Pediatric Infections
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USMLE Step 2 CK › Pediatric Infections
A 3-year-old girl with cough and fever has decreased breath sounds and dullness to percussion on the right. Exam: tachypnea and mild retractions. Labs: WBC 20,100/µL with neutrophil predominance. Chest radiograph shows a right pleural effusion with adjacent consolidation. Which of the following is the most appropriate next step in management?
Provide supportive care only because this is viral
Delay treatment until sputum culture results return
Start oral azithromycin only and observe at home
Order MRI chest to characterize the effusion
Perform diagnostic thoracentesis and start IV antibiotics
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of pleural effusion with consolidation and neutrophil predominance indicates complicated bacterial pneumonia, guiding the clinician towards drainage and antibiotics. The correct choice, B, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option D is incorrect because it represents a common misconception such as assuming viral etiology in bacterial complication. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.
A 10-day-old newborn has poor feeding and irritability. Pregnancy and delivery were uncomplicated; mother reports painful genital lesions near delivery. Exam: temperature 38.3°C, vesicular lesions on scalp, lethargy. Labs: WBC 9,200/µL; AST elevated. CSF shows lymphocytic pleocytosis. Which of the following is the most appropriate next step in management?
Start oral amoxicillin for 10 days
Reassure family and schedule outpatient follow-up
Give aspirin for fever control
Administer live attenuated varicella vaccine
Start IV acyclovir and obtain HSV PCR from CSF and lesions
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of vesicular lesions, maternal genital lesions, and CSF pleocytosis indicates neonatal HSV infection, guiding the clinician towards antiviral therapy and testing. The correct choice, A, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option B is incorrect because it represents a common misconception such as treating viral HSV with bacterial antibiotics. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.
A 6-year-old girl has 2 days of high fever, severe abdominal pain, and frequent bloody diarrhea after eating undercooked ground beef. Exam: diffuse abdominal tenderness; no peritoneal signs. Labs: WBC 15,600/µL; platelets normal; creatinine normal. Stool is positive for Shiga toxin. Which of the following is the most appropriate next step in management?
Administer aspirin for abdominal pain
Start trimethoprim-sulfamethoxazole immediately
Supportive care and avoid antibiotics and antimotility agents
Start loperamide to reduce stool frequency
Begin high-dose amoxicillin-clavulanate
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of bloody diarrhea and positive Shiga toxin indicates EHEC infection, guiding the clinician towards supportive care to avoid complications. The correct choice, A, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option B is incorrect because it represents a common misconception such as using antibiotics which may worsen HUS risk. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.
A 2-day-old newborn has poor feeding, temperature instability, and lethargy. Pregnancy was complicated by prolonged rupture of membranes; mother’s GBS status is unknown. Exam: hypotonia, tachypnea, mottled skin; capillary refill 4 seconds. Labs: WBC 3,000/µL, ANC low; glucose 38 mg/dL; CRP elevated. Chest radiograph shows diffuse granular opacities. Which of the following is the most appropriate next step in management?
Start IV acyclovir only
Obtain blood cultures and start IV ampicillin plus gentamicin
Provide supportive care only because illness is likely viral
Delay antibiotics until lumbar puncture confirms meningitis
Start oral amoxicillin and discharge with follow-up
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of leukopenia, hypoglycemia, elevated CRP, and granular opacities on CXR indicates early-onset neonatal sepsis, guiding the clinician towards empiric antibiotics. The correct choice, A, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option B is incorrect because it represents a common misconception such as assuming viral etiology in high-risk neonates. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.
A 3-year-old boy presents with high fever, toxic appearance, and drooling. He sits leaning forward and refuses to lie down. Exam: inspiratory stridor, muffled voice; no cough. Lateral neck radiograph shows an enlarged epiglottis. Which of the following is the most appropriate next step in management?
Give oral dexamethasone only
Administer nebulized albuterol and reassess
Secure the airway and start IV ceftriaxone
Start oral amoxicillin-clavulanate and discharge
Attempt oropharyngeal examination with tongue depressor
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of drooling, stridor, and enlarged epiglottis on radiograph indicates epiglottitis, guiding the clinician towards airway security and antibiotics. The correct choice, B, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option A is incorrect because it represents a common misconception such as risking airway compromise with examination. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.
A 5-year-old girl has fever and cough after daycare exposure. She develops a nonblanching petechial rash on the legs and becomes lethargic. Exam: tachycardia, delayed capillary refill, nuchal rigidity. Labs: WBC 18,500/µL; platelets 90,000/µL; lactate elevated. What is the most appropriate next step in management?
Delay antibiotics until lumbar puncture results return
Give IV ceftriaxone immediately after obtaining blood cultures
Provide supportive care only because illness is likely viral
Administer IM epinephrine and observe for 4 hours
Start oral amoxicillin and discharge with follow-up
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of petechial rash, lethargy, nuchal rigidity, and elevated lactate indicates meningococcemia, guiding the clinician towards immediate empiric antibiotics. The correct choice, B, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option E is incorrect because it represents a common misconception such as assuming viral etiology despite signs of sepsis. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.
A 5-year-old girl has fever and sore throat for 2 days after a daycare outbreak. She now has a fine, sandpaper-like rash on the trunk and erythematous oropharynx with palatal petechiae. Exam: tender anterior cervical nodes, no cough. Labs: WBC 14,800/µL with neutrophil predominance; CRP elevated. Rapid antigen detection test for group A strep is positive. What is the first-line treatment for this infection?
Supportive care only; antibiotics are not indicated
Oral azithromycin for all patients regardless of allergy
Aspirin for fever and inflammation
Oral acyclovir
Oral amoxicillin or penicillin V
Explanation
This question tests clinical knowledge of pediatric infections and decision-making skills as assessed in USMLE Step 2 CK. Understanding the differentiation between bacterial and viral infections is crucial for appropriate management. Bacterial infections often require antibiotics, whereas viral infections do not. In the vignette, the presence of sandpaper-like rash, palatal petechiae, and positive rapid strep test indicates scarlet fever from group A streptococcus, guiding the clinician towards antibiotic therapy. The correct choice, A, aligns with clinical guidelines, ensuring effective treatment and improving patient outcomes. Option D is incorrect because it represents a common misconception such as misidentifying bacterial pharyngitis as viral and withholding antibiotics. To help students, emphasize recognizing key diagnostic indicators and adhering to guideline-based management. Practice differentiating similar presentations with different etiologies and understanding the implications of each choice.