Infectious Diseases — MCQs

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 221: What is helpful in a child with severe falciparum malaria with high parasitemia?

A. IV corticosteroids
B. Exchange transfusion (Correct Answer)
C. Hyperbaric oxygen
D. All the above

Explanation: **Explanation:** Severe falciparum malaria is a medical emergency characterized by high parasite density (hyperparasitemia) and multi-organ dysfunction. **Why Exchange Transfusion is correct:** Exchange transfusion is considered an adjunctive therapy in severe malaria, particularly when parasitemia exceeds **10-15%** or if there are signs of organ failure (e.g., cerebral malaria, ARDS, or renal failure). The procedure works by: 1. **Rapidly reducing parasite load:** Physically removing infected red blood cells (RBCs). 2. **Improving Rheology:** Removing rigid, parasitized RBCs that cause microvascular sequestration and replacing them with flexible donor cells, thereby improving tissue perfusion. 3. **Reducing Toxicity:** Clearing parasite-derived toxins, cytokines, and free hemoglobin. **Why other options are incorrect:** * **IV Corticosteroids:** Previously used for cerebral malaria to reduce brain edema, clinical trials (like those by Warrell et al.) proved they are **contraindicated**. They increase the risk of secondary infections and gastrointestinal bleeding without improving survival. * **Hyperbaric Oxygen:** There is no established clinical evidence or physiological basis for its use in treating the pathophysiology of malaria. **NEET-PG High-Yield Pearls:** * **WHO Criteria for Hyperparasitemia:** >10% in low-transmission areas or >20% in high-transmission areas. * **Drug of Choice:** IV **Artesunate** is the gold standard for severe malaria (superior to Quinine). * **Common Complication in Children:** Hypoglycemia and severe anemia are more frequent in pediatric severe malaria compared to adults. * **Blackwater Fever:** Characterized by massive intravascular hemolysis and hemoglobinuria, often associated with Quinine use.

Question 222: Which of the following is NOT a feature of the classical triad of congenital rubella syndrome?

A. Cataract
B. Congenital heart disease (CHD)
C. Deafness
D. Glaucoma (Correct Answer)

Explanation: **Explanation:** The correct answer is **Glaucoma**. While glaucoma can occur in Congenital Rubella Syndrome (CRS), it is not a component of the **Gregg Triad** (the classical triad). **1. Why Glaucoma is the correct answer:** The classical triad of CRS specifically includes **Cataract**, **Sensorineural Hearing Loss**, and **Congenital Heart Disease**. Glaucoma is considered a "late-acting" or associated clinical feature rather than a primary component of the triad. In CRS, cataracts are typically "pearly white" and central, whereas glaucoma occurs in only about 10% of cases. **2. Analysis of Incorrect Options:** * **Cataract (Option A):** This is the most common ocular manifestation of the triad. It is often bilateral and results from direct viral invasion of the lens fiber before the lens capsule forms. * **Congenital Heart Disease (Option B):** A key component of the triad. The most characteristic lesion is **Patent Ductus Arteriosus (PDA)**, followed by peripheral pulmonary artery stenosis. * **Deafness (Option C):** Sensorineural hearing loss is the **most common** overall manifestation of CRS. It may be the only presenting sign in some infants and is often bilateral and permanent. **Clinical Pearls for NEET-PG:** * **Expanded CRS:** Includes the triad plus "Blueberry muffin" spots (extramedullary hematopoiesis), radiolucent bone lesions (celery stalking), and hepatosplenomegaly. * **Timing:** The risk of fetal damage is highest if the mother is infected during the **first trimester** (up to 90% risk before 11 weeks). * **Diagnosis:** Confirmed by the presence of **Rubella-specific IgM** antibodies in the neonate or persistence of IgG beyond 6–12 months. * **Prevention:** Rubella is a live-attenuated vaccine (RA 27/3 strain). It is contraindicated in pregnancy; pregnancy should be avoided for 1 month post-vaccination.

Question 223: What is the most common presentation of neonatal meningitis?

A. Bulging fontanels
B. Nuchal rigidity
C. Poor feeding (Correct Answer)
D. Convulsions

Explanation: **Explanation:** In neonates, the clinical presentation of meningitis is notoriously **non-specific and subtle**. Unlike older children or adults, neonates lack a mature inflammatory response and have open cranial sutures, which prevents the early development of classic meningeal signs. **1. Why "Poor feeding" is correct:** The most common symptoms of neonatal meningitis are constitutional and mimic neonatal sepsis. **Poor feeding** (refusal to suck) is the most frequent presenting feature, often accompanied by lethargy, irritability, or temperature instability (hypothermia or fever). Because these symptoms are vague, a high index of suspicion is required; any "sick-looking" neonate must be evaluated for meningitis via lumbar puncture. **2. Why other options are incorrect:** * **Bulging fontanels (A):** This is a late sign indicating increased intracranial pressure. It occurs in only about 25–30% of cases and is rarely present at the onset. * **Nuchal rigidity (B):** Classic signs of meningeal irritation (Kernig’s, Brudzinski’s, and neck stiffness) are absent in the majority of neonates because their neck musculature is poorly developed and the open fontanels decompress the pressure. * **Convulsions (D):** While seizures occur in approximately 30–50% of cases and indicate a poor prognosis or focal brain involvement, they are usually a secondary manifestation rather than the initial presenting complaint. **High-Yield Clinical Pearls for NEET-PG:** * **Most common causative agents:** *Group B Streptococcus* (most common globally), *E. coli*, and *Listeria monocytogenes*. * **Gold Standard Diagnosis:** Lumbar puncture (CSF analysis). * **CSF Findings:** In bacterial meningitis, look for low glucose (<40 mg/dL), high protein (>100 mg/dL), and pleocytosis (predominantly PMNs). * **Treatment:** Empirical therapy usually involves Ampicillin + Cefotaxime (or Gentamicin). Avoid Ceftriaxone in neonates due to the risk of biliary sludging and kernicterus.

Question 224: A 20-day-old infant presents with fever and irritability. Fontanelles are bulging and neck stiffness is present. Which of the following is the commonest cause of meningitis in the postneonatal period?

A. Mycobacterium tuberculosis
B. Staphylococcus aureus
C. Streptococcus pneumoniae
D. Listeria monocytogenes (Correct Answer)

Explanation: **Explanation:** The correct answer is **Listeria monocytogenes**. **1. Why Listeria monocytogenes is correct:** The neonatal period is defined as the first 28 days of life. In this age group (0–28 days), the most common causative organisms for bacterial meningitis are **Group B Streptococcus (GBS)**, **Escherichia coli**, and **Listeria monocytogenes**. Since the infant in the question is 20 days old, they fall within the neonatal/early postneonatal window where these pathogens predominate. Listeria is a classic cause of late-onset neonatal sepsis and meningitis, often transmitted via the maternal GI tract or environmental exposure. **2. Why the other options are incorrect:** * **Streptococcus pneumoniae:** This is the most common cause of bacterial meningitis in children **older than 3 months** and adults. While it can occur in neonates, it is not the primary pathogen for this age group. * **Staphylococcus aureus:** This is usually associated with post-neurosurgical procedures, head trauma, or infected shunts, rather than community-acquired neonatal meningitis. * **Mycobacterium tuberculosis:** While a significant cause of meningitis in endemic areas like India, it typically presents with a more subacute or chronic course and is rare in the first month of life. **3. NEET-PG High-Yield Pearls:** * **0–3 Months:** GBS (most common), *E. coli*, *Listeria*. * **3 Months–5 Years:** *Streptococcus pneumoniae*, *Neisseria meningitidis*, *Haemophilus influenzae* type b (Hib - incidence decreased due to vaccination). * **Empiric Treatment (Neonates):** Ampicillin (to cover *Listeria*) + Cefotaxime or an Aminoglycoside. **Avoid Ceftriaxone** in neonates due to the risk of biliary sludging and displacement of bilirubin (kernicterus). * **Bulging Fontanelle:** A key clinical sign of increased intracranial pressure/meningitis in infants, as neck stiffness (Brudzinski/Kernig signs) is often absent in the very young.

Question 225: Eye examination of a child shows blue sclera. In which condition is it characteristically observed?

A. Amelogenesis Imperfecta
B. Tetracycline hypoplasia
C. Osteogenesis imperfecta (Correct Answer)
D. Fluorosis

Explanation: **Explanation:** **Osteogenesis Imperfecta (OI)**, also known as "Brittle Bone Disease," is the correct answer. The underlying medical concept involves a genetic defect in **Type I collagen** synthesis. The sclera of the eye is primarily composed of collagen; in OI, the scleral collagen is abnormally thin. This thinness allows the underlying **uveal pigment** (choroid) to show through, giving the sclera a characteristic **blue or slate-gray appearance**. This is a classic clinical sign, particularly in Type I (the most common and mildest form) and Type II (the lethal form) of the disease. **Analysis of Incorrect Options:** * **Amelogenesis Imperfecta:** This is a hereditary disorder affecting dental enamel formation. While it affects the teeth (making them yellow or brown), it does not involve collagen defects that affect the sclera. * **Tetracycline Hypoplasia:** This occurs due to the ingestion of tetracycline during the period of tooth calcification. It causes permanent yellow-brown discoloration of the **teeth**, not the sclera. * **Fluorosis:** Chronic ingestion of high levels of fluoride leads to "mottled enamel." It affects the appearance of the teeth (chalky white patches or brown staining) but has no association with blue sclera. **High-Yield Clinical Pearls for NEET-PG:** * **Triad of OI (Type I):** Blue sclera, fragile bones (multiple fractures), and early-onset conductive hearing loss (otosclerosis). * **Dentinogenesis Imperfecta:** Often associated with OI; teeth appear translucent or opalescent. * **Differential Diagnosis for Blue Sclera:** Apart from OI, consider **Ehlers-Danlos Syndrome (Type VI)**, Marfan Syndrome, and Pseudoxanthoma Elasticum. * **Wormian Bones:** Multiple small bones within the cranial sutures, often seen on X-rays of patients with OI.

Question 226: Which of the following is not seen in congenital rubella syndrome?

A. Atrial septal defect (Correct Answer)
B. Ventricular septal defect
C. Patent ductus arteriosus
D. Pulmonary stenosis

Explanation: **Explanation:** Congenital Rubella Syndrome (CRS) is caused by the transplacental transmission of the Rubella virus, typically during the first trimester. While CRS is associated with a specific constellation of cardiac defects, **Atrial Septal Defect (ASD)** is not considered a classic or characteristic feature of the syndrome. **Why ASD is the correct answer:** In CRS, the virus interferes with organogenesis, specifically affecting the development of the great vessels and the pulmonary artery. While ASDs can occur sporadically in any population, they are not part of the "Gregg’s Triad" or the typical cardiac profile of Rubella. **Analysis of Incorrect Options:** * **Patent Ductus Arteriosus (PDA):** This is the **most common** cardiac lesion in CRS (seen in ~60% of cases). The virus causes damage to the vascular endothelium and inhibits the normal muscular contraction required for ductal closure. * **Pulmonary Artery Stenosis:** Specifically **Peripheral Pulmonary Artery Stenosis**, this is the second most common lesion. It occurs due to the inhibition of longitudinal growth of the arterial wall. * **Ventricular Septal Defect (VSD):** While less common than PDA or Pulmonary Stenosis, VSD is a documented component of the cardiac anomalies associated with CRS. **High-Yield Clinical Pearls for NEET-PG:** * **Gregg’s Triad:** 1. Cataracts (or glaucoma), 2. Sensorineural hearing loss (most common overall finding), 3. Cardiac defects (PDA/Pulmonary Stenosis). * **Classic Sign:** "Salt and pepper" retinopathy. * **Dermatological Finding:** "Blueberry muffin" spots (extramedullary hematopoiesis). * **Radiology:** "Celery stalking" (longitudinal lucencies in the metaphysis of long bones). * **Timing:** Risk is highest if infection occurs before 11 weeks of gestation.

Question 227: Streptococcal vaginitis in a child is treated with:

A. Systemic penicillin
B. Local gentian violet
C. Estrogens
D. Penicillin and estrogens (Correct Answer)

Explanation: **Explanation:** **Streptococcal vaginitis** (typically caused by Group A Beta-hemolytic Streptococcus) is a common cause of prepubertal vulvovaginitis. The treatment of choice is a combination of **systemic penicillin and estrogens**. 1. **Why Penicillin and Estrogens?** * **Penicillin:** This is the definitive treatment to eradicate the causative organism (*S. pyogenes*). * **Estrogens:** In prepubertal girls, the vaginal mucosa is thin, atrophic, and has a neutral/alkaline pH due to low estrogen levels. This makes the tissue highly susceptible to infection. Administering low-dose estrogen (usually as a local cream) thickens the vaginal epithelium and promotes a more resistant environment, accelerating the healing process and preventing recurrence. 2. **Analysis of Incorrect Options:** * **A. Systemic penicillin:** While it treats the infection, using it alone results in a higher rate of recurrence compared to the combination therapy because the underlying atrophic state of the mucosa remains unchanged. * **B. Local gentian violet:** This is an old-fashioned antiseptic/antifungal treatment. It is messy, can cause skin irritation, and is not the standard of care for bacterial streptococcal infections. * **C. Estrogens:** Estrogens alone cannot eradicate a bacterial pathogen; they only modify the host environment. **Clinical Pearls for NEET-PG:** * **Most common cause of prepubertal vaginitis:** Non-specific (poor hygiene). * **Most common specific bacterial cause:** *Streptococcus pyogenes* (Group A Strep). * **Clinical Clue:** Look for a history of recent respiratory infection or "scarlet fever" rash, as the bacteria is often transferred from the upper respiratory tract to the perineum via the hands. * **Presentation:** Characterized by bright red, "beefy" erythema of the vulva and a serosanguinous discharge.

Question 228: A 10-year-old child presents to the OPD with fever, neck rigidity, convulsions, and signs of meningeal irritation. Cerebrospinal fluid (CSF) examination shows normal glucose, slightly elevated proteins, and appears clear on gross examination. What is the most probable diagnosis?

A. Viral meningitis (Correct Answer)
B. Bacterial meningitis
C. Tubercular meningitis
D. Sub-arachnoid hemorrhage

Explanation: ### Explanation The clinical presentation of fever, neck rigidity, and convulsions indicates **meningitis**. The key to differentiating the etiology lies in the **CSF analysis**. **1. Why Viral Meningitis is Correct:** Viral (Aseptic) meningitis typically presents with a **clear CSF appearance**. The biochemical markers are characteristic: * **Glucose:** Normal (Viruses do not consume glucose). * **Proteins:** Normal to slightly elevated (usually <100 mg/dL). * **Cell count:** Predominantly lymphocytic pleocytosis (though neutrophils may appear very early). The combination of meningeal signs with normal glucose and clear CSF is the classic "textbook" description of a viral etiology. **2. Why Other Options are Incorrect:** * **Bacterial Meningitis:** CSF is typically **turbid/purulent**. It shows **markedly low glucose** (hypoglycorrhachia), significantly elevated proteins, and a high polymorphonuclear (neutrophil) count. * **Tubercular Meningitis (TBM):** CSF is often clear or "cobweb" appearance. However, TBM is characterized by **very low glucose** and **very high protein** levels. The clinical course is usually more subacute/chronic compared to viral meningitis. * **Sub-arachnoid Hemorrhage:** While it causes signs of meningeal irritation (chemical meningitis), the CSF would be **grossly bloody or xanthochromic** (yellowish) rather than clear, with a high RBC count. **Clinical Pearls for NEET-PG:** * **Most common cause of viral meningitis:** Enteroviruses (Coxsackie, Echovirus). * **Mumps Meningitis:** Unique among viral causes as it can sometimes show *low* CSF glucose. * **CSF Glucose Rule:** Normal CSF glucose is approximately **2/3rd (60-70%)** of the simultaneous blood glucose level. * **Latex Agglutination Test:** Useful for rapid diagnosis of bacterial meningitis if the patient has already received prior antibiotics (partially treated meningitis).

Question 229: What is the most common complication of measles in children?

A. Subacute sclerosing panencephalitis (SSPE)
B. Pulmonary hypertension
C. Otitis media (Correct Answer)
D. Oophoritis

Explanation: **Explanation:** Measles (Rubeola) is a highly contagious viral infection that leads to generalized immunosuppression, predisposing children to secondary bacterial infections. **Why Otitis Media is the correct answer:** While pneumonia is the most common cause of measles-related *death* in children, **Otitis Media** is statistically the **most common complication** overall. It occurs in approximately 5–10% of cases. The virus causes inflammation of the respiratory tract and Eustachian tube dysfunction, allowing secondary bacterial pathogens (like *S. pneumoniae*) to infect the middle ear. **Analysis of Incorrect Options:** * **A. Subacute sclerosing panencephalitis (SSPE):** This is a fatal, progressive degenerative neurological disorder. While it is a classic association, it is a **rare, late complication** occurring years after the initial infection (incidence ~1 in 10,000 to 100,000). * **B. Pulmonary hypertension:** This is not a recognized direct complication of measles. However, giant cell pneumonia (Hecht pneumonia) is a severe respiratory complication, especially in immunocompromised patients. * **D. Oophoritis:** This is a classic complication of **Mumps**, not Measles. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication:** Otitis Media. * **Most common cause of death:** Pneumonia. * **Most common neurological complication:** Post-measles encephalitis (Acute Disseminated Encephalomyelitis). * **Pathognomonic sign:** Koplik spots (found on the buccal mucosa opposite the lower 2nd molars). * **Vitamin Supplementation:** Vitamin A reduces morbidity and mortality in all children with acute measles. * **First sign of recovery:** Fading of the rash in the same order it appeared, often leaving behind "branny desquamation" and brownish staining.

Question 230: A boy presented with multiple non-suppurative osteomyelitic dactylitis with sickle cell anaemia. What is the likely causative organism?

A. Salmonella typhi (Correct Answer)
B. S. aureus
C. H. influenzae
D. Peptococcus magnus

Explanation: **Explanation:** In patients with **Sickle Cell Anemia (SCA)**, there is a unique predisposition to osteomyelitis. While **Staphylococcus aureus** remains the most common cause of osteomyelitis in the general pediatric population, **Salmonella species** (specifically *S. typhi* and *S. typhimurium*) are the most common pathogens isolated in children with SCA. **Why Salmonella?** 1. **Hyposplenism:** Functional asplenia in SCA reduces the clearance of encapsulated organisms. 2. **Bowel Infarction:** Micro-infarctions in the gut mucosa allow *Salmonella* to translocate into the bloodstream. 3. **Bone Infarction:** Vaso-occlusive crises create areas of ischemic bone (infarcts), which act as a nidus for hematogenous seeding of *Salmonella*. 4. **Dactylitis (Hand-Foot Syndrome):** This is often the first manifestation of SCA in infants, presenting as symmetrical, non-suppurative swelling of the short tubular bones of the hands and feet. **Analysis of Incorrect Options:** * **B. S. aureus:** Although it is the #1 cause of osteomyelitis in healthy children, it is statistically surpassed by *Salmonella* in the specific context of Sickle Cell Anemia. * **C. H. influenzae:** Previously a common cause of septic arthritis/osteomyelitis in children, its incidence has plummeted due to the Hib vaccine. * **D. Peptococcus magnus:** This is an anaerobic organism occasionally associated with prosthetic joint infections or chronic osteomyelitis, but it is not a primary pathogen in SCA dactylitis. **Clinical Pearls for NEET-PG:** * **Radiology:** In *Salmonella* osteomyelitis, look for **diaphyseal involvement** and extensive involucrum formation. * **Dactylitis vs. Osteomyelitis:** Dactylitis is often due to infarction (ischemia), but if it presents with fever and systemic symptoms in an SCA patient, *Salmonella* must be ruled out. * **Treatment:** Third-generation cephalosporins (Ceftriaxone) or Fluoroquinolones are preferred.

Practice by Chapter

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Immunization Schedule

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Common Childhood Infections

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Pediatric HIV

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Congenital Infections

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Fever in Infants and Children

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Meningitis and Encephalitis

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Respiratory Tract Infections

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Gastrointestinal Infections

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Parasitic Infections

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Tuberculosis in Children

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Opportunistic Infections

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