IB. Medical Mycology | 23. Microbiological diagnosis of diseases caused by fungi.

Question 1

What is mycosis?

Answer 1

mycosis= infection caused by fungi

Question 2

I. Laboratory diagnosis of fungal diseases
1. What are the methods of Laboratory diagnosis of fungal diseases?

Answer 2

1. Culture
2. Microscopy
3. Biochemical Reactions
4. Serology
5. Molecular biology
6. MALDI - TOF
7. FISH
8. E test

Question 3

I. Laboratory diagnosis of fungal diseases
2. What are the specimens we need to prepare for Laboratory diagnosis of fungal diseases?

Answer 3

1. scrapings from the skin and the nails
2. hairs plucked from involved areas
3. Microsporum-infected hairs fluoresce under Wood’s light (365 nm) in a darkened room

Question 4

I. Laboratory diagnosis of fungal diseases
2. Why do we need culture for Laboratory diagnosis of fungal diseases?

Answer 4

the identification of dermatophyte species requires cultures

Question 5

I. Laboratory diagnosis of fungal diseases
3A. How do we use CULTURE in Laboratory diagnosis of fungal diseases?

Answer 5

1. specimens are inoculated onto inhibitory mould agar or Sabouraud’s agar plates containing cycloheximide and chloramphenicol
2. species are identified on the basis:
   - colonial morphology (growth rate,
   surface texture, and any pigmentation)
   - microscopic morphology (macroconidia, microconidia)
   - nutritional requirements
3. long time incubation (for negative result) - about 14 days

Question 6

I. Laboratory diagnosis of fungal diseases - CULTURE
3B. What is the basis for identification of the species?

Answer 6

• colonial morphology (growth rate,
  surface texture, and any pigmentation)
• microscopic morphology (macroconidia, microconidia)
• nutritional requirements

Question 7

I. Laboratory diagnosis of fungal diseases - CULTURE
3C. What are specimens inoculated on?

Answer 7

specimens are inoculated onto inhibitory mould agar or Sabouraud’s agar plates containing cycloheximide and chloramphenicol

Question 8

I. Laboratory diagnosis of fungal diseases
4. How do we use microscopy in Laboratory diagnosis of fungal diseases?

Answer 8

1. WET MOUNT is a glass slide holding a specimen suspended in a drop of liquid (as water) for microscopic examination
2. simple staining (eg. methylene blue)
3. before native examination 30% KOH => keratolysis

Question 9

I. Laboratory diagnosis of fungal diseases
5. What are biochemical reactions we can use to identify fungal diseases?

Answer 9

• sugar fermentation
• sugar assimilation test
• nitrate assimilation test

Question 10

II. What are the 5 types of mycological diseases?

Answer 10

• Dermatomycoses = Superficial, cutaneous, and subcutaneous mycoses
• Systemic mycoses
• Opportunistic mycoses
• Allergic reactions
• Intoxications

Question 11

III. Therapy of fungal infection
1. What are the 3 main therapies for fungal reaction?

Answer 11

1. Polygenes
2. 5-fluorocystosine
3. Azoles

Question 12

III. Therapy of fungal infection
2. How does Polygenes work?

Answer 12

• bind egosterol
• Weaken the cell membrane
• form pores
• Leakage of K+ and Na+
• Fungal cell death
• Also cause mammalian toxicity

Question 13

III. Therapy of fungal infection
3. How does Azoles work?

Answer 13

It will inhibit the enzyme that synthesize egosterol

Question 14

III. Therapy of fungal infection
4. How does 5-fluorocystosine work?

Answer 14

Block the synthesis of nucleic acid

Question 15

III. Therapy of fungal infection
4. Make a schematic diagram for the biosynthetic pathway of ergosterol and points of activity by anti-fungal agent?

Answer 15

Question 16

III. Therapy of fungal infection
5A. Give the anti-fungal agent classification based on mechanism of action

Answer 16

Question 17

III. Therapy of fungal infection
6. What are the features of Polyene antifungal agents?

Answer 17

Question 18

III. Therapy of fungal infection
7. What are the features of Nystatin

Answer 18

Question 19

IV. Classification of fungal disease
1. Give the Classification of fungal disease?

Answer 19

1. Fungal allergies
   - “sick building syndrome”, generally occur in individuals with other allergies
2. Mycotoxicosis
   - may result from ingestion of fungal- contaminated foods (generally an animal problem) or mushrooms

Question 20

IV. Classification of fungal disease
2. What are the features of fungal allergies?

Answer 20

• “sick building syndrome”, generally occur in individuals with other allergies

Question 21

IV. Classification of fungal disease
3. What are the features of Mycotoxicosis?

Answer 21

Mycotoxicosis
- may result from ingestion of fungal- contaminated foods (generally an animal problem) or mushrooms