Abstract
Background.
Young children have frequent viral/bacterial infections and antibiotic exposures. Whether these events promote translocation of bacterial factors from oral cavity into the bloodstream remains poorly studied.
Method.
We performed 16S sequencing and immune profiling of blood in 210 healthy children of 1–2-year age range. Observed bacterial DNA signatures were analyzed in the context of host cytokine and antibody responses.
Results.
About 12% of toddlers showed a DNA signature related to oral commensals and pathogenic bacteria in their blood. These bacterial species included Streptococcus, Staphylococcus, Haemophilus, Deinococcus, Neisseria and Veillonella. Streptococcus had the most prominent (9%) signature. High resolution 16S rRNA sequencing revealed that majority of the observed signature belonged to commensal Streptococci including S. oralis, S. mitis, S. parasanguinis, and S. salivaris, S. pneumoniae. This signature was enriched in those with history of multiple bacterial and viral infections. Some children retained the Streptococcus DNA signature overtime. Serum IFN-γ, IL-1a, Il-1b, IL-6, and IL-8 were significantly associated with the observed Streptococcus DNA signature. Host transcriptome analysis showed upregulated antigen presentation and inflammatory pathways in Streptococcus DNA positive subset. Antibody repertoire profiling suggested that Streptococcus DNA positive was correlated with Influenza B and Respiratory Syncytial Virus (RSV) antibodies.
Conclusions.
A commensal Streptococci DNA signature was identified in the pediatric blood, which correlated with elevated inflammatory cytokines and anti-viral antibodies.