A 14-month-old boy is brought to the emergency department by his parents due to persistent… — USMLE Step 2 CK

A $14$ -month-old boy is brought to the emergency department by his parents due to persistent fever, worsening cough, and rapid breathing. Four days ago, he was seen at an urgent care clinic for a runny nose, low-grade fever, and diffuse wheezing. At that time, he was diagnosed with a viral upper respiratory tract infection and discharged with supportive care. Over the past $24$ hours, his temperature has spiked to $39.8^\circ\text{C}$ ( $103.6^\circ\text{F}$ ). The patient has a history of mild atopic dermatitis. His immunizations are up to date, including the pneumococcal conjugate and Haemophilus influenzae type b vaccines. Vital signs show a heart rate of $165/\text{min}$ , respiratory rate of $58/\text{min}$ , and blood pressure of $90/55\text{ mm Hg}$ . Oxygen saturation is $92\%$ on room air. On physical examination, the child appears acutely ill but is alert and interactive. Lung auscultation reveals diffuse expiratory wheezing and new focal crackles in the right lower lung field. A chest radiograph demonstrates a dense right lower lobe consolidation with a small, free-flowing right-sided pleural effusion. Which of the following is the most appropriate next step in pharmacologic management?

Intravenous ampicillinAnswer
B
Intravenous ceftriaxone and vancomycin
C
Nebulized albuterol and oral dexamethasone
D
Intravenous clindamycin
E
Oral azithromycin

Answer

Intravenous ampicillin is the most appropriate pharmacologic management.

The patient has secondary bacterial community-acquired pneumonia (CAP), evidenced by the biphasic illness, new-onset high fever, focal crackles, and right lower lobe consolidation. The most common bacterial cause of CAP in this age group is Streptococcus pneumoniae. For a fully immunized infant requiring hospitalization (due to tachypnea and borderline hypoxia) who is alert and hemodynamically stable, narrow-spectrum intravenous antibiotics such as ampicillin or penicillin G are the recommended first-line therapy. This approach effectively targets S. pneumoniae while strictly adhering to the principles of antibiotic stewardship.

Step-by-Step Solution

Identify the primary diagnosis from the clinical presentation.

The biphasic illness (initial viral URI followed by high fever) with focal crackles and lobar consolidation indicates a secondary bacterial community-acquired pneumonia (CAP).

Recognizing the transition from a viral process to a bacterial complication is critical for initiating appropriate therapy.

Assess the patient's severity and immunization status.

The patient is fully immunized, alert, and hemodynamically stable, though he requires hospitalization due to tachypnea and borderline hypoxia.

Immunization status directly dictates the likely pathogens (Streptococcus pneumoniae is most common; H. influenzae type b is unlikely) and the required antibiotic spectrum.

Select the guideline-recommended antibiotic regimen.

Narrow-spectrum intravenous ampicillin (or penicillin G) is the standard of care.

Empiric broad-spectrum coverage is not indicated for uncomplicated CAP in a fully immunized, non-toxic infant.

Key Concept

First-line empiric treatment for hospitalized, fully immunized children with uncomplicated community-acquired pneumonia is narrow-spectrum therapy with intravenous ampicillin or penicillin G.

Estimated Time:1m 30s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic