Examkin

Question

Difficulty: HardPediatric Infectious Diseases

Match each pediatric clinical vignette describing a severe infection with the most likely causative pathogen based on the specific diagnostic or microbiological clues provided.

  • A 14-day-old neonate presents with fever, lethargy, and focal motor seizures. Cerebrospinal fluid analysis reveals a mononuclear pleocytosis, mildly elevated protein, and a significantly elevated red blood cell count despite an atraumatic lumbar puncture.Herpes simplex virus
  • A 3-week-old infant presents with fever, irritability, and poor feeding. Cerebrospinal fluid shows a neutrophilic pleocytosis. The isolated pathogen is a Gram-positive rod that is inherently resistant to all cephalosporins, necessitating the inclusion of ampicillin in the empiric regimen.Listeria monocytogenes
  • A 4-year-old child presents with sudden-onset high fever, headache, and a rapidly spreading non-blanching purpuric rash. The patient quickly develops hemodynamic instability. Blood cultures grow an organism that oxidizes both maltose and glucose.Neisseria meningitidis
  • A 5-day-old neonate born to a mother with poor prenatal care develops respiratory distress and temperature instability. Blood cultures grow a Gram-positive, catalase-negative coccus that is bacitracin-resistant and demonstrates an enlarged zone of hemolysis when grown near Staphylococcus aureus.Streptococcus agalactiae (Group B Streptococcus)

Answer

The correct pairings link specific pathognomonic clues to their pathogens: Herpes simplex virus with hemorrhagic CSF (RBCs); Listeria monocytogenes with cephalosporin resistance; Neisseria meningitidis with maltose/glucose oxidation and purpura; and Streptococcus agalactiae with a positive CAMP test.
Each pathogen has a distinct, highly testable characteristic: Herpes simplex virus causes hemorrhagic CSF; Listeria monocytogenes is a cephalosporin-resistant Gram-positive rod; Neisseria meningitidis oxidizes maltose and glucose; and Streptococcus agalactiae is a bacitracin-resistant, CAMP-positive coccus.

Step-by-Step Solution

1
Analyze the first vignette describing a neonate with focal seizures and hemorrhagic CSF.
Identify Herpes simplex virus as the match.
Herpes simplex virus classically causes temporal lobe hemorrhagic necrosis, leading to an elevated red blood cell count in atraumatic CSF analysis.
2
Evaluate the second vignette describing a cephalosporin-resistant pathogen requiring ampicillin.
Identify Listeria monocytogenes as the match.
Listeria intrinsically lacks the specific penicillin-binding proteins targeted by cephalosporins, requiring the addition of ampicillin for neonatal meningitis coverage.
3
Assess the third vignette featuring purpura, shock, and maltose/glucose fermentation.
Identify Neisseria meningitidis as the match.
Meningococcemia is uniquely associated with rapidly progressive purpura and shock; oxidizing both maltose and glucose differentiates it from other Neisseria species.
4
Review the fourth vignette involving neonatal sepsis and a positive CAMP test.
Identify Streptococcus agalactiae (Group B Streptococcus) as the match.
The CAMP test (producing an arrowhead of enhanced hemolysis near S. aureus) is a classic laboratory identifier for Group B Streptococcus.

Key Concept

Microbiological identification and classic clinical presentations of severe pediatric central nervous system and systemic infections.
Rate this question

Topics

Pediatric Infectious Diseases

More questions from this topic