Oral microbiota composition in children and adults during Spanish COVID-19 lockdown: impact of home self-confinement and SARS-CoV-2 infection

Background: The COVID-19 pandemic altered societal habits due to social restrictions and health measures implemented during the first half of 2020. Objective: This study aimed to evaluate the association between oral microbiota composition and age, household cohabitation, SARS-CoV-2 infection, and COVID-19 severity among children and adults under home confinement in Barcelona, Spain. Design: A prospective study was conducted between April and June 2020 in the Barcelona Metropolitan Area, including children and adults confined during the pandemic. Multiple participants from the same family households were enrolled. Saliva samples were collected from all participants, and oral microbiota composition was characterized using 16S rRNA gene sequencing. Results: A total of 142 adults and 265 children from 121 households were included. All adults had confirmed SARS-CoV-2 infection, and 20 (14.08%) experienced severe COVID-19. Among children, 58/265 (21.89%) tested positive; all were asymptomatic. In children, oral microbiota diversity and composition did not differ by infection status. In adults, severe COVID-19 was associated with lower diversity and distinct composition compared with mild disease. Marked age-related differences were observed in younger children. Cohabiting individuals shared more amplicon sequence variants than non-cohabitants. Conclusions: Age and cohabitation strongly influenced oral microbiota composition. In adults, microbiota varied with COVID-19 severity, whereas no differences were observed among asymptomatic children.