Fungi – Microbiology Answers – Flashcards
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Unlock answers| What are the agents of systemic mycoses? |
Dimorphic Fungi --> Blastomyces dermatitidis Histoplasma capsulatum Coccidioides immitis Paracoccidioides brasiliensis |
| What is a dimorphic fungi? |
Mold form at 25-30°C (in natural environment)
Yeast form at 35-37°C (in host) |
| What is the infectious form of the systemic mycoses? |
| Conidia |
| What is the clinical form of the systemic mycoses? |
| Yeast and/or spherules |
| How are systemic mycoses contracted? |
| Inhalation of conidia |
| In which group are systemic mycoses the most prevalent? |
| Middle-aged men |
What is blastomycosis caused by Blastomyces dermatitidis also known as? |
Gilchrist's disease North American blastomycosis Chicago disease |
What is the natural reservoir of Blastomyces dermatitidis? ; |
| Soil |
| How would you culture Blastomyces dermatitidis? |
Use nonselective media such as Sabouraud dextrose agar or brain-heart infusion agar ; Culture two sets at 25;C and 37;C |
| What is the sexual form of Blastomyces dermatitidis called? |
| Ajellomyces dermatitidis |
| What is the colonial apperance of Blastomyces dermatitidis at 25;C? |
| The center can have raised areas called spicules or prickles |
| What are the microscopic characteristics of Blastomyces dermatitidis at 25;C? |
| Conidia are on short lateral branches and are ovoid to dumbbell shaped |
| What are the characteristics of Blastomyces dermatitidis at 37;C? |
| Broad based budding yeast that are sphericle and refratile |
| How do you confirm the identity of Blastomyces dermatitidis? |
| Conversion of mold form to yeast form or the exoantigen immunodiffusion test |
| What makes the exoantigens detected in the axoantigen immunodiffusion test? |
| Mycelia |
| How do Blastomyces dermatitidis;infections present in immunocompetent patients? |
Initially they are usually asymptomatic Pulmonary disease may follow and it may spread to the skin and bone |
; How do;Blastomyces dermatitidis;infections present in immunosuppressed patients? ; |
| May disseminate to multiple organ systems and rapidly fatal |
| What is histoplasmosis caused by Histoplasma capsulatum;also called? |
Reticuloendothelial cytomycosis Cave disease Sperlunker's disease |
| What is the reservoir for Histoplasma capsulatum? |
| Soil contaminated with bat and bird feces |
| What specimens can be used for Histoplasma capsulatum? |
| Specimens from the respiratory tract, liver, spleen, bone marrow, blood and exudates from lesions |
| Which specimens are best for finding Histoplasma capsulatum in AIDS patients? |
| Bone marrow and blood |
| How would you cultures Histoplasma capsulatum? |
Culture two sets on Sabroud dextrose, brain-heart infusion or inhibitory mold agar One set at 25°C and the other at 37°C |
| How do you confirm the ID of Histoplasma capsulatum? |
| The conversion of mold form to yeast form though complete conversion is rarely seen |
| What tests can you perform to detect Histoplasma capsulatum? |
Exoantigen immunodiffusion test to look for H and M antigens Immunodiffusion with complement fixation Skin testing |
| What are the early and mature microscopic characteristics of the mycelial culture of Histoplasma capsulatum? |
Early: round to pyriform microconidia Mature: large echinulate or tuberculate macroconidia |
| What cells do the microconidia of Histoplasma capsulatum invade? |
| They are pahagocytized by macrophages in the lungs |
| How does histoplasmosis present in patients with an intact immune system? |
Light exposure: imited and usually asymptomatic, organisms can remain viable for years
Heavy exposure: acute pulmonary disease |
| How does histoplasmosis present in immunocompromised patients? |
| Disseminated potentially fatal disease |
| How does Histoplasmosis capsulatum appear under direct dectection? |
Small yeasts Oval to round budding cells Often clustered within monocytes and macrophages |
| What is coccidioidomycosis caused by Coccidioides immitis also known as? |
California disease Valley fever Desert rheumatism
|
| Where ecologically can Coccidioides immitis be found? |
| the Lower Snoran Life Zone |
| Which mycotic agent is the most virulent to humans? |
| Coccidioides immitis |
| What are the characteristics of the arthroconidia of Coccidioides immitis? |
| Barrel shaped, convert to spherules in host |
| How would you culture Coccidioides immitis? |
Does not convert readily to spherules at 35°C Culture one set at 25°C |
| What are the colonial characteristics of Coccidioides immitis? |
Initially white to gray, moist, glaborous Develops mycelium and appears to "bloom" Mature colonies are tan to brown to lavender |
| What are the microscopic characteristics of Coccidioides immitis? |
Aerial hyphae grow at right angles to the vegetative hyphae Arthroconidia are seperated by disjunctor cells |
| What tests can be used to detect Coccidioides immitis? |
Latex agglutination with immunodiffusion Complement fixation especially for prognostic studies |
| What are possible complications of a primary Coccidioides immitis infection? |
Pulmonary disease Allergy Toxic erythema Erythema nodosum (desert bumps) Erythema multiforme (valley fever) Arthritis (desert rheumatism) |
| How are primary infections of Coccidioides immitis treated? |
| Usually resolve without therapy |
| What does the coccidioidin skin test detect? |
Infection with Coccidioides immitis confers strong immunity to reinfection This is detected using the coccidioidin skin test |
| What are possible complications of a secondary infection of Coccidioides immitis? |
Lung nodules Cavitary lesions Progressive pulmoary disease Dissemination Meningial involvment is common |
| What is paracoccidioidomycosis caused by Paracoccidioides brasiliensis also known as? |
South American blastomycosis Brazilian blastomycosis Lutz-Splendore-Almeida disease Paracoccidioidal granuloma |
| How would you culture Paracoccidioides brasiliensis? |
| Culture two sets, one at 25°C and one at 35°C |
| What tests can be used to detect Paracoccidioides brasiliensis? |
Complement fixation Immunodiffusion |
| What are the characteristics of the yeast form of Paracoccidioides brasiliensis? |
| Multipolar budding on the periphery resembling a "mariner's wheel" |
| What is the usual route of infection for Paracoccidioides brasiliensis? |
| Pulmonary |
| What are possible complications of infection with Paracoccidioides brasiliensis? |
Often asymptomatic Ulcerative granulomatous lesions Disemination - predilection for adrenal glands |
| What phylum causes opportunistic infections? |
| Zygomyces |
| What does the Zygomyces show a strong predilection for invading? |
| Blood vessels |
| What is the most common disease caused by Zygomyces? |
| Rhinocerebral zygomycosis |
| What is Rhinocerebral zygomycosis? |
Most common Zygomycoses Effects diabetics the most Originates in paranasal sinus and can extend to the brain |
| What are the characteristics of the Zygomycete Mucor? |
Rapid grower Cottony dirty white colonies No rhizoids |
| What are the characteristics of the Zygomycete Rhizopus? |
Rapid grower Brown rhizoids Clusters of sporangiophores are joined by stolons |
| What are the characteristics of Penicillium? |
Rapid grower Green or blue-green colonies Phialides with oval conidia in chains |
| What are the three species of Aspergillus? |
Aspergillus fumigatus flavus niger |
| What is the most commonly found genus of fungi in the clinical lab? |
| Aspergillus |
| What is the most common isolate of Aspergillus? |
| Aspergillus fumigatus |
| What is the infectious form of Aspergillus? |
| Conidia |
| What are the hypersensitivity reactions to Aspergillus? |
Types 1 and 4 Allergic bronchopulmoary infection Asthma
|
| What is an aspergilloma? |
"Fungus ball" Occurs in cavities from tuberculosis or cancers |
| What does Aspergillus cause in immunocompromised patients? |
| Invasive penumonia and dissemination |
| What causes aspergillus poisoning? |
Aspergillus flavus makes the toxin aflatoxin which contaminates food supplies Causes liver damage and cancer |
| What is the clinical form of Aspergillus? |
| Hyphae |
| What is the leading cause of yeast infections? |
| Candida albicans |
| How is Candida albicans acquired? |
Endogenously It's part of the normal flora |
| What are the characteristics of Candida albicans under direct examination? |
Yeast and pseudohyphae Cells usually exhibit budding Pseudohyphae are constricted at ends and remain linked like sausages |
| What are the Candida albicans germ tube test results? |
| Positive, usually sufficient for ID |
| What does Candida albicans look like on cornmeal agar? |
| Produces blastoconidia, pseudohyphae, true hyphae and chlamydoconidia |
| What are the Candida albicans urease results? |
| Negative |
| Cryptococcus neoformans is a major cause of oppurtunistic infections in what group? |
| AIDS patients |
| What is the reservoir for Cryptococcus neoformans? |
| Soil contaminated with pidgeon droppings |
| What are the diseases caused by Cryptococcus neoformans? |
Pneumonia Meningitis Fungemia
|
| What is the colonial appearance of Cryptococcus neoformans? |
| Mucoid due to capsule |
| What are the Cryptococcus neoformans germ tube test results? |
| Negative |
| What does Cryptococcus neoformans look like on cornmeal agar? |
| Does not produce pseudohyphae or true hyphae |
| What are the Cryptococcus neoformans urease results? |
| Positive |
| What does Pneumocystis jiroveci cause in AIDS patients? |
| Pulmonary infections |
| What is the infective stage of Pneumocystis jiroveci? |
| Cyst that contains up to eight spores |
| What kind of parasites are Microsporidia? |
| Unicellular and obligate intracellular |
| Which Microsporidia are human pathogens? |
| Enterocytozoon bieneusi and Encephalitozoon intestinalis |
| What kind of infections do Microsporidia cause? |
| Castrointestinal infections |
| What is Amphotericin B? |
A polyene macrolide antifungal agent Drug of choice for serious systemic infections |
| Which antifungal agents are polyene macrolides? |
| Amphotericin B and Nystatin |
| Why is Amphotericin B callwed "amphoterrible"? |
| It has very serious side effects such as nephrotoxicity |
| What are the antifungal agents? |
| Polyene macrolides (Amphotericin B and Nystatin), azole drugs, Griseofulvin and potassium iodide |
| What is the causative agent of superficial mycoses? |
| Malassezia furfur |
| What disease does Malassezia furfur cause? |
| Tinea versicolor |
| What does Malassezia furfur look like in a KOH preparation? |
Spaghetti and meatball appearance Septate hyphae Budding yeast |
| What are the causative agents of dermatophytosis? |
| Trichophyton, Microsporum and |
