INTRODUCTION

In this study, new data on the specific microbiota of the tuberculomas caseous foci were obtained. A further understanding of the hypothesis about microbiota, which forms a polymicrobial biofilm, increasing resistance to the anti-TB drugs used in treatment, is formulated.

PURPOSE OF THE STUDY

Analysis of microbial diversity of caseous necrosis of tuberculous foci by molecular biological methods.

MATERIAL AND METHODS

Surgical material (388 samples) for 2018—2019 was studied by PCR method (GeneXpert) for the presence of mycobacterial DNA and mutations of rifampicin resistance.

RESULTS

According to the results of the GeneXpert study, rifampicin resistance was present in 131 cases (34%), rifampicin sensitivity was found in 222 samples (57%), tuberculosis DNA was not detected in 35 cases (9%). Tuberculomas were in the vast majority of the studied surgical material. Based on the well-known eubacterial primers EUB335L/EUB775R and new TaqMan probes a PCR test was designed. It is appropriate for comparative determination of the concentration of mycobacterial DNA (mbtDNA) in the locus, relative to total eubacterial (eubDNA). The results indicate that the studied microbial communities in tuberculomas foci are divided into at least two types: (i) mycobacterial caseoma (tuberculoma), in which 70% or more of the genomes correspond to MBT; (ii) a polymicrobial community, in which the MBT concentration ranges from 0 to 10%. Metagenomic analysis of amplicons was performed for two samples; five samples from the collection were subjected to molecular cloning and Sanger sequencing. About two-thirds of the identified genera of satellite microbiota caseomas belonged to Gram (–) genera, and nearly one-third ones were Gram (+) cocci.

CONCLUSION

Microbial contents in tuberculomas were estimated at 10⁴—10⁸ bacterial genomes per 1 g. It is assumed that the total amount of microbial DNA, including mycobacterial, in the necrotic content in tuberculomas, does not exceed 10% of the total composition.