Mycology Practice Questions

Q: A 35-year-old female presents with vaginal discharge and vulvar itching. Wet mount examination shows budding yeast cells with pseudohyphae. Vaginal pH is 4.5. What is the most likely causative organism?

Candida albicans. ***Candida albicans*** - The microscopic finding of **budding yeast cells** and **pseudohyphae** on the wet mount is pathognomonic for **Vulvovaginal Candidiasis (VVC)**. - The characteristic symptoms include intense **vulvar pruritus** (itching) and thick, white, **curd-like discharge**, often associated with an acidic vaginal pH (usually 4.0 to 4.5). *Gardnerella vaginalis* - This organism is the key agent in **Bacterial Vaginosis (BV)**, which is characterized by a thin, grey, homogenous discharge with a **fishy odor**. - BV is diagnosed by the presence of **clue cells** on wet mount and a high vaginal pH (typically >4.5, often 5.0–6.0). *Trichomonas vaginalis* - This protozoan causes **trichomoniasis**, which commonly presents with a **profuse, frothy, greenish-yellow discharge** and often causes inflammatory symptoms like a "strawberry cervix." - Wet mount examination would reveal motile, **flagellated trichomonads**, and the vaginal pH is usually elevated (>5.0). *Neisseria gonorrhoeae* - This bacterium is primarily a cause of **cervicitis** and **urethritis**, often presenting asymptomatically or with mucopurulent discharge, but rarely causing significant vulvar itching. - Diagnosis is based on identifying Gram-negative **intracellular diplococci** on Gram stain or using **NAAT**, not yeast forms.

Q: All of the following are dimorphic fungi except:

Cryptococcus. ***Cryptococcus*** - *Cryptococcus neoformans* is a **monomorphic yeast** and does NOT exhibit thermal dimorphism - It exists as an **encapsulated budding yeast** at both room temperature (25°C) and body temperature (37°C) - Unlike dimorphic fungi, it does **not transform between mold and yeast forms** based on temperature - Causes **meningitis** and pulmonary infections, especially in immunocompromised patients - This is the **correct answer** as it is the only non-dimorphic fungus in the list *Incorrect - Coccidioides* - Classic dimorphic fungus showing **mold-to-spherule conversion** - In environment (25°C): filamentous mold with infectious **arthroconidia** - In tissue (37°C): transforms into large, thick-walled **spherules** containing endospores - Endemic to southwestern USA and parts of Central/South America *Incorrect - Histoplasma* - Classic dimorphic fungus showing **mold-to-yeast conversion** - In environment (25°C): filamentous mold in soil enriched with bird/bat droppings - In tissue (37°C): small, narrow-based **budding yeast** forms within macrophages - *Histoplasma capsulatum* is endemic to Mississippi and Ohio river valleys *Incorrect - Talaromyces* - *Talaromyces marneffei* (formerly *Penicillium marneffei*) is a **dimorphic fungus** - In environment (25°C): grows as mold producing red pigment - In tissue (37°C): exists as yeast-like cells dividing by **fission** (not budding) - Endemic to **Southeast Asia** and associated with HIV/AIDS patients

Q: A white patch is observed in the oral cavity of an immunocompromised patient. Which of the following findings is most likely on microscopy?

Pseudo-hyphae. ***Pseudo-hyphae*** - The clinical presentation of a white patch in an immunocompromised patient is highly suggestive of **oral candidiasis** (thrush), typically caused by *Candida albicans*. - In tissue samples (like oral scrapings), *Candida albicans* characteristically appears as **budding yeast** cells along with distinct chains of elongated yeast cells known as **pseudo-hyphae**. ***Branching septate hyphae*** - These structures are characteristic of filamentous fungi, such as **Aspergillus** species or dermatophytes (e.g., *Tinea* infections). - While *Candida* can form true hyphae under certain conditions, **pseudo-hyphae** are the hallmark feature observed in routine smear microscopy for oral candidiasis. ***Budding yeast with capsule*** - This microscopic finding is pathognomonic for **Cryptococcus neoformans**, which causes cryptococcosis. - The capsule is often visualized using special stains like mucicarmine or India ink, and *Cryptococcus* typically causes systemic disease or **meningoencephalitis**, not simple oral thrush. ***Sulfur granules*** - **Sulfur granules** are characteristic aggregates of filamentous bacteria seen in infections caused by **Actinomyces israelii**, leading to **Actinomycosis**. - Actinomycosis usually presents as chronic, indolent abscesses that drain sinus tracts, most commonly in the cervicofacial region.

Q: A male patient presents with fever, cough, and hemoptysis. Bronchoalveolar lavage (BAL) fluid examination shows septate hyphae with acute angle (dichotomous) branching under microscopy. What is the most likely diagnosis?

Aspergillosis. ***Aspergillosis*** - The characteristic finding of **septate hyphae** displaying uniform **acute angle (dichotomous) branching** (typically 45°) in the **Bronchoalveolar lavage (BAL)** fluid is the defining microscopic feature of *Aspergillus* infection [1], [2]. - The clinical picture of fever, cough, and **hemoptysis** suggests an invasive pulmonary fungal infection, which *Aspergillus* commonly causes, especially in immunocompromised hosts [1], [2]. *Mucormycosis* - This diagnosis is characterized by **broad, non-septate (aseptate) hyphae** that exhibit irregular branching, typically at a **wide angle (90°)**. - The absence of septae and the differing angle of branching rule out mucormycosis based on the microscopic findings. *Histoplasmosis* - *Histoplasma capsulatum* appears in tissue and BAL primarily as **small, oval, budding yeast forms** (2–4 µm) that are often **intracellular** within macrophages. - It is not a hyphal infection in tissue form and therefore does not show septate hyphae with dichotomous branching. *Candidiasis* - *Candida* is identified by the presence of both **budding yeast cells** and **pseudohyphae** (links of elongated yeast cells) [2]. - Although true septate hyphae can occasionally be seen, it lacks the highly characteristic, uniform **acute-angle dichotomous branching** that is specific to *Aspergillus*. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 396-397. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Respiratory Tract Disease, pp. 318-319.

Q: A patient presents with low-grade fever, chronic cough, and weight loss. Fungal culture from respiratory secretions shows the following organism with characteristic tuberculate macroconidia on microscopy. What is the most likely diagnosis?

Histoplasmosis. ***Histoplasmosis*** - The image displayed shows characteristic large, spiny, thick-walled structures known as **tuberculate macroconidia**, which are pathognomonic for the mold phase of ***Histoplasma capsulatum*** grown at 25°C. - The clinical presentation of chronic cough, low-grade fever, and weight loss is typical of chronic pulmonary **Histoplasmosis** in immunocompetent individuals and often mimics tuberculosis. *Blastomycosis* - The yeast form of *Blastomyces dermatitidis* is characterized by having distinctive **broad-based budding** and large size (8-15 µm). - The mold phase of *Blastomyces* produces oval to pear-shaped microconidia on short or long stalks, not the tuberculate macroconidia seen in the picture. *Cryptococcosis* - *Cryptococcus neoformans* is a yeast encapsulated with a polysaccharide capsule and typically demonstrates smooth, **narrow-based budding** without forming true hyphae or macroconidia in culture. - Although it can cause pulmonary disease, its yeast morphology and lack of dimorphism differentiate it from the organism shown. *Coccidioidomycosis* - The mold form of *Coccidioides immitis* produces thin-walled, barrel-shaped structures called **arthroconidia**, which are highly infectious. - The tissue phase is defined by large **spherules containing endospores**, a morphology that is distinctly different from the tuberculate macroconidia shown.

Q: A patient presents with irregular swelling over the foot, multiple discharging sinuses, and black granules. A KOH mount is performed on the discharge. What is the most likely observation?

Slender dematiaceous fungi. ***Slender dematiaceous fungi*** - The clinical triad of irregular swelling, multiple discharging sinuses, and the presence of **black granules** strongly suggests **black-grained eumycetoma** (e.g., caused by *Madurella mycetomatis*). - KOH mount of the black granule reveals densely packed, brown-to-black pigmented (**dematiaceous**) septate hyphal elements and chlamydospores, consistent with slender dematiaceous fungi. *Arthrospores* - Arthrospores are typically seen in superficial infections like **dermatophytosis** (e.g., Tinea capitis, *Trichophyton*) or are characteristic of the parasitic phase of *Coccidioides immitis*. - They are not the primary microscopic finding within the tissue granule of mycetoma. *Yeast* - Yeast forms are characteristic of systemic infections like **Candidiasis**, Cryptococcosis, or Histoplasmosis, or are seen as sclerotic (Medlar) bodies in **Chromoblastomycosis**. - Mycetoma granules are formed by highly organized masses of filamentous hyphae, not unicellular yeast. *Septate hyphae 4-5* - This describes the general morphology and width of hyphae seen in common molds like **Aspergillus** or *Fusarium*. - This description is incomplete for black-grained mycetoma as it omits the distinctive feature of the fungus being pigmented (**dematiaceous**), which is critical for identifying the organism within the black granule.

Q: A patient presented with headache and projectile vomiting and altered sensorium. The following organism was demonstrated on India ink staining. What is the likely diagnosis?

Cryptococcus. ***Cryptococcus*** - The image displays encapsulated yeast cells, characteristic of **_Cryptococcus neoformans_** or **_Cryptococcus gattii_**, which are commonly highlighted by **India ink staining** due to their large polysaccharide capsule. - The clinical presentation of headache, projectile vomiting, and altered sensorium strongly suggests **cryptococcal meningitis**, especially in immunocompromised individuals. *Blastomyces* - **_Blastomyces dermatitidis_** appears as large, broad-based budding yeast, which is distinct from the encapsulated yeasts seen in the image. - While it can cause CNS infection, its morphological characteristics under microscopy are different, and India ink is not its primary diagnostic stain. *Histoplasma* - **_Histoplasma capsulatum_** is a small, intracellular yeast, often seen within macrophages, and does not possess a prominent capsule that would be stained by India ink. - Neurological involvement is less common than with _Cryptococcus_ and the microscopic appearance is different. *Coccidioides* - **_Coccidioides immitis_** forms **spherules** containing **endospores** in tissue samples, a distinct morphology not seen in the provided image. - Although it can cause meningitis, its microscopic identification relies on finding these spherules, not encapsulated yeasts with India ink.

Q: Which of the following is correct about the vegetative fungal spores?

A = Blastospores, B= Arthrospores, C= Chlamydospores. **A = Blastospores, B= Arthrospores, C= Chlamydospores** - Image A depicts **blastospores**, which are asexually produced spores formed by **budding** from a parent cell, giving them a distinct tear-drop or oval shape. - Image B illustrates **arthrospores**, which are formed by the **fragmentation** of a hyphal cell into barrel-shaped segments. - Image C shows **chlamydospores**, characterized by their **thick-walled**, resistant, and usually spherical or oval structure within a hypha. *A = Arthrospores, B= Blastospores, C= Chlamydospores* - This option incorrectly identifies image A as arthrospores, which are typically barrel-shaped and result from hyphal fragmentation, not the budding pattern seen in image A. - Image B is incorrectly labeled as blastospores, but the fragmentation pattern is characteristic of arthrospores. *A = Blastospores, B= Chlamydospores, C= Arthrospores* - While image A is correctly identified as blastospores, this option misidentifies image B as chlamydospores. - Image C does not show arthrospores; the thick-walled structure is characteristic of chlamydospores, not the barrel-shaped arthrospores. *A = Chlamydospores, B= Arthrospores, C= Blastospores* - This option incorrectly identifies image A as chlamydospores, which are thick-walled resistant structures, not the budding spores visible in the image. - It also incorrectly labels image C as blastospores; the thick-walled appearance is typical of chlamydospores, not budded blastospores.

Q: All are correct about the organism causing the following lesion except:

Reynold Braude phenomenon. ***Reynold Braude phenomenon*** - The **Reynolds-Braude phenomenon** is associated with **Staphylococcus aureus** and refers to the increased invasiveness of *S. aureus* in the presence of certain other bacteria. - This phenomenon is **not characteristic of *Candida albicans***, the organism responsible for the oral candidiasis (thrush) shown in the image. - **This is the correct answer** to this "except" question. *Gram positive yeast cells* - *Candida albicans* is a **Gram-positive yeast** that appears purple/blue on Gram staining. - It typically shows **budding yeast cells** and **pseudohyphae** on microscopy. - This statement is TRUE for *Candida albicans*. *Chlamydospores obtained on cornmeal agar* - **Chlamydospores** are thick-walled, large, round terminal spores that are characteristic of *Candida albicans*. - They are best demonstrated on **cornmeal agar with Tween 80** (or rice agar), which is the standard medium for their production. - The presence of chlamydospores is a key identifying feature that helps differentiate *C. albicans* from other *Candida* species. - This statement is TRUE for *Candida albicans*. *Creamy patches that on removal lead to red oozing patches* - The image shows **creamy white patches** on an inflamed oral mucosa, characteristic of **pseudomembranous candidiasis** (oral thrush). - These patches can be **scraped off**, revealing an **erythematous, bleeding** (red oozing) underlying surface. - This is a classic clinical presentation of oral candidiasis. - This statement is TRUE for *Candida albicans*.

Q: All are correct about the image shown except:

Primary site of infection is CNS. ***Primary site of infection is CNS*** - While *Cryptococcus neoformans* is well-known for causing **meningitis** (a CNS infection), the **primary site of infection** is typically the **lungs**, acquired through inhalation of spores. Dissemination to the CNS occurs subsequently, especially in immunocompromised individuals. *Cryptococcus neoformans* - The image, showing encapsulated yeast cells with varying sizes and budding, is characteristic of **Cryptococcus neoformans** under India ink stain, where the capsule excludes the ink, creating a halo effect. - This fungus is known for its distinctive **thick polysaccharide capsule** and its tendency to be found in environments contaminated with bird droppings. *Thick polysaccharide capsule* - The clear halo around the yeast cells in the image directly demonstrates the presence of a **thick polysaccharide capsule**, which is a key virulence factor distinguishing *Cryptococcus neoformans*. - This capsule is responsible for the organism's unique appearance in **India ink preparations** and plays a crucial role in immune evasion. *Mucicarmine stain can be used* - The **mucicarmine stain** specifically stains the **polysaccharide capsule** of *Cryptococcus neoformans* bright red, aiding in its identification in tissue samples. - This stain is a valuable diagnostic tool, particularly when dealing with tissue biopsies where the capsule might not be as distinctly visible with India ink due to cellular debris.

Question 1

A 35-year-old female presents with vaginal discharge and vulvar itching. Wet mount examination shows budding yeast cells with pseudohyphae. Vaginal pH is 4.5. What is the most likely causative organism?

Accepted Answer

Candida albicans

Answer

Gardnerella vaginalis

Answer

Trichomonas vaginalis

Answer

Neisseria gonorrhoeae

Question 2

All of the following are dimorphic fungi except:

Accepted Answer

Cryptococcus

Answer

Coccidioides

Answer

Histoplasma

Answer

Talaromyces

Question 3

A white patch is observed in the oral cavity of an immunocompromised patient. Which of the following findings is most likely on microscopy?

Accepted Answer

Pseudo-hyphae

Answer

Branching septate hyphae

Answer

Budding yeast with capsule

Answer

Sulfur granules

Question 4

A male patient presents with fever, cough, and hemoptysis. Bronchoalveolar lavage (BAL) fluid examination shows septate hyphae with acute angle (dichotomous) branching under microscopy. What is the most likely diagnosis?

Accepted Answer

Aspergillosis

Answer

Mucormycosis

Answer

Histoplasmosis

Answer

Candidiasis

Question 5

A patient presents with low-grade fever, chronic cough, and weight loss. Fungal culture from respiratory secretions shows the following organism with characteristic tuberculate macroconidia on microscopy. What is the most likely diagnosis?

Accepted Answer

Histoplasmosis

Answer

Cryptococcosis

Answer

Coccidioidomycosis

Answer

Blastomycosis

Question 6

A patient presents with irregular swelling over the foot, multiple discharging sinuses, and black granules. A KOH mount is performed on the discharge. What is the most likely observation?

Accepted Answer

Slender dematiaceous fungi

Answer

Yeast

Answer

Septate hyphae 4-5

Answer

Arthrospores

Question 7

A patient presented with headache and projectile vomiting and altered sensorium. The following organism was demonstrated on India ink staining. What is the likely diagnosis?

Accepted Answer

Cryptococcus

Answer

Blastomyces

Answer

Histoplasma

Answer

Coccidioides

Question 8

Which of the following is correct about the vegetative fungal spores?

Accepted Answer

A = Blastospores, B= Arthrospores, C= Chlamydospores

Answer

A = Arthrospores, B= Blastospores, C= Chlamydospores

Answer

A = Blastospores, B= Chlamydospores, C= Arthrospores

Answer

A = Chlamydospores, B= Arthrospores, C= Blastospores

Question 9

All are correct about the organism causing the following lesion except:

Accepted Answer

Reynold Braude phenomenon

Answer

Gram positive yeast cells

Answer

Chlamydospores obtained on cornmeal agar

Answer

Creamy patches that on removal lead to red oozing patches

Question 10

All are correct about the image shown except:

Accepted Answer

Primary site of infection is CNS

Answer

Cryptococcus neoformans

Answer

Thick polysaccharide capsule

Answer

Mucicarmine stain can be used

Mycology — MCQs

Mycology — MCQs

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