Multicenter Retrospective Analysis of 702 Pediatric Cases of Bone and Joint Infections: Definition of Clinical and Biological Features to Discriminate K. kingae, S. aureus, and Other Bacterial Infections

This study aimed to identify key differences between <i>K. kingae</i> infections and those caused by <i>S. aureus</i> or other pathogens. Differentiating these infections is crucial due to their nonspecific clinical presentations and overlapping laboratory and radiological findings, particularly when isolates are unavailable. We retrospectively analyzed data from 702 pediatric patients with bone and joint infections from 2010 to 2023 across two hospitals. The most common diagnoses were osteomyelitis (35.3%) and arthritis (29.6%), with fever present in 46.0% of cases. Pathogen identification showed <i>K. kingae</i> (40.9%) and <i>S. aureus</i> (36.5%) as the most frequent. Patients with <i>K. kingae</i> were significantly younger (median age 1.5 years) than those with <i>S. aureus</i> (10.4 years) or other pathogens (6.8 years) (<i>p</i> < 0.001). Fever was more common in <i>S. aureus</i> (64.3%) and other pathogens (57.5%) than in <i>K. kingae</i> (26.4%) (<i>p</i> < 0.001). CRP levels were lower in <i>K. kingae</i> infections (median 1.5 mg/dl) compared to <i>S. aureus</i> (6.1 mg/dl) and other pathogens (5.0 mg/dl) (<i>p</i> < 0.001). <i>K. kingae</i> infections were predominantly treated with penicillin-clavulanate and had shorter treatment durations and lower sequelae rates (2.3%) compared to other pathogens (19.0%). These findings emphasize <i>K. kingae</i>'s distinct clinical profile and milder course compared to <i>S. aureus</i> and other pathogens.