Infectious Diseases Practice Questions

Q: A previously healthy child develops bacterial meningitis. Assuming no specific contraindications, which of the following is the drug of choice?

Ceftriaxone. **Explanation:** The primary goal in treating bacterial meningitis is the rapid administration of bactericidal antibiotics that achieve high concentrations in the cerebrospinal fluid (CSF). **Why Ceftriaxone is the Correct Answer:** Ceftriaxone (a 3rd-generation cephalosporin) is the drug of choice for empirical treatment of bacterial meningitis in children. It covers the most common pathogens—*Streptococcus pneumoniae* and *Neisseria meningitidis*. Its advantages include excellent CSF penetration, a long half-life (allowing once or twice daily dosing), and high efficacy against penicillin-resistant strains of *S. pneumoniae*. **Why the Other Options are Incorrect:** * **Erythromycin:** This is a macrolide that is primarily bacteriostatic and has very poor penetration into the blood-brain barrier (BBB), making it ineffective for CNS infections. * **Penicillin V:** This is an oral penicillin with low bioavailability and poor CSF penetration; it is never used for meningitis. * **Penicillin G:** While historically used for meningococcal meningitis, increasing resistance in *S. pneumoniae* and the requirement for very frequent dosing make it a second-line agent compared to Ceftriaxone. **High-Yield Clinical Pearls for NEET-PG:** * **Empirical Therapy:** In children >1 month, the standard regimen is **Ceftriaxone + Vancomycin** (to cover highly resistant *S. pneumoniae*). * **Neonatal Meningitis (<1 month):** The common organisms are *GBS, E. coli,* and *Listeria*. The drug of choice is **Ampicillin + Cefotaxime** (or Gentamicin). * **Avoid Ceftriaxone in Neonates:** It can displace bilirubin from albumin, increasing the risk of **kernicterus**, and can precipitate with intravenous calcium. * **Steroids:** Dexamethasone should be given *before* or with the first dose of antibiotics to reduce the risk of hearing loss, especially in *H. influenzae* type b meningitis.

Q: A 3-year-old child presents with fever, malaise, and oral ulcers, making swallowing difficult. What is the most likely diagnosis?

Acute herpetic gingivostomatitis. ### Explanation **Correct Answer: C. Acute herpetic gingivostomatitis** **1. Why it is correct:** Acute herpetic gingivostomatitis is the most common clinical manifestation of **primary Herpes Simplex Virus Type 1 (HSV-1)** infection in children, typically occurring between ages 6 months and 5 years. The clinical triad of **high-grade fever, malaise, and painful oral ulcers** (often involving the gingiva, tongue, and buccal mucosa) is classic. The pain is often severe enough to cause drooling and refusal to swallow, leading to dehydration—a common reason for hospitalization in this age group. **2. Why the other options are incorrect:** * **Aphthous stomatitis:** These are "canker sores." While painful, they are typically **not associated with systemic symptoms** like high fever or malaise. They are usually solitary or few in number and do not involve the diffuse gingival edema seen in primary herpes. * **Herpes labialis:** This represents **reactivation** (secondary infection) of HSV-1. It is characterized by localized "cold sores" or vesicular lesions on the vermilion border of the lips. It lacks the diffuse intraoral involvement and severe systemic toxicity seen in primary gingivostomatitis. **3. NEET-PG High-Yield Pearls:** * **Etiology:** HSV-1 is the most common cause; HSV-2 is rare in the oral cavity. * **Diagnosis:** Primarily clinical. If testing is required, **Tzanck smear** shows multinucleated giant cells and Cowdry type A inclusion bodies. * **Treatment:** Supportive (hydration/analgesia). Oral **Acyclovir** is effective if started within 72 hours of onset. * **Differential:** Hand-Foot-Mouth Disease (Coxsackie A16) also presents with oral ulcers but is distinguished by the presence of vesicular rashes on the palms and soles.

Q: Which of the following is TRUE about measles, EXCEPT?

It is not infective before the rash appears.. **Explanation:** The correct answer is **D**, as the statement is false. Measles is highly contagious and is infective **4 days before to 4 days after** the appearance of the rash. The period of maximum infectivity occurs during the prodromal stage (catarrhal stage) due to high viral shedding in respiratory secretions through coughing and sneezing. **Analysis of other options:** * **Option A:** **Koplik spots** are pathognomonic for measles. They appear on the buccal mucosa opposite the lower second molars during the **prodromal stage**, usually 1–2 days before the rash, and disappear shortly after the rash starts. * **Option B:** In measles, the fever typically **increases (spikes)** with the onset of the rash and then gradually subsides. This is a distinguishing feature from Roseola Infantum, where the fever drops *before* the rash appears. * **Option C:** Under the National Immunization Schedule (NIS) in India, the first dose of the Measles-Rubella (MR) vaccine is administered at **9 completed months** (up to 12 months) to avoid interference from maternal antibodies. **High-Yield Clinical Pearls for NEET-PG:** * **Agent:** RNA Paramyxovirus (Genus *Morbillivirus*). * **Rash Pattern:** Maculopapular, starts behind the ears (retro-auricular), spreads cephalocaudally, and disappears with **brownish discoloration/desquamation**. * **Vitamin A:** Supplementation is mandatory in all children with measles to prevent complications like blindness and reduce mortality. * **Complications:** Most common is **Otitis Media**; most common cause of death is **Pneumonia**; most serious late complication is **SSPE** (Subacute Sclerosing Panencephalitis).

Q: What is the most common complication of mumps?

Orchitis and oophoritis. **Explanation:** Mumps is an acute viral infection caused by the **Rubulavirus** (Paramyxoviridae family), primarily characterized by the painful swelling of the parotid glands. **Why Orchitis and Oophoritis are correct:** Epididymo-orchitis is the **most common extra-salivary complication** of mumps in post-pubertal males, occurring in approximately 20-30% of cases. It is usually unilateral and can lead to testicular atrophy, though permanent sterility is rare. Oophoritis (inflammation of the ovaries) occurs in about 5% of post-pubertal females. The virus has a predilection for glandular tissue and the central nervous system. **Analysis of Incorrect Options:** * **B. Encephalitis:** While CNS involvement is common (often presenting as asymptomatic pleocytosis or viral meningitis), true encephalitis is a rare but severe complication (<1% of cases). * **C. Pneumonia:** Unlike other paramyxoviruses like Measles or RSV, mumps rarely involves the lower respiratory tract. * **D. Myocarditis:** This is an extremely rare complication of mumps, usually presenting with transient ECG changes rather than clinical heart failure. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Aseptic meningitis. * **Most common cause of acute pancreatitis in children:** Mumps virus. * **Neurological sequelae:** Mumps is a classic cause of **sudden onset sensorineural deafness** (usually unilateral). * **Diagnosis:** Elevated **Serum Amylase** is a key biochemical marker due to parotid and pancreatic involvement. * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) as part of the MMR vaccine.

Q: Which of the following conditions does NOT typically present with a maculopapular rash?

Scarlet fever. The correct answer is **Scarlet fever** because it presents with a **sandpaper-like punctate erythematous rash**, rather than a classic maculopapular rash. ### 1. Why Scarlet Fever is the Correct Answer Scarlet fever, caused by Group A Streptococcus (GAS), is characterized by a **finely papular, "sandpaper" rash** on an erythematous base. It typically begins in the flexures (Pastia’s lines) and spreads to the trunk and extremities. Unlike maculopapular rashes, which consist of flat and raised spots, the rash in Scarlet fever is distinctively rough to the touch and is followed by desquamation. ### 2. Analysis of Incorrect Options * **Measles (Rubeola):** This is the prototype of a **maculopapular rash**. It typically begins behind the ears at the hairline and spreads cranio-caudally, becoming confluent. * **Exanthem Subitum (Roseola Infantum):** Caused by HHV-6, it presents with a high fever that subsides, followed by the sudden appearance of a **rose-pink maculopapular rash** starting on the trunk. * **Infectious Mononucleosis (EBV):** While not always present, a **maculopapular rash** frequently occurs in patients with IM, especially after the administration of aminopenicillins (Ampicillin/Amoxicillin). ### 3. High-Yield Clinical Pearls for NEET-PG * **Scarlet Fever Triad:** Strawberry tongue, circumoral pallor, and Pastia’s lines. * **Koplik Spots:** Pathognomonic for Measles (found on buccal mucosa opposite the lower 2nd molars). * **Forchheimer Spots:** Small petechiae on the soft palate seen in **Rubella** (German Measles). * **Nagayama Spots:** Erythematous papules on the soft palate/uvula seen in **Roseola**. * **Slapped Cheek Appearance:** Characteristic of Erythema Infectiosum (Fifth Disease/Parvovirus B19).

Q: Which of the following symptoms is NOT suggestive of Scarlet fever?

Nagayama spots. **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.

Q: Which of the following statements regarding typhoid in children is false?

Relative bradycardia is invariably seen in children.. **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.

Q: In rubella syndrome, all are seen except?

Macrophthalmos. **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.

Q: What management is indicated for an infant born to an HIV-positive mother?

Antiretroviral therapy (AZT). **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**.

Q: A 4-year-old child presented with cough persisting for 1 month and low-grade fever. There was a history of contact with TB. What is the chest X-ray suggestive of?

Primary TB. ***Primary TB*** - A 4-year-old child with **TB contact** and persistent cough typically presents with **primary TB complex** (Ghon focus + hilar lymphadenopathy). - Primary TB in children characteristically shows **hilar lymphadenopathy** with or without parenchymal infiltrates, forming the **Ranke complex**. *Pleural effusion* - More commonly seen in **adolescents and adults** with post-primary TB, not typical in young children. - Would present with **decreased breath sounds** and **dullness to percussion**, which are not mentioned here. *Miliary TB* - Chest X-ray would show **diffuse tiny nodules** (2-3mm) throughout both lung fields, resembling millet seeds. - Represents **hematogenous dissemination** and typically presents with more severe systemic symptoms than described. *Cavitation* - A feature of **post-primary (adult-type) TB**, extremely rare in children under 10 years of age. - Occurs due to **caseous necrosis** and tissue breakdown, which is uncommon in primary TB due to immature immune response.

Question 1

A previously healthy child develops bacterial meningitis. Assuming no specific contraindications, which of the following is the drug of choice?

Accepted Answer

Ceftriaxone

Answer

Erythromycin

Answer

Penicillin V

Answer

Penicillin G

Question 2

A 3-year-old child presents with fever, malaise, and oral ulcers, making swallowing difficult. What is the most likely diagnosis?

Accepted Answer

Acute herpetic gingivostomatitis

Answer

Aphthous stomatitis

Answer

Herpes labialis

Answer

None of the above

Question 3

Which of the following is TRUE about measles, EXCEPT?

Accepted Answer

It is not infective before the rash appears.

Answer

Koplik spots appear in the prodromal stage.

Answer

Fever stops after the onset of the rash.

Answer

The vaccine is given at 9 months of age.

Question 4

What is the most common complication of mumps?

Accepted Answer

Orchitis and oophoritis

Answer

Encephalitis

Answer

Pneumonia

Answer

Myocarditis

Question 5

Which of the following conditions does NOT typically present with a maculopapular rash?

Accepted Answer

Scarlet fever

Answer

Measles

Answer

Exanthem subitum

Answer

Infectious mononucleosis

Question 6

Which of the following symptoms is NOT suggestive of Scarlet fever?

Accepted Answer

Nagayama spots

Answer

Gooseflesh rash

Answer

Desquamation of palms

Answer

Strawberry tongue

Question 7

Which of the following statements regarding typhoid in children is false?

Accepted Answer

Relative bradycardia is invariably seen in children.

Answer

Splenomegaly may be seen.

Answer

Neutropenia may be present.

Answer

Urine and stool culture may show the organism after 2 weeks of illness.

Question 8

In rubella syndrome, all are seen except?

Accepted Answer

Macrophthalmos

Answer

Salt and paper chorioretinopathy

Answer

Congenital cataract

Answer

Cloudy cornea

Question 9

What management is indicated for an infant born to an HIV-positive mother?

Accepted Answer

Antiretroviral therapy (AZT)

Answer

BCG vaccine should not be given

Answer

Separation from the mother

Answer

All vaccinations except BCG should be administered

Question 10

A 4-year-old child presented with cough persisting for 1 month and low-grade fever. There was a history of contact with TB. What is the chest X-ray suggestive of?

Accepted Answer

Primary TB

Answer

Pleural effusion

Answer

Miliary TB

Answer

Cavitation

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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