Spoligotype-defined population structure of drug-resistant Mycobacterium tuberculosis isolates in Eastern Poland

Abstract

Introduction. The most detrimental impact on the epidemiology of tuberculosis (TB) in Poland may have the spread of tubercle bacilli from outside the country. This is because Poland is geographically situated in close proximity to the former Soviet Union countries, such as Latvia, Estonia, Ukraine, and Russia, where the incidence of TB, including drugresistant (DR) TB is exceptionally high. Aim. To describe the genetic diversity of DR Mycobacterium tuberculosis isolates, circulating in four provinces (Lublin, Podkarpacie, Podlasie, and Warmia-Masuria) constituting the so-called “Eastern Wall” of Poland. Material and methods. A total of 44 DR M. tuberculosis isolates were spoligotyped. The results were compared with the international spoligotype database (SpolDB4). SpolDB4 and the web-based program SpotClust were used to classify isolates into phylogenetic clades. Results. Spoligotyping resulted in 25 distinct patterns, of which five were not recorded in the SpolDB4. Of the remaining 20 types, 16 (80%) had already been reported in Poland. Most of the spoligotypes (56%) identified were found to be present in Poland’s neighbors, such as Germany, the Czech Republic, Latvia, and Russia. At the phylogenetic level, the T and Haarlem families accommodated 80% of the isolates. Conclusions. The M. tuberculosis population in Eastern Poland displayed features characteristic of a European country. Given the low frequency of imported genotypes and the absence of foreign-born patients, DR-TB in Eastern Poland appears to be due to the local transmission of M. tuberculosis strains that have been active in Poland for many years, rather than to the importation of strains from neighboring countries.