Fungi Flashcards
What are fungal cell walls made from?
Glucans and chitin
(different from bacteria => beta-lactam abx won’t kill fungi)
What major component of the fungal cell membrane is different from the mammalian cell membrane?
The sterol
Fungi have ergosterol, mammals have cholesterol
What are the 3 major targets of antifungal drugs?
Give examples
- Membrane disruption
- Polyenes: Bind to ergosterol to cause leaks
- Amphotericin B, nystatin
- Polyenes: Bind to ergosterol to cause leaks
- Sterol synthesis inhibitors
- Azoles (Inhibit CYP)
- Ketoconazole, fluconazole, itraconazole, etc.
- Allylamines (Inhibit squalene epoxidase)
- Terbinafine
- Azoles (Inhibit CYP)
- Glucan synthesis inhibition
- Echinocandins (inhibit beta-1,3 glucan production)
- Micafungin, caspofungin, anidulafungin)
- Echinocandins (inhibit beta-1,3 glucan production)
What is the only fungal infection that can be treated with an antibiotic?
Which antibiotic?
Pneumocystosis caused by pneumocystis jiroveci
Treat wiht trimethoprim-sulfamethoxazole
(Other anti-fungals will not work)
What are the three phyla of fungi that are pathogenic to humans?
Name a few organisms in each category
- Ascomycetes
- Candida
- Coccidioides
- Blastomyces
- Histoplasma
- Zygomycetes (cause murcormycosis)
- Rhizopus
- Rhizomucor
- Mucor
- Basidiomycetes
- Cryptococcus
- Malassezia
Which organisms can cause endemic mycosis?
What infections do they cause?
- Coccidioides immitis -> Coccidioidomycosis
- Histoplasma capsulatum -> Histoplasmosis
- Blastomyces dermatitidis -> Blastomycosis
Describe the clinical presentation of coccidioidomycosis
How is it different from the other endemic mycoses?
- Mild pulmonary infection
- May be subclinical
- Severe pulmonary infection in an immunocompromised host
Less likely to disseminate than other endemic mycosis
Endemic to the Southern USA and Latin America
Describe the clinical presentation of histoplasmosis
How is it different from the other endemic mycosis?
- Pulmonary infection that replicates in macrophages
- May cause acute pulmonary disease if exposure is high
- May form caseating or non-caseating granulomas
- May look like M**ycobacterium tuberculosis
- May disseminate to RES organs
- More likely in immunocompromised host
More likely to disseminate than coccidiodomycosis
Forms granulomas
Less likely to involve CNS than blastomycosis
Endemic to central and eastern USA
Describe the clinical presentation of blastomycosis
How is it different from the other endemic mycosis?
- Pulmonary infection
- Lower respiratory
- May spread to CNS, gonadal tissues, bone
Look for broad-based budding yeast
More likely to involve CNS than coccidioidomycosis or histoplasmosis
Does not form granulomas like histoplasmosis
Endemic to North America, Canada, Africa, South America, Asia
You see broad-based budding yeast in a patient sample.
Which organism is likely causing this?
Blastomycosis
Describe the clinical presentation of murcormycosis
How is it different from the other opportunisitic mycoses?
- Highly invasive local tissue infections
- May spread to CNS
- Thrombosis, infarction
More invasive tissue involvement than other opportunistic mycoses
High risk in Diabetes Mellitus patients (DKA)
Look for 90 degree angle growth of hyphae
Treatment may require surgery
What is likely causing this infection?
A dermatophyte (Trichophyton, microsporum, epidermophyton)
Cutaneous mycoses - tinea corporis
What is likely causing this infection?
Sporothris schenkii
Subcutaneous mycoses - Sporotrichosis
Nodular lesions with lymphatic spread
Which organism is shown in this picture?
Blastomyces dermatidis
(look for broad-based budding yeast)
Which organism exhibits this characteristic pattern:
- Enter the cell and remodel into spherical cells
- Endospores divide
- Rupture and release endospores into tissue
Coccidioidomycosis - spherules!
Assume that the white patches would scrape off of you tried
What organism is causing this?
One of the Candida spp
This mucosal infection is associated with T-cell dysfunction (invasive is associated with neutrophils)
Which organism exhibits this pattern of hyphae growth?
Aspergillus spp.
Lookd for septate hyphae and acut angle branching
