Tracking transmission of Mycobacterium tuberculosis strains in a population of humans and animals is the basis of modern epidemiology of tuberculosis. Molecular methods are used for the analysis of small patient population, as well as a global studies, which monitor the variation and geographic distribution of mycobacteria. A special role is played by genotyping methods that allow to control the spread of drug-resistant-TB and Beijing-TB. Beijing strains, especially drug-resistant clones, are regarded as one of the most dangerous mycobacteria. They have a high pathogenicity, the ability to rapidly acquire drug resistance and unpredictable response to treatment. The aim of this study was molecular and epidemiological analysis of M. tuberculosis Beijing strains isolated from patients with pre-XDR-TB, detected in Poland, and investigate the probable route of transmission of infection between patients.
Material and methods: Material for analysis was a collection of more than 10,000 strains of M. tuberculosis collected in the years 2001-2011 in the National TB Reference Laboratory at the National Tuberculosis and Lung Diseases Research Institute in Warsaw. Analysis of phenotypic resistance to primary and secondary drugs allowed the selection of 47 pre-XDR strains, and genotyping--18 pre-XDR-Beijing strains. Molecular analysis included 2 genotyping methods--spoligotyping and MIRU-VNTR analysis.
Results: Genotyping results allowed the identification of 5 epidemiological groups of 13 patients with pre-XDR-Beijing-TB, between which transmission could occur. Based on the available epidemiological and demographic data, it was found that in isolated groups, 5 patients could be in close or casual contact.
Conclusions: This analysis shows that in Poland, one of the causes of drug resistance and the spread of M. tuberculosis Beijing type, is the transmission of infection between patients. This observation requires conducting active molecular and epidemiological investigations among patients, as well as studies of people with their environment.