Infectious Diseases Practice Questions

Q: Herpes simplex infection can lead to which of the following?

Temporal lobe involvement. Explanation: **Correct Answer: C. Temporal lobe involvement** Herpes Simplex Virus (HSV-1) is the most common cause of sporadic fatal encephalitis worldwide. The hallmark of **Herpes Simplex Encephalitis (HSE)** is its striking predilection for the **limbic system**, specifically the **medial temporal lobes** [1] and the inferior frontal lobes. The virus typically reaches the brain via retrograde axonal transport along the olfactory or trigeminal nerves. Pathologically, it causes acute necrotizing hemorrhage and edema in these regions [1]. Clinically, this manifests as sudden onset fever, headache, seizures, and characteristic behavioral changes or aphasia. **Why other options are incorrect:** * **A & B (Frontal/Parietal lobe infarction):** While HSE can cause localized edema and necrosis, it is not primarily a vascular/ischemic event (infarction). Furthermore, while the inferior frontal lobe can be involved, the **temporal lobe** is the classic, most high-yield site of involvement. * **D (Occipital neuralgia):** This is a paroxysmal pain condition involving the greater or lesser occipital nerves. While HSV can remain latent in sensory ganglia (like the trigeminal ganglion) [2], it is not a recognized cause of occipital neuralgia. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard Diagnosis:** CSF PCR for HSV DNA (highly sensitive and specific). * **EEG Findings:** Periodic Lateralizing Epileptiform Discharges (**PLEDs**) over the temporal lobes are characteristic. * **Imaging:** MRI is the investigation of choice; it shows T2/FLAIR hyperintensity in the medial temporal lobes. * **Treatment:** Immediate IV **Acyclovir** (10 mg/kg every 8 hours) should be started empirically if HSE is suspected, as delay increases mortality.

Q: A middle-aged man presents with a two-week history of fever, occasional night sweats, and significant weight loss. Bronchoalveolar lavage (BAL) was performed, and Mycobacterium tuberculosis (MTB) was not detected. Extrapulmonary tuberculosis is suspected. Which of the following sites is most likely affected?

Lymph nodes. **Explanation:** **1. Why Lymph Nodes is Correct:** Extrapulmonary tuberculosis (EPTB) refers to TB involving organs other than the lungs. Globally and specifically in the Indian subcontinent, **Lymph Node Tuberculosis (Tuberculous Lymphadenitis)** is the most common form of EPTB. The cervical lymph nodes are most frequently involved (historically termed 'Scrofula'). It typically presents with painless, firm, or matted lymphadenopathy accompanied by constitutional symptoms like fever and weight loss, as seen in this patient. **2. Analysis of Incorrect Options:** * **Skeletal System (Option A):** While Pott’s spine (tuberculosis of the spine) is a significant cause of morbidity, skeletal TB is less common than lymph node involvement. * **Gastrointestinal Tract (Option B):** Abdominal TB (commonly involving the ileocecal region) is a major form of EPTB in India, but it ranks below lymphadenopathy in overall prevalence. * **Genitourinary Tract (Option D):** This is a common site for EPTB in Western countries; however, in the Indian context, it is less frequent than lymph node or pleural involvement. **3. NEET-PG High-Yield Pearls:** * **Most common site of EPTB:** Lymph nodes (Cervical > Axillary > Inguinal). * **Most common site of Skeletal TB:** Spine (Pott’s Disease), specifically the lower thoracic and upper lumbar vertebrae. * **Diagnosis:** Fine Needle Aspiration Cytology (FNAC) showing granulomatous inflammation and Caseous necrosis is the initial investigation of choice for TB lymphadenitis. * **Gold Standard:** Culture on Lowenstein-Jensen (LJ) medium or rapid molecular tests like CBNAAT/GeneXpert on the lymph node aspirate.

Q: A 6-week pregnant lady is diagnosed with sputum-positive tuberculosis. What is the best management?

Start Category I ATT in the first trimester.. ### Explanation **1. Why Option B is Correct:** The management of Tuberculosis (TB) in pregnancy follows the principle that the risk of untreated TB to the mother and fetus far outweighs the risk of the drugs used for treatment. According to **RNTCP (NTEP) and WHO guidelines**, a pregnant woman diagnosed with TB should start **Category I ATT (2HREZ + 4HRE)** immediately, regardless of the gestational age [1]. Most first-line drugs (Isoniazid, Rifampicin, Ethambutol, and Pyrazinamide) are considered safe in the first trimester and are not associated with increased teratogenic risks. **2. Why Other Options are Incorrect:** * **Option A:** Delaying treatment until the second trimester increases the risk of maternal morbidity, spontaneous abortion, and congenital TB. Treatment should never be deferred. * **Option C:** Category II (which included Streptomycin) is no longer the standard of care under current NTEP guidelines. Furthermore, **Streptomycin is contraindicated** in pregnancy as it is ototoxic to the fetus (causes 8th cranial nerve damage). * **Option D:** Category III is an obsolete classification. All new cases are treated with the standard 6-month regimen (Category I). **3. High-Yield Clinical Pearls for NEET-PG:** * **Drug Safety:** H, R, E, and Z are safe. **Streptomycin** is the only first-line drug that is strictly **contraindicated**. * **Pyridoxine (Vitamin B6) Supplementation:** Mandatory (10–25 mg/day) for all pregnant women on ATT to prevent Isoniazid-induced peripheral neuropathy in the mother and seizures in the newborn [1]. * **Breastfeeding:** ATT is not contraindicated during breastfeeding. The concentration of drugs in breast milk is too low to protect the baby or cause toxicity. * **Congenital TB:** The most common site of primary complex in congenital TB is the **Liver** (via the umbilical vein).

Q: What is the minimum period required for post-exposure chemoprophylaxis for HIV?

4 weeks. **Explanation:** The correct answer is **4 weeks (28 days)**. Post-exposure prophylaxis (PEP) for HIV is a medical emergency aimed at preventing viral replication and systemic dissemination following potential exposure (e.g., needle-stick injury or sexual assault). **Why 4 weeks is correct:** According to the National AIDS Control Organization (NACO) and WHO guidelines, the standard duration for PEP is **28 days**. This timeframe is based on the biological rationale that it takes approximately 4 weeks of continuous antiretroviral therapy to effectively inhibit the virus from establishing a permanent infection in the host's lymphoid tissues after the initial inoculation. **Analysis of Incorrect Options:** * **6 weeks & 8 weeks:** These durations are unnecessarily long. Extending the regimen beyond 28 days does not provide additional protection but significantly increases the risk of drug toxicity and poor patient compliance. * **12 weeks:** This is often the timeframe used for **follow-up antibody testing** to confirm seroconversion status, but it is not the duration for medication intake. **High-Yield Clinical Pearls for NEET-PG:** * **The "Golden Period":** PEP should ideally be started within **2 hours**, and no later than **72 hours** post-exposure. It is not recommended after 72 hours. * **Preferred Regimen (NACO):** A 3-drug regimen is now standard, typically consisting of **Tenofovir (300mg) + Lamivudine (300mg) + Dolutegravir (50mg)** as a once-daily fixed-dose combination. * **Follow-up Schedule:** Testing for HIV antibodies should be done at baseline, 6 weeks, and 3 months (12 weeks) post-exposure.

Q: Which of the following clinical features is NOT typically seen in leptospirosis?

Massive splenomegaly. Leptospirosis is a zoonotic infection caused by the spirochete Leptospira interrogans [1]. The severe form of the disease, known as Weil’s Disease, is characterized by the triad of jaundice, renal failure, and hemorrhage [1]. **Why "Massive Splenomegaly" is the correct answer:** While mild splenomegaly can occur in about 15–25% of cases, **massive splenomegaly** is not a feature of leptospirosis. In the context of infectious diseases in India, massive splenomegaly should instead point toward diagnoses like Chronic Malaria, Visceral Leishmaniasis (Kala-azar), or Schistosomiasis [2]. **Analysis of incorrect options:** * **Jaundice (Option A):** This is a hallmark of severe leptospirosis [1]. Unlike viral hepatitis, the jaundice in leptospirosis is often "orange-yellow" and occurs despite relatively mild elevations in liver enzymes (AST/ALT rarely exceed 500 U/L). * **Hemorrhage (Option B):** Capillary fragility and thrombocytopenia lead to bleeding manifestations, ranging from epistaxis and petechiae to life-threatening pulmonary hemorrhage (a leading cause of death) [1]. * **Hepatomegaly (Option C):** Enlargement of the liver is common in the icteric phase [1]. The liver is often tender, though true hepatic failure is rare as the jaundice is primarily due to hepatocellular dysfunction and canalicular cholestasis rather than necrosis. **NEET-PG High-Yield Pearls:** * **Conjunctival Suffusion:** The most characteristic clinical sign (redness without inflammatory exudate). * **Biphasic Pattern:** Leptospiremic phase (fever, myalgia) followed by the Immune phase (meningitis, uveitis, renal failure) [1]. * **Lab Clue:** Disproportionately high Bilirubin with mildly raised Transaminases and elevated Creatine Phosphokinase (CPK) due to myositis. * **Treatment:** Doxycycline (prophylaxis/mild disease) or IV Penicillin G (severe disease).

Q: In which of the following conditions are steroids useful in treating a tuberculosis patient?

Lymphadenitis. **Explanation:** The use of corticosteroids in tuberculosis (TB) is primarily indicated to suppress the host's exaggerated inflammatory response, which can lead to tissue damage or obstructive complications. **Why Lymphadenitis is correct:** In **Tuberculous Lymphadenitis**, steroids are indicated specifically when there is a **paradoxical worsening** (Immune Reconstitution Inflammatory Syndrome - IRIS) or when massive lymphadenopathy causes pressure symptoms on adjacent structures (e.g., airway or major vessels) [3]. Steroids help reduce the size of the nodes and prevent sinus formation or suppuration by modulating the delayed-type hypersensitivity reaction. **Analysis of Incorrect Options:** * **Endobronchial TB:** While steroids were historically used to prevent bronchial stenosis, current evidence suggests they do not significantly alter the long-term outcome of airway narrowing compared to antitubercular therapy (ATT) alone. * **Tuberculous Osteomyelitis:** Treatment is strictly pharmacological (ATT) and sometimes surgical [1], [2]. Steroids have no proven role and may interfere with bone healing or mask secondary infections. * **Pneumonia:** Standard TB pneumonia is managed with ATT. Steroids are only considered in cases of severe respiratory failure/ARDS or miliary TB with hypoxia, but not as a routine treatment for localized pneumonia. **NEET-PG High-Yield Pearls:** Absolute indications for steroids in TB (The "Must-Know" List): 1. **TB Meningitis:** Reduces mortality and neurological sequelae (Stage II and III) [1]. 2. **TB Pericarditis:** Prevents constrictive pericarditis and reduces the need for pericardiectomy [1]. 3. **Adrenal TB (Addison’s Disease):** Replacement therapy for adrenal insufficiency. 4. **Miliary TB:** If there is associated hypoxia or ARDS. 5. **Genitourinary TB:** To prevent ureteral strictures.

Q: What is the most common neoplasm among HIV-positive homosexual males?

Kaposi's sarcoma. **Explanation:** **Kaposi’s Sarcoma (KS)** is the most common neoplasm associated with HIV infection, particularly among men who have sex with men (MSM). It is an angioproliferative disorder caused by **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi’s sarcoma-associated herpesvirus (KSHV). In the context of HIV, it is classified as an AIDS-defining illness [1]. **Analysis of Options:** * **Option A: Non-Hodgkin's Lymphoma (NHL):** While NHL is the second most common malignancy in HIV patients and is also an AIDS-defining illness (specifically Burkitt’s and Diffuse Large B-Cell Lymphoma), its overall incidence remains lower than Kaposi’s sarcoma in the MSM population. * **Option B: Glomus Tumor:** This is a rare, benign vascular neoplasm typically found in the subungual region (under the fingernails). It has no established association with HIV or HHV-8. * **Option D: None of the above:** Incorrect, as Kaposi’s sarcoma is the well-documented leading neoplasm in this group. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Characterized by painless, non-pruritic, violaceous (purple/red) macules, plaques, or nodules [1]. It can involve the skin, oral mucosa (especially the hard palate), and visceral organs (GI tract and lungs) [1]. * **Histology:** Features spindle-shaped cells, slit-like vascular spaces, and extravasated red blood cells. * **Treatment:** The primary treatment is the initiation of **Highly Active Antiretroviral Therapy (HAART)**, which often leads to lesion regression. For advanced cases, systemic chemotherapy (e.g., liposomal doxorubicin) may be used. * **Other HIV-Associated Cancers:** Invasive cervical cancer and Primary CNS Lymphoma are also AIDS-defining. Non-AIDS-defining cancers (like Anal Cancer) are also increasing in incidence due to prolonged survival on HAART.

Q: Which is the drug of choice for prophylaxis of meningococcal meningitis in pregnancy?

Ceftriaxone. **Explanation:** The primary goal of chemoprophylaxis in meningococcal meningitis is to eradicate the nasopharyngeal carriage of *Neisseria meningitidis* to prevent the spread of the disease to close contacts [1]. **1. Why Ceftriaxone is the Correct Answer:** Ceftriaxone is the **drug of choice for pregnant women** because it is highly effective at eradicating the carrier state and has an established safety profile in pregnancy (FDA Category B). It is administered as a single intramuscular (IM) dose of 250 mg. It is also the preferred choice for children. **2. Why Other Options are Incorrect:** * **Rifampicin:** While it is the standard drug of choice for the general population (600 mg twice daily for 2 days), it is **contraindicated in pregnancy** due to potential teratogenicity (demonstrated in animal studies) [1]. * **Penicillin & Ampicillin:** Although these are used for the *treatment* of active meningococcal disease, they are ineffective for *prophylaxis* because they do not achieve sufficient concentrations in nasopharyngeal secretions to reliably eradicate the carrier state. **3. High-Yield Clinical Pearls for NEET-PG:** * **Standard Prophylaxis (Non-pregnant adults):** Rifampicin is the first-line agent [1]. Ciprofloxacin (500 mg single dose) is an alternative but is generally avoided in pregnancy and children due to concerns regarding cartilage damage. * **Close Contacts:** Prophylaxis is indicated for "close contacts" (household members, daycare contacts, or healthcare workers exposed to respiratory secretions) and should ideally be started within 24 hours of identification of the index case [1]. * **Azithromycin:** Can be used as a single-dose oral alternative if other options are unavailable.

Q: A sewage worker presents to the Emergency Department with fever and jaundice. Laboratory findings reveal an elevated BUN and serum creatinine suggestive of renal failure. Which of the following antibiotics is recommended?

Penicillin G. ### Explanation **Correct Option: D (Penicillin G)** The clinical presentation of a **sewage worker** (occupational exposure) with **fever, jaundice, and renal failure** (elevated BUN/Creatinine) is classic for **Weil’s Disease**, the severe form of **Leptospirosis**. Leptospirosis is caused by the spirochete *Leptospira interrogans*, typically transmitted through water contaminated by the urine of infected rodents. **Why Penicillin G is the correct answer:** For severe leptospirosis (Weil’s Disease), the treatment of choice is intravenous **Penicillin G** (1.5 million units every 6 hours). Alternatively, IV Ceftriaxone can be used. For mild or uncomplicated cases, oral Doxycycline is preferred. **Analysis of Incorrect Options:** * **A. Co-trimoxazole:** Not indicated for spirochetal infections like Leptospirosis; it is primarily used for UTI, Nocardia, or Pneumocystis pneumonia. * **B. Erythromycin:** While it has some activity against *Leptospira*, it is not the first-line treatment for severe cases involving renal and hepatic failure. * **C. Ciprofloxacin:** Fluoroquinolones are not the standard of care for Leptospirosis and have shown inferior efficacy compared to beta-lactams in clinical settings. **High-Yield Clinical Pearls for NEET-PG:** * **Occupational Risk:** Sewage workers, farmers, miners, and veterinarians are at high risk. * **Weil’s Syndrome Triad:** Jaundice, Renal Failure, and Hemorrhage (often pulmonary). * **Diagnosis:** The gold standard is the **Microscopic Agglutination Test (MAT)**. * **Chemoprophylaxis:** For high-risk individuals (e.g., during floods), **Doxycycline 200 mg once weekly** is recommended. * **Jarisch-Herxheimer Reaction:** Can occur after starting antibiotics due to the release of endotoxins from dying spirochetes.

Question 1

Herpes simplex infection can lead to which of the following?

Accepted Answer

Temporal lobe involvement

Answer

Frontal lobe infarction

Answer

Parietal lobe infarction

Answer

Occipital neuralgia

Question 2

A middle-aged man presents with a two-week history of fever, occasional night sweats, and significant weight loss. Bronchoalveolar lavage (BAL) was performed, and Mycobacterium tuberculosis (MTB) was not detected. Extrapulmonary tuberculosis is suspected. Which of the following sites is most likely affected?

Accepted Answer

Lymph nodes

Answer

Skeletal system

Answer

Gastrointestinal tract

Answer

Genitourinary tract

Question 3

A 6-week pregnant lady is diagnosed with sputum-positive tuberculosis. What is the best management?

Accepted Answer

Start Category I ATT in the first trimester.

Answer

Wait for the second trimester to start anti-tuberculosis treatment (ATT).

Answer

Start Category II ATT in the first trimester.

Answer

Start Category III ATT in the second trimester.

Question 4

What is the minimum period required for post-exposure chemoprophylaxis for HIV?

Accepted Answer

4 weeks

Answer

6 weeks

Answer

8 weeks

Answer

12 weeks

Question 5

Which of the following clinical features is NOT typically seen in leptospirosis?

Accepted Answer

Massive splenomegaly

Answer

Jaundice, which may be intense

Answer

Hemorrhage

Answer

Hepatomegaly

Question 6

In which of the following conditions are steroids useful in treating a tuberculosis patient?

Accepted Answer

Lymphadenitis

Answer

Endobronchial tuberculosis

Answer

Tuberculous osteomyelitis

Answer

Pneumonia

Question 7

What is the most common neoplasm among HIV-positive homosexual males?

Accepted Answer

Kaposi's sarcoma

Answer

Non-Hodgkin's lymphoma

Answer

Glomus tumor

Answer

None of the above

Question 8

Following accidental needle-stick exposure to blood from an HIV-positive patient with a CD4 count of 20 cells/microL and a viral RNA load exceeding 10^7 copies/mL, what is the recommended post-exposure prophylaxis for the exposed nurse?

Accepted Answer

Administer a four-week regimen of zidovudine with lamivudine.

Answer

Monitor the nurse's blood for signs of HIV transmission.

Answer

Administer zidovudine at full therapeutic doses for two weeks.

Answer

Add acyclovir to a four-week course of zidovudine.

Question 9

Which is the drug of choice for prophylaxis of meningococcal meningitis in pregnancy?

Accepted Answer

Ceftriaxone

Answer

Penicillin

Answer

Rifampicin

Answer

Ampicillin

Question 10

A sewage worker presents to the Emergency Department with fever and jaundice. Laboratory findings reveal an elevated BUN and serum creatinine suggestive of renal failure. Which of the following antibiotics is recommended?

Accepted Answer

Penicillin G

Answer

Co-trimoxazole

Answer

Erythromycin

Answer

Ciprofloxacin

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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