T19 - Systemic Mycosis (Yeast)

What three primary morphological forms are exhibited by Candida albicans?

Yeast, pseudohyphae, and true hyphae

What major components of the Candida cell wall serve as targets for antifungal drugs?

Beta-1,3-glucan and beta-1,6-glucan

What secretory cytolytic peptide is produced by Candida albicans to damage host immune cells?

Candidalysin

Which Candida virulence factor involves forming opaque cells to resist neutrophil engulfment?

Phenotypic switching

What environmental cues induce Candida albicans yeast-to-hyphal morphogenesis?

Temperature, serum, alkaline pH, nutrient starvation, and CO2

What fungal structure makes Candida highly resistant to antifungals and host immune defense?

Biofilms

What is the term for the characteristic overgrowth of Candida in the oral cavity often due to inhaled corticosteroids?

Oral thrush

Which two Candida species are part of the C. albicans complex and are hard to differentiate morphologically?

Candida dubliniensis and Candida africana

What iatrogenic factor is a major predisposing factor for systemic Candida fungemia in hospitalized patients?

Prolonged intravenous catheterization

What rapid laboratory test identifies Candida albicans based on growth in serum within 3 hours?

Germ tube test

What thick-walled resting structure does Candida albicans uniquely form on corn meal agar?

Chlamydospore

How does Candida dubliniensis chlamydospore production on corn meal agar differ from C. albicans?

Produces abundant clusters of chlamydospores

Which Candida albicans complex species generally lacks chlamydospore production?

Candida africana

What color do Candida albicans colonies appear when grown on CHROMagar?

Light green

What color do Candida tropicalis colonies appear on CHROMagar?

Dark blue

What color do Candida glabrata colonies appear on CHROMagar?

Pink to white with a dark center

What color do Candida krusei colonies appear on CHROMagar?

Pink and fuzzy

Which Candida species features tiny budding yeast cells but does NOT produce hyphae or pseudohyphae?

Candida glabrata

Which two sugars are exclusively assimilated and fermented by Candida glabrata?

Glucose and trehalose

Which Candida species typically forms spider or crossed matchstick colonies on corn meal agar?

Candida parapsilosis

Does Candida parapsilosis form true hyphae?

No

Which Candida species exhibits intrinsic, inherent resistance to fluconazole?

Candida krusei

Which Candida species occasionally exhibits intrinsic echinocandin resistance?

Candida parapsilosis

What enzyme is less sensitive to the drug or uses an efflux pump to confer fluconazole resistance in Candida krusei?

14-alpha-demethylase

What newly emerged Candida species is considered a superbug due to its resistance to three major antifungal drugs?

Candida auris

How many clades of Candida auris have been globally identified?

Six clades

What distinct morphological finding on blood or chocolate agar indicates the presence of Candida colonies?

Starry projections or candida feet

What specific fungal cell wall component is detected by a common diagnostic kit for invasive mycoses?

Beta-D-glucan

What sugar assimilation test result differentiates Candida africana from Candida albicans?

Negative for xylose assimilation

Can Candida dubliniensis grow at a temperature of 45°C?

No

What is the most common non-albicans Candida species isolated in candidemia cases in Thailand?

Candida tropicalis

What test differentiates Candida species based on their ability to use varying carbon sources resulting in a color or pH change?

Sugar assimilation test kit

What morphological feature characterizes Candida krusei when viewed under a microscope?

Small elongated to ovoid budding yeast with pseudohyphae

What visual change occurs during a positive rapid trehalose assimilation broth test for C. glabrata?

Dye turns to a yellow or yellow-green color

Which Candida species produces a dark green colony on CHROMagar?

Candida dubliniensis

What opportunistic saprophytic yeast produces a capsule like Cryptococcus but is distinguished by a red or orange pigment?

Rhodotorula

What related Saccharomyces species can cause an opportunistic infection in immunocompromised patients?

Saccharomyces boulardii

What common non-specific staining method demonstrates budding yeast and pseudohyphae of Candida albicans?

Gram stain

In Candida biofilm development, what structure forms after the initial attachment of yeast cells?

Hyphae

Which two Cryptococcus species are the primary causes of human cryptococcosis?

Cryptococcus neoformans and Cryptococcus gattii

What is the teleomorph (sexual) state name for Cryptococcus neoformans?

Filobasidiella neoformans

Which serotype is associated with Cryptococcus neoformans var. grubii?

Serotype A

Which serotypes are associated with Cryptococcus gattii?

Serotypes B and C

Which Cryptococcus species is more noted for causing disease in immunocompetent hosts?

Cryptococcus gattii

What is the primary environmental reservoir for Cryptococcus neoformans?

Bird droppings

What environmental sources are strongly associated with the habitat of Cryptococcus gattii?

Eucalyptus trees and koalas

What is the initial site of infection when a host is exposed to Cryptococcus spores?

Lungs (pulmonary infection)

What is the most severe and typical clinical manifestation of disseminated cryptococcosis?

Meningitis or meningoencephalitis

Which specific autoantibodies are recognized as a predisposing factor for cryptococcal infection?

Granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies

What type of cutaneous lesion can occur in disseminated cryptococcosis?

Pustular or molluscum-like lesions

By what proposed mechanism does Cryptococcus cross the blood-brain barrier inside macrophages?

Trojan Horse mechanism

What major virulence factor of Cryptococcus masks PAMPs and prevents phagocytosis?

Polysaccharide capsule

What enzyme in Cryptococcus catalyzes the production of melanin?

Phenol oxidase

What is the primary function of melanin in Cryptococcus virulence?

Protects against oxidative stress

What morphological transition allows Cryptococcus to become too large to be engulfed by host cells?

Titan cell formation

What enzyme allows Cryptococcus to digest host cell membranes during infection?

Phospholipase

What are the two major carbohydrate components of the Cryptococcus capsule?

Galactoxylomannan and glucuronoxylomannan

What typical cerebrospinal fluid (CSF) findings are associated with cryptococcal meningitis?

High protein and low sugar

What rapid negative staining technique is used to visualize the Cryptococcus capsule in CSF?

India ink preparation

What specific cytochemical stain is used to identify the mucopolysaccharide capsule of Cryptococcus in tissue biopsies?

Mucicarmine stain

What temperature is used to test for the thermotolerance virulence factor of Cryptococcus neoformans?

37 degrees Celsius

What unique carbon source can Cryptococcus assimilate that aids in its laboratory identification?

Inositol

Is Cryptococcus positive or negative for urease production?

Positive

What specialized culture medium is used to detect phenol oxidase activity in Cryptococcus?

Bird seed agar (Staib medium)

What color do Cryptococcus neoformans colonies turn when grown on Bird seed agar?

Brown to black

What highly sensitive serological test detects Cryptococcus components in CSF or serum?

Cryptococcal antigen (CrAg) latex agglutination

What phenomenon can cause a false negative result in the cryptococcal latex agglutination test?

Post-zone phenomenon

What fungal organism can cross-react and cause a false positive in the cryptococcal antigen test?

Trichosporon

What is the standard initial antifungal drug combination used to treat cryptococcal CNS infection?

Amphotericin B combined with flucytosine

What oral antifungal is used for prolonged consolidation therapy and prophylaxis against Cryptococcus?

Fluconazole

What medical procedure may be needed to reduce elevated intracranial pressure in cryptococcal meningitis?

Lumbar puncture

What paradoxical complication can occur in HIV patients treated for cryptococcal meningitis after initiating antiretroviral therapy?

Immune reconstitution inflammatory syndrome (IRIS)

How is Pneumocystis jirovecii transmitted between human hosts?

Air-borne transmission

What specific host cell in the lung serves as the primary target for Pneumocystis jirovecii?

Type I alveolar epithelial cell

Why are standard antifungal drugs targeting ergosterol ineffective against Pneumocystis?

It lacks ergosterol and contains cholesterol instead

In what state does Pneumocystis exist in healthy, immunocompetent individuals?

Latent infection

What are the two main life cycle forms of Pneumocystis jirovecii observed in the host?

Trophic forms and cysts

How many intracystic bodies (spores) are typically found within a mature Pneumocystis cyst?

Eight

By what process do Pneumocystis haploid trophic forms fuse to become a diploid precyst?

Conjugation

What is the classical triad of symptoms in Pneumocystis pneumonia (PCP)?

Fever, non-productive cough, and progressive exertional dyspnea

What characteristic pattern is typically seen on a chest X-ray of a patient with Pneumocystis pneumonia?

Bilateral diffuse interstitial infiltrates or ground glass pattern

What types of respiratory specimens are required for the definitive diagnosis of Pneumocystis pneumonia?

Lung biopsy or bronchoalveolar lavage

What microscopic stain is used to visualize the intracystic bodies of Pneumocystis jirovecii?

Giemsa stain

What stain is used to specifically visualize the cyst wall of Pneumocystis jirovecii?

Gomori methenamine silver (GMS) stain

How are Pneumocystis cysts often morphologically described when viewed with a GMS stain?

Crushed ping pong balls or flat beach balls

What serum biomarker can be elevated in patients with Pneumocystis pneumonia due to cell wall components?

Beta-D-glucan

What is the first-line treatment and prophylaxis drug for Pneumocystis pneumonia?

Trimethoprim-sulfamethoxazole

Name an alternative drug used for the treatment of Pneumocystis pneumonia if the first-line agent cannot be used.

Primaquine or atovaquone

Is Pneumocystis jirovecii generally considered an extracellular or intracellular pathogen in the alveoli?

Extracellular pathogen attaching to the epithelium

What structural component distinguishes the cell wall of Pneumocystis cysts from Candida?

Pneumocystis contains an O-linked glycan core and cholesterol

In which patient population does Pneumocystis pneumonia predominantly cause severe, reactivated disease?

Immunocompromised patients

What lateral flow assay method can rapidly detect cryptococcal disease without requiring a central lab?

Lateral flow assay for cryptococcal antigen