Glossary of Micro - mycology
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- What are the 3 morphological types of fungi?
- Describe the yeast form.
*reproduce by budding
- Describe general features of molds
*reproduce via spores
- What are the two forms dimorphic fungi take? What spurs the transition? Name 3 dimorphic fungi.
- 1.mold at ambient temp (~25); has infectious spores
2.yeast at body temp; pathogenic form
*histoplasma, blastomyces, coccidioides
- What are conida?
- The spores produced by mold fungi.
- Describe a structural variation found among hyphae.
- *aseptate: no cross walls present (is multinucleate)
*septate: has cross walls
- What is a dematiatious fungus? What's the prognosis with it?
- *has black and brown pigmented hyphae
*difficult to treat - poor prognosis
- What fungus might be visulaized with an india ink stain? What feature of this fungus would be particularly evident?
- Cryptococcus; reveals capsule
- What substances are present in the cell wall and in the cytoplasmic membrane of fungi that are not found in bacteria?
- *wall: chitin
- Antibacterials are generally not effective against fungi, but there is an exception. What is it?
- PCP is susceptible to SMZ-TMP.
In general, bacteria are larger than yeasts.
- False: yeasts are larger than bacteria.
- What is the mechanism of action of amphoteracin B?
- It binds to ergosterol in the cell membrane - this causes loss of membrane integrity.
- Amphoteracin B is a broad spectrum anti-fungal and effective at killing - so why is its use reserved?
- It is very toxic, especially to the kidneys.
- What modifications may make amphoteracin more widely used? What is the drawback to these changes?
- New liposome technology reduces toxicity, but is extremely expensive.
- What is the mode of action of the azoles? What fungi are they effective against?
- *inhibit ergosterol synthesis
*active against yeasts, Aspergillus, and some dimorphics
- What is the mode of action of the echinocendins?
- Block glucan synthesis - glucan is an impt component of the cell wall and is used in the synthesis of chitin.
- What form are dermophytes? What is their site of infection?
- They are molds that produce keratinases and target keratinized tissues (hair, skin, nails)
- Name 3 common maladies caused by dermophytes.
- 1.Ring worm
Dermophytes are generally resolved by an antibody-mediated immune response.
- False: B/c they generally do not invade tissue, dermophytes seldom elicit an immune response of any variety.
- What are the 3 genuses of dermophytes that commonly affect humans?
- What form is Sporothrix schenckii? How is it commonly contracted?
- *dimorphic; cigar-shaped as yeast and thin, septate hyphae with pyriform conidia as mold
*infects SC tissue after trauma with splinters or thorns
- What happens after sporothrix enters the skin?
- *forms a papule
*can ascend along lymphatics
Patients with systemic infection by dimorphic fungus must be kept in negative pressure rooms to prevent spread of infection.
- False: There is no p-p spread with infections of this type. The infection is acquired by inhalation of spores from the environment.
- Where is coccidioides considered indigenous? What effect does this environment have on their life cycle?
- In arid, or semi-arid regions like the american SW and northern Mexico. Dessication leads to formation of infectious spores.
The yeast form of coccidioides, the spherule, contains infectious endospores.
- False: contrary to their name, endospores are not true spores and are not infectious.
- What environmental factors favor the growth of Histoplasma? Which group of hobbyists are likely to become infected?
- *bird and bat feces
- Which part of the Histoplasma mold form is infectious - microconidia or macroconidia?
- Microcondida are infectious; the tuberculated macroconidia are not.
- Histoplasma is prevalent in what geographical areas?
- Lower Mississippi River valley, Caribbean basin.
- What does the yeast form of histoplasma look like? In what cell can this form be found?
- *small and lemon-shaped
*seen in macrophages
- The CXR of a patient with histoplasma can be confused with miliary TB. Why is this?
- The presence of widespread granulomatous lesions in the lung fields.
- Systemic Histoplasma is seen in immunocompromised patients. Specifically, what population and how is the disease manifested?
- *HIV pts w/CH4+ < 100
*chronic pulmonary presentation
- How can histoplasma be diagnosed?
*bone marrow cultures
- Name 4 infections that present similar to TB and can be differentiated based on bone marrow culture.
- What is characteristic of the yeast phase for Blastomyces?
- Broad-base budding
- How can blastomycosis present in its disseminated form?
- *chronic pulmonary form
*may affect any part of the body: skin lesions, osteomyelitis, and prostate
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