Abstract
A child's mouth is the gateway to many species of bacteria. Changes in the oral microbiome may affect the health of the entire body. The aim of the study was to evaluate the changes in the oral microbiome of childhood cancer survivors. Saliva samples before and after anti-cancer treatment were collected from 20 patients aged 6-18 years, diagnosed de novo with cancer in 2018-2019 (7 girls and 13 boys, 7.5-19 years old at the second time point). Bacterial DNA was extracted, and the microbial community profiles were assessed by 16S rRNA sequencing. The relative abundances of Cellulosilyticum and Tannerella genera were found to significantly change throughout therapy (p = 0.043 and p = 0.036, respectively). However, no differences in the alpha-diversity were observed (p = 0.817). The unsupervised classification revealed two clusters of patients: the first with significant changes in Campylobacter and Fusobacterium abundance, and the other with change in Neisseria. These two groups of patients differed in median age (10.25 vs. 16.16 years; p = 0.004) and the length of anti-cancer therapy (19 vs. 4 months; p = 0.003), but not cancer type or antibiotic treatment.