Search

Bovine tuberculosis is one of the most dangerous zoonotic diseases. Despite the near-complete elimination of the disease from cattle breeding in Poland achieved in 2009, its re-emergence is now observed. Globally, the number of human cases is underestimated and the importance of free-living animals as reservoirs of tuberculosis is growing. As a species highly susceptible to Mycobacterium tuberculosis complex infection, the European bison (Bison bonasus) has a role in the transmission of the disease in Poland. The purpose of the investigation was to assess the epidemiological situation of tuberculosis in Polish European bison serologically.

Since 2009, Poland has been recognised as a country officially free of bovine tuberculosis (bTB), although in each year of the last five there were from 8 to 18 outbreaks of the disease. In 2008–2016, the largest number of cattle infected with bovine mycobacteria were eliminated in the Masovian Province (the central region of Poland) and the largest number of outbreaks of this zoonosis were recorded in this area. The close proximity of farms where bTB was found led to the suspicion that tuberculosis could have been transmitted between the affected herds. The aim of the study was the molecular characterisation of the pertinent M. bovis/caprae strains and determination of the epidemiological relationship of various bTB outbreaks.

Introduction: Tuberculosis is a highly infectious disease affecting humans and animals. It is caused by the Mycobacterium tuberculosis complex (MTBC) – Mycobacterium bovis and Mycobacterium caprae, which are aetiological factors of bovine tuberculosis (bTB). In Poland, the bTB eradication programme exists. Animals diagnosed with tuberculosis are in the majority of cases not treated, but removed from their herd and then sanitary slaughtered.

Abstract Background Rifampin is a first line antituberculosis drug active against bacilli in logarithmic and stationary phase, which interferes with RNA synthesis by binding to bacterial RNA polymerase. Tubercle bacilli achieve resistance to rifampin by accumulation of mutations in a short-81 bp region of the rpoB gene. Among many mutations identified in the rpoB gene, few were verified by molecular genetic methods as responsible for resistance to rifampin (RMP). Results In this study eight different mutations identified in an 81 bp section of a "hot spot" region of the rpoB gene of RMP resistant Mycobacterium tuberculosis clinical strains were evaluated in respect to drug resistance. It was found that: mutations in positions 526 (H/D), 516 (D/V) and 531 (S/L) result in high level resistance to rifampin; mutations in positions 516 (D/Y), 515 (M/I), 510 (Q/H) or a double mutation in codons 512 (S/I) and 516 (D/G) relate to low level of resistance. Gene rpoB carrying mutations in codon 513 (Q/L) introduced into an M. tuberculosis laboratory strain did not cause resistance to rifampin, however the same gene introduced into two different clinical strains did, with the level of resistance depending on the host strain. Conclusion Mutations in an 81 bp "hot spot" region of the rpoB of M. tuberculosis lead to different levels of resistance to rifampin. Some mutations in this "hot spot" region of rpoB require a specific genetic background for the host strain to develop resistance to rifampin. Therefore, the identification of such mutations in a clinical M. tuberculosis strain is not enough to classify the given strain as resistant to rifampin.