Mycology (Superficial, Subcutaneous, Systemic, Opportunistic Fungi) MCQs

Microbiology · 65 free questions with answers & explanations.

1. An AIDS patient (CD4 count 40 cells/μL) develops severe headache and meningism. CSF India ink preparation shows encapsulated yeast cells. The most sensitive and specific rapid diagnostic test for this infection is:
2. A neutropenic patient post-bone marrow transplantation develops fever with pulmonary infiltrates. Bronchoalveolar lavage shows broad, ribbon-like non-septate (pauci-septate) hyphae branching at right angles. CT shows perihilar infiltrates with a tendency for vascular invasion. The most likely diagnosis is:
3. A patient on long-term voriconazole therapy for Aspergillus fumigatus infection develops breakthrough infection with a Mucor species. The most important mechanism of intrinsic mucormycetes resistance to voriconazole is:
4. Cryptococcus neoformans causes meningoencephalitis preferentially in immunocompromised patients. Its polysaccharide capsule is a major virulence factor. Capsular material detected in CSF by India ink preparation reveals:
5. Sporothrix schenckii infection follows a traumatic inoculation in a gardener who presents with a nodular lymphangitic pattern of lesions tracking up the arm. Laboratory diagnosis is best confirmed by:
6. Cryptococcus neoformans meningitis in AIDS patients has a characteristically gelatinous appearance on autopsy. The specific reason for the absence of inflammatory response despite high fungal burden is:
7. A diabetic patient with poor glycemic control develops rapidly progressing black eschar of the palate and orbital cellulitis. Culture grows broad aseptate hyphae with irregular branching at right angles. The mechanism linking diabetic ketoacidosis to this infection is:
8. Histoplasma capsulatum causes pulmonary infection after inhaling microconidia, which convert to yeast form in lung macrophages. The temperature-dependent dimorphism switch from mold to yeast is mediated by:
9. In Aspergillus fumigatus invasive infection in neutropenic patients, galactomannan (GM) antigen detection in serum is used for early diagnosis. The galactomannan antigen is a component of:
10. A 58-year-old diabetic patient with poorly controlled blood glucose develops periorbital swelling, proptosis, black eschar over the palate, and a CT scan shows invasion into the orbit and cavernous sinus. KOH smear of biopsy material reveals broad, aseptate ribbon-like hyphae with right-angle branching at 90°. The organism most likely responsible and its primary virulence mechanism are:
11. Cryptococcus neoformans infection in an immunocompromised patient is diagnosed by India ink preparation of CSF. The polysaccharide capsule of Cryptococcus primarily evades host immunity by which mechanism?
12. A 35-year-old farmer from Bihar presents with a chronic painless swelling on his foot for 3 years with multiple draining sinuses discharging black granules. Histopathology shows the Splendore-Hoeppli phenomenon. The most likely diagnosis and its causative organism are:
13. Candida auris is an emerging multidrug-resistant yeast of major concern in hospital outbreaks. Which diagnostic limitation is clinically important regarding C. auris identification?
14. Cryptococcus neoformans is an encapsulated yeast that causes meningitis primarily in immunocompromised patients. Which virulence factor is detected by the India ink preparation and also by the latex agglutination test in CSF?
15. Aspergillus fumigatus causes invasive aspergillosis in profoundly neutropenic patients. Galactomannan ELISA on serum is used for early diagnosis. What is the structural basis of galactomannan antigenicity and which other fungus can cause false-positive results?
16. Sporothrix schenckii causes lymphocutaneous sporotrichosis. What is the temperature-dependent dimorphism of this organism and which medium/characteristic is used for diagnosis at the laboratory bench?
17. Candida albicans is distinguished from other Candida species by which two laboratory tests that can be performed rapidly in the clinical microbiology laboratory?
18. Cryptococcus neoformans virulence in immunocompromised hosts is primarily due to its polysaccharide capsule. The capsule's main mechanism of immune evasion involves:
19. A patient with AIDS develops pulmonary infiltrates and BAL shows broad-based budding yeast with double-contoured cell wall on KOH preparation. The organism grows as white to tan colonies on SDA at 25°C (mold phase) and converts to yeast at 37°C. Serology shows complement-fixing antibodies at 1:32. The diagnosis is:
20. Aspergillus fumigatus resistance to azole antifungals (voriconazole, itraconazole) most commonly involves which molecular mechanism?
21. A patient on prolonged broad-spectrum antibiotics develops thrush. Candida albicans is isolated. The virulence factor that allows C. albicans to switch from yeast to hyphal (filamentous) form and invade tissue is:
22. A 45-year-old man with HIV (CD4 45/µL) from Bangalore presents with severe headache, neck stiffness, and altered sensorium. CSF shows elevated opening pressure, lymphocytic pleocytosis, low glucose, and India ink preparation reveals large encapsulated yeasts. Which property of the capsule is primarily responsible for virulence?
23. A patient with haematological malignancy on prolonged antifungal prophylaxis with voriconazole develops a pulmonary infection. CT shows a halo sign followed by air-crescent sign on follow-up. BAL galactomannan is elevated. Biopsy shows septate hyphae branching at acute angles (45°). Treatment is initiated with voriconazole, but the fungus tests resistant. The most likely organism and resistance mechanism is:
24. An AIDS patient (CD4 = 45/µL) presents with headache, fever and confusion for one week. CSF shows: opening pressure 320 mmH₂O, WBC 5/µL (lymphocytes), protein 60 mg/dL, glucose 35 mg/dL (serum 90 mg/dL), and India ink preparation shows encapsulated yeast. Which virulence factor of Cryptococcus neoformans directly explains the large capsule seen?
25. A patient with uncontrolled diabetes mellitus develops periorbital oedema, black necrotic lesion on the palate extending to the nasal septum, proptosis and rapid progression. MRI shows cavernous sinus thrombosis. What is the pathogenetic basis for the invasive behaviour of Mucor/Rhizopus in diabetic ketoacidosis?
26. A farmer from Tamil Nadu presents with a painless swelling on the foot with multiple discharging sinuses containing black granules. He reports working barefoot for years. The granules are crushed and show branched septate hyphae. What is the MOST likely causal organism of this mycetoma?
27. A neutropenic patient (ANC <100/µL) on 3 weeks of broad-spectrum antibiotics develops fever unresponsive to antibiotics, new pulmonary infiltrates and a lung CT showing a 'halo sign' (ground glass density surrounding a nodule). Serum galactomannan ELISA is positive at index >0.5. Which pathological process creates the halo sign?
28. A 60-year-old diabetic patient on broad-spectrum antibiotics for 2 weeks develops oral thrush and then systemic candida fungaemia. Blood cultures grow yeast. The MOST appropriate antifungal for non-critically ill patients without prior azole exposure, according to current guidelines, is:
29. Cryptococcus neoformans produces a unique virulence factor detected by India ink preparation of CSF in meningitis. This virulence factor is also detected serologically by latex agglutination. What is this factor?
30. A neutropenic patient post-chemotherapy develops right-sided facial swelling, black nasal eschar, and a right-sided ptosis. CT shows orbital involvement. KOH mount of the nasal tissue shows broad, non-septate, ribbon-like hyphae with wide-angle branching. The drug of choice is:
31. A Wood's lamp examination shows yellow-green fluorescence of scalp hairs in a child with tinea capitis. This fluorescence is produced by which dermatophyte group?
32. A 35-year-old patient with HIV (CD4 30 cells/μL) develops severe headache, fever, and neck stiffness. CSF analysis shows: lymphocytic pleocytosis, low glucose, high protein, and India ink preparation shows encapsulated yeast cells. Cryptococcal antigen (CrAg) titer in CSF is 1:1024. Which treatment regimen is recommended for induction therapy for cryptococcal meningoencephalitis in HIV patients (WHO/IDSA 2022)?
33. A 50-year-old immunocompromised patient from Maharashtra develops a painless, firm, slow-growing swelling over the ankle with multiple discharging sinuses releasing black grains (melanin-pigmented). Histopathology shows thick-walled brown sclerotic cells (Medlar bodies/muriform cells). The MOST likely diagnosis is:
34. A burn patient in ICU develops Candida bloodstream infection. Species identification by MALDI-TOF mass spectrometry identifies Candida auris. Which feature of C. auris makes this infection particularly challenging to manage compared to C. albicans?
35. A neutropenic patient post-chemotherapy develops fever unresponsive to antibiotics, new pulmonary infiltrate on CT (halo sign), and serum galactomannan index of 2.3 on two consecutive samples. The most appropriate initial antifungal is:
36. A 35-year-old farmer in Maharashtra develops painless subcutaneous swelling on the foot with multiple sinuses discharging black granules. The most likely causative organism and its staining characteristics are:
37. India ink preparation of CSF in an HIV patient with CD4 = 30 shows encapsulated yeast cells. Cryptococcal antigen (CrAg) is 1:1024. The treatment protocol recommended by WHO for cryptococcal meningitis includes:
38. A diabetic patient with recent COVID-19 pneumonia and prolonged steroid use develops rapidly progressing black eschar over the palate and necrotic ulcers in the nasal cavity. Sputum KOH mount shows broad, irregular, non-septate (pauciseptate) hyphae at right angles. Biopsy confirms angioinvasion. Which combination of management steps is most appropriate?
39. An HIV patient (CD4 = 60 cells/µL) presents with headache, photophobia, and positive India ink preparation of CSF showing encapsulated budding yeast with a wide clear halo. CSF cryptococcal antigen (CrAg) titre is 1:2048. What is the significance of the capsule, and which antifungal treatment phase applies?
40. A 55-year-old man on long-term steroids for ILD develops fever, haemoptysis, and a CT chest showing a cavitary lesion with 'halo sign' (zone of consolidation surrounding a central nodule). Bronchoalveolar lavage Galactomannan index is 3.2 (positive >0.5). Fungal culture grows septate hyphae with V-shaped branching at 45°. What is the most appropriate first-line treatment?
41. A 40-year-old man from Maharashtra presents with a chronic swelling of the foot with multiple draining sinuses discharging white granules (sulphur granules). Microscopy of the granules shows branching filaments with a club-like fringe (Splendore-Hoeppli phenomenon). What is the most likely organism and treatment?
42. In a patient with AIDS (CD4 <50 cells/µL) presenting with headache, neck stiffness, and CSF showing India ink preparation with encapsulated yeast cells and opening pressure of 280 mm H2O, cryptococcal antigen (CrAg) is positive 1:2048. What is the recommended induction therapy?
43. An HIV patient with CD4 < 50 cells/µL develops headache, meningism, and raised intracranial pressure. India ink preparation of CSF shows encapsulated yeast with a polysaccharide capsule. Cryptococcal antigen (CrAg) is positive. The drug regimen for induction therapy is:
44. A diabetic patient with poorly controlled diabetes develops proptosis, ophthalmoplegia, and black necrotic eschar over the nasal bridge and hard palate after a dental procedure. Tissue biopsy shows broad, pauci-septate (aseptate) hyphae with wide-angle branching. The most appropriate treatment is:
45. An immunocompromised patient post-bone marrow transplant has fever unresponsive to broad-spectrum antibiotics. Chest CT shows a 2 cm pulmonary nodule with a halo sign. Serum galactomannan ELISA shows an ODI of 1.8 (cut-off > 0.5). The diagnosis and first-line treatment are:
46. A farmer from Karnataka presents with a painless warty plaque on the foot present for 6 years. KOH mount shows brown, rounded, thick-walled 'muriform cells' (sclerotic bodies) dividing by cross-wall formation. The organism belongs to which group of fungi?
47. An immunocompromised patient develops sinusitis with a black, necrotic eschar over the palate and cheek. CT scan shows bony erosion. KOH preparation of tissue shows broad aseptate hyphae branching at right angles. Which organism is responsible?
48. An HIV-positive patient with CD4 count 30 cells/µL presents with headache and neck stiffness. CSF shows India ink preparation with encapsulated budding yeast cells. Cryptococcal antigen latex agglutination test (CRAG) of CSF is positive at 1:512. What is the treatment protocol?
49. A farmer in Maharashtra presents with a painless nodular lesion on the foot with discharging sinuses and black granules. Histopathology shows fungal grains with brown-black melanin pigment. What is this condition called and which organism most commonly causes it in India?
50. A 55-year-old diabetic patient with poorly controlled glycaemia presents with unilateral facial pain, black nasal discharge and proptosis developing over 4 days. CT shows sinus erosion and orbital invasion. Tissue biopsy shows broad aseptate hyphae with right-angle branching. Which antifungal and surgical approach constitutes first-line management?
51. A patient with chromoblastomycosis (warty plaque on foot) has biopsy showing thick-walled, dark brown, muriform (sclerotic) bodies dividing by fission in multiple planes ('copper pennies'). The most common causative species in India is which of the following?
52. A patient with uncontrolled diabetes mellitus presents with acute rhinosinusitis with black eschar on the hard palate and periorbital oedema. MRI shows invasion of the orbital apex and cavernous sinus. The organism most likely to be isolated on Sabouraud medium is:
53. The mechanism by which Cryptococcus neoformans evades host phagocytosis is primarily through:
54. Sporothrix schenckii infection (sporotrichosis) classically presents as a nodular lymphangitic pattern. The characteristic microscopic finding in tissue at 37°C (yeast phase) is:
55. A patient with uncontrolled Type 1 diabetes mellitus presents with severe facial pain, periorbital swelling, black necrotic nasal discharge, and right-sided ptosis. MRI shows infiltration of the right orbit and cavernous sinus. KOH preparation of nasal scraping shows broad (10–20 µm), aseptate (non-septate), ribbon-like hyphae with right-angle branching. What is the diagnosis and empirical antifungal treatment?
56. A 25-year-old male presents with a painless, slowly progressive verrucous plaque on the dorsum of the right foot for 3 years following a thorn prick. Biopsy shows pseudoepitheliomatous hyperplasia with 'Medlar bodies' (muriform cells — round, brown, thick-walled cells with internal septa). Which organism most commonly causes this infection in India?
57. A patient undergoing hematopoietic stem cell transplantation develops breakthrough invasive fungal infection on micafungin prophylaxis. The mould cultured shows hyphae with 45° branching and parallel walls on lactophenol cotton blue. Galactomannan index is 2.5. Voriconazole is started, but the patient deteriorates. Susceptibility testing reveals elevated MIC for voriconazole. The MOST likely mechanism of resistance is:
58. Mucormycosis (caused by Mucor, Rhizopus, Cunninghamella species) characteristically produces angioinvasion. The virulence factor responsible for this affinity for vascular endothelium is:
59. Candida auris, an emerging multidrug-resistant yeast, is distinguished from other Candida species by which key property?
60. A 38-year-old HIV patient with CD4 count of 60 cells/μL presents with headache, fever, and altered sensorium. CSF reveals an India ink preparation showing encapsulated yeast cells with a wide polysaccharide capsule. Which organism is responsible?
61. A 50-year-old farmer from Maharashtra presents with a chronic swelling of the foot with multiple sinuses discharging yellow sulfur-like granules. Microscopy of the granules shows broad, branching fungal hyphae with chlamydospores. Which of the following is the MOST common cause of eumycetoma in India?
62. A 24-year-old woman presents with a pruritic, ring-shaped, scaly lesion on her inner thigh with central clearing. KOH mount of skin scraping shows septate hyphae and arthrospores. The organism responsible fluoresces under Wood's lamp. Which dermatophyte is most commonly responsible for this infection at this site?
63. A 45-year-old man with poorly controlled diabetes mellitus presents with facial pain, black necrotic nasal discharge, periorbital swelling, and proptosis. CT shows invasion of the nasal sinuses and orbit. This presentation is most consistent with rhinocerebral mucormycosis caused by fungi of which order?
64. Sporothrix schenckii infection (sporotrichosis) classically presents as a painless nodule at the site of thorn-prick injury that ulcerates and then develops a chain of similar nodules along the lymphatic drainage (lymphocutaneous sporotrichosis). Which morphological form of this dimorphic fungus is found in human tissues?
65. A blood culture from a neonate on total parenteral nutrition via a central venous catheter grows a yeast that requires exogenous long-chain fatty acids for growth. The organism produces no pseudohyphae or germ tubes. Which organism is most likely?