Infectious Diseases Practice Questions

Q: A person presents with difficulty of breathing and a CD-4 count of 200. What is the most probable diagnosis?

Pneumocystis pneumonia. **Explanation:** The clinical presentation of dyspnea in an immunocompromised patient with a **CD4 count of 200 cells/mm³** strongly points toward **Pneumocystis pneumonia (PCP)**, caused by *Pneumocystis jirovecii*. **Why Pneumocystis pneumonia is correct:** PCP is the most common opportunistic infection in patients with HIV when the CD4 count falls below **200 cells/mm³** [1]. It typically presents with a subacute onset of progressive dyspnea, non-productive cough, and low-grade fever. A hallmark feature is **exertional desaturation** (hypoxia out of proportion to radiologic findings). **Analysis of Incorrect Options:** * **Tuberculosis (A):** While common in HIV, TB can occur at **any CD4 count**. However, at CD4 >200, it usually presents with typical cavitary lesions. PCP is the more "classic" association specifically at the 200 threshold [1]. * **Histoplasmosis (B):** This fungal infection usually occurs when the CD4 count drops below **150 cells/mm³**. It often presents with systemic features like hepatosplenomegaly or lymphadenopathy. * **Candidiasis (C):** Mucocutaneous candidiasis (thrush) occurs at CD4 <250, but **Esophageal Candidiasis** (an AIDS-defining illness) typically occurs at CD4 <100. It presents with odynophagia rather than primary respiratory distress. **High-Yield Clinical Pearls for NEET-PG:** * **Investigation of Choice:** Induced sputum or Bronchoalveolar Lavage (BAL) with **Gomori Methenamine Silver (GMS)** stain showing "crushed ping-pong ball" cysts [1]. * **Radiology:** Characterized by bilateral perihilar **"ground-glass opacities."** * **Treatment:** High-dose **Trimethoprim-Sulfamethoxazole (TMP-SMX)** [1]. * **Steroid Indication:** Add corticosteroids if $PaO_2 35$ mmHg to prevent inflammatory worsening [1]. * **Prophylaxis:** Started when CD4 count is **< 200 cells/mm³**.

Q: All are risk factors for antituberculosis treatment related hepatotoxicity, EXCEPT?

HBeAg negative hepatitis B. Antituberculosis therapy (ATT)-induced hepatotoxicity is a common and potentially serious adverse effect, primarily associated with Isoniazid (INH), Rifampicin, and Pyrazinamide. [1] **Why HBeAg negative hepatitis B is the correct answer:** While chronic viral hepatitis (HBV and HCV) is a well-established risk factor for ATT-induced liver injury, the risk is specifically associated with **chronic carriers** or those with **active viral replication**. HBeAg (Hepatitis B e-antigen) is a marker of high viral replication and infectivity. Being "HBeAg negative" typically implies a lower viral load and lower replication state (unless it is a precore mutant), making it a less significant risk factor compared to active hepatitis or other systemic factors. [2] **Analysis of Incorrect Options:** * **CYP2E1 status:** Polymorphisms in the Cytochrome P450 2E1 gene (especially the c1/c1 genotype) are linked to increased production of hepatotoxic metabolites of INH, significantly increasing risk. * **HLA haplotype associations:** Genetic predisposition plays a major role. Specific HLA alleles (e.g., HLA-B*52, HLA-DQA1*0102, and HLA-DQB1*0502) have been strongly associated with an increased susceptibility to ATT-induced hepatotoxicity. * **Female gender:** Epidemiological studies consistently show that females are at a higher risk for developing drug-induced liver injury (DILI) from ATT compared to males. **High-Yield Clinical Pearls for NEET-PG:** * **Most hepatotoxic drug:** Pyrazinamide (PZA) > Isoniazid (INH) > Rifampicin (RIF). * **Other Risk Factors:** Age >35 years, malnutrition (low albumin), chronic alcohol consumption, and "Slow Acetylator" status (NAT2 polymorphism). * **Management Rule:** Discontinue ATT if Serum Bilirubin >1.5 mg/dL or if Transaminases are >3 times the upper limit of normal (with symptoms) or >5 times (if asymptomatic). [1]

Q: Which of the following is not used in post-exposure prophylaxis for HIV?

Acyclovir. **Explanation:** The correct answer is **D. Acyclovir**. **1. Why Acyclovir is the correct answer:** Post-Exposure Prophylaxis (PEP) for HIV requires the use of **Antiretroviral Therapy (ART)** to prevent the integration of HIV into the host genome. Acyclovir is an **anti-herpetic antiviral** drug that inhibits DNA polymerase in Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV). It has no inhibitory activity against HIV (a retrovirus) and therefore plays no role in HIV prophylaxis. **2. Analysis of Incorrect Options:** * **A. Zidovudine + Lamivudine:** Historically, this dual Nucleoside Reverse Transcriptase Inhibitor (NRTI) backbone was the standard "basic regimen" for PEP. While current guidelines prefer Tenofovir, this combination remains a valid HIV treatment/prophylaxis option. * **B. Nelfinavir:** This is a Protease Inhibitor (PI). In older protocols, Nelfinavir was used as the third drug in "expanded regimens" for high-risk exposures. * **C. Stavudine + Didanosine:** Although rarely used now due to toxicity (lactic acidosis/peripheral neuropathy), these are NRTIs that were historically included in PEP protocols. **3. High-Yield Clinical Pearls for NEET-PG:** * **Ideal Timing:** PEP should be started as soon as possible, ideally within **2 hours**, and no later than **72 hours** after exposure. * **Duration:** The standard duration for PEP is **28 days**. * **Current WHO/NACO Preferred Regimen:** The current "all-in-one" preferred regimen is **Tenofovir (TDF) + Lamivudine (3TC) + Dolutegravir (DTG)**. * **Baseline Testing:** Always perform a baseline HIV test on the exposed individual to ensure they are not already HIV-positive before starting PEP.

Q: Which of the following drugs is NOT used in the treatment of candidiasis?

Ketoconazole. ### Explanation The correct answer is **Ketoconazole**. **1. Why Ketoconazole is the correct answer:** While Ketoconazole is an antifungal agent belonging to the imidazole class, it is **no longer used for the systemic treatment of Candidiasis**. This is due to its significant side-effect profile, specifically **severe hepatotoxicity** and its tendency to cause **adrenal insufficiency** by inhibiting steroidogenesis (CYP450 inhibition) [1]. In modern clinical practice, its use is largely restricted to topical formulations (e.g., shampoos for seborrheic dermatitis) or specifically for managing Cushing’s syndrome [1]. **2. Why the other options are incorrect:** * **Fluconazole:** This is the first-line agent for many forms of candidiasis (e.g., esophageal, vaginal, and urinary tract infections) due to its excellent bioavailability and safety profile [1]. * **Itraconazole:** Used as an alternative for mucosal candidiasis, especially in cases where there is resistance to fluconazole, though it has more erratic absorption. * **Voriconazole:** A second-generation triazole with a broad spectrum. It is highly effective against *Candida* species, including some fluconazole-resistant strains like *Candida krusei* [2]. **3. NEET-PG High-Yield Clinical Pearls:** * **Drug of Choice (DOC):** For **Invasive Candidiasis** in hemodynamically unstable patients, **Echinocandins** (e.g., Caspofungin, Micafungin) are now the preferred first-line agents over azoles [2]. * **Resistance Pattern:** *Candida krusei* is inherently resistant to Fluconazole. *Candida glabrata* often shows dose-dependent susceptibility or resistance. * **Side Effect Highlight:** Ketoconazole causes **Gynecomastia** and decreased libido in males because it inhibits the synthesis of testosterone [1]. * **Newer Agent:** **Ibrexafungerp** is a first-in-class triterpenoid antifungal recently approved for vulvovaginal candidiasis.

Q: Which one of the following is typically associated with the given clinical finding?

Treatment with a sulfonylurea. ***Treatment with a sulfonylurea*** - **Diabetes mellitus** is the most typical association with **rhinocerebral mucormycosis**, accounting for approximately **70% of cases**. - **Sulfonylureas** are antidiabetic medications indicating underlying diabetes, which creates the **hyperglycemic** and **acidotic** environment that favors **Mucor** growth. *Bulimia nervosa* - Not a recognized risk factor for **mucormycosis** as it doesn't create the immunocompromised state necessary for fungal invasion. - Primarily associated with **dental erosion** and **electrolyte imbalances**, not opportunistic fungal infections. *Recent endotracheal intubation* - While trauma can predispose to infections, **endotracheal intubation** is not a classic risk factor for **mucormycosis**. - More commonly associated with **bacterial pneumonia** or **aspiration pneumonia** rather than invasive fungal infections. *Acquired immunodeficiency syndrome (AIDS)* - Although **AIDS** can predispose to mucormycosis, it is **less commonly** the typical association compared to diabetes. - **AIDS patients** are more prone to **Candida**, **Cryptococcus**, and **Pneumocystis** infections rather than mucormycosis.

Q: What is the common presenting symptom of Pneumocystis jirovecii pneumonia?

Breathlessness. **Explanation:** *Pneumocystis jirovecii* pneumonia (PCP) is a classic opportunistic infection, most commonly seen in patients with HIV/AIDS (typically when CD4 counts fall below 200 cells/µL) or those on chronic immunosuppressants. **Why Breathlessness is Correct:** The hallmark presentation of PCP is a **triad of progressive exertional dyspnea (breathlessness), dry cough, and fever.** The underlying pathophysiology involves the organism causing alveolar damage and impaired gas exchange, leading to significant hypoxemia [1]. A characteristic clinical finding is "desaturation on exertion," where a patient’s oxygen levels drop significantly even with minimal physical activity. Diagnosis and management often involve silver stains, broncho-alveolar lavage, and high-dose co-trimoxazole [1]. **Analysis of Incorrect Options:** * **A. Cavity on X-ray:** PCP typically presents with **bilateral, diffuse interstitial infiltrates** (ground-glass opacities) [1]. Cavitation is rare in PCP and should raise suspicion for Tuberculosis, Fungal infections (Aspergillus), or *Staphylococcus aureus*. * **B. Hemoptysis:** This is not a feature of PCP. Hemoptysis is more commonly associated with Pulmonary TB, Bronchiectasis, or Pulmonary Infarction. * **D. Purulent Sputum:** The cough in PCP is characteristically **non-productive (dry)**. Purulent sputum suggests a bacterial pneumonia (e.g., *Streptococcus pneumoniae*). **High-Yield Clinical Pearls for NEET-PG:** * **Investigation of Choice:** Bronchoalveolar Lavage (BAL) is the most sensitive diagnostic tool [1]. * **Staining:** Silver stains (Gomori Methenamine Silver - GMS) or Toluidine blue are used to identify the cysts [1]. * **Drug of Choice:** Trimethoprim-Sulfamethoxazole (TMP-SMX) [1]. * **Steroid Indication:** Add corticosteroids if PaO2 35 mmHg to prevent inflammatory worsening [1]. * **Radiology:** "Bat-wing" appearance or ground-glass opacities on HRCT.

Question 1

Which of the following infections does NOT typically cause acute hepatic and renal failure?

Accepted Answer

Shigellosis

Answer

Leptospirosis

Answer

Malaria

Answer

Hantavirus

Question 2

A person presents with difficulty of breathing and a CD-4 count of 200. What is the most probable diagnosis?

Accepted Answer

Pneumocystis pneumonia

Answer

Tuberculosis

Answer

Histoplasmosis

Answer

Candidiasis

Question 3

Following extraction of an upper central incisor, a patient develops ophthalmoplegia, meningitis, and lateral rectus paralysis. What is the most likely diagnosis?

Accepted Answer

Cavernous sinus thrombosis

Answer

Not related

Answer

Cellulitis

Answer

Ludwig's angina

Question 4

All are risk factors for antituberculosis treatment related hepatotoxicity, EXCEPT?

Accepted Answer

HBeAg negative hepatitis B

Answer

CYP2E1 status

Answer

HLA haplotype associations

Answer

Female gender

Question 5

What is the most common hematologic finding associated with pulmonary tuberculosis?

Accepted Answer

Mild anemia, leukocytosis, thrombocytosis with slightly elevated ESR

Answer

Mild anemia, leukopenia, thrombocytopenia with marked elevation in ESR

Answer

Mild anemia, Leukocytosis, Thrombocytopenia with marked elevation in ESR

Answer

Mild anemia leukocytosis, thrombocytosis with normal ESR

Question 6

A 35-year-old man developed a lesion on his chest during treatment for a respiratory tract infection. What is the diagnosis?

Accepted Answer

Fixed drug eruption

Answer

Acute urticaria

Answer

Drug-induced pemphigus

Answer

Erythema annulare

Question 7

Which of the following is not used in post-exposure prophylaxis for HIV?

Accepted Answer

Acyclovir

Answer

Zidovudine + Lamivudine

Answer

Nelfinavir

Answer

Stavudine + Didanosine

Question 8

Which of the following drugs is NOT used in the treatment of candidiasis?

Accepted Answer

Ketoconazole

Answer

Itraconazole

Answer

Voriconazole

Answer

Fluconazole

Question 9

Which one of the following is typically associated with the given clinical finding?

Accepted Answer

Treatment with a sulfonylurea

Answer

Bulimia nervosa

Answer

Recent endotracheal intubation

Answer

Acquired immunodeficiency syndrome (AIDS)

Question 10

What is the common presenting symptom of Pneumocystis jirovecii pneumonia?

Accepted Answer

Breathlessness

Answer

Cavity on X-ray

Answer

Hemoptysis

Answer

Purulent sputum

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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