Infectious Diseases Practice Questions

Q: What is the next step in the management of a patient with a positive sputum smear for tuberculosis but a negative chest X-ray?

Start anti-tuberculosis treatment (ATT). **Explanation:** The diagnosis of Pulmonary Tuberculosis (PTB) in the National Tuberculosis Elimination Programme (NTEP) is primarily microbiological. A positive sputum smear indicates the presence of acid-fast bacilli (AFB), which is sufficient evidence of active disease, regardless of radiological findings. **1. Why Option B is Correct:** In clinical practice, a positive sputum smear has high specificity. A negative chest X-ray (CXR) does not rule out TB, as early-stage disease or endobronchial TB may not show visible parenchymal shadows. According to NTEP guidelines, any "Microbiologically Confirmed" case must be initiated on **Anti-Tuberculosis Treatment (ATT)** immediately to interrupt the chain of transmission and prevent clinical deterioration. **2. Why Other Options are Incorrect:** * **Option A & D:** Repeating tests (CXR or Smear) leads to unnecessary "diagnostic delay." A single positive smear is diagnostic in a symptomatic patient. * **Option C:** While CBNAAT (GeneXpert) is the preferred initial diagnostic tool under NTEP for its high sensitivity and ability to detect Rifampicin resistance, the question states the patient is *already* smear-positive. Treatment should not be withheld while waiting for further tests unless drug resistance is specifically suspected. **Clinical Pearls for NEET-PG:** * **Microbiologically Confirmed TB:** Defined as a patient with a biological specimen positive for AFB by smear microscopy, or positive for *M. tuberculosis* by NAAT (like CBNAAT/Truenat) or culture. * **Radiology vs. Microbiology:** Microbiology is the "Gold Standard." A positive smear always supersedes a negative X-ray. * **Infectivity:** Smear-positive patients are the most infectious; prompt ATT is the most effective public health intervention to reduce the "Annual Risk of Tuberculosis Infection" (ARTI).

Q: CSF examination of a patient shows high protein, markedly low sugar, low chloride, and increased neutrophils. What is the most likely diagnosis?

Meningococcal meningitis. The CSF findings described—**high protein, markedly low sugar, and increased neutrophils**—are the classic biochemical signature of **Acute Bacterial Meningitis**. [1] ### 1. Why Meningococcal Meningitis is Correct Meningococcal meningitis (caused by *Neisseria meningitidis*) is a form of pyogenic bacterial meningitis. * **Increased Neutrophils (Polymorphonuclear Leucocytosis):** Bacteria trigger a massive recruitment of neutrophils to the subarachnoid space. * **Markedly Low Sugar (Hypoglycorrhachia):** Bacteria and active WBCs consume glucose; additionally, glucose transport into the CSF is impaired. * **High Protein:** Increased permeability of the blood-brain barrier and the presence of bacterial debris/inflammatory exudate raise protein levels. [1] * **Low Chloride:** Often seen in systemic infections and severe meningeal inflammation. ### 2. Why Other Options are Incorrect * **Viral Meningitis:** Typically presents with **lymphocytic** pleocytosis, **normal sugar**, and only mildly elevated protein. [1] * **Tuberculous Meningitis (TBM):** While it features high protein and low sugar, the predominant cells are **lymphocytes**, not neutrophils. TBM also typically has the lowest chloride levels among all types. * **Fungal Meningitis:** Similar to TBM, it presents with a **lymphocytic** picture and low sugar (though often not as low as bacterial). ### 3. NEET-PG Clinical Pearls * **Normal CSF Glucose:** 40–70 mg/dL (or >60% of blood glucose). * **Normal CSF Protein:** 15–45 mg/dL. * **The "Cobweb Coagulum":** Classically associated with Tuberculous Meningitis if the CSF is left standing. * **Drug of Choice:** For Meningococcal meningitis, **IV Ceftriaxone** is the mainstay. Prophylaxis for close contacts is **Rifampicin** (or Ciprofloxacin/Ceftriaxone).

Q: Corticosteroids are absolutely contraindicated in which of the following types of tuberculosis?

Intestinal. **Explanation:** In the management of Tuberculosis (TB), corticosteroids are used as an adjuvant to anti-tubercular therapy (ATT) to reduce life-threatening inflammation and prevent complications like fibrosis or adhesions [1]. However, they are **absolutely contraindicated in Intestinal TB.** **Why Intestinal TB?** The primary concern in Intestinal TB is the risk of **bowel perforation**. Corticosteroids inhibit the healing process and mask signs of peritonitis. Since intestinal TB often involves ulceration of the Peyer's patches and thinning of the bowel wall, steroids can lead to "silent" perforation, which is a surgical emergency with high mortality. **Analysis of Other Options:** * **Meningeal TB (Option B):** This is a **strong indication** for steroids (e.g., Dexamethasone). They reduce cerebral edema, prevent basal arachnoiditis, and decrease the incidence of hydrocephalus and neurological deficits [1]. * **Miliary TB (Option A):** Steroids are often used as an adjunct, especially if there is associated adrenal insufficiency or severe respiratory distress (ARDS) to improve oxygenation and reduce the systemic inflammatory response. * **Renal TB (Option D):** Steroids are indicated specifically to prevent **ureteric strictures** and subsequent hydronephrosis during the healing phase of the disease. **High-Yield Clinical Pearls for NEET-PG:** * **Indications for Steroids in TB:** TB Meningitis (most common indication), TB Pericarditis (to prevent constrictive pericarditis), Pleural effusion (for rapid resolution), and Renal TB (to prevent strictures) [1]. * **Contraindications:** Intestinal TB (due to perforation risk) and Multi-Drug Resistant TB (MDR-TB) unless life-threatening inflammation is present. * **Standard Regimen:** Prednisolone (1-2 mg/kg) tapered over 4–8 weeks is the typical adjuvant protocol.

Q: All of the following are indications for steroid use in Tuberculosis except?

Bone TB. The use of corticosteroids in Tuberculosis (TB) is based on the principle of reducing the detrimental host inflammatory response, which can cause tissue damage or mechanical obstruction. **Why Bone TB is the correct answer:** In **Bone and Joint TB** (including Pott’s spine), there is no evidence that steroids improve outcomes [1]. Management relies strictly on Anti-Tubercular Therapy (ATT) and, in specific cases, surgical intervention for stabilization or decompression [2]. Steroids do not prevent deformity or improve neurological recovery in these patients. **Analysis of Incorrect Options:** * **Tubercular Meningitis (TBM):** This is the most definitive indication. Steroids (Dexamethasone/Prednisolone) reduce cerebral edema, intracranial pressure, and vasculitis, significantly decreasing mortality and neurological deficits [1]. * **Pericardial Effusion:** Steroids reduce the risk of constrictive pericarditis and the need for repeated pericardiocentesis by decreasing fibrin deposition and pericardial thickening [1]. * **Massive Pleural Effusion:** While not mandatory for all pleural TB, steroids are indicated in **massive** effusions to hasten the resolution of fluid, prevent pleural thickening (fibrothorax), and alleviate severe respiratory distress. **High-Yield Clinical Pearls for NEET-PG:** 1. **Other Indications:** Adrenal TB (Addisonian crisis), Laryngeal TB (to prevent airway obstruction), and Miliary TB (if severe hypoxia/ARDS is present). 2. **IRIS:** Steroids are the treatment of choice for Paradoxical IRIS (Immune Reconstitution Inflammatory Syndrome) in HIV-TB co-infected patients. 3. **Rule of Thumb:** Steroids should **never** be given without concurrent ATT coverage to prevent uncontrolled mycobacterial replication.

Q: A young patient presents with fever and right upper quadrant pain. Clinical examination reveals hepatomegaly but no jaundice. Ultrasound reveals a solitary, homogeneous, hypoechoic lesion in the right lobe measuring 5 cm x 5 cm x 4 cm. Tests for hydatid disease were negative. Which of the following is the best recommendation for initial treatment?

Antiamoebics/antibiotics alone. **Explanation:** The clinical presentation of fever, right upper quadrant pain, and hepatomegaly in a young patient, combined with a solitary hypoechoic lesion in the right lobe of the liver, is classic for an **Amoebic Liver Abscess (ALA)**. The negative hydatid serology further supports this diagnosis over Echinococcal cysts. **1. Why Option C is Correct:** The primary treatment for an uncomplicated amoebic liver abscess is **medical management** with antiamoebic drugs (e.g., Metronidazole or Tinidazole). Approximately 90-95% of patients respond dramatically to antibiotics alone within 48–72 hours. Unlike pyogenic abscesses, which often require drainage, uncomplicated amoebic abscesses resolve well with pharmacotherapy. **2. Why Other Options are Incorrect:** * **Options A & B:** Routine aspiration or catheter drainage is **not** recommended as initial therapy. Drainage is reserved for specific indications: lack of clinical response to drugs after 48-72 hours, large abscesses (>10 cm) at risk of rupture, abscesses in the left lobe (high risk of pericardial rupture), or if the abscess is thin-walled and imminent to burst. * **Option D:** Hepatectomy is a radical surgical procedure and is never the initial treatment for an infectious abscess. Surgery is only considered for complications like rupture into the peritoneal cavity causing peritonitis. **Clinical Pearls for NEET-PG:** * **Most common site:** Right lobe (due to the streaming effect of portal blood flow). * **Classic appearance:** "Anchovy sauce" pus (chocolate-colored, odorless). * **Radiology:** Typically a solitary, peripheral, hypoechoic lesion without a prominent wall (unlike pyogenic abscesses which are often multiple and have thicker walls). * **Gold Standard Diagnosis:** Serology (IHA/ELISA) is highly sensitive; imaging helps in localization.

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

Focal neurologic deficit. **Explanation:** Cerebral malaria, caused by *Plasmodium falciparum*, is defined as a clinical syndrome characterized by coma (Glasgow Coma Scale <11 in adults) at least 1 hour after the termination of a seizure, in the presence of asexual malaria parasites on a blood film. **Why Focal Neurologic Deficit is the correct answer:** Cerebral malaria is typically a **diffuse encephalopathy**. While patients present with altered consciousness and generalized seizures, **focal neurological deficits** (such as hemiplegia or cranial nerve palsies) are **uncommon** and should prompt a search for alternative diagnoses like a brain abscess, stroke, or post-ictal state (Todd’s paralysis). **Analysis of other options:** * **Retinal Hemorrhages:** These are a classic and specific finding in cerebral malaria (malarial retinopathy). They are highly prognostic; their presence correlates with the severity of brain involvement and increased mortality. * **Extensor Plantar Reflex (Babinski Sign):** Upper motor neuron signs are common in cerebral malaria due to diffuse cortical dysfunction. An extensor plantar response is frequently observed during the comatose state. * **Absent Abdominal Reflex:** This is a common clinical finding in cerebral malaria, reflecting the involvement of the corticospinal tracts. **NEET-PG High-Yield Pearls:** * **Pathogenesis:** Sequestration of parasitized RBCs in cerebral microvasculature (cytoadherence) leading to hypoxia and cytokine release [1]. * **Drug of Choice:** Intravenous **Artesunate** is the gold standard (superior to Quinine). * **Poor Prognostic Markers:** Deep coma, retinal hemorrhages, metabolic acidosis (most important predictor of death), and hyperlactatemia. * **CSF Findings:** Usually normal or slightly elevated protein; pleocytosis is rare (helps differentiate from bacterial meningitis).

Q: All are features of tabes dorsalis, except?

Hyperreflexia. **Explanation:** Tabes dorsalis is a late (tertiary) manifestation of neurosyphilis characterized by the slow degeneration of the **posterior columns** and **dorsal roots** of the spinal cord [1]. **Why Hyperreflexia is the correct answer:** In tabes dorsalis, the primary pathology involves the destruction of the dorsal (sensory) roots [1]. This interrupts the afferent limb of the spinal reflex arc. Because the reflex arc is broken at the sensory level, the result is **hyporeflexia or areflexia** (specifically loss of knee and ankle jerks), rather than hyperreflexia [2]. Hyperreflexia is a feature of Upper Motor Neuron (UMN) lesions, whereas tabes dorsalis presents with Lower Motor Neuron-like reflex loss [2]. **Analysis of other options:** * **Ataxia:** Patients develop **sensory ataxia** due to the loss of proprioception (posterior column involvement) [1]. This results in a characteristic "slapping gait" and a positive Romberg’s sign [3]. * **Argyll Robertson Pupil:** A classic hallmark of neurosyphilis where the pupil shows "Accommodation Reflex Present, but Light Reflex Absent" (ARP). * **Bladder disturbances:** Deafferentation of the bladder leads to an **atonic bladder** (overflow incontinence), as the patient loses the sensory urge to void. **NEET-PG High-Yield Pearls:** * **Charcot’s Joints:** Painless joint destruction (most commonly the knee) due to loss of pain sensation. * **Lightning Pains:** Sudden, stabbing pains in the lower limbs are often the earliest symptom. * **Lhermitte’s sign:** May be positive. * **Treatment:** Intravenous Penicillin G is the drug of choice for neurosyphilis.

Q: What is the drug of choice for the treatment of latent syphilis?

Penicillin. Explanation: Penicillin G remains the gold standard and drug of choice for all stages of syphilis, including latent syphilis. The underlying medical concept is that Treponema pallidum is exquisitely sensitive to penicillin, and despite decades of use, no documented resistance has emerged. For latent syphilis, the goal is to prevent progression to tertiary syphilis and transmission. * Early Latent Syphilis ( 1 year or unknown duration): Treated with three weekly doses of Benzathine Penicillin G (7.2 million units total). Analysis of Incorrect Options: * B. Erythromycin: While once used, it is no longer recommended due to high rates of treatment failure and increasing resistance. It also does not reliably cross the placental barrier. * C. Tetracycline (or Doxycycline): These are considered second-line alternatives for non-pregnant, penicillin-allergic patients. However, they are less effective than penicillin and require longer courses (28 days for late latent). * D. Ciprofloxacin: Fluoroquinolones have no clinical role in the treatment of syphilis. High-Yield Clinical Pearls for NEET-PG: 1. Jarisch-Herxheimer Reaction: An acute febrile reaction occurring within 24 hours of starting penicillin; it is caused by the release of endotoxins from dying spirochetes. It is not an allergic reaction. 2. Pregnancy: Penicillin is the only acceptable treatment. If a pregnant woman is allergic, she must undergo desensitization followed by penicillin treatment. 3. Neurosyphilis: Requires Aqueous Crystalline Penicillin G (IV), as Benzathine penicillin does not achieve therapeutic levels in the CSF.

Question 1

What is the next step in the management of a patient with a positive sputum smear for tuberculosis but a negative chest X-ray?

Accepted Answer

Start anti-tuberculosis treatment (ATT)

Answer

Repeat chest X-ray

Answer

Perform CBNAAT

Answer

Repeat sputum smear

Question 2

CSF examination of a patient shows high protein, markedly low sugar, low chloride, and increased neutrophils. What is the most likely diagnosis?

Accepted Answer

Meningococcal meningitis

Answer

Viral meningitis

Answer

Tuberculous meningitis

Answer

Fungal meningitis

Question 3

Corticosteroids are absolutely contraindicated in which of the following types of tuberculosis?

Accepted Answer

Intestinal

Answer

Miliary

Answer

Meningeal

Answer

Renal

Question 4

All of the following are indications for steroid use in Tuberculosis except?

Accepted Answer

Bone TB

Answer

Tubercular meningitis

Answer

Pericardial effusion

Answer

Massive pleural effusion

Question 5

A young patient presents with fever and right upper quadrant pain. Clinical examination reveals hepatomegaly but no jaundice. Ultrasound reveals a solitary, homogeneous, hypoechoic lesion in the right lobe measuring 5 cm x 5 cm x 4 cm. Tests for hydatid disease were negative. Which of the following is the best recommendation for initial treatment?

Accepted Answer

Antiamoebics/antibiotics alone

Answer

Multiple aspirations and antiamoebics/antibiotics

Answer

Catheter drainage and antiamoebics/antibiotics

Answer

Hepatectomy followed by antiamoebics/antibiotics

Question 6

A 17-year-old man presents with fatigue, malaise, fever, and sore throat. He has no significant past medical history and is not on any medications. Physical examination reveals enlarged, palpable cervical lymph nodes. He reports no weight loss or night sweats. Laboratory investigations include a normal chest x-ray, negative throat swab, and an abnormal blood film with atypical lymphocytes. His hemoglobin is 15.5 g/dL; hematocrit 42%; platelets 290,000/mL; WBC 10,500/mL, with 45% segmented neutrophils, 1% eosinophils, and 54% lymphocytes, of which 36% were atypical. Which of the following is the most appropriate initial diagnostic test?

Accepted Answer

Heterophil antibody (Monospot) test

Answer

Lymph node biopsy

Answer

Bone marrow examination

Answer

Erythrocyte sedimentation rate (ESR)

Question 7

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

Accepted Answer

Focal neurologic deficit

Answer

Retinal hemorrhages

Answer

Extensor plantar reflex

Answer

Absent abdominal reflex

Question 8

All are features of tabes dorsalis, except?

Accepted Answer

Hyperreflexia

Answer

Ataxia

Answer

Argyll Robertson's pupil

Answer

Bladder disturbances

Question 9

CMV retinitis in HIV occurs when the CD4 counts fall below which of the following levels?

Accepted Answer

50 cells/µL

Answer

100 cells/µL

Answer

200 cells/µL

Answer

150 cells/µL

Question 10

What is the drug of choice for the treatment of latent syphilis?

Accepted Answer

Penicillin

Answer

Erythromycin

Answer

Tetracycline

Answer

Ciprofloxacin

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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