Intro to Mycology Flashcards
Single cell forms of fungi are ____.
Yeasts
Multicellular forms of fungi are ____.
Mold
What are Spores?
sexual reproductive elements of fungi
What are Conidia?
asexual reproductive elements of fungi
Are fungi eukaryotic or prokaryotic?
Eukaryotic saprophytes (recycle organic matter for use)
How do fungi differ from animal cells?
Cell wall made up of chitin and ergosterol in cell membranes (rather than cholesterol in animals)
How is asexual reproduction of yeasts accomplished?
budding (blastoconidium)
How is sexual reproduction of yeasts accomplished?
ascospores (spores that are surrounded by ascos)
What is a mycelium?
intertwined mass of hyphae
What is dimorphism?
a virulence factor for fungi in which they can change forms from mold to yeast to establish infection in humans. Yeast form in tissue and culture at 37C and mold form in environment and at room temp in culture. Yeast form is the invasive form
What are some important dimorphic fungi?
Blastomyces dermatitidis
Coccidiodes immitis
Histoplasma capsulatum
Paracoccidiodes brasliensis
Candida Albicans occurs in what form always?
yeast only (so is cryptococcus neoformans-capsulated and causes meningitis)
Aspergilus fumigatus.
always a mold even when it establishes infection in the body (not really infection but just grows as mold)
T or F. In general, fungi produce sub-acute, self-limiting infections.
T. and there are no known toxins involved in human infection unlike bacteria
Opportunistic molds are sensitive to what part of human immunity?
Neutrophils
Is most of the human response to fungi T-cell mediated or humoral in nature?
T-cell mediated
How is microscopic diagnosis of fungi infection done?
tissue is treated with 10% KOH to dissolve any animal and soft tissue associated with the yeast and mold forms and the chitin wall of fungi cells remains and is visible.
How is culturing diagnosis of fungi infection done?
done on Sabouraud’s medium which is high glucose and has a pH of 5.6 which favors fungi growth over bacteria growth. If the plate is incubated at 37C yeast would growth and if incubated at 25C molds would grow up. Molds are differentiated by morphology. yeast yield bacterial-like colonies.
T or F. Antifungal are usually more toxic than antibacterial.
T. Due to similarities to humans . And the treatment regimens often last months due to slow growth of fungi
What are the three major targets of antifungals?
Cell membrane (ergosterol),
cell wall, and
genome replication
In general, how are localized or superficial/cutaneous fungal infections treated?
left to observation or topical creams
Disseminated infections are treated with Ampho B and/or AZOLES
Immunocompromised patients are left on AZOLES for life to limit recurrences
Classification of fungi
Zygomycetes,
Ascomycetes (majority of human pathogens),
Basidiomycetes (Aspergilus),
Deuteromycetes (fungi imperfecti)-lack sexual stage
or
Superficial (least severe) Cutaneous Subcutaneous Systemic (can disseminate in immunocompetent people-most virulent) Opportunistic (most severe)
Tinea (ringworm)
Involved skin, hair, and nails
Caustive agents are Dermatophytes. Three genera:
Epidermophyton
Microsporum
Trichophyton
Always molds
Dogs and cats are reservoir for infection
A single form of tinea can be caused by more than one dermatophyte and assigned dermatophyte can cause more than one tinea so we don’t typically look for a specific dermatophyte
Tinea Capitis
tinea of the scalp- itchy and hair falls out
can be diagnosed using a Woods lamp
Tinea Corporis
tinea on the body
Subcutaneous mycoses
Example is sporotrichosis caused by sporothrix schenckii that is dimorphic and can borrow into deeper layers of dermis or bone
commonly found in soil or vegetation and the leaves and pedals of rose bushes
can’t penetrate epidermis unless break in skin
think rose bush prick
fixed and lymphocutaneous forms
Systemic mycoses
often are endemic. Where person became infected is important
Three fungi:
Blastomycosis
Histoplasmosis
Coccidoidomycosis
Where is Blastomycosis common?
East (MidSouth all the way up through Ohio and New York, and Minnesota into Canada)
Where is Histoplasmosis common?
Southeast (Illinois, TN, AR, LA, GA, Kentucky)
mississippi and ohio river valleys
Where is Coccidioidomycosis common?
Southwest (texas to southern CA)
san juaquin valley (called valley fever here)
Histoplasmosis
inhalation of Histoplasma capsulatum confided
grows in soil containing bat or bird shit (common near Mississippi River)
H. capsulatum is dimorphic, converts to yeast forms in host that can replicate in macrophages by reducing acidification of phagolysosome or inhibits fusion of phagolysosome
80% of residents have been infected
95% asymptomatic or mild flu-like
5% result in a cute pneumonia
1% disseminate in macrophages, leading to short, and renal and hepatic failure
Diagnosis of Histoplasmosis
- presence in endemic area
- treburculate macroconidia (bumpy surface) in mold or
yeast is isolated and budding yeast form inside macrophages can be diagnostic
Opportunistic Mycoses
Candidias (thrush=overgrowth of candidia- seen in chemotherapy patients)
