TOPIC 8 - MYCOLOGY PART 2

Question 1

What are the mechanisms involved in fungal diseases?

Answer 1

1. Tissue invasion (mycosis)
2. Toxin production (mycotoxicosis)
3. Induction of hypersensitivity

Question 2

Fungal diseases which result from
tissue invasion can be categorized
according to the sites of lesions. These are?

Answer 2

1. Superficial mycoses (dermatomycoses or dermatophytoses)
2. Subcutaneous mycoses
3. Systemic mycoses

Question 3

Site of lesion categorization: Opportunistic infections of
the skin or mucocutaneous
junctions result from
overgrowth of fungi

Answer 3

Dermatomycoses

Question 4

Give fungal species capable of inflicting dermatomycoses.

Answer 4

1. Candida species
2. Malassezia pachydermatis

Question 5

Superficial mycoses that is clinically more important since it has communicability and zoonotic potential.

Answer 5

Dermatophytoses

Question 6

Site of lesion categorization: Associated with invasion and destruction of keratinized structures

Answer 6

Dermatophytoses

Question 7

Give fungal species capable of inflicting dermatophytoses.

Answer 7

1. Microporum species
2. Trichophyton species

Question 8

Tumour-like granulomatous
lesions

Answer 8

Mycetomas

Question 9

Infection is caused by pigmented fungi

Answer 9

Phaeohyphomycosis

Question 10

Site of lesion categorization: Result from localized
fungal invasion of the dermis and subcutis, often following penetration by a foreign body.

Answer 10

Subcutaneous mycoses

Question 11

Site of lesion categorization: Often originate in the respiratory or digestive tracts, usually follow opportunistic infection by saprophytic fungi

Answer 11

Systemic mycoses

Question 12

What are the factors which predispose the individual to systemic mycoses infection?

Answer 12

• alteration in the normal microbial flora as a result of
• prolonged antimicrobial therapy
• immunosuppression
• following corticosteroid therapy or viral infection
• exposure to high infective doses of spores in confined spaces

Question 13

Group of diseases resulting from the ingestion of fungal toxins which
have been pre-formed in stored food or standing crops

Answer 13

Mycotoxicoses

Question 14

Hypersensitivity reactions to fungal infections are rare in domestic animals, they can be associated with chronic pulmonary disease in cattle and horses. True or False?

Answer 14

True

Question 15

Mycological cultural procedures should
be performed in a biohazard cabinet
because of the risk of human infection
from spore ____.

Answer 15

Aerosols

Question 16

How do you diagnose fungal diseases?

Answer 16

*Clinical signs and history particularly in
dermatophytosis
*Specimens for diagnosis: hair and skin scrapings
and biopsy
*Direct microscopic examination of wet
preparations may be confirmatory

Question 17

_____ _____ can be demonstrated, in
cerebrospinal fluid mixed with India ink or nigrosine, as
budding cells with wide capsules.

Answer 17

Cryptococcus neoformans

Question 18

_____ _____ surrounding infected hairs or hyphae in infected tissues may be demonstrable after clearing specimens in a few drops of 10% KOH under a coverslip for some hours.

Answer 18

Ringworm arthrospores

Question 19

Sporing heads can be examined under a coverslip after
mounting a sample from a colony in a drop of _____ _____ _____.

Answer 19

lactophenol cotton blue

Question 20

Yeast cells can be stained with
methylene blue or by the Gram method. True or False?

Answer 20

True

Question 21

Fungi are usually isolated on ____ _____ agar (pH 5.5) which inhibits growth of most bacteria.

Answer 21

Sabouraud dextrose

Question 22

What are the other methods for direct examination of fungis?

Answer 22

1. Slide culture
2. Transparent adhesive tape techniques

Question 23

Addition of ____ and _____ increases selectivity by inhibiting some of the fastgrowing contaminating fungi such as zygomycetes

Answer 23

Chloramphenicol; cycloheximide

Question 24

To stimulate growth of the yeast phase of dimorphic fungi, enriched media, such as ____-____ ____
agar with ___% blood, and incubation at ___°C are required

Answer 24

brain-heart infucsion; 5%; 37 celcius

Question 25

The ____ ____-____ reaction or ____ ____ ____ can be used to demonstrate fungal elements in tissue sections.

Answer 25

periodic acid-Schiff (PAS); methenamine silver impregnation

Question 26

The presence of a
mature sporangium identifies the fungus as _____.

Answer 26

Zygomycete

Question 27

Features of vegetative hyphae which can be used for differentiation include ?

Answer 27

• Presence or absence of septa
• Either hyaline (colourless) or dematiaceous (pigmented)
• Specific hyphal structures such as racquet-shaped and spiral hyphae

Question 28

Colonial characteristics of fungi are determined by ?

Answer 28

• Size and appearance after specified incubation time
• Color of both obverse and reverse sides
• Surface elevations or depressions

Question 29

Dimorphic fungi grow as molds when cultured on ____ ____ agar at ___ C and as yeasts when cultured on enriched media at ____ C.

Answer 29

Sabouraud dextrose; 25 C; 37 C

Question 30

Soluble ____ produced by dimorphic fungi
can be used for identification in immunological tests

Answer 30

antigens

Question 31

Specific ____ ____ ____ are being developed
for rapid and reliable identification of dimorphic fungi.

Answer 31

nucleic acid probes

Question 32

It inhibits ergosterol biosynthesis.

Answer 32

Ketoconazole (azoles)

Question 33

Give the polyene antifungal drugs that bind selectively to ergosterol.

Answer 33

1. Nystatin
2. Amphotericin B

Question 34

_____ is used for treatment of ringworm, accumulates in keratinized tissues and is absorbed by
invading dermatophytes. It also interact with fungal microtubules and disruption of mitotic spindles inhibits dermatophyte growth

Answer 34

Griseofulvin