Microbial metabolites, particularly those derived from gut microbiota, are increasingly recognized as crucial mediators between host and microbial communities. These metabolites, such as phenolic compounds, play significant roles in inflammation and infection development, influencing clinical outcomes in various patient populations, such as those with sepsis, post-surgical complications, and post-COVID-19 syndrome. Understanding their profiles and functions is essential for advancing personalized medicine and improving diagnostic and prognostic strategies in clinical practice.

Modern studies utilize gas chromatography–mass spectrometry (GC-MS) as a primary tool to quantitatively assess microbial metabolites within blood serum and fecal samples. This technique is prized for its sensitivity, specificity, and reproducibility, allowing for comprehensive detection of both phenolic compounds and dicarboxylic acids. Enhanced analytical power is achieved through careful sample processing, including extraction and derivatization, while advanced multivariate statistical approaches relate metabolite data to patient outcomes.

Notably, distinct serum elevations in phenyllactic, 4-hydroxyphenyllactic, and 4-hydroxyphenylacetic acids have been observed among sepsis patients, far exceeding levels seen in healthy controls. These findings lend support to the idea that sepsis is accompanied by gut microbial metabolic disturbances, as substantiated by experimental models.

In cardiac surgery patients, marked deviations in both microbial and mitochondrial metabolites have been recorded. Combining metabolic profiles with clinical information in multivariate models enables robust prediction of postoperative complications, achieving high accuracy and reliability.

Furthermore, individuals with post-COVID-19 syndrome display persistent abnormalities in microbial metabolite spectra—particularly elevated levels of 4-hydroxybenzoic, succinic, and fumaric acids—that do not normalize even after extended rehabilitation.

In summary, serum metabolite profiling via GC-MS represents a promising avenue for diagnosing, monitoring, and prognosticating various disease states, enhancing patient-specific clinical care. Integrating microbial metabolite analysis into clinical practice can enhance personalized medicine, improve patient outcomes, and guide the development of targeted therapies for a range of acute and chronic conditions.