The objective of the research was to assess the susceptibility of the slowly growing nontuberculous mycobacteria strains to the antimicrobial drugs used for mycobaterioses treatment using SLOMYCO test system. We assessed 363 NTM strains: 177 MAC (161 M. avium, 16 M. intracellulare), 112 M. kansasii and 74 M. xenopi collected from the respiratory material of the patients were under the treatment or under diagnostic procedures at our Center, affiliates and the diagnostic department in 2010–2016. Drug sucseptibility for NTM was tested using the Sensititre SLOWMYCO system (TREK DIAGNOSTIC Systems Ltd., UK). MICs were established by microdilutions in Mueller-Hinton broth on polystyrene 96-well plates. The statistical analysis was done using the StatGraphics Plus 5.0 software. The data were compared pairwise using Pearson χ² test with Yates correction. 95% confidence interval (CI) were calculated. Statistically significant differences were considered for p <0.05. Log-rank test and Kaplan-Meier curves were used to assess the concentration-dependent surveillance probability. The statistically significant differences were revealed in sensitivity/resistance isolates of M. avium and M. intracellulare: M. avium strains were resistant to higher concentrations of amikacin, clarithromycin, linezolid and streptomycin (p <0.01); M. intracellulare strains were resistant to higher concentrations of ethionamide (p <0.05). The isolates of M. avium were significantly more resistant than M. kansasii to amikacin, doxycycline, isoniazid, clarithromycin, linezolid, moxifloxacin, rifabutin, rifampicin, streptomycin, trimethoprim/sulfamethoxazole, ciprofloxacin, ethambutol, ethionamide (visible growth of M. avium were inhibited by higher drug concentrations, p <0.01). The isolates of M. avium showed significantly higher resistance than M. xenopi to amikacin, doxycycline, isoniazid, clarithromycin, linezolid, moxifloxacin, rifampicin, streptomycin, trimethoprim/sulfamethoxazole, ciprofloxacin, ethambutol, and ethionamide (visible growth of M. avium were inhibited by higher drug concentrations, p <0.01). Statistically significant differences in the dynamics of the response to the antibacterial effects of isoniazid, linezolid, moxifloxacin, rifampicin, trimethoprim/sulfamethoxazole, ethambutol, and ethionamide were found for M. intracellulare and M. xenopi (complete inhibition of the visible growth of M. intracellulare required higher drugs concentrations, p <0, 05). Comparison of the Kaplan-Meyer curves revealed statistically significant differences in survialence probability of M. kansasii and M. xenopi for amikacin, doxycycline, rifampicin, trimethoprim/sulfamethoxazole, ciprofloxacin, ethambutol, and ethionamide (a higher number of isolates of M. xenopi were inhibited by low drugs concentrations, p <0.05). Our data show that M. avium and M. intracellulare were more resistant to the majority of the studied drugs than M. kansasii and M. xenopi.

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 Bactec^TM MGIT^TM 960 system and the Sensititre^TM 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, P_fabG1, and inhA for most isolates in the Moscow region. The promoter mutation P_fabG1 c(-15)t predicts resistance to ethionamide with high specificity but low sensitivity.

Introduction. Nontuberculous mycobacteria (NTM) are widespread in the environment and can cause various diseases in humans, especially immunocompromised patients. Hypothesis. Treatment of diseases caused by NTM is a complicated issue, mainly due to the resistance of the pathogen to most antimicrobial agents. Bedaquiline (Bdq) is now widely used for the treatment of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB). Aim. The main goal of our study was to evaluate the activity of Bdq against Mycobacterium avium complex (MAC), the most common species among NTM. Methodology. A total of 166 MAC cultures (124 Mycobacterium avium and 42 Mycobacterium intracellulare ) were studied. The minimum inhibitory concentrations (MICs) of Bdq for M. avium and M. intracellulare were obtained by twofold serial dilutions in the Middlebrook 7H9 medium. MIC ranges were determined and the MIC₅₀, MIC₉₀ and ECOFF values were obtained. Results. The MICs in respect of M. avium ranged from 0.003 to 1.0 µg ml⁻¹; those for M. intracellulare ranged from 0.003 to 0.5 µg ml⁻¹. The Bdq MIC₅₀ and MIC₉₀ values were found to be 0.015 and 0.12 µg ml⁻¹ , respectively, for M. avium and 0.007 and 0.06 µg ml⁻¹, respectively, for M. intracellulare . The tentative ECOFF values for M. avium and M. intracellulare were 0.12 and 0.06 µg ml⁻¹, respectively. Conclusion. The main bedaquiline susceptibility parameters for MAC strains isolated in the Moscow region were determined.

Today, within the context of harmonisation of requirements in the international pharmaceutical market, there is a trend towards development of common standards, including in the field of preclinical studies. The reliability and reproducibility of experimental data obtained in various laboratories using animals cannot be guaranteed unless the 3Rs principles are observed (the principles of humane experimental technique) to ensure the welfare of animals. The present paper analyses Russian and foreign recommendations on different administration routes and administered volumes as applied to mice, rats, guinea pigs, and rabbits – the most frequently used laboratory animals. The paper systematises literature data on oral/intragastric, subcutaneous, intramuscular, intravenous and intraperitoneal routes of administration. It assesses potential complications of each route of administration, and negative effects on both health and well-being of laboratory animals, as well as on the results of experiments. The paper also touches upon some anatomical and physiological characteristics of laboratory animals, potential opportunities for feed and water deprivation, ways of reducing pain in animals. The results of comparison of administered volumes helped to determine optimal recommended and maximum administered volumes.

There has been a sharp increase in the number of diseases associated with potentially pathogenic microorganisms of the genus Mycobacterium, which differ from Mycobacterium tuberculosis. These bacteria are known as atypical mycobacteria or nontuberculosis mycobacteria (NTM), and the diseases they cause are called mycobacteriosis. NTMs include more than 20 species of acid-resistant microorganisms that are widespread in the environment and that are not members of the M. tuberculosis complex. However, the role of certain types of NTMs in the pathogenesis of human diseases is rather ambiguous. The aim of the paper was to analyse the current rise in the incidence of NTM diseases, as well as the main areas of research on early diagnosis of mycobacteriosis and the detection and testing of drug susceptibility of these microorganisms. The paper summarises current views on NTM species differences, their prevalence and pathogenicity for humans and animals. The authors analysed the main efforts aimed at diagnosis and treatment of NTM diseases. The paper cites the results of the study of NTM susceptibility/resistance to anti-tuberculosis drugs. The diagnosis of mycobacteriosis remains extremely difficult, mainly because of the similarity of the clinico-radiological evidence with that of tuberculosis. Detection of NTM multiple and extensive drug resistance to the majority of anti-tuberculosis drugs complicates the treatment of the NTM disease. Further study of various aspects of NTM diseases is especially important given the increase in the incidence and prevalence of mycobacteriosis all over the world, challenging differential diagnosis, and detection of NTM extensive drug resistance.

Background: Linezolid, bedaquiline, and newer fluoroquinolones are currently placed as priority Group A drugs for the treatment of drug-resistant tuberculosis. The number of reported linezolid-resistant clinical strains is still low, and the correlation of molecular determinants with phenotype is not perfect. Methods: We determined the linezolid MICs for clinical isolates from the Moscow region and identified mutations in rplC and rrl genes. Results: All 16 linezolid-resistant isolates had previously reported mutations in the rplC or rrl loci, and 13 of them bore a RplC C154R substitution. Detection of this substitution in a heteroresistant state was not successful, probably, due to the more stable DNA secondary structure of the mutated fragment, which precludes its amplification in mixes with the wild-type DNA. Strains with an rplC mutation had higher linezolid MIC compared to isolates with rrl mutations. Conclusions: Linezolid resistance mostly emerged during treatment with the latest regimen. Three primary cases with linezolid resistance question the possible transmission of totally drug-resistant tuberculosis in the Moscow region, which demands further investigation.