Infectious Diseases — MCQs
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Which of the following symptoms is NOT suggestive of Scarlet fever?
A 2-year-old child in shock presents with multiple non-blanching purple lesions of various sizes scattered on the trunk and extremities. Petechiae are noted, and oozing from the venipuncture site has been observed. The child's peripheral blood smear is shown below. Clotting studies are likely to show which of the following?
At what age is Streptococcus pneumoniae pneumonia most commonly present?
A neonate presents with periventricular calcifications on CT scan of the brain. What is the most appropriate diagnostic method for the suspected etiological agent?
Which of the following statements regarding typhoid in children is false?
A 3-year-old female child presented with low-grade fever, poor feeding, and a rash described as a 'slapped cheek' rash. Which of the following is the predominant site of action of the causative organism?
Which of the following acts as a means of transmission of HIV infection in a newborn?
In rubella syndrome, all are seen except?
A 4-year-old girl with a history of hydrocephalus presents with severe headache and fever. She underwent surgery for a ventricular-peritoneal shunt 2 months ago. The neurologist suspects an infection. Which organism would most likely be isolated from the shunt tubing?
What management is indicated for an infant born to an HIV-positive mother?
Infectious Diseases Indian Medical PG Practice Questions and MCQs
Question 111: Which of the following symptoms is NOT suggestive of Scarlet fever?
- A. Gooseflesh rash
- B. Nagayama spots (Correct Answer)
- C. Desquamation of palms
- D. Strawberry tongue
Explanation: **Explanation:** **Nagayama spots** are the correct answer because they are characteristic of **Roseola Infantum (Exanthema Subitum)**, caused by Human Herpesvirus 6 (HHV-6), not Scarlet fever. These are small, erythematous papules or ulcers found on the soft palate and uvula. **Scarlet Fever** is caused by Group A Streptococcus (Streptococcus pyogenes) producing erythrogenic toxins. The other options are classic clinical features of this condition: * **Gooseflesh rash (Sandpaper rash):** This is the hallmark rash of Scarlet fever. It is a fine, erythematous, punctate rash that blanches on pressure and feels rough, similar to sandpaper or "gooseflesh." * **Strawberry tongue:** Initially, the tongue has a white coating with red papillae (White Strawberry Tongue); by day 4-5, the white coat sloughs off, leaving a bright red, inflamed surface (Red Strawberry Tongue). * **Desquamation:** As the rash fades, the skin undergoes "fine branny" desquamation, which is particularly prominent on the palms, soles, and tips of the fingers/toes. **Clinical Pearls for NEET-PG:** * **Pastia’s lines:** Linear petechiae in skin folds (axilla, antecubital fossa) seen in Scarlet fever. * **Circumoral pallor:** A pale area around the mouth contrasting with flushed cheeks. * **Treatment:** Penicillin is the drug of choice. * **Differential Diagnosis:** Nagayama spots = Roseola; Koplik spots = Measles; Forchheimer spots = Rubella.
Question 112: A 2-year-old child in shock presents with multiple non-blanching purple lesions of various sizes scattered on the trunk and extremities. Petechiae are noted, and oozing from the venipuncture site has been observed. The child's peripheral blood smear is shown below. Clotting studies are likely to show which of the following?
- A. Increased levels of factors V and VIII
- B. A decreased prothrombin level
- C. An increased fibrinogen level
- D. The presence of fibrin split products (Correct Answer)
Explanation: ***The presence of fibrin split products*** - The clinical presentation of **shock**, **non-blanching purple lesions**, **petechiae**, and **oozing from venipuncture sites** strongly suggests **disseminated intravascular coagulation (DIC)**. - In DIC, **fibrinogen** is converted to **fibrin** and subsequently broken down by **plasmin**, leading to elevated **fibrin degradation products (FDPs)** and **D-dimers** as hallmark findings. *Increased levels of factors V and VIII* - In DIC, **coagulation factors** including **factors V and VIII** are **consumed** during the coagulation cascade, resulting in **decreased** rather than increased levels. - The **consumption coagulopathy** depletes clotting factors as they are utilized in widespread **microthrombi formation** throughout the circulation. *A decreased prothrombin level* - While **prothrombin (factor II)** levels may be decreased due to consumption in DIC, this is not the **most characteristic** or **reliable** finding. - **Fibrin split products** are more **specific** and **sensitive** markers for diagnosing DIC compared to individual factor levels. *An increased fibrinogen level* - **Fibrinogen** levels are typically **decreased** in DIC due to **consumption** during widespread **fibrin formation** and subsequent **fibrinolysis**. - The **schistocytes** visible on blood smear indicate **microangiopathic hemolytic anemia**, supporting the diagnosis of DIC where fibrinogen is consumed.
Question 113: At what age is Streptococcus pneumoniae pneumonia most commonly present?
- A. Less than 5 years (Correct Answer)
- B. 5 - 15 years
- C. 20 - 25 years
- D. 30 - 40 years
Explanation: **Explanation:** *Streptococcus pneumoniae* (Pneumococcus) is the most common bacterial cause of community-acquired pneumonia (CAP) across almost all age groups. however, its incidence is highest in children **less than 5 years of age**. **Why Option A is Correct:** In children under 5, the immune system is still developing, particularly the ability to mount a robust response to polysaccharide-encapsulated bacteria like *S. pneumoniae*. Furthermore, nasopharyngeal colonization rates are highest in this age group (up to 60-90% in some settings), serving as a reservoir for invasive disease. According to WHO and Nelson’s Pediatrics, pneumonia remains a leading cause of mortality in children under 5 globally, with *S. pneumoniae* being the primary bacterial pathogen. **Why Other Options are Incorrect:** * **Option B (5-15 years):** While *S. pneumoniae* still occurs, "atypical" pathogens like *Mycoplasma pneumoniae* and *Chlamydophila pneumoniae* become increasingly prevalent in school-aged children and adolescents. * **Options C & D (Adults):** Although *S. pneumoniae* is the most common cause of CAP in adults, the absolute incidence and the burden of disease are significantly lower compared to the vulnerable under-5 pediatric population. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of CAP:** *S. pneumoniae* is the #1 cause in children >3 weeks of age through adulthood. * **Most common cause of Neonatal Pneumonia (<3 weeks):** Group B Streptococcus (GBS) and *E. coli*. * **Radiology:** Typically presents as **lobar consolidation** with air bronchograms. * **Vaccination:** The PCV-13 (Pneumococcal Conjugate Vaccine) is part of India’s Universal Immunization Programme (UIP) to reduce mortality in the under-5 age group. * **Drug of Choice:** Amoxicillin remains the first-line treatment for pediatric pneumococcal pneumonia.
Question 114: A neonate presents with periventricular calcifications on CT scan of the brain. What is the most appropriate diagnostic method for the suspected etiological agent?
- A. Urine examination (Correct Answer)
- B. Liver biopsy
- C. Blood examination
- D. Cerebrospinal fluid examination
Explanation: **Explanation:** The clinical presentation of **periventricular calcifications** in a neonate is a classic hallmark of **Congenital Cytomegalovirus (CMV) infection**, the most common intrauterine infection worldwide. **Why Urine Examination is Correct:** The gold standard for diagnosing congenital CMV is the detection of the virus in **urine or saliva** via **Viral Culture** or **PCR** within the first 3 weeks of life. Urine is the preferred specimen because CMV is shed in very high titers in the urine of infected neonates, making it highly sensitive and specific. Detection after 3 weeks may represent post-natal acquisition rather than congenital infection. **Why Other Options are Incorrect:** * **Liver Biopsy:** While CMV can cause hepatitis and "owl’s eye" inclusion bodies may be seen on histology, it is an invasive procedure and not the primary diagnostic modality. * **Blood Examination:** While PCR can be done on blood, it is generally less sensitive than urine or saliva testing for CMV screening in neonates. * **Cerebrospinal Fluid (CSF) Examination:** CSF PCR can be used to evaluate neurological involvement, but it is not the first-line diagnostic test for confirming the systemic etiological agent. **NEET-PG High-Yield Pearls:** * **CMV:** Periventricular calcifications, microcephaly, sensorineural hearing loss (SNHL)—the most common non-genetic cause of SNHL. * **Congenital Toxoplasmosis:** Contrast with CMV; it presents with **diffuse/scattered** intracerebral calcifications and chorioretinitis. * **Treatment:** Symptomatic neonates are treated with **Valganciclovir** (oral) or Ganciclovir (IV) to improve hearing and neurodevelopmental outcomes.
Question 115: Which of the following statements regarding typhoid in children is false?
- A. Splenomegaly may be seen.
- B. Neutropenia may be present.
- C. Urine and stool culture may show the organism after 2 weeks of illness.
- D. Relative bradycardia is invariably seen in children. (Correct Answer)
Explanation: **Explanation:** Typhoid fever (Enteric fever), caused by *Salmonella Typhi*, presents differently in the pediatric population compared to adults. **Why Option D is the Correct Answer (False Statement):** Relative bradycardia (Faget’s sign) is a classic clinical sign of typhoid fever where the heart rate does not increase proportionally with the rise in body temperature. While this is a hallmark in adults, it is **not invariably seen in children**. In pediatric patients, especially younger children, tachycardia is a more common finding during the febrile phase. **Analysis of Other Options:** * **Option A (Splenomegaly):** This is a common clinical finding in typhoid fever, occurring due to the infiltration of the reticuloendothelial system by the bacteria. It usually appears by the end of the first week. * **Option B (Neutropenia):** Hematological changes in typhoid typically include leucopenia with a relative lymphocytosis. Neutropenia is a characteristic feature and helps differentiate it from pyogenic infections where neutrophilia is expected. * **Option C (Urine and Stool Culture):** The diagnostic yield of cultures changes over time. While blood cultures are most sensitive in the 1st week, stool and urine cultures become positive later, typically after the **2nd week** of illness as the bacteria are shed from the gallbladder and kidneys. **NEET-PG High-Yield Pearls:** * **Gold Standard Diagnosis:** Bone marrow culture (highest sensitivity, even after starting antibiotics). * **Most Common Culture:** Blood culture (positive in 90% of cases in the 1st week). * **Widal Test:** Significant only after the 1st week; look for a four-fold rise in titers. * **Drug of Choice:** Ceftriaxone (due to widespread multi-drug resistance/NALD strains). * **Complications:** Intestinal perforation and hemorrhage usually occur in the 3rd week.
Question 116: A 3-year-old female child presented with low-grade fever, poor feeding, and a rash described as a 'slapped cheek' rash. Which of the following is the predominant site of action of the causative organism?
- A. Spleen
- B. Liver
- C. Bone marrow (Correct Answer)
- D. Nerves
Explanation: **Explanation:** The clinical presentation of a low-grade fever followed by a characteristic **'slapped cheek' rash** (erythema infectiosum or Fifth disease) is diagnostic of **Parvovirus B19** infection. **Why Bone Marrow is correct:** Parvovirus B19 has a specific tropism for **erythroid progenitor cells** (specifically proerythroblasts) in the **bone marrow**. The virus enters these cells by binding to the **P-antigen** (globoside) on the cell surface. Once inside, it replicates and causes cell lysis, leading to a temporary cessation of erythropoiesis. In healthy children, this is clinically insignificant, but in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis), it can trigger a life-threatening **Aplastic Crisis**. **Why other options are incorrect:** * **Spleen:** While the spleen clears damaged RBCs, it is not the primary site of Parvovirus replication. * **Liver:** The liver is a site of extramedullary hematopoiesis in fetuses (where Parvovirus can cause *Hydrops Fetalis*), but in a 3-year-old, the bone marrow is the definitive site. * **Nerves:** Neurotropism is characteristic of viruses like Poliovirus, Rabies, or VZV, but not Parvovirus B19. **High-Yield Clinical Pearls for NEET-PG:** * **Biphasic Illness:** Initial viremic phase (fever, malaise) followed by an immune-mediated phase (rash and arthralgia). * **Infectivity:** The child is **no longer infectious** once the rash appears. * **Pregnancy:** Infection during pregnancy can lead to **Hydrops Fetalis** due to severe fetal anemia and high-output cardiac failure. * **Diagnosis:** IgM antibodies (acute) or PCR (especially in immunocompromised/aplastic crisis).
Question 117: Which of the following acts as a means of transmission of HIV infection in a newborn?
- A. Transplacental
- B. Breast feeding
- C. During delivery
- D. All of these (Correct Answer)
Explanation: **Explanation:** Transmission of HIV from an infected mother to her child is known as **Vertical Transmission** or **Mother-to-Child Transmission (MTCT)**. It can occur at three distinct stages, making "All of these" the correct answer. 1. **Transplacental (Antenatal):** HIV can cross the placental barrier during pregnancy. This accounts for approximately **20–25%** of vertical transmission cases. 2. **During Delivery (Intranatal):** This is the period of highest risk (**60–65%**). Transmission occurs through contact with infected maternal blood and cervicovaginal secretions in the birth canal, or via micro-transfusions during uterine contractions. 3. **Breastfeeding (Postnatal):** HIV is present in breast milk. Prolonged breastfeeding increases the risk of transmission by **10–15%**. **Why other options are not "the" single answer:** While A, B, and C are all valid routes, selecting any one individually would be incomplete. In the absence of intervention, the cumulative risk of transmission across all three routes is approximately 25–45%. **High-Yield Clinical Pearls for NEET-PG:** * **Most common timing:** The majority of transmissions occur **intranatally** (during labor and delivery). * **Prevention (PMTCT):** The risk can be reduced to <2% with Highly Active Antiretroviral Therapy (HAART), elective cesarean section (if viral load is high), and avoidance of breastfeeding. * **Diagnosis in Infants:** Standard antibody tests (ELISA) are unreliable until 18 months due to persisting maternal IgG. The gold standard for diagnosis in infants <18 months is **HIV DNA PCR**. * **Prophylaxis:** Infants born to HIV-positive mothers should receive **Nevirapine** or Zidovudine prophylaxis for 6–12 weeks.
Question 118: In rubella syndrome, all are seen except?
- A. Salt and paper chorioretinopathy
- B. Congenital cataract
- C. Macrophthalmos (Correct Answer)
- D. Cloudy cornea
Explanation: **Explanation:** Congenital Rubella Syndrome (CRS) is characterized by a classic triad of **Cataracts, Cardiac defects (PDA), and Sensorineural deafness**. The correct answer is **Macrophthalmos** because CRS typically causes **Microphthalmos** (abnormally small eyes) due to the virus inhibiting cell division during ocular development. Macrophthalmos (large eyes) is characteristic of Congenital Glaucoma (Buphthalmos), which is a separate entity, though glaucoma can occasionally occur in CRS. **Analysis of Options:** * **Salt and Pepper Chorioretinopathy:** This is the **most common** ocular manifestation of CRS. It involves fine pigmentary changes in the retina that do not usually affect vision but are diagnostic. * **Congenital Cataract:** A hallmark of the "Gregg Triad." It is often bilateral and described as a "pearled" nuclear opacification. * **Cloudy Cornea:** This occurs in CRS due to either transient neonatal corneal edema or secondary to infantile glaucoma, which is a known (though less frequent) complication of the syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad (Gregg Triad):** Cataract, PDA (continuous machinery murmur), and Deafness. * **Skin Manifestation:** "Blueberry muffin" spots (extramedullary hematopoiesis). * **Radiology:** "Celery stalking" appearance of long bones (metaphyseal lucencies). * **Timing:** Risk is highest if the mother is infected during the **first trimester** (especially the first 8 weeks). * **Diagnosis:** Detection of Rubella-specific IgM in the neonate or persistence of IgG beyond 6 months.
Question 119: A 4-year-old girl with a history of hydrocephalus presents with severe headache and fever. She underwent surgery for a ventricular-peritoneal shunt 2 months ago. The neurologist suspects an infection. Which organism would most likely be isolated from the shunt tubing?
- A. Staphylococcus aureus
- B. Streptococcus
- C. Staphylococcus epidermidis (Correct Answer)
- D. Meningococcus
Explanation: ### Explanation **Correct Answer: C. Staphylococcus epidermidis** **Why it is correct:** Ventricular-peritoneal (VP) shunt infections are a common complication following neurosurgery for hydrocephalus. The most frequent causative organisms are **Coagulase-Negative Staphylococci (CoNS)**, specifically ***Staphylococcus epidermidis*** (accounting for approximately 50–60% of cases). The underlying medical concept is the ability of *S. epidermidis* to produce a **biofilm (extracellular polysaccharide slime)**. This biofilm allows the bacteria to adhere strongly to the synthetic material of the shunt tubing and protects them from the host's immune response and systemic antibiotics. Most infections occur within the first few months post-surgery due to skin flora contamination during the procedure. **Why other options are incorrect:** * **A. Staphylococcus aureus:** This is the second most common cause (approx. 20%). While it causes more acute and fulminant presentations, it is less frequent than *S. epidermidis*. * **B. Streptococcus:** These are common causes of respiratory or skin infections but are rarely implicated in prosthetic device infections unless there is a specific focus or hematogenous spread. * **D. Meningococcus (*Neisseria meningitidis*):** This is a leading cause of community-acquired bacterial meningitis in children but is not associated with foreign body/shunt-related infections. **High-Yield Clinical Pearls for NEET-PG:** 1. **Timing:** Most shunt infections occur within **6 months** of placement (highest risk in the first 2 months). 2. **Presentation:** In children, look for signs of increased intracranial pressure (headache, vomiting, irritability) and fever. 3. **Management:** The gold standard treatment is **shunt removal**, external ventricular drainage (EVD), and IV antibiotics (usually Vancomycin to cover MRSE), followed by shunt replacement once CSF is sterile. 4. **Distinction:** If the question mentions a "distal" infection (peritonitis), consider Gram-negative bacilli like *E. coli*.
Question 120: What management is indicated for an infant born to an HIV-positive mother?
- A. BCG vaccine should not be given
- B. Antiretroviral therapy (AZT) (Correct Answer)
- C. Separation from the mother
- D. All vaccinations except BCG should be administered
Explanation: **Explanation:** The primary goal in managing an infant born to an HIV-positive mother is the prevention of parent-to-child transmission (PPTCT). **1. Why Option B is Correct:** Post-exposure prophylaxis (PEP) is mandatory for all HIV-exposed infants to reduce the risk of vertical transmission. According to current guidelines (NACO/WHO), **Zidovudine (AZT)** or Nevirapine (NVP) is initiated as soon as possible after birth (ideally within 6–12 hours) and continued for 6 to 12 weeks, depending on the risk stratification. **2. Why Other Options are Incorrect:** * **Option A & D:** In HIV-exposed infants, **BCG is NOT contraindicated** unless the infant is clinically symptomatic or confirmed to be HIV-positive with severe immunosuppression. In most endemic settings like India, BCG is administered at birth regardless of HIV exposure status. * **Option C:** Separation from the mother is contraindicated. Rooming-in is encouraged to promote bonding. Regarding feeding, exclusive breastfeeding for the first 6 months is recommended (provided the mother is on ART), or exclusive replacement feeding if it is "AFASS" (Affordable, Feasible, Acceptable, Sustainable, and Safe). Mixed feeding must be strictly avoided. **NEET-PG High-Yield Pearls:** * **Diagnosis:** The gold standard for diagnosing HIV in infants <18 months is **HIV DNA PCR** (at 6 weeks). Antibody tests (ELISA) are unreliable due to the persistence of maternal IgG antibodies. * **Prophylaxis:** **Cotrimoxazole prophylaxis** should be started at 6 weeks of age for all HIV-exposed infants to prevent *Pneumocystis jirovecii* pneumonia, continuing until the infant is confirmed HIV-negative. * **Confirmatory Test:** A definitive negative status is usually determined by antibody testing at **18 months**.
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Vaccine-Preventable Diseases
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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
Practice Questions
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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