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44 Cards in this Set
- Front
- Back
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What are some of the ways fungal infections can be transmitted? |
Respiratory inhalation (major factor), cutaneous inoculation, systemic invasion by opportunistic normal flora, contact with infected hosts, hypersensitivy, or mycotoxins. |
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What are some risk factors for fungal infections? |
Location, travel, occupation, congenital and acquired T cell deficiency (AIDS), immunosuppression (transplants and malignancies), and diabetes mellitus. |
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What are the general characteristics of fungi? |
Aerobic: obligate or facultative Eukaryotic: membrane bound nucleus and cytoplasmic organelles (maybe multinucleate) Achlorophyllous, unicellular or multicellular, saprophytic (heterotrophic). |
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What are the characteristics of fungal cells? |
Cell wall: multilayered polysaccharide (cellulose, glucans, mannans, chitin, polypeptides). No teichoic acids, peptidoglycan, or LPS. Cell membrane: phospholipid bilayer, ergosterol (relate to chemotherapy) Cytoplasm - typical eukaryotic organelles. Nucleus - either uninucleate or multinucleate. |
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Describe the capsule of fungal cells. What is its purpose? |
It is an amorphous polysaccharide coating that is both antiphagocytic and antigenic. It is only found in some species such as Cryptococcus neoformans. |
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What are some of the growth forms for fungal cells and an example of each? |
yeast - unicellular fungi that reproduce by budding (Cryptococcus) Mold - hyphae - septate hyphae (Aspergillus) or non-septate, coenocytic hyphae (Mucor) Pseudohyphae - (Candida albicans) Thermal Dimorphism - (Blastomyces dermatitidis) |
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What is the difference between septate hyphae and non-septate hyphae? |
Septate - parallel walls with separators called septate. Non-septate - walls are not as parallel, more ribbon like. |
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What are conidia? |
Spores - asexual structures. |
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What are blastospores and chlamydosproes? |
Blastospores - formed by budding yeasts (Blastomyces) Chlamydosproes - terminal or intercalary cells with thick walls (Candida albicans) |
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What are arthrosproes and sproangiosproes? |
Arthrospores - formed by fragmentation of hyphae (Coccidioides immitis) Sporangiospores - formed in sporangia by cleavage (Rhizopus) |
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What are the 4 classifications for fungi that are based on sexual phase? |
Ascomycetes, basidiomycetes, zygomycetes, and deuteromycetes. |
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Give examples of ascomycetes and basidiomycetes. |
Ascomycetes: Aspergillus, histoplasma, blastomyces, Dermatophytes. Basidiomycetes: Cryptococcus, mushrooms |
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Give examples of Zygomycetes and Deuteromycetes. |
Zygomycetes - order Mucorales - Mucor, Rhizopus. Deuteromycetes (Fungi Imperfecti): Sporothrix, Coccidioides, Candida. |
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What are some of the microscopic examinations used to determine fugal infections? |
Gram stain, Giemsa, india ink, potassium hydroxide (KOH) wet prep, hematoxylin and eosin stain, periodic-acid Schiff stain (PAS), Gomori-Methenamine Silver stain (GMS), Mucicarmine or Alcian blue stain. |
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What is india ink specific for? |
Capsule detection and capsule formation. |
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What does KOH do? |
It digests and degrades the host material, leaving behind the yeast. It is often combined with a stain. |
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What is the GMS stain for? |
It is very good at telling apart septate or non-septate organisms. |
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What are some of the histopathological responses to fungal infections? |
Acute pyogenic abscess (Candida) Chronic granuloma formation (Dermatophytes) Mixed pyogenic and granulomatous inflammation (Blastomyces) Blood vessel invasion with thrombosis and infarction (Mucor, Aspergillus) Hypersensitivity without tissue reaction. |
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What do you use to grow fungal cultures? |
Sabouraud agar with antibiotics. |
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What are the identification criteria for fungal cultures? |
Temperature of growth, rate of growth, colonial and microscopic morphology, sporulation pattern, biochemical reaction (yeast) |
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True/False: Serology and skin tests are extremely useful for identifying fungal infections. |
False! They are actually very poor and not useful. |
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Why are skin tests for DTH not very useful? |
There is often cross-reactivity and there is a high positive rate in endemic areas. |
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Where are the clinical manifestations of Candidiasis? |
Mucosal (vaginitis, esophagitis, oral thrush) Cutaneous, or chronic mucocutaneous Systemic (fungemia, hepato-spleenic, endophthalmitis, renal) Urinary tract. |
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What is the most common opportunistic fungal infection? |
Candidiasis. |
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What is common to find in a wet mount of Candidiasis? |
Hyphae, little budding yeast, and lots of pus cells covered with bacteria. |
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Which is more common, oral candidiasis or mucocutaneous candidiasis? |
Oral. |
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True/False: Candida species produce multiple morphologic forms. |
TRUE!! They are NOT dimorphic fungi because they can produce multiple forms: pseudohyphae, budding yeasts, etc. |
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What is the most common opportunistic mold infection? What are its clinical manifestations? |
Aspergillosis that can cause pneumonia, aspergilloma, allergic bronchopulmonary, disseminated multiorgan involvement. |
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Where are the clinical manifestations of zygomycosis? |
Sinusitis, rhinocerebral (severe form), pulmonary, and renal. |
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What are the clinical manifestations of histoplasmosis? |
Most cases are mild or sub-clinical pulmonary disease, pneumonia, chronic progressive pulmonary (cavity), histoplasmona, often disseminated. It can often be found in bone marrow and there are often calcified lesions. |
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What are some of the FDA approved chemotherapy drugs? |
Polyenes: (Amphotericin B, lipid encapsulated forms Azoles: (fluconazole, itraconazole, ketoconazole) Echinocandin: (Caspofungin, micafungin) Less common: nucleoside derivatives, allyamines, microtubule disruption. |
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What are some of the investigational chemotherapy drugs? |
Nikkomycins - chitin synthase inhibitors Echinocandin/pnemocandin/lipopeptide class - inhibit glycan synthesis. |
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What is the mode of action for Amphotericin B? |
It is fungicidal and binds to ergosterol, increases membrane permeability resulting in leakage of cytoplasmic components and cell death. |
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What type of drug is Amphotericin B and what is its spectrum of activity? |
It is a Polyene and works against Candida, Crypto, Aspergillus, Histo, Blasto, Cocci, etc. So a Broad spectrum. |
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What is the limitations to amphotericin B? |
Nephrotoxicity - azotemia, renal tubular acidosis, impaired renal concentrating ability and electrolyte abnormalities like hypokalemia and sodium and magnesium wasting. |
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What is the mode of action for Fluconazole? |
It is fungistatic and prevents ergosterol synthesis by inhibiting the C-14 demethylation step (cytochrome P-450 rx). |
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What type of drug is Fluconazole and what is its spectrum of activity? |
It is an Azole and affects Candida, Crypto, Trichsporonosis, dermatophytes. |
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What are the limitations to Fluconazole? |
There is resistance in some Candida species - krusei and glabrata and is not effective for non-dermatophyte molds. |
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What is the mode of action for Echinocandins? |
They are fungistatic and prevent synthesis of beta 1,3-glucan required for cell wall. |
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What is its spectrum of activity for Echinocandins? |
It affects Aspergillus, Candida but is NOT effective against Cryptococcus or zygomycetes. |
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What are the obstacles to early diagnosis of invasive fungal infections? |
Immunosuppression often causes many symptoms to be absent, few clinical features are uniquely specific for systemic fungal infections, sputum and blood cultures are often negative, and invasive procedures may be necessary for definitive diagnosis and are often complicated for immunocompromised patients. |
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What are the benefits to early invasive fungal infections? |
Permits selection of a therapy of maximal effectiveness and early intervention with antifungal therapy may help decrease the high mortality rate associated with serious systemic mycoses. |
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What are the differences between bacteria and fungi in cell diameter, nucleus, cytoplasmic organelles, and cell membrane sterols? |
Cell diameter (fungi bigger) nucleus (fungi eukaryotic, bacteria prokaryotic) cytoplasmic organelles (fungi present, bact. absent) Cell membrane sterols (fungi - ergosterol, bact. absent) |
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What are the differences between bacteria and fungi in regards to cell wall, metabolism, and thermal dimorphism? |
Cell wall (fungi-chitin, glucans, mannans, peptides, bact-teichoic acids, PG, LPS) Metabolism: Fungi-mainly aerobes, facultative aerobes, bacteria-obligate and facultative aerobes and anaerobes. Thermal dimorphism: Fungi-common in many pathogenic species, bacteria - absent. |
