonary infection or chronic infection which both result in (fever coughing, lost weight) or disseminated in 1% (immunocompromised)

Question 8

How to sample, culture and diagnose Coccidodes immitis

Answer 8

Sample - Biopsy or cytology
Culture - SDA or blood agar (very contagious so rarely done)
Diagnosis - Serology (latex agglunitation)

Question 9

Describe general properties of Penicillium spp and what disease it causes

Answer 9

Dimorphic opportunistic fungi, emerged pathogen in HIV patients. P. marneffei opportunistic causer of keratitis and otomycosis. In immunocompromised inhaled conidia results in granulomatous pneumonia which disseminates to other parts of body

Question 10

How to sample, culture and diagnose Penicillium spp

Answer 10

Sample - biopsy
Culture - SDA
Diagnosis - microscopy have tree like conidia

Question 11

Describe the fungal antibiotic Amphrotercin B, where it is derived from and how it attacks

Answer 11

Derived from streptomyces nodosus, binds to ergosterol on fungi and makes cell membrane permeable so able to be attacked. Can have side effects and is reserved for serious/invasive mycoses

Question 12

Describe the fungal antibiotic Flucytosine, where it is derived from and how it attacks

Answer 12

Is a fluorinated pyrimidine, incorporates into fungal RNA and disrupts pyrimidine metabolism and makes faulty proteins. Yeasts however have started to become resistant. Has side effects

Question 13

Describe the fungal antibiotic Azole derivative, where it is derived from and how it attacks

Answer 13

Many different types of azoles which can intefere with biosynthesis of ergosterol