The WHO Southeast Asia and Western Pacific regions, home to more than half of the world's population, bear a disproportionate burden of antimicrobial resistance (AMR), including some of the most severe resistance patterns. The convergence of rapidly growing economies and persistent health system challenges in these regions creates a critical platform for understanding the dynamics of AMR and developing scalable governance approaches relevant to other low- and middle-income countries. This Viewpoint reviews current progress in AMR governance globally and study regions, with a focus on country-specific National Action Plans, and highlights the discrepancies between policy intentions and actual implementation. Implementation science, developed to address research-to-practice gaps, provides a systematic framework for identifying and overcoming barriers to implementation, thereby translating political commitments into actionable interventions. Given the cross-sectoral complexity of AMR, we propose novel strategic priorities to enhance AMR governance by embedding implementation science within the One Health approach. This involves a four-step process: selecting and adapting evidence-based practices, assessing multilevel barriers and enablers, selecting, using and adapting implementation strategies, and evaluating and sustaining their impact. Together, this framework provides a blueprint for localising and operationalising overarching policy concepts into concrete, context-specific actions, with potential lessons for other regions globally.

Background:Antimicrobial resistance (AMR) constitutes a critical global health challenge with major implications for public health and economic stability, increasing infection- and sepsis-related mortality. Despite growing evidence on its contribution to disease burden, comprehensive assessments of long-term trends at the regional level remain limited in the World Health Organization (WHO) Southeast Asia Region (SEAR) and Western Pacific Region (WPR). Methods:We used data from the Global Research on Antimicrobial Resistance (GRAM) Project to evaluate sepsis- and AMR-related deaths and disability-adjusted life-years (DALYs) for 11 infectious syndromes, 22 pathogens, and 84 pathogen-drug combinations across 42 countries and territories in the WHO SEAR and WPR from 1990 to 2021. AMR burden was estimated under two counterfactual scenarios: deaths and DALYs attributable to AMR (representing the burden if drug-resistant infections were replaced by drug-susceptible infections), and deaths and DALYs associated with AMR (representing the burden if infections did not occur at all). We reported numbers, crude rates, and age-standardized rates, and generated forecasts of AMR burden to 2050 using an autoregressive integrated moving average model. Results:In SEAR and WPR, there were 8.36×106 [95% uncertainty interval (UI) 7.93-8.79] sepsis-related deaths in 1990, which decreased to 6.03×106 (95% UI 5.68-6.39) in 2019 before increasing to 8.31×106 (95% UI 7.86-8.76) in 2021. The number of deaths associated with AMR ranged from 2,445,875 (95% UI 2,221,769-2,670,192) in 1990 to 2,358,190 (95% UI 2,173,521-2,545,190) in 2021, while deaths attributable to AMR ranged from 546,479 (95% UI 487,669-605,277) to 587,103 (95% UI 534,165-639,903) over the same period. From 1990 to 2021, deaths attributable to AMR decreased among people <25 years, with a 76.1% [95% confidence interval (CI) 70.6-81.6] reduction occurring among children <5 years, while those among adults aged ≥70 years more than doubled, increasing from 133,013 (95% UI 124,066-141,922) to 298,366 (95% UI 284,023-312,475). The largest increase in the number of deaths attributable to AMR was caused by methicillin-resistant Staphylococcus aureus [from 30,168 (95% UI 24,956-35,351) in 1990 to 66,946 (95% UI 57,544-76,479) in 2021]. In 2021, Kiribati had the highest age-standardized mortality rate (per 100,000 person-years) attributable to AMR [30.9 (95% UI 24.1-37.8)], whereas New Zealand had the lowest [3.2 (95% UI 2.6-3.8)] among the two regions. By 2050, the number of deaths associated with AMR is predicted to reach 3,875,753 (95% UI 1,502,402-9,998,297) in these two regions, of which 952,592 (95% UI 766,353-1,184,090) deaths are attributable to AMR. Conclusions:This study highlights the escalating burden of AMR in SEAR and WPR, emphasizing the urgent need for attention to this persistent and growing crisis. Our analyses underscore the dual challenge of sustaining gains among people <25 years while addressing the alarming increase of AMR in elderly populations. Given the high variability of AMR burden by pathogen, age group, and country, strengthened surveillance and improved laboratory capacity are essential to accurately characterize resistance patterns and guide clinical decision-making.

Northern Russia is characterized by socio-environmental conditions contributing to the spread of tuberculosis (TB) and a high ~30% rate of primary multidrug-resistant (MDR) TB. We applied high-resolution molecular methods to study the Mycobacterium tuberculosis population in the Arkhangelsk region of Northern Russia. All available M. tuberculosis isolates recovered from newly diagnosed patients from January to December 2018 (n = 88) were genotyped using 24-loci MIRU-VNTR, spoligotyping, and, partly, by whole-genome sequencing (WGS). The population structure revealed a predominance of the Beijing genotype and Euro-American lineage, with significant drug resistance burden associated with Beijing and its B0/W148 strain. Beijing strains showed a significantly higher association with MDR and pre-extensively drug-resistant (pre-XDR) TB compared to non-Beijing strains (P = 0.0013). All Beijing B0/W148 isolates were MDR, whereas the majority (71.4%) of Beijing Central Asian/Russian subtype strains were drug-sensitive. WGS analysis of newly discovered Beijing clusters 3828-32 and 10167-32 in this area indicated a historical transmission over several decades, reflecting long-term endemic circulation. The presence of compensatory mutations in rpoC among MDR strains suggests enhanced fitness facilitating their ongoing transmission. An intriguing cluster of recent transmission of a non-Beijing strain (spoligotype SIT53, L4.8 sublineage) was identified through combined epidemiological and genomic investigation. To conclude, the prevalence of Beijing strains rose from 39.3% in 1998 to 67.0% (P < 0.001), and Russian epidemic MDR strain B0/W148 increased its rate from 11.2% in 1998 to 20.5% (P = 0.097). This highlights the key role of MDR Beijing strains, including new resistant clusters, in disseminating MDR-TB in the region and the importance of continuous surveillance using high-resolution genotyping.IMPORTANCEThe Arkhangelsk region is the largest province of northern European Russia. One-third of newly diagnosed tuberculosis patients are infected with multidrug-resistant (MDR) Mycobacterium tuberculosis strains. We assessed the molecular population structure of M. tuberculosis in the Arkhangelsk region in the COVID-19 pre-pandemic year 2018. We identified important MDR clusters and elucidated tuberculosis transmission patterns. An intriguing cluster of recent transmission was identified through the combined use of epidemiological investigation and whole-genome sequencing. The prevalence of Beijing genotype strains increased from 39.3% in 1998 to 67.0%, and the Russian epidemic MDR strain B0/W148 doubled from 11.2% in 1998 to 20.5%. Furthermore, we described new MDR clusters emerging within the Beijing genotype. This highlights the key impact of the MDR Beijing strains and the importance of continuous surveillance using high-resolution genotyping. This study of the pre-pandemic strain collection provides an indispensable intermediate time point between earlier studies carried out 25 years ago and ongoing surveillance.

Background Tuberculosis (TB) remains a major public health challenge in Morocco, with marked regional disparities shaped by social and environmental conditions. We investigated the molecular epidemiology of Mycobacterium tuberculosis complex (MTBC) strains circulating in Tétouan, Morocco, focusing on strain diversity, lineage distribution, transmission dynamics, and associated sociodemographic factors using 24-locus MIRU-VNTR genotyping. Methods In this prospective cross-sectional study, 103 MTBC isolates from bacteriologically confirmed pulmonary TB patients diagnosed in Tétouan between 2020 and 2023 were analyzed using the 24-locus MIRU-VNTR scheme. Genetic diversity was assessed using the Hunter–Gaston Discriminatory Index (HGDI) and locus-level allelic diversity ( h ). Phylogenetic relationships were analyzed using UPGMA dendrograms and minimum spanning tree (MST) analysis via the MIRU-VNTR plus platform and recent transmission was estimated using the n − 1 method. Associations between clonal complex (CC) assignment and sociodemographic variables were evaluated using binary logistic regression. To explore the evolutionary context of the locally dominant Beijing and LAM strains, their profiles were compared to representative global datasets. Results The 24-locus MIRU-VNTR scheme demonstrated excellent discriminatory power (HGDI = 0.9896). Among the 103 isolates, 52 (50.5%) were assigned to established lineages: LAM (29.1%), Beijing (9.7%), Ghana (3.9%), S (2.9%), Haarlem (1.9%), West African 1 (1.9%), and West African 2 (1.0%). UPGMA analysis identified 17 (16.5%) isolates grouped into five identical-profile clusters, translating to a recent transmission rate of 11.6%. MST analysis revealed 10 CCs encompassing 40 (38.8%) isolates. Residence in the Old Medina slum area was the only independent predictor of CC membership ( p =.001). Conclusion The MTBC population in Tétouan is characterized by high genetic diversity and limited evidence of recent transmission, with residence in informal urban settlements (slums) emerging as a potential predictor of transmission. The first reported detection of Ghana, West African 1, and West African 2 lineages in Morocco suggests recent strain introductions, while the phylogeographic structure of Beijing and LAM strains reflects multiple historical dissemination routes involving Northern Eurasia, the Mediterranean basin, Africa, and possibly South America, followed by local diversification. Our findings support strengthening molecular surveillance through high-resolution genomic approaches and implementing geographically targeted public health interventions to interrupt TB transmission in lower-middle-income countries such as Morocco.

Background:Human respiratory syncytial virus (HRSV) is a leading cause of acute respiratory infections in children. COVID-19 NPIs significantly suppressed HRSV transmission. This study analyzed six-year epidemiological dynamics of pediatric HRSV infections in Henan Province, China, focusing on NPI suppression effects, the 2023 resurgence, and "Immune debt" impact. Methods:We retrospectively collected respiratory specimens from 80,920 children with acute respiratory diseases at Henan Children's Hospital (2019-2024). HRSV was detected using RT-qPCR. Positivity rates were analyzed by year, season, and age group. Results:During 2019-2024, HRSV positivity fluctuated markedly: 14.65% (2019), 16.34% (2021), 3.27% (2022 under strict NPIs), 21.47% (2023 post-NPIs), and 6.80% (2024). Interrupted time-series analysis indicated that NPI lifting in 2023 was associated with a significant surge in infection risk (OR = 668.77, 95% CI: 47.03-9509.28). Seasonal patterns shifted substantially, with the characteristic winter peak replaced by an off-season spring outbreak in April 2023 (57.41%). Multivariable logistic regression identified age as the strongest predictor, with infants <1 year having the highest risk (aOR = 9.02, 95% CI: 8.31-9.79) and a 4.91-fold higher positivity rate than school-aged children (22.98% vs. 4.68%; 95% CI: 4.59-5.25; P < 0.001). Conclusions:NPIs dramatically affected HRSV epidemiology. The intense post-suppression rebound strongly supports the "Immune debt" theory-accumulation of susceptible children driving resurgence. Establishing year-round, multi-pathogen surveillance systems is crucial for post-pandemic public health challenges.

The Haarlem genotype is a significant yet understudied part of the Euro-American lineage of Mycobacterium tuberculosis, characterized by unique pathogenetic features. Spoligotyping is a primary method for its detection, but it is not suitable for isolates with long blocks of deleted spacers. We have developed a simple and robust method to detect the Haarlem genotype. The real-time PCR (RT-PCR) assay with LNA probes was designed to detect the Rv0282 211 C > T mutation that was shown to be specific for the Haarlem genotype. The developed RT-PCR assay was optimized with 68 isolates with known whole-genome sequencing (WGS) data and applied to the geographically and genetically diverse collection of 428 isolates. As a result, 396 isolates were concordantly assigned to either Haarlem or non-Haarlem genotypes by both methods, whereas 32 isolates were discrepant cases. Twenty-two isolates of "unknown genotype" (Russia, Belarus, and Poland) were assigned to Haarlem by SNP-based assay. WGS of these isolates confirmed the results of the RT-PCR assay. To conclude, the developed RT-PCR method provides a reliable detection of the Haarlem genotype in retrospective collections and under prospective epidemiological surveillance. Its actual proportion in M. tuberculosis populations in certain world regions is higher than previously thought. Abridged spoligoprofiles with large deleted blocks of spacers require caution in interpretation.

This study included tuberculosis (TB) patients from high-burden Russian regions of Siberia and Far East. We aimed to assess the impact of the COVID-19 pandemic on the genotypic structure of Mycobacterium tuberculosis population and on epidemiology and clinical course of tuberculosis in TB and TB/COVID-19 coinfected patients. A total of 456 M. tuberculosis isolates were studied and submitted to drug susceptibility testing and genotyping. The modern Beijing genotype and its main Russian epidemic and endemic clusters (B0/W148 and Central Asian/Russian), and ancient Beijing sublineage were detected by PCR assays targeting specific molecular markers. Non-Beijing isolates were spoligotyped and compared to SITVIT2 database. More than 80

Caseum, the central necrotic material of tuberculous lesions, is a reservoir of drug-resistant persisting Mycobacterium tuberculosis (MTB). However, tubercle bacilli are not the only bacterial inhabitants of this necrosis. We discuss the available data on metagenomic and amplicon sequencing of 16S rRNA of caseous necrosis from surgically excised tuberculosis (TB) foci. This approach facilitated the characterization of the biodiversity and the potential biochemical pathways of these bacterial communities. We postulate that in terms of MTB content relative to satellite anaerobic lipophilic bacteria, caseum may present two distinct terminal states. "True" TB necrosis, containing 99.9% tubercle bacilli, and a polymicrobial community wherein anaerobic lipophilic bacteria predominate over MTB. Isolation from caseum and genomic characterization of several Corynebacterium and Staphylococcus species support this concept.

Background/Objectives: New anti-tuberculosis compounds are needed to treat patients infected with multi- or extensively drug-resistant Mycobacterium tuberculosis strains. Studies based on spontaneous in vitro mutagenesis can provide insights into the possible modes of action and resistance mechanisms of such new compounds. We evaluated the primary response of M. tuberculosis in vitro to the action of new aroylhydrazones and nitrofuroylamides. Methods: The reference strain H37Rv was cultured on solid media with compounds at increased concentrations relative to MIC. Resistant clones were investigated using whole-genome sequencing and bioinformatics tools to assess the role and potential impact of identified mutations. Results: Some of the mutations are significant (based on in silico analysis), located in essential genes, and therefore of particular interest. Frameshift mutations were observed in (i) Rv2702/ppgK, which is associated with starvation-induced drug tolerance and persistence in mice, and (ii) Rv3696c/glpK, which has been described as a switch on/off mutation associated with drug tolerance. Nonsynonymous substitutions were found in Rv0506/mmpS2, which belongs to the Mmp protein family involved in transport and drug efflux, and in infB, encoding the translation initiation factor IF-2. Conclusions: The primary adaptation of M. tuberculosis to the selective pressure of the tested compounds is complex and multifaceted. It involves multiple unrelated genes and pathways linked to non-specific drug tolerance, efflux systems, or mechanisms counteracting oxidative stress.

In this study, we utilized a C57BL/6 mouse model to investigate the pathogenic properties of well-characterized multidrug-resistant Mycobacterium tuberculosis strains belonging to the Beijing and Latin American Mediterranean (LAM) genotypes. Control animal groups were untreated, while experimental groups received adequate chemotherapy with new-generation drugs. On days 78 and 177 post-infection, mice were euthanized and analyzed for pathological changes, bacterial load, and biochemical indicators of liver damage. Bacterial isolates cultured from the lungs were subjected to whole genome sequencing (WGS) followed by bioinformatics analysis. A complete course of anti-TB therapy reduced inflammation and extent of lung damage across all groups. Mice infected with highly virulent Beijing 396 exhibited the most severe lung damage, while those infected with less virulent Beijing 6691 and LAM 7074 strains showed the least. Treatment was most effective in mice infected with strains 6691 and 7074. However, by day 177 p.i. compared to day 78 p.i., all treated groups (except for those infected with low-virulent 7074) displayed a slight increase in the bacterial load of the lungs. WGS identified a mutation inactivating the tgs3 gene, related to lipid metabolism, tolerance, and persistence, in the lung isolates from treated animals infected with Beijing 396. To conclude, some of the found differences in inflammatory response distinguish between low-virulent (Beijing 6691 and LAM 7074) and highly-virulent (Beijing 396) strains. Some other features appear common for strains of the same genotype and might correlate with deeply rooted evolutionary changes in genomes characteristic for phylogenetically distant East-Asian and Euro-American M. tuberculosis lineages.

This study aimed to evaluate the impact of different Mycobacterium tuberculosis strains on the blood proteinase-inhibitor system and structural changes in the renal parenchyma during the pathogenesis of renal tuberculosis in a rabbit model. Renal tuberculosis was modeled on 60 male Soviet Chinchilla rabbits. The susceptible virulent strain M. tuberculosis H37Rv (Euro-American lineage, group 1) and the low-lethal multidrug-resistant strain 5582 (Beijing Central Asian/Russian cluster; group 2) were injected into the cortex of the lower pole of the left kidney. Blood levels of biomarkers and enzymes were measured at baseline (pre-infection), and 2.5 and 22 weeks after infection. Morphological changes in nephron structures were assessed using 26 indicators at 22 weeks. Whole genome sequencing of M. tuberculosis DNA was performed on the DNBSEQ-G50 MGI platform. At 2.5 weeks, group 1 exhibited a significant increase in matrix metalloproteinases (MMP)-1/9 and cystatin C compared to group 2 (p = 0.02). After 22 weeks, group 1 showed elevated levels of MMP-9 and ceruloplasmin, alongside reduced levels of tissue inhibitor of metalloproteinases-1 (TIMP-1), cystatin C, and albumin (p = 0.02). Group 1 demonstrated a larger area of specific inflammation and less severe fibrotic changes compared to group 2 (p = 0.02). Genome of clinical strain 5582 harboured 55 frameshift and 8 stop codon mutations some of which were in genes known to be involved in intracellular survival and pathogenesis. In quantitative terms, the structural changes observed in the kidneys of rabbits were inversely related to the virulence of the strains. Specifically, the more virulent strain (H37Rv) induces less pronounced structural changes. Renal tuberculosis induced by H37Rv is characterized by a pronounced imbalance in the MMP/TIMP-1 system, marked by increased MMP-1 and − 9 levels and decreased TIMP-1 levels in the blood. This imbalance is associated with structural kidney damage, including specific and paraspecific changes typical of an immediate hypersensitivity reaction. In contrast, infection with Beijing 5582 maintained a relative balance in the MMP/inhibitor system, with a significant increase in cystatin C and moderately pronounced productive changes in the renal parenchyma, consistent with a delayed hypersensitivity reaction.

Mycobacterium tuberculosis of the Beijing Modern Sublineage displays increased virulence when compared with strains of the Ancient Sublineage. Here, we report the full genome of strains of the two sublineages isolated from tuberculosis patients from Brazil, Mozambique, and Russia.

More than a quarter of the world's population is infected with Mycobacterium tuberculosis. However, only about 10% of those infected develop active TB. This indicates a key role for innate immunity in limiting M. tuberculosis replication. Most often, bacteria can regulate the expression of host-specific molecules and weaken host immunity. OBJECTIVE:To use a biological model, in order to determine significant molecular immunohistochemical markers characterizing the virulence of the "Buryat" and "Omsk" subtypes of the M. tuberculosis Beijing genotype in lung tissue. MATERIAL AND METHODS:Lung samples of the C57BL/6 male mice were obtained during experimental infection with M. tuberculosis strains: the reference laboratory strain H37Rv, multidrug-resistant clinical strains 396 (highly lethal and hypervirulent «Buryat» genotype Beijing 14717-15) and 6691 (low-lethal and low-virulent "Omsk" genotype Beijing 1071-32) on days 14, 21, 60 and 120. They were studied by histological and immunohistochemical methods. The relative areas of expression of IL-6, IL-12A, iNOS, and TNF-α in the lung tissue of model animals were established. RESULTS:A study of strain 396 showed that both disease progression and damage to lung tissue are associated with a highly reactive immune response and increased synthesis of iNOS and strain characteristics that block the production of TNF-α. On the contrary, for strain 6691 a low reactivity of the immune response was revealed, with statistically significantly lower values of the relative area of expression of NOS and TNF-α during all observation periods (days 14-120). All animals that survived to day 120 showed a similar morphological picture with differences in cytokine levels, indicating a nonlinear relationship between proinflammatory factors and the damage substratum. CONCLUSION:The progression of the disease and damage of lung tissue were associated with a highly reactive immune response and increased synthesis of iNOS, strain properties that block the TNF-α production. Thus, iNOS and TNF-α can act as molecular markers characterizing the virulence of the "Buryat" and "Omsk" subtypes of M. tuberculosis in lung tissue.

We investigated the rise of nontuberculous mycobacteria (NTM) infections in Bulgaria, focusing on species identification and distribution from 2018 to 2022. Utilizing advanced diagnostic tools, including the Hain Mycobacterium CM/AS method, Myco-biochip assay, and whole-genome sequencing, the study identifies and characterizes a diverse range of Mycobacterium species from clinical samples. While M. avium, M. gordonae, M. fortuitum, and M. chelonae were dominating, a number of rare species were also found. They include such species as M. marseillense and M. celatum. Moreover, the noticeable prevalence of M. terrae complex species missed by conventional testing was observed. We identified a rare species, highly homologous to previously described strains from Japan; based on genome-genome distance data, we propose its reannotation as a new species. Further, a novel species was identified, which is significantly distinct from its closest neighbor, M. iranicum, with ANI = 87.18%. Based on the SeqCode procedure, we propose to name this new species Mycobacterium bulgaricum sp. nov. Dynamic changes in NTM species prevalence in Bulgaria observed from 2011 to 2022 highlight the emergence of new species and variations tied to environmental and demographic factors. This underscores the importance of accurate species identification and genotyping for understanding NTM epidemiology, informing public health strategies, and enhancing diagnostic accuracy and treatment protocols.

Buryatia is a multidrug-resistant tuberculosis (MDR-TB) high-burden region in the Russian Far East with ethnically diverse population (30% Mongoloid Buryats and 65% Russians). Two hundred M. tuberculosis strains from newly-diagnosed patients were subjected to phenotypic testing and genotyping. The Beijing genotype was more prevalent among Russians than Buryats (68% vs 53%; P=0.055). European non-Beijing genotypes (LAM, Ural, Haarlem) were double more prevalent in Buryats vs Russians (39.2% vs 20.5%; P=0.01). Higher prevalence of Beijing among former prison inmates (79% vs 61% in other patients, P=0.1) suggests its increased transmissibility. The Russian epidemic cluster B0/W148 was in 9.5%, double smaller than elsewhere in Siberia. The hypervirulent Beijing 14717-15-cluster was endemic in Buryatia but paradoxically enough, it was more frequently isolated from Russians than Buryats (9.1% vs 3.9%; P=0.2). Beijing subtypes B0/W148, CAO, and 14717-15 were associated with poly/multi-drug resistance (P=0.01-0.0001). HIV coinfection was more frequent in Russians than in Buryats: 35/141 (24.8%) vs 5/51 (9.8%), P=0.03. To conclude, M. tuberculosis population structure in Buryatia retained its singularities compared to other parts of Russia and remains strikingly different from the neighboring Mongolia. A circulation of strongly MDR-associated Beijing subtypes and drug-resistant non-Beijing strains highlights a risk of their broader dissemination.

Introduction. Fluoroquinolones remain the key second-line anti-tuberculosis drugs. The aim of the study was the molecular characterization of fluoroquinolone-resistant Mycobacterium tuberculosis strains from newly diagnosed tuberculosis patients in the Northwest of the Russian Federation. Materials and methods. The retrospective study collection included M. tuberculosis isolates isolated in 2015–2019 from previously untreated tuberculosis patients. Susceptibility to antituberculosis drugs (including the fluoroquinolone ofloxacin) was determined using the BACTEC MGIT960 or absolute concentration method. Mutations in the gyrA gene as a marker of resistance to fluoroquinolones, were detected by real-time PCR. Beijing genotype and its subtypes were detected by PCR and real-time PCR methods. Non-Beijing strains were spoligotyped. Results and discussion. Phenotypic resistance to ofloxacin was detected in 6.7% (40/599) of strains and in 17.4% (40/230) of MDR strains. 34 of 40 (85%) ofloxacin-resistant strains belonged to the Beijing genotype. 18 (45%) strains were assigned to the Russian epidemic subtype Beijing B0/W148 and 12 (30%) to Beijing Central Asian/Russian. The remaining 6 ofloxacin-resistant strains belonged to the Euro-American phylogenetic lineage. Mutations in the gyrA gene were found in 97.5% (39/40) of strains. The most common were mutations in codon 94 (69.2%, 27/39). The Asp94Gly substitution was identified in 57.5% (23/40) of ofloxacin-resistant strains and was dominant among Beijing (19/34) and non-Beijing (4/6) strains. The second most common substitution was Ala90Val (25%, 10/40). More than half of the ofloxacin-resistant strains, Beijing B0/W148 (10/18) and Central Asian/Russian (7/12), carried the Asp94Gly mutation. Conclusion. In the Northwest of Russia in 2016-2019, primary resistance of M. tuberculosis to fluoroquinolones was 6.7% in the total collection and 17.4% of MDR strains, and was mainly caused by the gyrA Asp94Gly and Ala90Val mutations. Beijing B0/W148 genotype was characterized by the largest proportion of fluoroquinolone-resistant strains.

Despite well-known limitations,mice remain useful as model animals to study tuberculosis (TB) pathogenesis,the basic immune response,the extent of lung pathology as well as efficacy of new drugs against Mycobacterium tuberculosis[1,2].

AIM Molecular characterization of M. tuberculosis isolates from newly diagnosed pre-XDR-TB patients in West Siberia, Russia. BACKGROUND Russia is among the top high-burden countries for multidrug-resistant tuberculosis (MDR-TB). Fluoroquinolones (FQ) are critical second-line drugs to treat MDR-TB. The current situation with TB is exacerbated by spread of pre-extensively drug-resistant TB (pre-XDR-TB), caused by Mycobacterium tuberculosis strains resistant to isoniazid, rifampicin, and any FQ. METHODS M. tuberculosis isolates (n=613, 2019-2022) were subjected to drug susceptibility testing (including FQ ofloxacin) and genotyping of major epidemic and endemic genotypes and subtypes. Mutations in gyrA as a marker of FQ resistance were detected using real-time PCR assay. RESULTS Among 613 isolates, 80 (13.1%) were phenotypically pre-XDR and all had a gyrA resistance mutation. The most frequently identified FQ-resistance mutations were gyrA D94G (54; 67.5%) and A90V (13; 16.3%). The majority of pre-XDR isolates belonged to the Beijing family (74; 92.5%). Main Beijing subtypes were Central Asian/Russian (23; 28.8%) and Russian epidemic strain B0/W148 (42; 52.5%). Thirty-nine (48.8%) pre-XDR isolates were resistant to at least one injectable drug. B0/W148 was more frequently resistant to injectable drugs than Central Asian/Russian subtype (57.1% vs. 21.7%, p=0.008). CONCLUSION In West Siberia, pre-XDR was detected in 13.1% of new TB cases. About half of pre-XDR M. tuberculosis isolates belong to the Russian epidemic strain Beijing B0/W148, which is also characterized by high level of resistance to other second-line drugs. Rapid drug susceptibility testing is necessary to enable effective treatment of MDR-TB and pre-XDR-TB.