Infectious Diseases Practice Questions

Q: A 65-year-old man presented with skin lesions six weeks after returning from a vacation in Belize, which included time spent at the beach and in the rainforest. What is the diagnosis?

Bot fly. ***Bot fly*** - **Bot fly myiasis** (Dermatobia hominis) is endemic in **Central America** including Belize, presenting as **boil-like lesions** with a central pore developing weeks after exposure. - The **6-week incubation period** and travel to **rainforest and beach areas** in Belize are classic for bot fly larval development under the skin. *Cutaneous leishmaniasis* - Caused by **Leishmania species** transmitted by **sandflies**, typically presents as **painless ulcers** with raised borders, not boil-like lesions. - More commonly associated with **Mediterranean, Middle Eastern, or South American** regions rather than Belize's specific epidemiology. *Onchocerciasis* - Caused by **Onchocerca volvulus**, transmitted by **blackflies**, primarily presents with **subcutaneous nodules** and **chronic skin changes**. - Endemic in **sub-Saharan Africa** and some parts of Central/South America, but skin lesions develop over **months to years**, not weeks. *Plague* - Caused by **Yersinia pestis**, transmitted by **flea bites** from infected rodents, presents with **painful lymphadenopathy** (bubonic) or systemic illness. - **Acute onset** within days, not weeks, and skin lesions are **eschars** at bite sites, not boil-like lesions.

Q: A patient presents with lower gastrointestinal bleeding. Sigmoidoscopy shows ulcers in the sigmoid. Biopsy from this area shows flask-shaped ulcers. Which of the following is the most appropriate treatment?

Intravenous metronidazole. **Explanation:** The clinical presentation of lower gastrointestinal bleeding combined with the pathognomonic finding of **flask-shaped ulcers** on biopsy is diagnostic of **Amoebic Colitis**, caused by *Entamoeba histolytica* [1]. 1. **Why Option B is correct:** *Entamoeba histolytica* trophozoites invade the intestinal mucosa, causing lateral spread in the submucosa, which creates the classic "flask-shaped" appearance. **Metronidazole** (or Tinidazole) is the drug of choice for invasive amoebiasis as it is a potent tissue amoebicide. In cases of severe colitis or systemic symptoms, intravenous administration is preferred to ensure rapid therapeutic levels. 2. **Why the other options are incorrect:** * **Option A (Ceftriaxone):** This is a third-generation cephalosporin used for bacterial infections like Enteric fever or Shigellosis. It has no activity against protozoa like *E. histolytica*. * **Options C & D (Steroids/Sulphasalazine):** These are used to treat Inflammatory Bowel Disease (IBD), specifically Ulcerative Colitis [2]. While IBD also presents with bloody diarrhea and ulcers, the biopsy would show crypt abscesses rather than flask-shaped ulcers. Importantly, giving steroids in a case of amoebiasis can lead to toxic megacolon or perforation. **Clinical Pearls for NEET-PG:** * **Pathology:** The "flask shape" occurs because the organism cannot easily penetrate the muscularis propria, leading to lateral expansion in the submucosa. * **Diagnosis:** Stool microscopy may show trophozoites with ingested RBCs (erythrophagocytosis) [1]. * **Treatment Protocol:** Always follow a tissue amoebicide (Metronidazole) with a **luminal amoebicide** (e.g., Diloxanide furoate or Paromomycin) to eradicate the cyst stage and prevent relapse/transmission. * **Complication:** The most common extra-intestinal manifestation is an Amoebic Liver Abscess (anchovy sauce pus) [1].

Q: Which of the following is NOT a characteristic feature of cerebral malaria?

Bloody cerebrospinal fluid. **Explanation:** Cerebral malaria is a severe neurological complication of *Plasmodium falciparum* infection, characterized by unarousable coma (Glasgow Coma Scale <11) in the absence of other identifiable causes [2]. **Why "Bloody Cerebrospinal Fluid" is the correct answer:** In cerebral malaria, the cerebrospinal fluid (CSF) is typically **clear and colorless**. While there may be a mild increase in opening pressure and a slight elevation in protein levels (<100 mg/dL), the CSF cell count is usually normal (pleocytosis is rare). The presence of bloody or xanthochromic CSF suggests an alternative diagnosis, such as subarachnoid hemorrhage or a traumatic tap, and is **not** a feature of malaria [1]. **Analysis of Incorrect Options:** * **Retinal Hemorrhages:** This is a key diagnostic and prognostic marker. "Malarial retinopathy" (including retinal whitening, vessel changes, and hemorrhages) is highly specific for cerebral malaria and correlates with the severity of brain sequestration. * **Extensor Plantar Reflex:** Upper motor neuron signs are common. Patients often exhibit decerebrate or decorticate posturing, hyperreflexia, and a positive Babinski sign (extensor plantar response) due to diffuse encephalopathy. * **Absent Abdominal Reflex:** This is a classic clinical finding in cerebral malaria, reflecting the involvement of the corticospinal tracts. **High-Yield NEET-PG Pearls:** * **Pathogenesis:** Sequestration of parasitized RBCs in cerebral microvasculature (cytoadherence via PfEMP-1) [3]. * **Drug of Choice:** Intravenous **Artesunate** is the gold standard (preferred over Quinine). * **Hypoglycemia:** Always check blood glucose, as both the disease and Quinine treatment can cause severe hypoglycemia [2]. * **Mortality:** Even with treatment, mortality remains 15–20%.

Q: What is the drug of choice for craniofacial mucormycosis?

Liposomal amphotericin B. **Explanation:** **Liposomal Amphotericin B** is the drug of choice for craniofacial (rhinocerebral) mucormycosis because *Mucorales* fungi are highly aggressive, angioinvasive, and naturally resistant to most conventional antifungals. Amphotericin B acts by binding to ergosterol in the fungal cell membrane, creating pores that lead to cell death. The **liposomal formulation** is preferred over the conventional deoxycholate form because it allows for higher dosing with significantly reduced nephrotoxicity and better penetration into the central nervous system. **Analysis of Incorrect Options:** * **Voriconazole:** This is the drug of choice for Invasive Aspergillosis but has **no activity** against *Mucorales*. Using it in suspected mucormycosis can lead to treatment failure. * **Itraconazole:** While it has some activity against certain fungi, it is ineffective against the species causing mucormycosis. * **Hyperbaric Oxygen:** This is an adjunctive therapy that may inhibit fungal growth in some cases, but it is never a primary treatment or the "drug of choice." **Clinical Pearls for NEET-PG:** * **Risk Factors:** Uncontrolled Diabetes Mellitus (especially Ketoacidosis), neutropenia, and post-transplant immunosuppression. * **Diagnosis:** Definitive diagnosis requires biopsy showing **broad, ribbon-like, non-septate hyphae** with **right-angle (90°) branching**. * **Management Triad:** 1. Aggressive surgical debridement (most critical step), 2. Liposomal Amphotericin B, 3. Control of underlying risk factors (e.g., reversing ketoacidosis). * **Step-down therapy:** Once the patient is stable, oral **Isavuconazole** or **Posaconazole** can be used for maintenance.

Q: What is the recommended post-exposure prophylaxis for HIV?

Raltegravir, Emtricitabine, and Tenofovir. **Explanation:** The current NACO (National AIDS Control Organisation) and WHO guidelines recommend a **triple-drug regimen** for HIV Post-Exposure Prophylaxis (PEP) to ensure maximum efficacy in preventing viral integration. **1. Why Option A is Correct:** The preferred regimen consists of **Tenofovir (TDF) 300 mg + Emtricitabine (FTC) 200 mg** (or Lamivudine) once daily, combined with **Raltegravir (RAL) 400 mg** twice daily (or Dolutegravir 50 mg once daily). This combination is favored because it is highly effective, has a superior safety profile, and involves minimal drug-drug interactions compared to older protease inhibitor-based regimens. **2. Analysis of Incorrect Options:** * **Option B:** This was an older regimen. Indinavir is rarely used now due to significant side effects like nephrolithiasis and metabolic disturbances. * **Option C:** Abacavir is not used in PEP due to the risk of life-threatening hypersensitivity reactions (associated with HLA-B*5701), which requires genetic testing before initiation—a delay not feasible in emergency PEP. * **Option D:** Maraviroc is an entry inhibitor (CCR5 antagonist) and is not part of the standard first-line PEP protocol; it requires a tropism assay before use. **High-Yield Clinical Pearls for NEET-PG:** * **Timing:** PEP should be started as soon as possible, ideally within **2 hours**, and no later than **72 hours** post-exposure. * **Duration:** The total duration of PEP treatment is **28 days**. * **Baseline Testing:** Always perform a baseline HIV test for the exposed individual to rule out pre-existing infection. * **Preferred Integrase Inhibitor:** While Raltegravir is a standard answer, **Dolutegravir (DTG)** is now increasingly preferred in many updated guidelines due to its once-daily dosing.

Question 1

A 65-year-old man presented with skin lesions six weeks after returning from a vacation in Belize, which included time spent at the beach and in the rainforest. What is the diagnosis?

Accepted Answer

Bot fly

Answer

Cutaneous leishmaniasis

Answer

Onchocerciasis

Answer

Plague

Question 2

Which of the following statements are true regarding tuberculous meningitis?

Accepted Answer

CSF is stored at 4°C during transportation; Hydrocephalus is a common sequela; Meningoencephalitis is a common manifestation.

Answer

Exudates are formed on the convexities of the brain; CSF is stored at 4°C during transportation; Hydrocephalus is a common sequela; Meningoencephalitis is a common manifestation.

Answer

Exudates are formed on the convexities of the brain; Meningoencephalitis is a common manifestation.

Answer

CSF is stored at 4°C during transportation; Meningoencephalitis is a common manifestation.

Question 3

An HIV patient developed goiter. On examination, there was non-tender diffuse enlargement of the thyroid. All of the following can be causes of this condition, except:

Accepted Answer

Aspergillus

Answer

Toxoplasma

Answer

Cryptococcus

Answer

Pneumocystis

Question 4

A patient presents with lower gastrointestinal bleeding. Sigmoidoscopy shows ulcers in the sigmoid. Biopsy from this area shows flask-shaped ulcers. Which of the following is the most appropriate treatment?

Accepted Answer

Intravenous metronidazole

Answer

Intravenous ceftriaxone

Answer

Intravenous steroids and sulphasalazine

Answer

Hydrocortisone enemas

Question 5

What is the recommended duration of treatment for multidrug-resistant tuberculosis (MDR-TB)?

Accepted Answer

16-24 months

Answer

8-12 months

Answer

12-16 months

Answer

2-3 years

Question 6

Which of the following is NOT a characteristic feature of cerebral malaria?

Accepted Answer

Bloody cerebrospinal fluid

Answer

Retinal hemorrhages

Answer

Extensor plantar reflex

Answer

Absent abdominal reflex

Question 7

Which of the following organisms is known to cause endocarditis?

Accepted Answer

HACEK

Answer

Coxiella

Answer

Chlamydia

Answer

Salmonella

Question 8

A 20-year-old male presents with fever and chronic cough. His ESR is 35 mm. Sputum cytology is negative for AFB, and a tuberculin test shows indurations of 19 x 23 mm. What is the probable diagnosis?

Accepted Answer

Pulmonary tuberculosis

Answer

Fungal pneumonia

Answer

Viral pneumonia

Answer

Bacterial pneumonia

Question 9

What is the drug of choice for craniofacial mucormycosis?

Accepted Answer

Liposomal amphotericin B

Answer

Voriconazole

Answer

Hyperbaric oxygen

Answer

Itraconazole

Question 10

What is the recommended post-exposure prophylaxis for HIV?

Accepted Answer

Raltegravir, Emtricitabine, and Tenofovir

Answer

Zidovudine, Lamivudine, and Indinavir

Answer

Zidovudine, Lamivudine, and Abacavir

Answer

Raltegravir, Emtricitabine, and Maraviroc

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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