Pathogenic Fungi Flashcards
Fungal morphology
Yeasts - unicellular, budding
Molds - mycelia, spores, filamentous (can be septate or non-septate,
Dimorphs - both
Thermal dimorphism
Fungi can be different at different temperatures. 30C, will be in yeast state (usually in host).
What is example of a thermal dimorph?
Candida is dimorphic
Compare opportunistic infections with true pathogenic infections.
A pathogenic infection can invade and grow in a healthy host. A pathogenic fungi will have high virulence, can invade a host with high resistance, usually has a respiratory mode of entry, can be symptomatic or asymptomatic, has specific immune functions in host (compared to weak with opportunistic), and is found in specific regions compared to opportunistic, which is found world-wide.
Types of mycoses
Systemic, superficial, cutaneous, subcutaneous, and deep mycoses. Superficial - on the surface (epidermis) - is very common. Cutaneous is upper layer of dermis and part of stratum corneum, Subcutaneous includes dermis and subcutaneous. Deep (invading multiple organs) not as much. Deep can lead to sepsis - “fungemia” which is similar to bacteremia. The more common ones enter where there is a wound already, while opportunistic enter through nasal sinuses, lungs, blood vessel (catheter), esophagus, stomach, intestines, etc.
Define fungal virulence factors:
Thermal dimorphism, toxins, polysaccharide capsule, adhesion factors, hydrolytic enzymes, delivery bags (protected from proteases), inflammatory stimulants. Cryptococcus is a good example of the wide variety of virulence factors.
What are the four true fungal pathogens?
Histoplasma, Blastomyces, Coccidioides, Paracoccidioides “His Blast Caused Pathogens.”
What is the morphology of Cryptococcus?
It is a yeast at both high and low temperatures. It also produces a characteristic capsule.
What is the morphology of Histoplasma?
It is a mold at low temperatures, and a yeast at higher temperatures.
What is the result of a deep systemic fungal infection if mortality is not caused?
Immunity.
What is the pattern of distribution for the four true fungal pathogens?
They are distributed in a predictable pattern geographically - climate, soil.
Describe the epidemiology, events, and major characteristics of fungal
diseases listed below and their etiological agents:
a. histoplasmosis
Dimorphic. Found in US Midwest. Causes enlargement of lymph nodes, liver, spleens, bore marrow. Most common true pathogen. Grows in moist soil with high nitrogen content. Inhaled pathogen causes chronic lung disease.
Describe the epidemiology, events, and major characteristics of fungal
diseases listed below and their etiological agents:
b. C. neoformans infections
Not dimorphic, only yeast. Has capsule. Many virulence factors. Mainly found in sub-Saharan Africa. Affects meninges and brain, can cause death. inhabits soil around pigeon roosts.
Describe the epidemiology, events, and major characteristics of fungal
diseases listed below and their etiological agents:
c. dermatophytes
Superficial infections that cause Athlete’s foot and ringworm. Least invasive of pathogenic fungi, but they can invade deeper, though rarely past sub-C. Can have human, animal, soil reservoir.
Describe the epidemiology, events, and major characteristics of fungal
diseases listed below and their etiological agents:
d. sporotrichosis
A type of subcutaneous fungi. Rose gardener’s disease. Cigar-shaped yeasts in host, conidia in soil (filamentous). Follows lymph drainage system.
