Age- and disease severity-associated changes in the nasopharyngeal microbiota of COVID-19 patients

Dysbiosis has been linked to the pathogenesis of multiple diseases. Although dozens of publications have associated changes in the nasopharyngeal microbiota to patients susceptibility to COVID-19, results from these studies are highly variable and contradictory in many cases. Addressing the limitations in previous research responsible for that variability, this study uses 16S rRNA gene sequencing to analyse the nasopharyngeal microbiota of 395 subjects, 117 uninfected controls and 278 COVID-19 patients, of different age groups that cover the entire lifespan and across varying disease severities. Importantly, our results reveal that bacterial diversity decreases progressively throughout life but only in severely ill COVID-19 patients, in whose nasopharynx, moreover, the opportunistic pathogen bacterial genera Staphylococcus, Corynebacterium, Streptococcus, Prevotella, Acinetobacter, and Pseudomonas are overrepresented. Notably, Scardovia wiggsiae appears only in severe COVID-19 patients over 60 years of age, suggesting a potential utility of this bacterial species as a COVID-19 severity biomarker in the elderly, who are the most susceptible individuals to suffer from serious forms of the disease and the age group that presents more differences in comparison with the other age groups according to the majority of the parameters analysed in this study. Our results provide valuable insights into age-associated dynamics within nasopharyngeal microbiota during severe COVID-19, offering potential avenues for further exploration and therapeutic interventions.