Concentrations of uremic bacterial metabolites in patients with post-COVID-19 syndrome.
Brigo, Natascha, Mayr, Wolfram, Taenzer, Maja et al. · Frontiers in cellular and infection microbiology · 2025 · DOI
Quick Summary
This small study looked at special waste products made by gut bacteria in the urine of people with long COVID, ME/CFS, and healthy people. Researchers found that people with long COVID and ME/CFS had different patterns of these bacterial products compared to healthy controls, and these patterns might be connected to their symptoms like fatigue and post-exertional malaise (feeling much worse after activity).
Why It Matters
This research addresses a critical knowledge gap about what causes ME/CFS and post-COVID symptoms by examining gut bacteria and their metabolic byproducts. If gut dysbiosis is confirmed as a contributing factor, it could lead to new diagnostic tests and treatments targeting the microbiome for ME/CFS patients.
Observed Findings
64% of post-COVID patients showed elevated bacterial uremic metabolites compared to 37.5% of healthy controls and ME/CFS patients
Elevated tryptamine and 4-hydroxyphenylpropionic acid (HPHPA) were found exclusively in post-infectious syndrome patients
Higher hippuric acid and trimethylamine concentrations were detected only in PCS and ME/CFS patients
Both PCS and ME/CFS patients showed significantly higher post-exertional malaise scores compared to healthy controls (p<0.001)
Distinct metabolic clustering patterns were identified between patient groups using heatmap analysis, despite no significant overall group differences
Inferred Conclusions
Specific patterns of gut bacterial metabolites may distinguish post-infectious syndromes from healthy states
Gut dysbiosis may play a role in the pathophysiology of both post-COVID-19 syndrome and ME/CFS
Urine metabolomic analysis could be a useful diagnostic or investigative approach for understanding post-infectious syndromes
The distinct metabolic signatures suggest shared pathogenic mechanisms between post-COVID-19 syndrome and ME/CFS
Remaining Questions
Do these altered bacterial metabolites cause symptoms, or are they secondary consequences of the illness?
What This Study Does Not Prove
This study does not prove that elevated bacterial metabolites cause ME/CFS or post-COVID symptoms—it only shows an association. The small sample size and pilot nature mean findings require replication in larger studies before clinical application. The cross-sectional design cannot establish whether dysbiosis is a cause, consequence, or coincidental feature of these conditions.
What specific gut bacteria are responsible for producing the metabolites that are elevated in PCS and ME/CFS patients?
Do bacterial metabolite levels change over time, and can they predict symptom severity or recovery?
Would treatments targeting gut dysbiosis (probiotics, diet, or antibiotics) reduce these metabolites and improve symptoms in ME/CFS and post-COVID patients?