Supplementary Material for: Gut Microbiota as a Key Player in Health and Disease with a Focus on Long-Term Alterations in Post-COVID

Introduction Gut microbiota plays a critical role in health and may contribute to post-COVID manifestations, as alterations in microbial communities have been observed in affected individuals. This study aimed to identify microbial and biochemical signatures in post-COVID individuals after an extended period following acute infection. Methods A total of 90 subjects were recruited, divided into three equal groups: post-COVID, fully recovered individuals, and healthy controls. The post-COVID group was further stratified by symptom duration and severity. Fecal microbiota was analyzed using 16S rRNA gene sequencing (V3-V4 region), with differential abundance assessed through LEfSE. Biochemical parameters were measured using the Mindray BS800 system. Spearman's correlation was applied to explore associations between taxonomic groups and biochemical markers. Results Several microbial taxa exhibited positive correlations with HDL levels and negative associations with non-HDL lipid parameters and CRP, highlighting their potential role in health. Individuals with a history of COVID-19 showed a significantly lower relative abundance of Phascolarctobacterium, Slackia, Enterorhabdus, and Senegalimassilia (p 2) compared to healthy controls. In participants with post-COVID symptoms, Eggerthella was significantly enriched, with Holdemania, Gemella, and two uncultured Lachnospiraceae showing a trend toward higher abundance. Severe post-COVID cases showed higher Parasutterella abundance, while long-lasting symptoms (> 1 year) were associated with Dialister enrichment and Phascolarctobacterium depletion compared to controls and fully recovered individuals. Conclusion Gut microbiota alterations were observed in post-COVID individuals even after a prolonged period following acute infection, suggesting a potential link between microbial imbalance and lingering symptoms, though causality cannot be confirmed.