Abstract
Limited research has investigated the connection between long COVID (LC) and the respiratory microbiome, particularly in older adults. This study aimed to characterize the respiratory microbiome of older LC patients (with an average age of 65 years old), through meta-transcriptomic sequencing of 201 individual samples. Marked differences in microbial diversity were observed between LC and non-LC patients, including disruptions in both pathogenic bacteria and fungi. Importantly, viral taxa, such as Herpes simplex virus type 1 and Human coronavirus 229E, were more frequently detected in LC patients, indicating the vulnerability of LC patients to viral infections. Functional annotation at the expression level revealed notable differences in microbial metabolism with alterations observed in pathways related to tryptophan-serotonin metabolism in LC patients. These findings underscore the altered microbial landscape, especially in older adults who developed LC, and fill the gap for the potentially clinical roles played by the respiratory microbiome.