INFECTIOUS AGENTS - Mycology Flashcards
What is mycology?
Mycology is the study of fungus
What are the three components of the fungi cell wall?
Chitins
Mannans
Glucans
What is the main sterol found in the fungal plasma membrane?
Ergosterol
What is the infectious form of fungi?
Fungal spores
What are the three diagnostic methods that can be used to diagnose a fungal infection?
Direct microscopy
Culture
Histopathology
What are the three main classifications of fungi?
Yeast
Filamentous
Dimorphic
How do yeast reproduce?
Yeast undergo budding
What is the term used to describe the structure formed when yeast daughter cells don’t detach from the original yeast?
Pseudohyphae
(T/F) Yeast stain as Gram negative (G-)
FALSE. Yeast stain as Gram positive (G+)
What are the three most important pathogenic yeast genera in veterinary medicine?
Candida
Malassezia
Cryptococcus
What should be used to grow candida and malassezia in culture?
Candida and malassezia should be grown on Sabouraunds dextrose agar at 37°C
Candida is polymorphic, what does this mean?
Candida has three forms - a yeast form, hyphae form and pseudohyphae form
What is the pathogenic form of candida fungi?
Hyphae
What is the name of the fungal spores produced by candida fungi?
Chlamydospores
What is the most common pathogenic species of candida?
Candida albicans (C. albicans)
What are the three diseases caused by candida albicans infection in cattle?
Mycotic abortion
Rumenitis
Mastitis
What are the three diseases caused by candida albicans infection in dogs?
Dermatitis
Enteritis
Vaginitis
Which test can be used to specifically test for Candida albicans?
Germ tube test
Give an example of a species of malassezia
Malassezia pachydermatitis (M. pachydermititis)
What are the two diseases caused by malassezia pachydermititis infection?
Dermatitis
Otitis externa
How does malassezia pachydermititis cause skin irritation?
M. pachydermitis produces urease which breaks down into ammonia and irritates the skin
What is the most common pathogenic species of cryptococcus?
Cryptococcus neoformans (C. neoformans)
Cryptococcus is an opportunistic pathogen. Which specific immunocompromised individuals does cryptococcus target?
Individuals with a defective cell-mediated immunity
Which disease is most commonly seen due to cryptococcus infection?
Rhinitis
Which virulence factor allows cryptococcus to be one of the only fungi that can cause meningitis?
Anti-phagocytic mucilaginous capsule
Which stain can be used to identify the mucilaginous capsule in culture?
India ink stain
What is the structure of filamentous fungi?
Filamentous fungi have a primary hyphae structure which branches to form mycelium (mould)
What are the two forms of filamentous mycelium?
Septate
Non-septate
What are the two most important pathogenic filamentous fungi categories in veterinary medicine?
Dermatophytes
Aspergillus
How should dermatophytes and aspergillus filamentous fungi be grown in culture?
Dermatophytes and aspergillus should be grown on Sabouraunds dextrose agar at 28°C
What do dermatophytes digest and how does this relate to where on the body they cause infection?
Dermatophytes digest keratin and thus cause hair, skin and nail infections
What is the name of the fungal spores produced by dermatophytes?
Arthrospores
What are the two types of fungal spore that are only produced by dermatophytes during lab culture?
Microconidia
Macroconidia
List two genera of dermatophytes
Microsporum
Trichophyton
Which disease is caused by microsporum and trichophyton?
Ring worm
How can a ‘wood lamp’ be used to identify a microsporum infection?
A ‘wood lamp’ produces ultraviolet (UV) light which causes fluorescence of microsporum lesions
Which species of microsporum causes ringworm in dogs and cats?
Microsporum canis (M. canis)
Which species of trichophyton causes ringworm in cattle?
Trichophyton verrucosum (T. verrucosum)
How can trichophyton verrucosum be easily identified in culture?
T. verrucosum is the only dermatophyte which grows at 37°C in Sabouraunds dextrose agar
What does aspergillus require in order to produce fungal spores?
Oxygen
What is the name of the fungal spores produced by aspergillus?
Conidia
What are the three diseases caused by aspergillus infection?
Pneumonia
Nasal aspergillosis
Mycotic abortion (in cattle)
What is the most common pathogenic species of aspergillus?
Aspergillus fumigatus (A. fumigatus)
Aspergillus conidia (spores) are in the air constantly. How does the immune system of healthy animals defend against these spores?
Aspergillus conidia and continually inhaled however macrophages phagocytose the conidia within the lungs. If any of the conidia get the chance to develop into hyphae, they will be phagocytosed by neutrophils
What are mycotoxins?
Mycotoxins and naturally occurring toxins produced by fungi
What is the carcinogenic mycotoxin produced by aspergillus fumigatus fungi?
Aflatoxin
What is ergotism?
Ergotism is a condition caused by the ingestion of mycotoxin which affects the nerves innervating arteriolar smooth muscle
What is mycotic oestrogenism?
Mycotic oestrogenism is a condition caused by mycotoxins which alter the oestrogen levels within the body
