Infectious Diseases Practice Questions

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: Which pathogenic organism is responsible for the causation of Donovaniasis?

Calymmatobacterium granulomatis. Donovaniasis, also known as Granuloma Inguinale, is a chronic, progressive bacterial infection of the genital and perianal skin [1]. 1. Why Option B is correct: The causative agent is Calymmatobacterium granulomatis (now reclassified as Klebsiella granulomatis). It is a Gram-negative, pleomorphic, intracellular bacterium. The hallmark of this disease is the presence of Donovan bodies—safety-pin-shaped organisms seen within the cytoplasm of large mononuclear cells (macrophages) on Giemsa or Wright stain [1]. Clinically, it presents as painless, beefy-red, velvety ulcers that bleed easily on touch (friable) and lack regional lymphadenopathy (pseudobuboes may occur) [1]. 2. Why the other options are incorrect: Option A (Chlamydia trachomatis): Serotypes L1, L2, and L3 cause Lymphogranuloma Venereum (LGV), characterized by painful lymphadenopathy (Groove sign) [1]. Option C (Haemophilus ducreyi): This causes Chancroid, which presents as painful, soft ulcers with ragged edges and painful inguinal buboes [1]. Option D (Herpes simplex virus): HSV-2 typically causes painful, multiple, vesicular lesions that recur. High-Yield Clinical Pearls for NEET-PG: Clinical triad: Painless ulcer + Beefy red appearance + No true lymphadenopathy. Diagnosis: Tissue smear/crush biopsy showing Donovan bodies (Safety-pin appearance). Drug of Choice: Azithromycin (1g orally once a week or 500mg daily) for at least 3 weeks or until lesions heal. Pseudobubo: Granulomatous process in the inguinal folds that mimics a bubo but is not true lymph node involvement [1].

Q: What is the most common opportunistic infection in HIV patients globally?

Pneumocystis jiroveci. **Explanation:** **Pneumocystis jiroveci pneumonia (PCP)** is historically and clinically recognized as the most common opportunistic infection (OI) defining AIDS globally [1]. While the incidence has decreased with the advent of Highly Active Antiretroviral Therapy (HAART) and trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis, it remains the leading opportunistic respiratory infection in patients with CD4 counts below 200 cells/mm³ [1]. **Analysis of Options:** * **A. Pneumocystis jiroveci (Correct):** It is the most frequent "defining" OI. It typically presents with a subacute onset of fever, non-productive cough, and exertional dyspnea. * **B. Candida species:** While oral candidiasis (thrush) is the most common *fungal* infection in HIV patients, it is often considered a "minor" OI or a precursor to more severe immunosuppression [1]. Esophageal candidiasis is the AIDS-defining condition but is less frequent than PCP. * **C. Mycobacterium tuberculosis:** TB is the most common cause of *death* among HIV patients globally and the most common cause of admission in countries with high incidence [1]. However, in global standardized examinations, PCP is traditionally cited as the most common opportunistic infection. * **D. Cryptococcus species:** *Cryptococcus neoformans* is the most common cause of opportunistic meningitis but is less prevalent than PCP or TB. **High-Yield Clinical Pearls for NEET-PG:** 1. **CD4 Thresholds:** PCP (<200), Toxoplasmosis (<100), MAC and CMV ( 35 mmHg to prevent paradoxical worsening [1].

Q: Hand, foot, and mouth disease is characterized by which of the following?

Causing mini-epidemics in schools. Hand, Foot, and Mouth Disease (HFMD) is a highly contagious viral illness primarily affecting children under 5 years of age. **1. Why Option A is Correct:** HFMD is notorious for causing **mini-epidemics in schools**, daycare centers, and summer camps [1]. Because the virus spreads through direct contact with nasal secretions, saliva, blister fluid, and the fecal-oral route, the close proximity of children in educational settings facilitates rapid outbreaks. **2. Analysis of Incorrect Options:** * **Option B:** The incubation period is typically **3 to 6 days**, not 3-10 days [1]. While this seems close, in competitive exams like NEET-PG, the standard textbook range (3-6 days) is preferred. * **Option C:** While HFMD is indeed caused by a virus (Coxsackievirus A16 and Enterovirus 71), this is a general characteristic [1]. In the context of multiple-choice questions, "causing mini-epidemics" is considered the more specific epidemiological hallmark of the disease. * **Option D:** HFMD in humans is **unrelated** to Foot-and-Mouth Disease (FMD) in cattle. FMD is caused by an Aphthovirus and does not infect humans; the two diseases are clinically and etiologically distinct. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** Most common cause is **Coxsackievirus A16**; the most severe outbreaks (associated with neurological complications/pulmonary edema) are caused by **Enterovirus 71** [1]. * **Clinical Presentation:** Characterized by a prodrome of fever, followed by painful oral vesicles (stomatitis) and a maculopapular or vesicular rash on the palms and soles [1]. * **Seasonality:** Peak incidence occurs in summer and autumn [1]. * **Management:** Treatment is purely supportive (hydration and analgesia) [1].

Q: A 9-year-old boy presents with a severe sore throat, fever, and dysphagia. Physical examination reveals grayish-white papulovesicular lesions on an erythematous base that have ulcerated. The lesions are located on the soft palate, anterior pillars of the tonsils, and uvula, but not on the gingiva, tongue, or lips. A clinical diagnosis of herpangina is made. Which of the following is the most likely causative organism?

Coxsackievirus A. The clinical presentation of fever, sore throat, and characteristic **grayish-white papulovesicular lesions** localized specifically to the **posterior oropharynx** (soft palate, tonsillar pillars, and uvula) is diagnostic of **Herpangina**. [1] 1. **Why Coxsackievirus A is correct:** Herpangina is most commonly caused by **Coxsackievirus Group A** (specifically types A1–A10, A12, and A22). The hallmark of this infection is the anatomical distribution of the ulcers; they are confined to the posterior structures of the mouth and spare the anterior oral cavity (lips, tongue, and gingiva). [1] 2. **Why other options are incorrect:** * **HSV-1:** Causes **Gingivostomatitis**. Unlike Herpangina, HSV-1 lesions typically involve the **anterior** mouth, including the gingiva (gums), lips (herpes labialis), and the tongue. * **Measles:** Associated with **Koplik spots**, which are bluish-white spots on an erythematous base found on the **buccal mucosa** opposite the lower molars, usually appearing during the prodromal phase. * **Rubella:** May present with **Forchheimer spots** (petechiae on the soft palate), but these are not ulcerative vesicles and are accompanied by prominent post-auricular lymphadenopathy. **NEET-PG High-Yield Pearls:** * **Herpangina vs. Hand-Foot-Mouth Disease (HFMD):** Both are caused by Coxsackievirus A (A16 is common for HFMD). HFMD includes the posterior pharyngeal lesions plus vesicles on the palms, soles, and buttocks. [1] * **Seasonality:** These infections typically peak in **summer and early autumn**. [1] * **Management:** Treatment is purely supportive (hydration and analgesics) as the condition is self-limiting. [1]

Q: Cryptococcal meningitis is most common in which of the following patient populations?

Renal transplant recipients. **Explanation:** **1. Why Renal Transplant Recipients is Correct:** *Cryptococcus neoformans* is an opportunistic encapsulated yeast that primarily affects patients with **defective cell-mediated immunity (CMI)** [1]. Renal transplant recipients are at high risk because their immunosuppressive regimen (e.g., corticosteroids, calcineurin inhibitors) specifically targets T-cell function. Among solid organ transplant recipients, *Cryptococcus* is the third most common invasive fungal infection and has a high predilection for the Central Nervous System (CNS) [1]. **2. Why Other Options are Incorrect:** * **B & D (Agammaglobulinemia and IgA deficiency):** These are **humoral (B-cell) immunity** defects. While antibodies play a minor role in opsonization, the primary defense against *Cryptococcus* is macrophage activation by T-helper cells (Th1 response). Patients with B-cell defects are more prone to sinopulmonary infections by encapsulated bacteria (e.g., *S. pneumoniae*). * **C (Neutropenia):** Neutrophils are the primary defense against molds like *Aspergillus* and *Mucor*. While neutrophils do participate in the early response to fungi, *Cryptococcus* is classically associated with T-cell deficits (HIV/AIDS, transplants, lymphomas) rather than isolated neutropenia. **Clinical Pearls for NEET-PG:** * **Most Common Cause:** *Cryptococcus* is the most common cause of fungal meningitis worldwide. * **Diagnosis:** The most sensitive screening test is the **Cryptococcal Antigen (CrAg)** in CSF or serum (Lateral Flow Assay). * **Microscopy:** **India Ink** preparation shows a "halolike" unstained capsule. * **Culture:** Grows on **Sabouraud Dextrose Agar (SDA)**; colonies appear creamy/mucoid. It is urease positive. * **Treatment:** Induction with **Amphotericin B + Flucytosine**, followed by maintenance with Fluconazole. * **CSF Finding:** Characteristically shows high opening pressure and low glucose.

Q: Which of the following statements regarding hepatitis C infection is true?

Hepatitis C is highly likely to cause chronic infection.. **Explanation:** **Hepatitis C Virus (HCV)** is a major cause of chronic liver disease worldwide. The correct answer is **B** because HCV is notorious for its high rate of chronicity. Unlike Hepatitis B, where only 5–10% of infected adults develop chronic disease [2], approximately **75%–85% of patients** infected with HCV fail to clear the virus and progress to chronic infection. **Analysis of Options:** * **Option A is incorrect:** Most acute HCV infections (approx. 80%) are **asymptomatic** or subclinical [1]. Patients rarely present with jaundice or fulminant hepatic failure during the initial phase, which often leads to a delayed diagnosis. * **Option C is incorrect:** HCV is primarily a **blood-borne pathogen**. Transmission occurs via IV drug use (most common), needle-stick injuries [1], or blood transfusions (pre-1992). Transmission via raw oysters is characteristic of **Hepatitis A or E** (fecal-oral route) [3]. * **Option D is incorrect:** HCV is a single-stranded, enveloped **RNA virus** belonging to the *Flaviviridae* family. **High-Yield NEET-PG Pearls:** * **Screening & Diagnosis:** The first-line test is **Anti-HCV antibody**. Confirmation of active infection requires **HCV RNA** (PCR) [1]. * **Extrahepatic Manifestations:** HCV is strongly associated with **Mixed Cryoglobulinemia**, Membranoproliferative Glomerulonephritis (MPGN), and Porphyria Cutanea Tarda. * **Treatment:** The current standard of care involves **Direct-Acting Antivirals (DAAs)** like Sofosbuvir, which achieve a Sustained Virologic Response (SVR) in >95% of cases. * **Complications:** Chronic HCV is a leading indication for liver transplantation and a major risk factor for **Hepatocellular Carcinoma (HCC)**.

Question 1

A 55-year-old man, a kidney transplant recipient of 5 years on tacrolimus and prednisone, presented with a two-day history of headache, fever, and generalized weakness. On neurologic examination, he was confused and incoherent. Cranial nerves were normal, but he had a hazy left retina. Magnetic resonance imaging of the brain with gadolinium showed multiple enhancing lesions in both cerebral hemispheres. The patient had a subretinal abscess; aspirate staining revealed findings suggestive of which of the following?

Accepted Answer

Weakly positive acid-fast bacilli

Answer

Gram-positive cocci

Answer

Gram-negative cocci

Answer

Coccobacillus

Question 2

What is the drug of choice for craniofacial mucormycosis?

Accepted Answer

Liposomal amphotericin B

Answer

Voriconazole

Answer

Hyperbaric oxygen

Answer

Itraconazole

Question 3

A 40-year-old male presented with altered mental status, seizures, and vomiting. He has no history of fever or neck stiffness. On CECT and MRI, a ring-enhancing lesion at the gray-white interface is seen. General hygiene was poor, and he has multiple dental caries. What is the next best step in the management of this patient?

Accepted Answer

Urgent parenteral antibiotics

Answer

Placement of ICP monitor

Answer

Lumbar puncture

Answer

Craniotomy

Question 4

Which pathogenic organism is responsible for the causation of Donovaniasis?

Accepted Answer

Calymmatobacterium granulomatis

Answer

Chlamydia trachomatis

Answer

Haemophilus ducreyi

Answer

Herpes simplex virus

Question 5

What is the most common opportunistic infection in HIV patients globally?

Accepted Answer

Pneumocystis jiroveci

Answer

Candida species

Answer

Mycobacterium tuberculosis

Answer

Cryptococcus species

Question 6

Hand, foot, and mouth disease is characterized by which of the following?

Accepted Answer

Causing mini-epidemics in schools

Answer

Incubation period of 3-10 days

Answer

Transmission by a virus

Answer

Similar clinical features to foot-and-mouth disease in cows

Question 7

A 9-year-old boy presents with a severe sore throat, fever, and dysphagia. Physical examination reveals grayish-white papulovesicular lesions on an erythematous base that have ulcerated. The lesions are located on the soft palate, anterior pillars of the tonsils, and uvula, but not on the gingiva, tongue, or lips. A clinical diagnosis of herpangina is made. Which of the following is the most likely causative organism?

Accepted Answer

Coxsackievirus A

Answer

Measles (Morbillivirus)

Answer

Rubella (Rubivirus)

Answer

Herpes simplex virus-1 (HSV-1)

Question 8

Cryptococcal meningitis is most common in which of the following patient populations?

Accepted Answer

Renal transplant recipients

Answer

Patients with agammaglobulinemia

Answer

Patients with neutropenia

Answer

Patients with IgA deficiency

Question 9

In the course of an epidemic of hepatitis, fulminant hepatitis is most commonly seen in which population group?

Accepted Answer

Children younger than 15 years

Answer

Malnourished children

Answer

Pregnant females

Answer

Elderly individuals

Question 10

Which of the following statements regarding hepatitis C infection is true?

Accepted Answer

Hepatitis C is highly likely to cause chronic infection.

Answer

Most patients experience severe symptoms during their initial infection.

Answer

Hepatitis C is transmitted through the consumption of raw oysters.

Answer

Hepatitis C is a DNA virus.

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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