**4. Conclusions**

*Mycobacterium tuberculosis* Beijing strains are particularly important in the surveillance of the spread of TB. The growing share of drug-resistant clones in this molecular family may significantly affect the global epidemiological situation and hinder the eradication of TB. It is therefore necessary to actively monitor the incidence of Beijing-TB and to implement effective methods of preventing its transmission. Considering the fact that the Beijing family includes subfamilies that are more virulent than others, the subtype of isolated Beijing strains should also be identified. Subtyping is also essential because studies have demonstrated a relationship between the Beijing subtype, drug resistance, disease course and treatment outcome.

**Author Contributions:** Conceptualization, M.K. and E.A.-K.; methodology, M.K., M.S. and P.G.; formal analysis, M.K. and M.S.; investigation, M.K. and E.A.-K.; writing—original draft preparation, M.K.; writing—review and editing, M.K., M.S. and E.A.-K.; funding acquisition, E.A.-K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Science Centre of Poland (Grant Number 2019/35/B/NZ7/00942). The study was undertaken as a part of the statutory activity of the Tuberculosis and Lung Diseases Research Institute (Research Task No. 1.17).

**Institutional Review Board Statement:** The Ethics Committee (in Tuberculosis and Lung Diseases Research Institute, Warsaw, Poland) approved the research on 14 December 2018, no. KB-64/2018.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study. Written informed consent has been obtained from the patients to publish this paper.

**Data Availability Statement:** The results of the presented research are archived in the documentation of Wielkopolska Pulmonology and Thoracic Surgery Centre of Eugenia and Janusz Zeyland, Szamarzewskiego 62, 60-569 Pozna ´n, Poland. Microbiological documentation has been archived at the Department of Microbiology, National Tuberculosis and Lung Diseases Research Institute, Plocka 26, 01-138 Warsaw, Poland.

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