Oral Microbiome Dynamics in Patients with Acute Lymphoblastic Leukemia and Oral Mucositis

The oral microbiome of patients with acute lymphoblastic leukemia (ALL) undergoes changes caused by the neoplasia as well as the antimicrobial activity of chemotherapy (CTX), which promotes the development of oral mucositis (OM). This study aimed to analyze the oral microbiome dynamics and salivary cytokine production in pediatric ALL patients before and during CTX, comparing children who did and did not develop OM. We conducted a longitudinal, observational, and analytical study including 32 newly diagnosed pediatric ALL patients (ages 2-16 years) undergoing CTX. Oral rinse and non-stimulated saliva samples were collected at baseline (day 0), day 14, and day 21 of induction of CTX, with an additional sample taken during OM episodes when possible. Microbiome analysis was performed using 16S rRNA sequencing on an Illumina MiSeq platform, and salivary cytokines were measured using a Luminex multiplex assay. The most pronounced microbiome changes occurred on day 14, particularly in patients who developed OM, characterized by higher α diversity, increased abundance of opportunistic taxa, and elevated IL-6 concentrations. In contrast, patients who did not develop OM exhibited a more stable microbial composition. Overall, these findings indicate that temporal oral dysbiosis and increased IL-6 may serve as early markers and potential predictors of OM development during chemotherapy in pediatric ALL patients.