INDICATORS OF QUANTITATIVE AND QUALITATIVE COMPOSITION OF THE GUT COMMENSAL MICROBIOTA AS BIOMARKERS OF HOMEOSTASIS

Introduction: In the first part of our review, we highlighted the significant role of the intestinal microbiome for the human body. Its functions can be broadly categorized into three main groups: protective, metabolic, and immune system stimulation. The effectiveness of these functions depends on changes in the specific composition of the human microbiome, influenced by environmental conditions, living conditions, human nutrition, climate, genetics, and other factors. The objective of this work is to provide guidance for doctors, higher education students, and medical interns in understanding the modern intricacies of microbial metabolism in the human gastrointestinal tract. This understanding will enable them to make informed decisions regarding the prescription of microbiome indicators for patients, as well as their subsequent interpretation and correction. Materials and methods. Materials and Methods: We reviewed 61 international literature sources from databases such as PubMed, Scopus, and Google Scholar. The search was conducted electronically, and only English-language studies were included. Results. For an objective assessment of the numerous data obtained by using the latest diagnostic methods, scientists have proposed indicators that for convenience are considered in the form of known ratios: Firmicutes / Bacteroidetes, Prevotella / Bacteroides, Fusobacterium nucleatum / Faecalibacterium prausnitzi. The ratio between Firmicutes/Bacteroidetes is the percentage value of the first (Firmicutes) divided by the percentage value of the second (Bacteroidetes) can range from infinity to zero. This ratio usually ranges from 0.1 to 10. The Prevotella/Bacteroides ratio varies widely and depends on gastronomic preferences, metabolic features, and concomitant pathologies. In turn, significant fluctuations in Prevotella /Bacteroides have signs of dysbiosis, which directly correlates with numerous human pathologies. A shift in the ratio of Fusobacterium nucleatum / Faecalibacterium prausnitzii towards the former, according to scientific studies, can be considered one of the screening indicators of early colorectal cancer. Conclusion. When using ratios and markers to evaluate the homeostasis of the gut microbiota and make a diagnosis, it is important to consider not only the intricate relationship between the microflora and the human body, but also the nuances of metabolism within the microbial community. Both aspects are currently undergoing study with revolutionary methods and modern systems, which will ultimately contribute to a deeper understanding of these processes.