Clinical Features, Treatment Outcomes, and Cytokine Levels in Pediatric Tularemia Patients in Türkiye.

Tularemia is a rare zoonotic infection with marked geographic clustering and long interepidemic periods. Pediatric data, particularly those on host immune responses during active disease and treatment, remain scarce. The authors aimed to evaluate clinical characteristics and treatment-associated cytokine dynamics in children with tularemia. In the present multicenter prospective study conducted in Türkiye, 40 pediatric patients with laboratory-confirmed tularemia and nine age- and sex-matched healthy controls were enrolled between April 2023 and November 2024. Clinical features, exposure history, and treatment outcomes were recorded. Serum cytokine levels, including interleukin (IL)-6, IL-2, IL-9, IL-5, IL-13, tumor necrosis factor-α, IL-10, interferon (IFN)-γ, IL-4, and IL-22, were measured using a multiplex bead-based assay and compared between patients and controls, between good and poor outcome groups, and longitudinally before and after therapy. A good outcome was defined as complete clinical resolution without suppuration, the need for surgical intervention, or relapse, whereas a poor outcome was defined as clinical nonresolution or progression. A total of 24 (60%) participants had a good outcome, and 16 (40%) had a poor outcome. Although baseline cytokine levels did not differ between groups, paired analyses revealed significant posttreatment reductions in IFN-γ (P = 0.018), IL-6 (P = 0.018), and IL-10 (P = 0.032), consistent with resolution of infection-associated immune activation. A poor outcome was associated with increased exposure to natural water sources and a higher frequency of suppurative lymphadenopathy requiring surgical drainage. Baseline cytokine profiles did not predict treatment response; however, dynamic changes in IFN-γ, IL-6, and IL-10 were associated with clinical recovery. These findings highlight the importance of longitudinal immune monitoring and provide insight into immune dynamics in pediatric tularemia.