Infectious Diseases Practice Questions

Q: A 19-year-old male tests positive for hepatitis C infection. He was arrested twice for stealing and belongs to a gang of friends. Which of the following is the most likely method of transmission?

Intravenous drug use. **Explanation:** The correct answer is **D. Intravenous drug use (IVDU).** Hepatitis C Virus (HCV) is primarily a **blood-borne pathogen**. [2] In developed and developing countries alike, the most common risk factor for HCV transmission is the sharing of needles and paraphernalia among intravenous drug users [3]. The clinical vignette provides behavioral clues—history of arrests for theft and gang affiliation—which are high-yield "social markers" in medical exams pointing toward a lifestyle associated with substance abuse and IVDU. **Analysis of Incorrect Options:** * **A. Fecal-oral:** This is the primary route for Hepatitis A and E ("The vowels hit the bowels"). HCV is not transmitted via the fecal-oral route. * **B. Fomite:** HCV is not typically spread through casual contact or inanimate objects (fomites) unless they are contaminated with fresh blood (e.g., shared razors or toothbrushes), but this is significantly less common than IVDU. * **C. Sexual transmission:** While possible, the efficiency of sexual transmission for HCV is remarkably low (unlike HBV or HIV). It is generally only a significant risk factor in individuals with multiple partners or co-infection with HIV. **NEET-PG High-Yield Pearls:** * **Most common cause of post-transfusion hepatitis:** Historically HCV, though now rare due to rigorous screening. * **Chronicity:** HCV has the highest rate of progression to chronic infection (~75–85%) among the hepatitis viruses. * **Screening:** Anti-HCV antibody is the initial screening test; HCV RNA (PCR) is the gold standard for confirming active infection. [1] * **Extrahepatic manifestations:** Essential mixed cryoglobulinemia, Membranoproliferative glomerulonephritis (MPGN), and Porphyria cutanea tarda (PCT).

Q: What is the recommended duration for isolation of a patient with bacterial meningitis?

24 hours after the start of antibiotic treatment. **Explanation:** In cases of bacterial meningitis, particularly those caused by *Neisseria meningitidis* and *Haemophilus influenzae* type b, the primary goal of isolation is to prevent droplet transmission. The correct answer is **24 hours after the start of effective antibiotic treatment** because most pathogenic bacteria are rapidly cleared from the nasopharynx within this timeframe. Once therapeutic levels of antibiotics (such as Ceftriaxone) are achieved, the patient is no longer considered contagious to others. **Analysis of Options:** * **Option A:** Waiting for a negative culture is impractical and unnecessary. Cultures can take 48–72 hours, and patients are typically non-infectious long before results are finalized. * **Option C & D:** Clinical markers like fever subsidence or resolution of neck rigidity are indicators of clinical recovery, not infectivity. A patient may remain symptomatic for several days despite being bacteriologically sterile and non-contagious. **High-Yield Clinical Pearls for NEET-PG:** * **Type of Isolation:** **Droplet Precautions** are mandatory for *N. meningitidis* and *H. influenzae*. For other causes like *S. pneumoniae*, standard precautions usually suffice, but 24-hour isolation is a safe general rule in clinical practice. * **Chemoprophylaxis:** Close contacts of patients with Meningococcal meningitis should receive prophylaxis (Rifampicin, Ciprofloxacin, or Ceftriaxone) as soon as possible. * **Steroids:** Dexamethasone should be administered **before or with the first dose** of antibiotics to reduce the risk of sensorineural hearing loss, especially in *H. influenzae* meningitis.

Q: What is the best treatment for a diabetic patient with the condition described below?

Amphotericin. ***Correct Answer: Amphotericin B*** The image shows **rhinocerebral mucormycosis** — a life-threatening fungal infection caused by *Mucor*, *Rhizopus*, or *Rhizomucor* species, seen characteristically in **poorly controlled diabetic patients** (especially those in diabetic ketoacidosis). **Key clinical features:** - **Black necrotic eschar** on nasal mucosa, hard palate, or periorbital region - Rapid spread to sinuses, orbit, and brain - Strongly associated with **diabetes mellitus** (high glucose + acidosis impairs phagocyte function) **Why Amphotericin B is correct:** - **Drug of choice** for mucormycosis - Liposomal Amphotericin B (L-AmB) is preferred for lower nephrotoxicity - Complete treatment of rhinocerebral mucormycosis requires **urgent surgical debridement** plus **intravenous liposomal amphotericin B** and **reversal of predisposing metabolic abnormalities** (e.g., correction of hyperglycemia and ketoacidosis); amphotericin B alone is not sufficient - Mucorales are **resistant to several azole antifungals** (including ketoconazole, fluconazole, and voriconazole), though isavuconazole and posaconazole do have activity against Mucorales and may be used in certain settings *Incorrect: Ketoconazole* - An azole antifungal — **not effective** against Mucorales; ketoconazole, fluconazole, and voriconazole lack meaningful activity, unlike isavuconazole or posaconazole - Would be appropriate for dermatophytosis or candidiasis, not mucormycosis *Incorrect: Ceftriaxone* - A 3rd-generation cephalosporin (antibiotic) — **no antifungal activity** - Irrelevant for this fungal infection *Incorrect: Vancomycin* - A glycopeptide antibiotic active against Gram-positive bacteria (MRSA, etc.) — **no antifungal activity** - Completely ineffective against Mucorales **Key mnemonic:** "Mucor = Must use Amphotericin — ketoconazole, fluconazole, and voriconazole fail, but isavuconazole and posaconazole have activity!"

Q: Which of the following is the most effective treatment of severe malaria?

Artemisinin-based combination therapy. **Explanation:** The management of malaria is a high-yield topic for NEET-PG. According to the latest WHO and National Vector Borne Disease Control Programme (NVBDCP) guidelines, **Artemisinin-based Combination Therapy (ACT)** is the treatment of choice for severe malaria and uncomplicated *P. falciparum* malaria. **Why ACT is Correct:** Artemisinin derivatives (like Artesunate or Artemether) are the most potent antimalarials. They produce a rapid reduction in parasite biomass and quick clinical resolution. In **severe malaria**, the standard of care is **Intravenous (IV) Artesunate** for at least 24 hours, followed by a full oral course of ACT [1]. ACTs combine a fast-acting artemisinin with a long-acting partner drug (e.g., Lumefantrine, Piperaquine) to ensure complete clearance of remaining parasites and prevent resistance. **Why Other Options are Incorrect:** * **Chloroquine:** Once the gold standard, it is now largely ineffective against *P. falciparum* due to widespread resistance. It remains the drug of choice only for sensitive *P. vivax* cases. * **Primaquine:** This is used primarily for its **gametocidal** action (to prevent transmission) and for **radical cure** (to kill hypnozoites in the liver) in *P. vivax* and *P. ovale*. It is not used as a primary treatment for acute severe malaria. * **Doxycycline:** This is a slow-acting antimalarial used as an adjunct to Quinine or for prophylaxis. It is never used as monotherapy for severe malaria. **High-Yield Clinical Pearls:** * **Drug of Choice for Severe Malaria:** IV Artesunate (preferred over Quinine due to lower risk of hypoglycemia) [1]. * **ACT in Pregnancy:** ACT is now recommended for *P. falciparum* in **all trimesters**, including the first. * **Blackwater Fever:** A complication of *P. falciparum* (and historically Quinine use) characterized by massive intravascular hemolysis and hemoglobinuria.

Q: All the following are characteristics of AIDS when CD4 cell count drops below 100 cells, EXCEPT:

Persistent generalized lymphadenopathy. The progression of HIV/AIDS is characterized by a predictable decline in CD4+ T-cell counts, which correlates with the onset of specific opportunistic infections and malignancies [1]. **Why Option B is the Correct Answer:** **Persistent Generalized Lymphadenopathy (PGL)** is defined as enlarged lymph nodes (>1 cm) in two or more extra-inguinal sites for more than three months. Crucially, PGL is a feature of the **early clinical stage** of HIV infection (WHO Stage 1 or 2), typically occurring when the CD4 count is still relatively preserved (**>500 cells/mm³**) [2]. As the disease progresses to advanced AIDS (CD4 <200), the architecture of the lymph nodes often collapses (lymphocyte depletion), and PGL may actually resolve. **Why the other options are incorrect:** * **CNS Toxoplasmosis (D):** This is the most common cause of space-occupying lesions in AIDS patients [3]. It typically occurs when the CD4 count drops below **100 cells/mm³** [1]. * **Cryptococcal Meningitis (C):** This fungal infection is a major cause of morbidity in AIDS. It is rarely seen unless the CD4 count is **<100 cells/mm³** (often <50). * **Non-Hodgkin Lymphoma (A):** High-grade B-cell lymphomas (like Burkitt’s or Primary CNS Lymphoma) are AIDS-defining illnesses that frequently occur at advanced stages of immunosuppression, typically when CD4 counts are **<100 cells/mm³** [3]. **High-Yield Clinical Pearls for NEET-PG:** * **CD4 <200:** *Pneumocystis jirovecii* pneumonia (PCP). * **CD4 <100:** Toxoplasmosis, Cryptococcosis, Cryptosporidiosis. * **CD4 <50:** *Mycobacterium avium* complex (MAC), CMV Retinitis, and Primary CNS Lymphoma. * **Prophylaxis:** Trimethoprim-Sulfamethoxazole (TMP-SMX) is started when CD4 <200 to prevent PCP and Toxoplasmosis [3].

Q: A young unvaccinated patient presents to the OPD with fever, cough, coryza, and red eyes. On examination, a maculopapular rash beginning on the face and spreading cephalocaudally down the trunk and extremities is observed. What is the most likely complication expected with this condition?

Pneumonia. ***Pneumonia*** - **Measles** (rubeola) most commonly causes **pneumonia** as its leading cause of measles-related mortality, occurring in both children and immunocompromised patients. - The clinical presentation of **fever**, **cough**, **coryza**, **conjunctivitis** (red eyes), and **cephalocaudal maculopapular rash** in an unvaccinated patient is classic for measles. - Pneumonia in measles may be due to direct viral involvement or secondary bacterial superinfection (e.g., *Streptococcus pneumoniae*, *Staphylococcus aureus*). *Myocarditis* - **Myocarditis** is a rare recognized complication of **measles** (rubeola), seen especially in adults and immunocompromised patients. - It is not the most likely or most common complication expected in a typical measles case. *Pancreatitis* - **Pancreatitis** is a well-known complication of **mumps**, not measles. - Measles primarily affects the **respiratory system**, **skin**, and can cause **cardiac** and **neurological** complications. *Orchitis* - **Orchitis** is a classic complication of **mumps** infection, occurring in post-pubertal males. - Measles is characterized by the **3 C's** (cough, coryza, conjunctivitis) with **cephalocaudal rash progression**, not mumps symptoms.

Q: Which of the following laboratory markers characterizes the recumbent stage of Hepatitis B?

Anti HBc. ### Explanation The "recumbent stage" (also known as the **Window Period**) of Hepatitis B is a critical diagnostic phase where HBsAg has disappeared from the blood, but Anti-HBs antibodies have not yet reached detectable levels [1]. **1. Why Anti-HBc is Correct:** During the window period, the only reliable serological marker of a recent HBV infection is **Anti-HBc IgM** (Antibody to Hepatitis B core antigen) [1]. Since HBsAg is negative and Anti-HBs is not yet present, testing for Anti-HBc is the only way to diagnose an acute infection during this gap [1]. **2. Why the Other Options are Incorrect:** * **Anti-HBs Ag:** This antibody appears during the **recovery/convalescence phase** and signifies immunity (either via natural infection or vaccination) [1]. In the recumbent stage, it is still below detectable limits. * **Anti-HBe Ag:** This indicates a decrease in viral replication and infectivity. While it may appear early, it is not the definitive marker used to define the window period. * **Anti-HBV:** This is a non-specific term. Diagnostic protocols specifically look for antibodies against specific components (Surface, Core, or e-antigen) rather than a generic "Anti-HBV." **3. NEET-PG High-Yield Pearls:** * **Window Period Markers:** HBsAg (-), Anti-HBs (-), **Anti-HBc IgM (+)** [1]. * **HBsAg:** The first marker to appear in blood (as early as 1–2 weeks post-exposure) [1]. * **Anti-HBs:** The only marker present in a **vaccinated** individual (Anti-HBc will be negative in vaccinated persons) [1]. * **Chronic Infection:** Defined by the persistence of HBsAg for >6 months [1]. * **HBeAg:** Indicates high viral replication and maximum infectivity.

Q: What is the true statement regarding the treatment of hepatic amoebiasis?

Mostly treated conservatively. **Explanation:** Amoebic Liver Abscess (ALA), caused by *Entamoeba histolytica*, is the most common extra-intestinal manifestation of amoebiasis. **Why Option C is correct:** The mainstay of treatment for ALA is **medical management**. Over 90-95% of patients respond dramatically to nitroimidazoles (e.g., **Metronidazole** 750 mg TID for 7-10 days). Surgical intervention or aspiration is rarely required and is reserved for specific complications like imminent rupture, lack of clinical response within 48-72 hours, or very large left-lobe abscesses. **Why other options are incorrect:** * **Option A:** ALA is significantly **more common in males** (ratio approx. 10:1), likely due to the protective effect of menstrual blood loss (iron deficiency inhibits amoebic growth) and higher alcohol consumption in men. * **Option B:** In approximately 70-80% of cases, ALA presents as a **solitary lesion**, most commonly located in the **right lobe** (posterosuperior segment) due to the bulk of the liver and the streaming effect of portal blood flow. * **Option C:** Jaundice is **uncommon** in uncomplicated ALA. If present, it usually indicates a massive abscess compressing the biliary tree or secondary bacterial infection. **Clinical Pearls for NEET-PG:** * **Classic Presentation:** Fever with right upper quadrant pain and "anchovy sauce" (chocolate brown) pus on aspiration. * **Diagnosis:** Ultrasound is the initial investigation; Serology (IHA/ELISA) is highly sensitive. * **Indications for Aspiration:** Large size (>10 cm), failure of medical therapy, left lobe abscess (risk of rupture into the pericardium), or to rule out a pyogenic abscess.

Q: A 55-year-old diabetic female patient presented with facial pain, numbness, conjunctival suffusion, and blurring of vision for 6 days. She was managed conservatively and discharged. After a week, she presented again with bilateral proptosis, chemosis, vision loss, and ophthalmoplegia, along with a characteristic lesion on the nose. A smear was prepared from the nasal lesion. What is the most appropriate initial management for a suspected fungal infection causing these symptoms?

Amphotericin B. ### Explanation **Diagnosis: Rhino-Orbito-Cerebral Mucormycosis (ROCM)** The clinical presentation of a diabetic patient with facial pain, proptosis, ophthalmoplegia, and a "characteristic lesion on the nose" (likely a black eschar) is classic for **Mucormycosis** [1]. This is an aggressive, angioinvasive fungal infection caused by fungi of the order Mucorales [1]. #### 1. Why Amphotericin B is Correct **Liposomal Amphotericin B** is the drug of choice and the first-line medical management for Mucormycosis [1]. It acts by binding to ergosterol in the fungal cell membrane, creating pores that lead to cell death. In ROCM, rapid initiation of high-dose Amphotericin B, along with aggressive surgical debridement and control of underlying risk factors (like diabetic ketoacidosis), is life-saving [1]. #### 2. Why Other Options are Incorrect * **B. Posaconazole:** While active against Mucorales, it is typically used as **salvage therapy** for patients intolerant to Amphotericin B or as step-down maintenance therapy. It is not the initial drug of choice for acute, fulminant disease. * **C. Itraconazole:** This azole has **no significant activity** against Mucorales. It is primarily used for Histoplasmosis, Blastomycosis, or Sporotrichosis. * **D. Caspofungin:** Echinocandins have **no activity** against Mucorales (which lack the target 1,3-β-D-glucan in their cell walls) [2]. They are used for Candida and Aspergillus infections [2]. #### 3. NEET-PG High-Yield Pearls * **Risk Factors:** Uncontrolled Diabetes Mellitus (especially DKA), neutropenia, and iron overload (deferoxamine use) [1]. * **Microscopy:** Look for **broad, ribbon-like, aseptate hyphae** with **right-angle (90°) branching**. * **Black Eschar:** Caused by tissue infarction due to the fungus invading blood vessels (angioinvasion) [1]. * **Radiology:** "Reverse Halo Sign" on chest CT is highly suggestive of pulmonary involvement.

Q: A 40-year-old man presents with fever, weight loss, and cough. His Mantoux test result is 18 x 19 mm, and sputum cytology is negative for Acid-Fast Bacilli (AFB). What is the most likely condition?

Pulmonary Tuberculosis. **Explanation:** The clinical presentation of fever, weight loss, and chronic cough in a 40-year-old male is a classic "constitutional" triad highly suggestive of **Pulmonary Tuberculosis (PTB)** [1]. 1. **Why the correct answer is right:** The **Mantoux test (TST)** result of 18 x 19 mm is strongly positive (induration >10 mm is significant in endemic areas like India) [2]. While a negative sputum smear for AFB does not rule out TB, it simply indicates a "paucibacillary" state or poor sample quality [3]. In clinical practice, if the clinical suspicion is high and the Mantoux is strongly positive, PTB remains the most likely diagnosis, often requiring further evaluation via Sputum CBNAAT (GeneXpert) or culture. 2. **Why other options are incorrect:** * **Pneumococcal Pneumonia:** Typically presents with acute onset high-grade fever, productive cough with rusty sputum, and leukocytosis, rather than chronic weight loss. * **Cryptococcal Infection:** Usually seen in immunocompromised patients (e.g., HIV/AIDS). While it can cause weight loss, it is far less common than TB in the general population. * **Viral Infection:** These are usually self-limiting, acute illnesses (lasting 1–2 weeks) and would not cause significant weight loss or a strongly positive Mantoux test. **Clinical Pearls for NEET-PG:** * **Mantoux Interpretation:** An induration of **≥15 mm** is considered positive in individuals with no known risk factors; **≥10 mm** is positive in high-prevalence areas or healthcare workers. * **Sputum Smear Sensitivity:** Conventional Ziehl-Neelsen (ZN) staining requires roughly 5,000–10,000 bacilli/ml to be positive [3]. A negative smear **never** excludes TB. * **Gold Standard:** Sputum culture (Liquid culture/MGIT) remains the gold standard for diagnosis, while **CBNAAT** is the preferred initial diagnostic test under NTEP guidelines.

Question 1

A 19-year-old male tests positive for hepatitis C infection. He was arrested twice for stealing and belongs to a gang of friends. Which of the following is the most likely method of transmission?

Accepted Answer

Intravenous drug use

Answer

Fecal-oral

Answer

Fomite

Answer

Sexual transmission

Question 2

What is the recommended duration for isolation of a patient with bacterial meningitis?

Accepted Answer

24 hours after the start of antibiotic treatment

Answer

Until the bacterial culture is negative

Answer

7 days after the subsidence of fever

Answer

3 days after the resolution of neck rigidity

Question 3

What is the best treatment for a diabetic patient with the condition described below?

Accepted Answer

Amphotericin

Answer

Ceftriaxone

Answer

Ketoconazole

Answer

Vancomycin

Question 4

Which of the following is the most effective treatment of severe malaria?

Accepted Answer

Artemisinin-based combination therapy

Answer

Chloroquine

Answer

Primaquine

Answer

Doxycycline

Question 5

All the following are characteristics of AIDS when CD4 cell count drops below 100 cells, EXCEPT:

Accepted Answer

Persistent generalized lymphadenopathy

Answer

Non-Hodgkin Lymphoma

Answer

Cryptococcal meningitis

Answer

CNS toxoplasmosis

Question 6

A young unvaccinated patient presents to the OPD with fever, cough, coryza, and red eyes. On examination, a maculopapular rash beginning on the face and spreading cephalocaudally down the trunk and extremities is observed. What is the most likely complication expected with this condition?

Accepted Answer

Pneumonia

Answer

Myocarditis

Answer

Orchitis

Answer

Pancreatitis

Question 7

Which of the following laboratory markers characterizes the recumbent stage of Hepatitis B?

Accepted Answer

Anti HBc

Answer

Anti HBs Ag

Answer

Anti HBe Ag

Answer

Anti HBV

Question 8

What is the true statement regarding the treatment of hepatic amoebiasis?

Accepted Answer

Mostly treated conservatively

Answer

More common in females

Answer

Multiple lesions

Answer

Jaundice is common

Question 9

A 55-year-old diabetic female patient presented with facial pain, numbness, conjunctival suffusion, and blurring of vision for 6 days. She was managed conservatively and discharged. After a week, she presented again with bilateral proptosis, chemosis, vision loss, and ophthalmoplegia, along with a characteristic lesion on the nose. A smear was prepared from the nasal lesion. What is the most appropriate initial management for a suspected fungal infection causing these symptoms?

Accepted Answer

Amphotericin B

Answer

Posaconazole

Answer

Itraconazole

Answer

Caspofungin

Question 10

A 40-year-old man presents with fever, weight loss, and cough. His Mantoux test result is 18 x 19 mm, and sputum cytology is negative for Acid-Fast Bacilli (AFB). What is the most likely condition?

Accepted Answer

Pulmonary Tuberculosis

Answer

Pneumococcal Pneumonia

Answer

Cryptococcal Infection

Answer

Viral Infection

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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