Pneumococcal Rib Osteomyelitis With Concurrent Lung and Chest Wall Abscess in an Infant.

We present a rare case of a 7-month-old infant with a complex invasive Streptococcus pneumoniae infection involving rib osteomyelitis, a pulmonary abscess, and a chest wall abscess. The patient presented with persistent fever and no respiratory symptoms. On day 9, chest radiography was performed because of persistent fever and marked leukocytosis, consistent with the American College of Radiology Appropriateness Criteria that recommend imaging in febrile infants with high fever (≥39°C) or elevated white blood cell counts (≥20 000/mm3). On day 14, the emergence of a chest wall mass prompted escalation to ultrasonography, which provided noninvasive assessment of soft tissue involvement. Subsequent contrast-enhanced computed tomography scans were undertaken to delineate the extent of contiguous spread, evaluate rib destruction, and exclude alternative diagnoses. Microbiological cultures of sputum and aspirated pus, along with metagenomic sequencing, confirmed the presence of macrolide-resistant S. pneumoniae. Because of benzylpenicillin and cephalosporin allergy, intravenous linezolid was selected, resulting in rapid clinical improvement. A 6-week course (intravenous infusion followed by oral) led to complete resolution on imaging, with no recurrence over 5 years. This case underscores the importance of appropriate imaging modalities in febrile infants without respiratory symptoms and the need to consider extrapulmonary spread in chest wall masses. It highlights the diagnostic value of metagenomic sequencing and susceptibility testing in guiding individualized antimicrobial therapy, particularly in macrolide-resistant settings.