Infectious Diseases — MCQs

A 4-year-old with fever, neck stiffness, and petechial rash presents with a positive Kernig sign, positive Brudzinski sign, heart rate of 140, respiratory rate of 30, and blood pressure of 90/50. CSF analysis shows increased white blood cells, decreased glucose, and increased protein. Analyze the situation and initiate the most appropriate treatment.

Q519

A child presents with a painful swelling below the ear, fever, and difficulty opening the mouth. What is the most likely diagnosis?

Q520

A child with acute otitis media who fails initial antibiotic therapy, what is the next step in management?

Infectious Diseases Indian Medical PG Practice Questions and MCQs

Question 511: A 5-year-old child presents with fever, ear pain, and a bulging tympanic membrane. What is the most likely diagnosis?

A. Otitis externa
B. Acute otitis media (Correct Answer)
C. Chronic otitis media
D. Eustachian tube dysfunction

Explanation: ***Acute otitis media*** - **Fever**, **ear pain**, and a **bulging tympanic membrane** are classic signs of inflammation and fluid accumulation in the middle ear space, characteristic of acute otitis media. - This condition is common in children due to their developing **Eustachian tubes** and frequent upper respiratory infections. *Otitis externa* - This condition is an inflammation of the **outer ear canal**, often called **"swimmer's ear"**. - Typically presents with **pain upon touching the earlobe** or during tragal pressure, and usually does not cause a bulging tympanic membrane or significant fever unless severe. *Chronic otitis media* - This involves **persistent inflammation** of the middle ear, often with a **perforated tympanic membrane** and ear discharge, lasting for weeks or months. - It does not typically present with the acute, severe symptoms of fever and a bulging tympanic membrane seen in this case. *Eustachian tube dysfunction* - This condition involves impaired function of the **Eustachian tube**, leading to a feeling of **fullness or pressure in the ear** and sometimes hearing loss. - While it can predispose to otitis media, it does not directly cause the acute inflammatory signs of fever, severe pain, and a bulging tympanic membrane.

Question 512: A newborn presents with hydrocephalus and intracranial calcifications. The mother has a history of consuming raw meat during pregnancy. What is the most likely diagnosis?

A. Cytomegalovirus infection
B. Rubella
C. Toxoplasmosis (Correct Answer)
D. Syphilis

Explanation: ***Correct: Toxoplasmosis*** - The classic triad of congenital toxoplasmosis includes **hydrocephalus**, intracranial calcifications, and chorioretinitis (though chorioretinitis is not mentioned here, the first two are highly suggestive). - Consuming **raw meat** or contact with cat feces are common routes of transmission for *Toxoplasma gondii*. - Intracranial calcifications in toxoplasmosis are typically **diffuse and scattered** throughout the brain parenchyma. *Incorrect: Cytomegalovirus infection* - While CMV can cause **intracranial calcifications**, they are typically **periventricular** (not diffuse), which helps differentiate from toxoplasmosis. - Hydrocephalus is less common than in toxoplasmosis. - Hearing loss and **microcephaly** (not hydrocephalus) are more frequently associated with congenital CMV. *Incorrect: Rubella* - Congenital rubella syndrome is characterized by sensorineural **deafness**, **cataracts**, and congenital **heart defects** (e.g., patent ductus arteriosus), not hydrocephalus or intracranial calcifications. - **Blueberry muffin rash** is also a characteristic skin manifestation. *Incorrect: Syphilis* - Congenital syphilis can present with **bone abnormalities** (e.g., metaphysitis), hepatosplenomegaly, and skin rashes. - Neurosyphilis can occur but typically involves **meningitis** or hydrocephalus secondary to inflammation, not primarily due to calcifications, and often presents later.

Question 513: A 12-year-old girl presents with fever, shortness of breath, and cough. A chest X-ray reveals complete consolidation of the left lower lung lobe. What is the most probable organism?

A. Streptococcus pneumoniae (Correct Answer)
B. Staphylococcus aureus
C. Klebsiella pneumoniae
D. Pseudomonas aeruginosa

Explanation: ***Streptococcus pneumoniae*** - This is the most common bacterial cause of **community-acquired pneumonia** in children and adults, and symptoms perfectly align with lobar consolidation. - **Lobar pneumonia**, as suggested by complete consolidation of a lung lobe on chest X-ray, is a classic presentation of *Streptococcus pneumoniae* infection. *Staphylococcus aureus* - While *Staphylococcus aureus* can cause pneumonia, it often leads to **necrotizing pneumonia** or **empyema**, and is more common in hospitalized patients or those with predisposing factors like cystic fibrosis or influenza. - Its presentation is typically more severe and less frequently causes simple lobar consolidation in an otherwise healthy child. *Klebsiella pneumoniae* - *Klebsiella pneumoniae* typically causes **severe, necrotizing pneumonia** often seen in individuals with chronic alcohol abuse, diabetes, or immunocompromised states. - It characteristically produces a **"currant jelly" sputum** and is less common in healthy children with classic lobar pneumonia. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* pneumonia is primarily associated with **hospital-acquired infections**, **ventilator-associated pneumonia**, or in patients with underlying lung disease like **cystic fibrosis** or bronchiectasis. - It is highly unlikely to be the causative organism in an otherwise healthy 12-year-old presenting with typical community-acquired pneumonia.

Question 514: What is the most common cause of urinary tract infections in children?

A. Klebsiella
B. Proteus
C. Staphylococcus aureus
D. Escherichia coli (Correct Answer)

Explanation: ***Escherichia coli*** - **Uropathogenic *E. coli*** (*UPEC*) is the most prevalent bacterium responsible for UTIs in children, accounting for approximately 80–90% of cases. - Its virulence factors, such as **P fimbriae**, enable it to adhere to uroepithelial cells and colonize the urinary tract. *Klebsiella* - While *Klebsiella* species can cause UTIs, they are a less common etiology than *E. coli*, particularly in uncomplicated cases. - More frequently associated with complicated UTIs, recurrent infections, or infections in hospitalized patients. *Proteus* - *Proteus mirabilis* is a notable cause of UTIs, particularly those associated with **struvite stones** due to its urease production. - However, its overall prevalence in pediatric UTIs is significantly lower compared to *E. coli*. *Staphylococcus aureus* - *S. aureus* is an uncommon cause of primary UTIs and is more typically associated with **hematogenous spread** to the kidneys, leading to renal abscesses, or with catheter-associated infections. - It almost never causes uncomplicated cystitis in children.

Question 515: At what age should children begin receiving the influenza vaccine?

A. 6 months (Correct Answer)
B. 2 years
C. At birth
D. 12 months

Explanation: ***6 months*** - The **influenza vaccine** is recommended annually for all individuals aged **6 months and older**. This age is chosen because infants younger than 6 months are at higher risk for severe influenza complications but cannot directly receive the vaccine. - For children aged 6 months to 8 years receiving the vaccine for the first time, **two doses** administered at least four weeks apart are recommended. *At birth* - Influenza vaccines are **not approved or recommended for infants younger than 6 months** due to lack of efficacy and safety data in this age group. - Protection for infants under 6 months relies on **maternal vaccination** during pregnancy and cocooning strategies (vaccinating household contacts). *12 months* - Waiting until 12 months means the child misses out on a full season or more of potential protection during their first year of life when they are particularly vulnerable if not vaccinated. - The recommendation is to start at 6 months, not to delay until 12 months, to provide timely protection against influenza. *2 years* - Delaying vaccination until 2 years old would leave a child unprotected through several high-risk influenza seasons. - Current guidelines uniformly recommend vaccination starting at 6 months, highlighting the importance of early protection against influenza.

Question 516: Which of the following is the most common cause of viral meningitis in children?

A. Enterovirus (Correct Answer)
B. Herpes simplex virus
C. Adenovirus
D. Cytomegalovirus

Explanation: ***Enterovirus*** - **Enteroviruses** (e.g., Coxsackievirus, Echovirus) are the most frequent cause of **aseptic meningitis** in children, particularly during summer and fall. - They are typically transmitted via the **fecal-oral route** and cause a relatively mild, self-limiting illness. *Herpes simplex virus* - While **Herpes simplex virus (HSV)** can cause meningitis, it is a less common cause than enteroviruses, especially in children, and is more often associated with **encephalitis**. - HSV meningitis can be recurrent (Mollaret's meningitis) but is not the most common overall cause of viral meningitis in children. *Adenovirus* - **Adenovirus** can cause a range of infections, including respiratory, gastrointestinal, and conjunctivitis, but it is a relatively uncommon cause of **viral meningitis** compared to enteroviruses. - When it does cause meningitis, it is often in immunocompromised individuals. *Cytomegalovirus* - **Cytomegalovirus (CMV)** is a significant cause of viral infections, particularly in immunocompromised individuals and congenitally infected infants, where it can cause neurological complications. - However, it is not the most common cause of **viral meningitis** in the general pediatric population.

Question 517: A 7-year-old boy presents with a barking cough and stridor. What is the most likely causative agent?

A. Respiratory syncytial virus
B. Parainfluenza virus (Correct Answer)
C. Adenovirus
D. Influenza virus

Explanation: ***Parainfluenza virus*** - **Parainfluenza virus** is the most common cause of **croup** (laryngotracheobronchitis), characterized by a **barking cough**, **stridor**, and hoarseness. - The patient's age and clinical presentation are highly consistent with parainfluenza infection. *Respiratory syncytial virus* - **RSV** is a primary cause of **bronchiolitis** and **pneumonia** in infants and young children, often leading to wheezing and respiratory distress. - While it can cause upper respiratory symptoms, it typically does not present with the classic **barking cough** and **stridor** of croup. *Adenovirus* - **Adenovirus** can cause a variety of infections, including **pharyngoconjunctival fever**, acute respiratory disease, and gastroenteritis. - Although it can cause respiratory symptoms, it is not the most common etiology for croup. *Influenza virus* - **Influenza virus** typically causes abrupt onset of fever, myalgia, headache, and a **non-barking cough**. - While it can cause severe respiratory illness, it is less commonly associated with the distinct **barking cough** and **stridor** seen in croup.

Question 518: A 4-year-old with fever, neck stiffness, and petechial rash presents with a positive Kernig sign, positive Brudzinski sign, heart rate of 140, respiratory rate of 30, and blood pressure of 90/50. CSF analysis shows increased white blood cells, decreased glucose, and increased protein. Analyze the situation and initiate the most appropriate treatment.

A. IV antibiotics + IV dexamethasone (Correct Answer)
B. IV antivirals + fluid resuscitation
C. Lumbar puncture + observation without antibiotics
D. Supportive care and observation only

Explanation: ***IV antibiotics + IV dexamethasone*** - The clinical picture of **fever**, **neck stiffness**, **petechial rash**, and positive **Kernig** and **Brudzinski** signs strongly indicates **bacterial meningitis**, which is a medical emergency. The CSF analysis with **increased WBCs**, **decreased glucose**, and **increased protein** further confirms bacterial meningitis. - **IV antibiotics** are crucial for killing the bacteria, while **IV dexamethasone** reduces inflammation in the brain, helping to prevent neurological complications such as hearing loss. *IV antivirals + fluid resuscitation* - While fluid resuscitation might be necessary for hemodynamic stability, **IV antivirals** are not the primary treatment for **bacterial meningitis**. - **Antivirals** are used for **viral meningitis** or encephalitis, but the CSF profile (especially **low glucose**) is more consistent with a bacterial infection. *Lumbar puncture + observation without antibiotics* - Performing a **lumbar puncture** is appropriate for diagnosis, but **observation without immediate antibiotics** in a case of suspected bacterial meningitis is extremely dangerous and can lead to rapid deterioration and death. - The patient's critical condition warrants urgent treatment, not just observation after diagnosis. *Supportive care and observation only* - **Supportive care** (e.g., fever reduction, fluid management) is necessary but not sufficient for **bacterial meningitis**. - **Observation only** without specific antimicrobial therapy would result in severe morbidity or mortality in a patient with confirmed bacterial meningitis.

Question 519: A child presents with a painful swelling below the ear, fever, and difficulty opening the mouth. What is the most likely diagnosis?

A. Bacterial parotitis
B. Mumps (Correct Answer)
C. Branchial cyst
D. Lymphadenitis

Explanation: ***Mumps*** - The classic presentation of **mumps** includes **parotitis** (painful swelling below the ear), fever, and sometimes difficulty opening the mouth due to pain, especially in a child. - Mumps is a **viral infection** that primarily affects the parotid glands. *Bacterial parotitis* - While it causes painful swelling and fever, **bacterial parotitis** is more common in **dehydrated** or **immunocompromised individuals**, or those with salivary duct obstruction. - It often presents with **purulent discharge** from Stensen's duct, which is not mentioned in this case. *Branchial cyst* - A **branchial cyst** is a congenital anomaly that presents as a **painless, soft swelling**, usually located on the side of the neck, not typically associated with acute fever or difficulty opening the mouth. - It is typically **non-inflammatory** unless secondarily infected. *Lymphadenitis* - **Lymphadenitis** involves swelling of the **lymph nodes**, which are usually more generalized in the neck or can be tender and inflamed, but typically do not cause the prominent, diffuse swelling below the ear characteristic of parotid involvement. - While it can cause fever, the primary swelling location and nature differ from parotitis.

Question 520: A child with acute otitis media who fails initial antibiotic therapy, what is the next step in management?

A. Repeat the initial antibiotic
B. Switch to a broader spectrum antibiotic (Correct Answer)
C. Add a second antibiotic to the regimen
D. Schedule for myringotomy

Explanation: ***Switch to a broader spectrum antibiotic*** - Failure of initial antibiotic therapy for **acute otitis media** suggests that the causative pathogen may be resistant to the initial drug or is a different organism requiring broader coverage. - Switching to an antibiotic with a **wider spectrum of activity** or one known to be effective against common resistant strains (e.g., high-dose amoxicillin-clavulanate) is generally the next appropriate step. *Repeat the initial antibiotic* - Repeating the same antibiotic without clinical improvement is unlikely to be effective, as it implies the initial drug failed to eradicate the infection, possibly due to **resistance** or an **incorrect diagnosis**. - This approach delays appropriate treatment and may contribute to **antibiotic resistance**. *Add a second antibiotic to the regimen* - While combination therapy is sometimes used for severe infections, simply adding a second antibiotic without considering the spectrum of the initial drug or the most likely resistant pathogens is not typically the first empirical step. - It increases the risk of side effects and can lead to unnecessary **polypharmacy**. *Schedule for myringotomy* - Myringotomy, with or without tympanostomy tube placement, is typically reserved for **recurrent acute otitis media**, persistent middle ear effusion, or complications, not immediately after the failure of an initial antibiotic course. - It is an invasive procedure and should only be considered after medical management options have been exhausted or if there are specific indications such as severe pain or complications (e.g., mastoiditis).

Practice by Chapter

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Respiratory Tract Infections

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Gastrointestinal Infections

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Parasitic Infections

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Opportunistic Infections

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