Candidiasis — MCQs
Which infection commonly spreads to newborns through caregivers?
Which drug should not be given with ketoconazole?
Most common catheter-related bloodstream infection is due to:
In an HIV-infected individual, the Gram stain of lung aspirate shows yeast-like morphology. Which of the following is the least likely diagnosis?
A 25 year old lady presented with curdy white discharge from the vagina is likely to be suffering from:-
A 65-year-old diabetic man presents with black necrotic tissue on his palate. What is the most likely causative organism?
Broad-based budding yeasts are seen in:
Brain abscess in immunodeficient person is due to :
Which statement is false regarding Cryptococcus neoformans?
Which of the following is a non-culturable fungus?
Candidiasis Indian Medical PG Practice Questions and MCQs
Question 1: Which infection commonly spreads to newborns through caregivers?
- A. Candida parapsilosis (Correct Answer)
- B. Candida albicans
- C. Candida tropicalis
- D. Candida glabrata
Explanation: ***Candida parapsilosis*** - This species is a well-known cause of **nosocomial bloodstream infections** in neonates, particularly in **premature infants** and those with central venous catheters. It is often spread via the hands of **healthcare workers**. - Its ability to form **biofilms on medical devices** (like catheters) further facilitates its transmission and makes it a significant infectious agent in neonatal intensive care units (NICUs). *Candida albicans* - While *Candida albicans* is the **most common Candida species** causing infections in humans, including superficial and invasive candidiasis in neonates, its transmission is less frequently linked to direct caregiver spread in the context of outbreaks compared to *C. parapsilosis*. - Neonatal *C. albicans* infections are often acquired **vertically from the mother** or through endogenous gut colonization. *Candida tropicalis* - *Candida tropicalis* can cause **invasive candidiasis**, especially in immunocompromised patients, but it is less frequently implicated in **outbreaks** attributed to hand-to-patient transmission by caregivers in NICUs than *C. parapsilosis*. - It is often associated with **neutropenia** and broad-spectrum antibiotic use. *Candida glabrata* - *Candida glabrata* is a significant pathogen, particularly in adults and immunocompromised individuals, known for its **fluconazole resistance**. - While it can cause bloodstream infections, it is not typically recognized as a primary cause of **caregiver-spread outbreaks** in newborns to the same extent as *C. parapsilosis*.
Question 2: Which drug should not be given with ketoconazole?
- A. Indinavir (Correct Answer)
- B. Macrolide
- C. All of the options
- D. Aminoglycoside
Explanation: ***Correct: Indinavir*** - **Indinavir** is a **protease inhibitor (antiretroviral)** that is primarily metabolized by **CYP3A4** - **Ketoconazole** is a **potent CYP3A4 inhibitor** that significantly increases indinavir plasma concentrations - Co-administration leads to **increased risk of indinavir toxicity** including nephrolithiasis, hyperbilirubinemia, and hepatotoxicity - **Dose reduction of indinavir is required** if concurrent use is necessary (typically reduce to 600 mg q8h from 800 mg q8h) *Incorrect: Macrolide* - Many **macrolides** (erythromycin, clarithromycin) are CYP3A4 substrates and can interact with ketoconazole - While caution is advised due to **QT prolongation risk**, this interaction is less severe than with indinavir - Not an absolute contraindication but requires monitoring *Incorrect: Aminoglycoside* - **Aminoglycosides** (gentamicin, amikacin, tobramycin) are **NOT metabolized by CYP450 enzymes** - They are **hydrophilic** and eliminated **unchanged by renal excretion** - **No clinically significant interaction** with ketoconazole - Can be safely co-administered without dose adjustment *Key Learning Point* - Ketoconazole inhibits CYP3A4, affecting metabolism of many drugs including **protease inhibitors, calcium channel blockers, statins, and some macrolides** - Always check for CYP3A4 substrate drugs when prescribing azole antifungals
Question 3: Most common catheter-related bloodstream infection is due to:
- A. Coagulase-negative Staphylococci (CoNS) (Correct Answer)
- B. Candida species
- C. Gram-negative bacilli
- D. Staphylococcus aureus (S. aureus)
Explanation: ***Coagulase-negative Staphylococci (CoNS)*** - **Coagulase-negative Staphylococci (CoNS)**, particularly *Staphylococcus epidermidis*, are the most common cause of **catheter-related bloodstream infections (CRBSIs)** due to their ability to form **biofilms** on catheter surfaces. - Their ubiquity on the skin, combined with their capacity for **adherence** and **biofilm production**, facilitates their entry and proliferation within the catheter lumen. *Candida species* - While *Candida species* (e.g., *Candida albicans*) are significant causes of CRBSIs, especially in **immunocompromised** patients or those on **broad-spectrum antibiotics**, they are less common overall than CoNS. - Risk factors for *Candida* CRBSIs include prolonged hospitalization, total parenteral nutrition, and **central venous catheters**. *Gram-negative bacilli* - **Gram-negative bacilli** (e.g., *Klebsiella pneumoniae*, *Escherichia coli*, *Pseudomonas aeruginosa*) are important pathogens in CRBSIs, often associated with **severe sepsis** and higher mortality rates. - However, their overall incidence in catheter-induced infections is lower than that of CoNS, though they are more prevalent in certain hospital units like **ICUs**. *Staphylococcus aureus (S. aureus)* - **Staphylococcus aureus** causes clinically significant CRBSIs, often leading to more severe infections, including **endocarditis** and **septic emboli**, than CoNS. - While *S. aureus* infections are serious, CoNS remain the most frequently isolated organism in all CRBSI cases, partly due to the high carriage rate of *S. epidermidis* on human skin.
Question 4: In an HIV-infected individual, the Gram stain of lung aspirate shows yeast-like morphology. Which of the following is the least likely diagnosis?
- A. Candida tropicalis
- B. Cryptococcus neoformans
- C. Aspergillus fumigatus (Correct Answer)
- D. Penicillium marneffei
Explanation: ***Aspergillus fumigatus*** - While *Aspergillus* can cause pulmonary infections in immunosuppressed individuals, it typically presents as **hyphae**, not yeast-like morphology, on Gram stain. - Identification usually requires visualization of **septate hyphae with acute-angle branching**. *Candida tropicalis* - *Candida* species are common causes of opportunistic infections in HIV patients and present as **yeast and pseudohyphae** (though true hyphae can also be seen). - *Candida tropicalis* lung infection would appear as **yeast-like forms** on Gram stain, making it a plausible diagnosis. *Cryptococcus neoformans* - *Cryptococcus neoformans* is a significant pathogen in HIV-infected individuals, causing pulmonary and disseminated disease, and is characterized by its **yeast morphology** and prominent capsule. - Staining would reveal **budding yeast cells**, often with a clear halo due to the capsule, fitting the description. *Penicillium marneffei* - *Penicillium marneffei* is a dimorphic fungus endemic in Southeast Asia that causes disseminated infection in HIV patients, and it grows as **yeast-like cells** at body temperature. - In infected tissues, it appears as **intracellular and extracellular oval yeast-like cells** with transverse septation, consistent with the description.
Question 5: A 25 year old lady presented with curdy white discharge from the vagina is likely to be suffering from:-
- A. Trichomoniasis
- B. Gonococcal vulvovaginitis
- C. Chlamydia trachomatis
- D. Candida vaginitis (Correct Answer)
Explanation: ***Candida vaginitis*** - **Candida vaginitis** is characterized by a **curdy white vaginal discharge**, often described as cottage cheese-like. - This condition is caused by an overgrowth of *Candida* species, typically *Candida albicans*, and is associated with **vaginal itching, burning**, and **dyspareunia**. *Trichomoniasis* - **Trichomoniasis** typically presents with a **frothy, greenish-yellow discharge** and a **foul odor**. - It often causes **severe itching, redness, and irritation**, which differ from the curdy discharge described. *Gonococcal vulvovaginitis* - **Gonococcal vulvovaginitis** in women can cause a **purulent or mucopurulent discharge**, often yellowish. - While it can lead to vaginal irritation, a **curdy white discharge** is not its classic presentation. *Chlamydia trachomatis* - **Chlamydia trachomatis** often causes an **asymptomatic infection**; when symptoms occur, they may include a **mucopurulent discharge**. - A **curdy white discharge** is not a typical symptom of *Chlamydia* infection.
Question 6: A 65-year-old diabetic man presents with black necrotic tissue on his palate. What is the most likely causative organism?
- A. Cryptococcus neoformans
- B. Candida albicans
- C. Mucor species (Correct Answer)
- D. Aspergillus fumigatus
Explanation: ***Mucor species*** - The presence of **black necrotic tissue** on the palate in a diabetic patient is highly suggestive of **mucormycosis**, an aggressive fungal infection caused by *Mucor* species. - **Diabetes mellitus**, particularly with ketoacidosis, is a major risk factor for mucormycosis due to impaired phagocytic function and increased iron availability. *Cryptococcus neoformans* - This fungus is primarily associated with **cryptococcal meningitis** or pneumonia, especially in immunocompromised individuals. - It does not typically cause **black necrotic lesions** on the palate. *Candida albicans* - While *Candida albicans* can cause oral infections (**thrush**), these typically present as white, creamy patches that can be scraped off, not black necrotic tissue. - Oral candidiasis is common in diabetics but does not usually involve tissue necrosis. *Aspergillus fumigatus* - *Aspergillus* species can cause invasive infections, particularly in immunocompromised patients, often affecting the lungs or sinuses. - While it can cause **necrotic lesions**, the characteristic rapid progression and specific presentation in the palate of a diabetic with black necrotic tissue points more strongly towards *Mucor*.
Question 7: Broad-based budding yeasts are seen in:
- A. Histoplasmosis
- B. Blastomycosis (Correct Answer)
- C. Candidiasis
- D. Coccidioidomycosis
Explanation: ***Blastomycosis*** - This fungal infection is classically characterized by **broad-based budding yeasts** seen on microscopic examination. - The yeast cells are typically large and have a characteristic wide connection between the mother and daughter cells during budding. *Histoplasmosis* - Characterized by **small, intracellular yeasts** often seen within macrophages. - These yeasts do **not exhibit broad-based budding**. *Candidiasis* - Primarily presents as **pseudohyphae** (elongated yeast cells resembling hyphae) and budding yeasts (blastoconidia) with **narrow bases**. - **True hyphae** may also be present depending on the species and growth conditions. *Coccidioidomycosis* - In tissue, it is characterized by **spherules** containing **endospores**, not budding yeasts. - The mycelial form is found in culture or environmental samples.
Question 8: Brain abscess in immunodeficient person is due to :
- A. Aspergillus
- B. Toxoplasma gondii (Correct Answer)
- C. Cryptococcus
- D. Candida
Explanation: ***Toxoplasma gondii*** - **Toxoplasma gondii** is a very common cause of **brain abscesses** (cerebral toxoplasmosis) in individuals with compromised immune systems, especially those with AIDS. - The parasite is usually latent in many people and reactivates when the immune system weakens. *Aspergillus* - While *Aspergillus* can cause central nervous system infections, including brain abscesses, this is usually seen in severely **neutropenic** or transplant patients. - *Aspergillus* typically invades via **hematogenous spread** from a primary pulmonary infection or directly from sinusitis. *Cryptococcus* - *Cryptococcus neoformans* is a significant cause of **meningitis** in immunocompromised patients, particularly those with HIV/AIDS. - While it can cause **cryptococcomas** (focal lesions), pure abscess formation is less common than with *Toxoplasma*. *Candida* - *Candida* species can cause **brain microabscesses** or multifocal lesions, especially in patients with disseminated candidiasis originating from prolonged hospitalization or indwelling catheters. - However, large, solitary brain abscesses are less typical for *Candida* compared to *Toxoplasma gondii*.
Question 9: Which statement is false regarding Cryptococcus neoformans?
- A. Grows at 5°C and 37°C
- B. Has 4 serotypes
- C. Urease negative (Correct Answer)
- D. Causes superficial skin infection
Explanation: **Explanation:** *Cryptococcus neoformans* is an encapsulated yeast primarily associated with pigeon droppings and is a significant opportunistic pathogen in immunocompromised patients (e.g., HIV/AIDS). **1. Why "Urease negative" is the False Statement:** *Cryptococcus neoformans* is characteristically **Urease positive**. The production of the urease enzyme is a key biochemical marker used in the laboratory to differentiate it from other yeasts like *Candida albicans* (which is urease negative). It hydrolyzes urea to produce ammonia, raising the pH and changing the indicator color. **2. Analysis of Other Options:** * **Option A (Grows at 5°C and 37°C):** This is true. Unlike many other pathogenic fungi, *C. neoformans* can grow at 37°C (essential for human pathogenicity) and also at lower temperatures like 4°C–5°C. * **Option B (Has 4 serotypes):** This is true. Based on capsular polysaccharide antigens, it is classified into four serotypes: **A, B, C, and D**. (Note: Serotype A is *C. neoformans var. grubii*, while B and C are now often classified as *C. gattii*). * **Option D (Causes superficial skin infection):** This is true. While meningitis is the most common presentation, primary or secondary cutaneous cryptococcosis can occur, presenting as papules, pustules, or ulcerations. **High-Yield Clinical Pearls for NEET-PG:** * **Virulence Factor:** The **Polysaccharide capsule** (Glucuronoxylomannan) is the most important; it inhibits phagocytosis. * **Staining:** **India Ink** preparation shows a "halo" (negative staining). **Mucicarmine** stains the capsule red. * **Culture:** Grows on **Bird Seed Agar** (Niger Seed Agar) producing brown/black colonies due to **Phenoloxidase** activity (melanin production). * **Drug of Choice:** Induction with Amphotericin B + Flucytosine, followed by Fluconazole.
Question 10: Which of the following is a non-culturable fungus?
- A. Rhinosporidium (Correct Answer)
- B. Candida
- C. Sporothrix
- D. Penicillium
Explanation: **Explanation:** The correct answer is **Rhinosporidium seeberi**. This organism is unique in medical mycology because it has **never been successfully cultured** on artificial laboratory media (like SDA) or in cell culture. Its classification was historically debated, but molecular analysis (18S rRNA sequencing) has placed it among the *Mesomycetozoea*, a group of aquatic fish parasites, though it is still traditionally studied in Mycology. **Why the other options are incorrect:** * **Candida:** A common yeast that grows readily on Sabouraud Dextrose Agar (SDA) within 24–48 hours, forming creamy white colonies. * **Sporothrix:** A dimorphic fungus that can be cultured at 25°C (mold form with "flower-like" sporulation) and 37°C (yeast form). * **Penicillium:** A common saprophytic mold that grows rapidly in culture, characterized by its "brush-like" conidiophores. **High-Yield Clinical Pearls for NEET-PG:** * **Disease:** Rhinosporidiosis typically presents as **friable, leafy, strawberry-like polypoid masses** in the nose or nasopharynx. * **Transmission:** Associated with bathing in stagnant freshwater (ponds/tanks). * **Diagnosis:** Since it cannot be cultured, diagnosis relies on **histopathology**. Look for large **sporangia** (up to 350 µm) containing thousands of **endospores**. * **Treatment:** Surgical excision with wide-base cauterization is the treatment of choice; medical therapy (Dapsone) has limited efficacy.
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