A 60-year-old man in a surgical ICU has had a central venous catheter for three weeks and has received broad-spectrum antibiotics. He is febrile and two blood cultures drawn from a peripheral vein grow Candida tropicalis. What is the next best step in management?

Start an echinocandin and remove the central catheter

Give amphotericin B through the same central catheter

Start fluconazole and keep the catheter for access

Repeat blood cultures before any antifungal treatment

A 34-year-old man with relapsed acute leukaemia has been on voriconazole prophylaxis for three weeks. He now develops left facial pain, numbness over the cheek and a black crust on the nasal septum, with periorbital swelling. Biopsy of the crust is awaited. What is the most likely cause of his new infection?

Mucormycosis, which voriconazole does not cover

Bacterial sinusitis with facial cellulitis

Invasive aspergillosis with voriconazole resistance

Candida sinusitis breaking through prophylaxis

A 38-year-old woman is on day 14 of chemotherapy for acute myeloid leukaemia with an absolute neutrophil count of 180/µL. She has fever and pleuritic chest pain despite broad-spectrum antibiotics; CT chest shows two nodules surrounded by ground-glass haloes. Which test best supports the suspected diagnosis?

Serum beta-D-glucan on a single sample only

Blood culture in a fungal bottle

Sputum smear for acid-fast bacilli

Fungal infections

19 NEET-PG practice questions on Fungal infections, part of Microbiology. The first 19 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
A dermatology resident is taught about dermatophyte infections. Consider four statements: 1. KOH mount from the active edge of the lesion shows septate branching hyphae. 2. Some Microsporum species infecting the scalp fluoresce green under Wood's lamp. 3. Nail infections need a longer course of treatment than infections of glabrous skin. 4. Dermatophytes commonly invade the blood and spread to internal organs. Which statements are correct?
1. A1 and 3 only
2. B1 and 2 only
3. C1, 2 and 3 only
4. D2 and 3 only
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Answer: C · 1, 2 and 3 only
Statements 1, 2 and 3 are correct. Scrapings from the advancing edge of a lesion, where the fungus is active, show septate branching hyphae in KOH, and some Microsporum species that infect hair give a greenish fluorescence under Wood's lamp while most Trichophyton species do not. Nails and hair grow slowly and hold the fungus deeply, so treatment runs for weeks to months rather than days. Statement 4 is false: dermatophytes are keratinophilic and remain in the stratum corneum, hair and nails, and do not disseminate in immunocompetent people.
- A: Omits the Wood's lamp fluorescence of some Microsporum species, which is correct.
- B: Omits the longer treatment needed for nails, which is correct.
- D: Omits the KOH finding from the active edge, which is correct.
Question 2 · Easy
A 45-year-old man who explores bat-infested caves in Madhya Pradesh has had fever, weight loss and an ulcer on the tongue for two months. He has hepatosplenomegaly and pancytopenia. Bone marrow smears show small oval yeasts packed inside macrophages. Which organism is most likely?
1. AAspergillus flavus
2. BCryptococcus neoformans
3. CHistoplasma capsulatum
4. DCandida tropicalis
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Answer: C · Histoplasma capsulatum
Histoplasma capsulatum grows in soil enriched by bat or bird droppings, and inhaled spores are taken up by alveolar macrophages, in which the small intracellular yeasts multiply. Progressive disseminated histoplasmosis presents with fever, weight loss, hepatosplenomegaly, pancytopenia and mucosal ulcers, and can closely mimic tuberculosis or kala-azar. Marrow or tissue showing intracellular yeasts, confirmed by culture, establishes the diagnosis. Treatment is amphotericin B followed by itraconazole in severe disease.
- A: Aspergillus forms septate hyphae in tissue and does not multiply inside macrophages.
- B: Cryptococcus is a larger capsulate yeast and is mainly extracellular in tissue.
- D: Candida appears as yeasts with pseudohyphae, not as small intracellular yeasts in macrophages.
Question 3 · Medium
A 60-year-old man in a surgical ICU has had a central venous catheter for three weeks and has received broad-spectrum antibiotics. He is febrile and two blood cultures drawn from a peripheral vein grow Candida tropicalis. What is the next best step in management?
1. AGive amphotericin B through the same central catheter
2. BStart fluconazole and keep the catheter for access
3. CStart an echinocandin and remove the central catheter
4. DRepeat blood cultures before any antifungal treatment
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Answer: C · Start an echinocandin and remove the central catheter
Candidaemia is treated as a true bloodstream infection: an echinocandin such as caspofungin or micafungin is started at once, and the intravascular catheter, which is usually colonised with biofilm, is removed or exchanged, as leaving it in place prolongs the infection. Repeat cultures are taken to document clearance, and a dilated fundus examination is done to look for endophthalmitis. Therapy is stepped down to fluconazole only when the isolate is susceptible and the patient has improved. Waiting for a second set of cultures before treating increases mortality.
- A: Giving the drug through the infected, biofilm-laden catheter does not deal with the source.
- B: Fluconazole is not the empirical choice in an unstable ICU patient, and keeping the line maintains the source.
- D: Delaying antifungal treatment in candidaemia increases mortality.
Question 4 · Hard
A 34-year-old man with relapsed acute leukaemia has been on voriconazole prophylaxis for three weeks. He now develops left facial pain, numbness over the cheek and a black crust on the nasal septum, with periorbital swelling. Biopsy of the crust is awaited. What is the most likely cause of his new infection?
1. ABacterial sinusitis with facial cellulitis
2. BInvasive aspergillosis with voriconazole resistance
3. CCandida sinusitis breaking through prophylaxis
4. DMucormycosis, which voriconazole does not cover
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Answer: D · Mucormycosis, which voriconazole does not cover
Mucorales are not inhibited by voriconazole, so an angioinvasive mould infection appearing in a patient already on that drug should suggest mucormycosis; facial pain with numbness, a black necrotic eschar and orbital swelling fit rhino-orbital disease. Confirmation is by biopsy showing broad, ribbon-like, sparsely septate hyphae branching at wide angles, and treatment is liposomal amphotericin B with urgent surgical debridement and correction of the underlying risk. Aspergillus is usually susceptible to voriconazole, so breakthrough infection on the drug argues against it. Candida does not typically cause an invasive necrotic sinus eschar, and bacterial sinusitis does not produce this pattern of tissue necrosis.
- A: Bacterial sinusitis does not cause black necrotic eschars with vascular invasion.
- B: Aspergillus is usually voriconazole-susceptible, so breakthrough on the drug argues against it.
- C: Candida rarely causes invasive necrotic sinus disease of this kind.
Question 5 · Medium
A 38-year-old woman is on day 14 of chemotherapy for acute myeloid leukaemia with an absolute neutrophil count of 180/µL. She has fever and pleuritic chest pain despite broad-spectrum antibiotics; CT chest shows two nodules surrounded by ground-glass haloes. Which test best supports the suspected diagnosis?
1. ASerum beta-D-glucan on a single sample only
2. BBlood culture in a fungal bottle
3. CSputum smear for acid-fast bacilli
4. DSerum galactomannan assay
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Answer: D · Serum galactomannan assay
Nodules with a surrounding halo in a profoundly neutropenic patient suggest invasive pulmonary aspergillosis, in which hyphae invade vessels and cause haemorrhagic infarction. Serum and bronchoalveolar lavage galactomannan is the most useful non-invasive marker and supports a probable diagnosis together with the imaging and the host risk factor. Blood cultures are almost always negative in invasive aspergillosis. Voriconazole is the usual first-line treatment, started early because mortality rises with delay.
- A: Beta-D-glucan is non-specific and is raised by many fungi, so it cannot point to Aspergillus.
- B: Blood cultures are characteristically negative in invasive aspergillosis.
- C: Acid-fast staining addresses tuberculosis, which does not give this halo pattern acutely.
Question 6 · Hard
A 40-year-old renal transplant recipient on tacrolimus is started on voriconazole for proven invasive aspergillosis. Five days later he has a tremor, headache and a rise in serum creatinine from 1.1 to 2.0 mg/dL, and his tacrolimus trough level is three times the target. What explains this change?
1. AVoriconazole induces CYP3A4 and raises tacrolimus clearance
2. BVoriconazole displaces tacrolimus from tissue stores
3. CAspergillus infection itself raises tacrolimus absorption
4. DVoriconazole inhibits CYP3A4 and raises tacrolimus levels
Answer and explanation in LearnFree account
Question 7 · Medium
A 58-year-old man in a medical ICU has candidaemia and the laboratory reports Candida krusei. Which drug is inappropriate for him because of the intrinsic resistance of this species?
1. AVoriconazole
2. BFluconazole
3. CLiposomal amphotericin B
4. DMicafungin
Answer and explanation in LearnFree account
Question 8 · Medium
A 26-year-old man has itchy annular scaly lesions over both groins and the trunk for eight months. He has been applying a cream bought over the counter that contains clobetasol, an antifungal and an antibacterial. The lesions are now extensive, with indistinct edges and little scaling. What is the most appropriate management?
1. AChange to a stronger topical steroid alone
2. BContinue the same cream for another month
3. CAdd an oral corticosteroid to settle the inflammation
4. DStop the combination cream and give a systemic antifungal
Answer and explanation in LearnFree account
Question 9 · Medium
A mould isolated from the bone marrow culture of a patient with suspected disseminated histoplasmosis is examined. Which pair of findings is characteristic of Histoplasma capsulatum?
1. ATuberculate macroconidia at 25°C and small budding yeasts at 37°C
2. BArthroconidia in alternate cells at 37°C only
3. CThick-walled spherules with endospores in tissue at both temperatures
4. DBroad-based budding yeasts at 25°C and hyphae at 37°C
Answer and explanation in LearnFree account
Question 10 · Medium
A 44-year-old woman has thickened, yellowish, crumbling nails of both great toes for two years, with scaling between the toes. Nail clippings and subungual debris are sent for KOH mount and culture. Which organism is the commonest cause of this condition?
1. AEpidermophyton floccosum
2. BMalassezia furfur
3. CMicrosporum canis
4. DTrichophyton rubrum
Answer and explanation in LearnFree account
Question 11 · Medium
A tertiary care hospital reports a cluster of bloodstream infections with Candida auris. The microbiologist warns that the organism is often missed by routine identification systems. Which method identifies it reliably?
1. ASugar fermentation on conventional biochemical panels
2. BIndia ink preparation of the broth culture
3. CGerm tube test in serum
4. DMALDI-TOF mass spectrometry with an updated database
Answer and explanation in LearnFree account
Question 12 · Medium
CSF from a patient with chronic meningitis is cultured. The yeast isolate splits urea rapidly and produces brown-black colonies on birdseed (Niger seed) agar. Which organism does this identify?
1. ACandida glabrata
2. BRhodotorula mucilaginosa
3. CTrichosporon asahii
4. DCryptococcus neoformans
Answer and explanation in LearnFree account
Question 13 · Easy
A 7-year-old boy is brought with a scaly patch on the scalp with broken-off hairs and mild itching for a month. KOH mount of plucked hairs shows fungal elements. Why does this infection need an oral antifungal rather than cream alone?
1. AThe organism is resistant to all topical agents
2. BScalp skin absorbs no topical drug at all
3. CThe fungus lies within the hair shaft and follicle
4. DTopical drugs are inactivated by sebum
Answer and explanation in LearnFree account
Question 14 · Easy
A 35-year-old man with advanced HIV is admitted with three weeks of headache and low-grade fever. CSF opening pressure is high, with 40 cells/µL, mostly lymphocytes. An India ink preparation of the CSF is examined. Which finding is expected?
1. ABroad ribbon-like hyphae with right-angle branching
2. BBudding yeasts with wide clear capsules
3. CSeptate hyphae branching at acute angles
4. DYeasts with pseudohyphae and blastoconidia
Answer and explanation in LearnFree account
Question 15 · Hard
A 32-year-old woman with newly diagnosed HIV and a CD4 count of 40 cells/µL has had fever and weight loss for six weeks. She has hepatosplenomegaly, a palatal ulcer, haemoglobin 7.6 g/dL, total leucocyte count 2,100/µL and platelets 70,000/µL. Sputum CBNAAT is negative and blood cultures are sterile. Which investigation is most likely to give a diagnosis quickly?
1. AMycobacterial blood culture alone
2. BSerum IgG antibody panel for endemic fungi
3. CBone marrow aspiration with special fungal stains
4. DRepeat sputum CBNAAT on three more samples
Answer and explanation in LearnFree account
Question 16 · Medium
A 48-year-old man treated for pulmonary tuberculosis six years ago has recurrent small haemoptysis. Sputum is repeatedly negative for acid-fast bacilli and CBNAAT is negative. CT chest shows a rounded soft tissue mass lying within an old thick-walled upper lobe cavity, with a crescent of air above it, which moves when he changes position. What is the most likely diagnosis?
1. ABronchogenic carcinoma in a scarred lobe
2. BAspergilloma in a healed tuberculous cavity
3. CRelapse of pulmonary tuberculosis
4. DInvasive pulmonary aspergillosis
Answer and explanation in LearnFree account
Question 17 · Easy
Blood culture from a patient in a Mumbai ICU grows a yeast. The laboratory suspends the yeast in human serum and incubates it at 37°C for two hours. Which finding identifies Candida albicans?
1. AGerm tube formation from the yeast cell
2. BCapsule swelling around the yeast
3. CProduction of brown pigment from caffeic acid
4. DRapid splitting of urea
Answer and explanation in LearnFree account
Question 18 · Medium
A 52-year-old man with type 2 diabetes in ketoacidosis develops facial pain and nasal crusting, and biopsy confirms invasive mucormycosis. Which feature of his metabolic state most favours the growth of Mucorales?
1. ARaised arterial oxygen content in the sinuses
2. BAcidosis releasing free iron from transferrin
3. CIncreased blood viscosity reducing capillary flow
4. DLow serum complement from glucose binding
Answer and explanation in LearnFree account
Question 19 · Hard
A physician reviews a patient with cryptococcal meningitis and advanced HIV. Consider four statements: 1. The capsular polysaccharide is the antigen detected by the CSF cryptococcal antigen test. 2. India ink microscopy is less sensitive than the antigen test on CSF. 3. The CSF usually shows a very high cell count with a neutrophil predominance. 4. Raised intracranial pressure is managed with repeated therapeutic lumbar punctures. Which statements are correct?
1. A1, 2 and 4 only
2. B1 and 3 only
3. C2 and 4 only
4. D1 and 2 only
Answer and explanation in LearnFree account

Fungal infections

A 45-year-old man who explores bat-infested caves in Madhya Pradesh has had fever, weight loss and an ulcer on the tongue for two months. He has hepatosplenomegaly and pancytopenia. Bone marrow smears show small oval yeasts packed inside macrophages. Which organism is most likely?

A 60-year-old man in a surgical ICU has had a central venous catheter for three weeks and has received broad-spectrum antibiotics. He is febrile and two blood cultures drawn from a peripheral vein grow Candida tropicalis. What is the next best step in management?

A 40-year-old renal transplant recipient on tacrolimus is started on voriconazole for proven invasive aspergillosis. Five days later he has a tremor, headache and a rise in serum creatinine from 1.1 to 2.0 mg/dL, and his tacrolimus trough level is three times the target. What explains this change?

A 58-year-old man in a medical ICU has candidaemia and the laboratory reports Candida krusei. Which drug is inappropriate for him because of the intrinsic resistance of this species?

A mould isolated from the bone marrow culture of a patient with suspected disseminated histoplasmosis is examined. Which pair of findings is characteristic of Histoplasma capsulatum?

A 44-year-old woman has thickened, yellowish, crumbling nails of both great toes for two years, with scaling between the toes. Nail clippings and subungual debris are sent for KOH mount and culture. Which organism is the commonest cause of this condition?

A tertiary care hospital reports a cluster of bloodstream infections with Candida auris. The microbiologist warns that the organism is often missed by routine identification systems. Which method identifies it reliably?

CSF from a patient with chronic meningitis is cultured. The yeast isolate splits urea rapidly and produces brown-black colonies on birdseed (Niger seed) agar. Which organism does this identify?

A 7-year-old boy is brought with a scaly patch on the scalp with broken-off hairs and mild itching for a month. KOH mount of plucked hairs shows fungal elements. Why does this infection need an oral antifungal rather than cream alone?

A 35-year-old man with advanced HIV is admitted with three weeks of headache and low-grade fever. CSF opening pressure is high, with 40 cells/µL, mostly lymphocytes. An India ink preparation of the CSF is examined. Which finding is expected?

Blood culture from a patient in a Mumbai ICU grows a yeast. The laboratory suspends the yeast in human serum and incubates it at 37°C for two hours. Which finding identifies Candida albicans?

A 52-year-old man with type 2 diabetes in ketoacidosis develops facial pain and nasal crusting, and biopsy confirms invasive mucormycosis. Which feature of his metabolic state most favours the growth of Mucorales?