An in-house <i>Kingella kingae</i> PCR in a large pediatric cohort: impact on diagnosis, antimicrobial stewardship, and clinical outcomes

<i>Kingella kingae</i> is a bacterial pathogen associated with bone and joint infections and a major pathogen in pediatric populations, particularly in those ≤5 years of age. Molecular detection methods have demonstrated significant increases in sensitivity compared to culture, allowing rapid and accurate identification. The objective of this study was to characterize the performance of an in-house <i>K. kingae</i> PCR (KKIN PCR) and determine its impact on antimicrobial utilization and clinical management in a pediatric population. Laboratory records from 1 September 2014 to 31 January 2024 were reviewed to identify subjects ≤18 years old who had KKIN PCR testing performed at Nationwide Children's Hospital. Demographics, symptoms, radiologic and laboratory findings, hospitalization status, antimicrobial therapy, and clinical outcomes were analyzed. During the study period, 500 unique subjects with KKIN PCR ordered had complete data available, among whom 46 had <i>K. kingae</i> detected by PCR or culture. Compared to the clinical diagnosis, KKIN PCR had sensitivity, specificity, and positive and negative predictive values of 95.7, 100, 100, and 99.6%, respectively. Thirty-six (80%) subjects were detected by PCR alone, improving case identification by fourfold compared to culture (<i>n</i> = 9). Among subjects ≤5 years old, <i>K. kingae</i> was the most common organism detected. The median time to result for KKIN PCR was 26.5 h, and 38 (84%) subjects had antimicrobial modifications within 1 day of KKIN PCR report, resulting in de-escalation or antimicrobial optimization. This study demonstrates that routine use of in-house KKIN PCR significantly increased the diagnosis, facilitated timely and targeted treatment, and improved management of pediatric bone and joint infections.IMPORTANCE<i>Kingella kingae</i> (KKIN) has long been recognized as a major cause of bone and joint infections in pre-school aged children. However, diagnosis and prevalence of KKIN infection are underestimated due to poor culture recovery. Previous studies have shown that molecular-based methods improve KKIN detection compared to culture, but these methods are not widely implemented or routinely used in clinical microbiology laboratories. This study describes the performance and clinical utility of an in-house laboratory-developed KKIN PCR in a large pediatric cohort over a nearly 10-year period. In addition to demonstrating improved KKIN detection compared to culture, it also shows that rapid availability of in-house KKIN PCR facilitated timely antimicrobial de-escalation and potentially contributed to shortened hospital length of stay compared to previous reports. This study highlights a critical diagnostic gap that can be alleviated with a validated laboratory-developed PCR to improve diagnosis and management of KKIN infections.