**5. Conclusions**

To sum up, the presence of numerous bacterial proteins present in the control material, which are absent in the material taken from the study group, may indicate their protective role. Similarly, the presence of bacterial proteins found only in the material obtained from people from the study group may indicate their potentially pathogenic nature.

However, we must remember that the proteome does not necessarily correspond to the content of the bacteria themselves, due to the variable expression of many proteins depending on their type and needs.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/ijms24086922/s1.

**Author Contributions:** Conceptualization, A.S., A.K. and A.G.-J.; Methodology, R.M., R.N. and A.G.-J.; Software, T.G.; Validation, P.P.; Formal analysis, R.M. and R.N.; Investigation, A.S., T.G., R.M. and A.G.-J.; Resources, P.P. and R.N.; Data curation, A.S., T.G. and W.K.; Writing—original draft, A.S. and A.G.-J.; Writing—review & editing, T.G., A.K. and R.M.; Visualization, R.M.; Supervision, A.K. and W.K.; Project administration, W.K.; Funding acquisition, A.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Medical University of Lublin grant number DS 128.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
