The introduction of novel drugs into treatment must be accompanied by continuous phenotypic susceptibility testing and the analysis of genetic determinants of resistance.

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The developed test has a high sensitivity and specificity and can be directly applied to clinical samples. The combination of mutation-based drug resistance profiling and basic genotyping could be useful for clinical microbiology studies and epidemiological surveillance of the M. tuberculosis complex.

Federation eIn addition to the obligatory pathogenic species of the Mycobacterium tuberculosis complex and Mycobacterium leprae, the genus Mycobacterium also includes conditionally pathogenic species that in rare cases can lead to the development of nontuberculous mycobacterial diseases. Because tuberculosis and mycobacteriosis have similar clinical signs, the accurate identification of the causative agent in a clinical microbiology laboratory is important for diagnostic verification and appropriate treatment. This report describes a low-density hydrogel-based microarray containing oligonucleotide probes based on the species-specific sequences of the gyrB gene fragment for mycobacterial species identification. The procedure included the amplification of a 352-nucleotide fragment of the gene and its hybridization on a microarray. The triple-species-specific probe design and the algorithm for hybridization profile recognition based on the calculation of Pearson correlation coefficients, followed by the construction of a profile database, allowed for the reliable and accurate identification of mycobacterial species, including mixed-DNA samples. The assay was used to evaluate 543 clinical isolates from two regions of Russia, demonstrating its ability to detect 35 mycobacterial species, with 99.8% sensitivity and 100% specificity when using gyrB, 16S, and internal transcribed spacer (ITS) fragment sequencing as the standard. The testing of clinical samples showed that the sensitivity of the assay was 89% to 95% for smear-positive samples and 36% for smear-negative samples. The large number of identified species, the high level of sensitivity, the ability to detect mycobacteria in clinical samples, and the up-to-date profile database make the assay suitable for use in routine laboratory practice. In addition to the obligatory pathogenic species of the Mycobacterium tuberculosis complex (MTC) and Mycobacterium leprae, the genus Mycobacterium also includes conditionally pathogenic species that in rare cases lead to the development of nontuberculous mycobacterial disorders in humans (1). The main risk factors for such diseases are immunosuppression and chronic obstructive pulmonary disease (2). Because tuberculosis and mycobacteriosis have common clinical signs, the proper identification of the causative agent in a clinical microbiology laboratory is one of the most important tasks for diagnostic verification and treatment with the correct medication (3).The conventional microbiological and biochemical methods used to detect Mycobacterium are labor-intensive and timeconsuming. Efficient mycobacterial species identification using high-performance liquid chromatography of mycolic acids (4) requires expensive equipment and high-level personnel qualifications. Moreover, the spectrum of species that can be identified by microbiological assays is rather narrow, making DNA-based methods preferable (5). A number of molecular genetic techniques have been developed, including in situ hybridization species-specific probes (6), mult...

Background: Ethionamide and prothionamide are now included in group C of the WHO recommended drugs for the treatment of tuberculosis resistant to rifampicin and multidrug-resistant tuberculosis. The clinical relevance of ethionamide and prothionamide has increased with the wide spread of resistant tuberculosis. Methods: We retrospectively analyzed 349 clinical isolates obtained between 2016 and 2020. The susceptibility to ethionamide was tested using both the BactecTM MGITTM 960 system and the SensititreTM MYCOTB plate. Results: The MIC of ethionamide increases with the total resistance of the isolates in a row from susceptible to XDR strains. A significant part of the isolates have a MIC below the breakpoint: 25%, 36%, and 50% for XDR, pre-XDR, and MDR strains. Sensitivity and specificity of detection of mutations were 96% and 86% using MGIT resistance as a reference. Conclusions: Phenotypic methods for testing ethionamide are imperfectly correlated, and the isolates with MIC of 5 mg/L have the intermediate resistance. A significant proportion of resistant TB cases are susceptible and eligible for ethionamide treatment. Resistance could be explained using only analysis of loci ethA, PfabG1, and inhA for most isolates in the Moscow region. The promoter mutation PfabG1 c(-15)t predicts resistance to ethionamide with high specificity but low sensitivity.

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