TOPIC 8 - MYCOLOGY PART 2 Flashcards
What are the mechanisms involved in fungal diseases?
- Tissue invasion (mycosis)
- Toxin production (mycotoxicosis)
- Induction of hypersensitivity
Fungal diseases which result from
tissue invasion can be categorized
according to the sites of lesions. These are?
- Superficial mycoses (dermatomycoses or dermatophytoses)
- Subcutaneous mycoses
- Systemic mycoses
Site of lesion categorization: Opportunistic infections of
the skin or mucocutaneous
junctions result from
overgrowth of fungi
Dermatomycoses
Give fungal species capable of inflicting dermatomycoses.
- Candida species
- Malassezia pachydermatis
Superficial mycoses that is clinically more important since it has communicability and zoonotic potential.
Dermatophytoses
Site of lesion categorization: Associated with invasion and destruction of keratinized structures
Dermatophytoses
Give fungal species capable of inflicting dermatophytoses.
- Microporum species
- Trichophyton species
Tumour-like granulomatous
lesions
Mycetomas
Infection is caused by pigmented fungi
Phaeohyphomycosis
Site of lesion categorization: Result from localized
fungal invasion of the dermis and subcutis, often following penetration by a foreign body.
Subcutaneous mycoses
Site of lesion categorization: Often originate in the respiratory or digestive tracts, usually follow opportunistic infection by saprophytic fungi
Systemic mycoses
What are the factors which predispose the individual to systemic mycoses infection?
- 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
Group of diseases resulting from the ingestion of fungal toxins which
have been pre-formed in stored food or standing crops
Mycotoxicoses
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?
True
Mycological cultural procedures should
be performed in a biohazard cabinet
because of the risk of human infection
from spore ____.
Aerosols
How do you diagnose fungal diseases?
*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
_____ _____ can be demonstrated, in
cerebrospinal fluid mixed with India ink or nigrosine, as
budding cells with wide capsules.
Cryptococcus neoformans
_____ _____ 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.
Ringworm arthrospores
Sporing heads can be examined under a coverslip after
mounting a sample from a colony in a drop of _____ _____ _____.
lactophenol cotton blue
Yeast cells can be stained with
methylene blue or by the Gram method. True or False?
True
Fungi are usually isolated on ____ _____ agar (pH 5.5) which inhibits growth of most bacteria.
Sabouraud dextrose
What are the other methods for direct examination of fungis?
- Slide culture
- Transparent adhesive tape techniques
Addition of ____ and _____ increases selectivity by inhibiting some of the fastgrowing contaminating fungi such as zygomycetes
Chloramphenicol; cycloheximide
To stimulate growth of the yeast phase of dimorphic fungi, enriched media, such as ____-____ ____
agar with ___% blood, and incubation at ___°C are required
brain-heart infucsion; 5%; 37 celcius
The ____ ____-____ reaction or ____ ____ ____ can be used to demonstrate fungal elements in tissue sections.
periodic acid-Schiff (PAS); methenamine silver impregnation
The presence of a
mature sporangium identifies the fungus as _____.
Zygomycete
Features of vegetative hyphae which can be used for differentiation include ?
- Presence or absence of septa
- Either hyaline (colourless) or dematiaceous (pigmented)
- Specific hyphal structures such as racquet-shaped and spiral hyphae
Colonial characteristics of fungi are determined by ?
- Size and appearance after specified incubation time
- Color of both obverse and reverse sides
- Surface elevations or depressions
Dimorphic fungi grow as molds when cultured on ____ ____ agar at ___ C and as yeasts when cultured on enriched media at ____ C.
Sabouraud dextrose; 25 C; 37 C
Soluble ____ produced by dimorphic fungi
can be used for identification in immunological tests
antigens
Specific ____ ____ ____ are being developed
for rapid and reliable identification of dimorphic fungi.
nucleic acid probes
It inhibits ergosterol biosynthesis.
Ketoconazole (azoles)
Give the polyene antifungal drugs that bind selectively to ergosterol.
- Nystatin
- Amphotericin B
_____ 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
Griseofulvin
