Introduction and objective:
The human oral cavity, the main part of masticatory system, is a dynamic environment still requiring quality research. The aim of the study is assessment of the status of the oral cavity and composition of intraoral microbiome of Polish patients in terms of threats to human health with infectious factors.

Material and methods:
The study utilised the data of generally healthy persons: 30 young aged 16–26 years and 30 middle-aged patients, aged 42–52 years. Intraoral swabs were assessed microscopically and by in vitro culture methods to detect/ identify microbiota.

Results:
Different microorganisms occurr in the oral cavity, including non-resident species. Parasitic protozoans Trichomonas tenax and Entamoeba gingivalis, facultative parasitic Acanthamoeba strains, yeast-like fungi of Candida albicans group, opportunistic and pathogenic bacteria, including endosymbionts, were identified with various frequency in particular regions of the oral cavity. Higher prevalences of bacteria and fungi strains occurred in middle-aged patients.

Conclusions:
The relationship between microbiota of the human oral cavity remains a rare subject of research. This study has shown the ability of different microorganisms to coexist intraorally. These components may pose clinically important threat that should be taken into account as infectious factors. Recognition of microbiome components as potentially contagious, early identification/monitoring/assessment of concomitant species, preventive elimination of the infectious strains during the treatment should be taken into consideration. Further quality research on the intraoral microbiome species that may pose severe local/general clinical diseases are needed to reduce the risk to human health.