Transcontinental spread and evolution of Mycobacterium tuberculosis W148 European/Russian clade toward extensively drug resistant tuberculosis

Evaluation of the role of whiB6 and kdpDE in the dominant multidrug-resistant clone Mycobacterium tuberculosis B0/W148

Multidrug-resistant (MDR) strains of Mycobacterium tuberculosis represent an obstacle to eradicating tuberculosis (TB) due to the low treatment success rate of MDR TB. Among them, the MDR B0/W148 clone has recently evolved from the M. tuberculosis Beijing lineage 2 and is widely disseminated in Russia and Europe. To get more insights into the genetic factors underlying the evolutionary success of the MDR M. tuberculosis B0/W148 clone in addition to environmental and patient-related features, we focused on two mutations specific to this clone that are found in the transcriptional regulators WhiB6 and KdpDE and investigated in a H37Rv strain background the transcriptional profile associated with these mutations and their impact on the in vitro and in vivo growth characteristics. Through the construction and use of H37Rv∆whiB6, H37Rv∆kdpDE, and complemented strains, neither mutation impaired the in vitro growth of M. tuberculosis in standard mycobacterial growth media. The mutation T51P in whiB6 prevented the upregulation of 9 genes in the esx-1 core region and 44 genes elsewhere in the genome, while the deletion of two nucleotides in kdpD leads to a fusion protein of KdpD with KdpE that inhibits the transcriptional activity of KdpE. Neither mutation led to hypervirulence in a mouse infection model. These results point to the role of other MDR B0/W148 specific mutations in the wide geographic diffusion of this clone and/or put in question a hypothesized hypervirulence as a driving factor for this large dissemination.

IMPORTANCE

Human tuberculosis (TB), caused by the bacterium Mycobacterium tuberculosis, remains a global public health issue estimated to have been responsible for 1.25 million deaths in 2023. Multidrug-resistant (MDR) strains of M. tuberculosis, resistant to rifampicin and isoniazid, lead to lower treatment success. Among them, the MDR B0/W148 clone has widely disseminated in Russia and Europe. To get more insights into the genetic factors underlying the evolutionary success of this clone, we investigated two strain-specific mutations found in the transcriptional regulators WhiB6 and KdpDE. By constructing and analyzing laboratory M. tuberculosis strains carrying these specific mutations, we found numerous changes in their transcriptional profiles, whereas we observed only a little impact of these mutations on the virulence of M. tuberculosis in a mouse infection model. Our study provides new insights into the transcriptional landscape of the selected MDR strains, although no direct connection to virulence could be established.

Multi-drug resistance and compensatory mutations in Mycobacterium tuberculosis in Vietnam

BACKGROUND

Vietnam is a hotspot for the emergence and spread of multidrug-resistant Mycobacterium tuberculosis. This study aimed to perform a retrospective study on the compensatory evolution in multidrug-resistant M. tuberculosis strains and the association with drug-resistant mutations and M. tuberculosis genotypes.

METHODS

Hundred and seventy-three strains resistant to rifampicin (n = 126) and/or isoniazid (n = 170) (multidrug-resistant = 123) were selected according to different drug-resistant patterns and genotypes. The genes/promoter regions including rpoA, rpoB, rpoC, katG, inhA, inhA promoter, ahpC, ahpC promoter, gyrA, gyrB, and rrs were sequenced for each strain.

RESULTS

Frequency of rifampicin- and isoniazid-resistant mutations in multidrug-resistant strains was 99.2% and 97.0%, respectively. Mutations associated with low -high levels of drug resistance with low- or no-fitness costs compared to the wild type, including rpoB_Ser450Leu, katG_Ser315Thr, inhA-15(A-T), gyrA_Asp94Gly, and rrs_A1401GA, accounted for 46.3%, 76.4%, 16.2%, 8.9%, and 11.4%, respectively, in the multidrug-resistant strains. Beijing and Euro-American genotype strains were associated with high-level drug-resistant mutations, rpoB_Ser450Leu, katG_Ser315Thr, and gyrA_Asp94Gly, while East African-Indian genotype strains were associated with low to high-level drug-resistant mutations, rpoB_His445Asp, rpoB_His445Tyr, inhA-15(C-T) and rrs_A1401G. Multidrug-resistant strains (19.5%) harboured compensatory mutations linked to rifampicin resistance in rpoA, rpoB, or rpoC. Notably, the frequency of compensatory mutations in Beijing genotypes was significantly higher than in East African-Indian genotypes (21.1% vs. 3.3%, OR = 7.7; 95% CI = 1.0 to 61.2, p = 0.03). The proportion of multidrug-resistant strains with rpoB_Ser450Leu mutations carrying rpoA-rpoC mutations was higher than that of strains with other rpoB mutations (OR = 5.4; 95% CI = 1.4 to 21.1, p = 0.02) and was associated with Beijing strains. Only 1.2% (2/170) isoniazid-resistant strains carried aphC-52(C-T) mutation in the promoter region of the ahpC gene, which was hypothesised to be the compensatory mutation in isoniazid-resistant strains. Meanwhile, 11 isoniazid-resistant strains carried a katG mutation combined with either inhA-8(T-C) or inhA-15(A-T) mutations and were associated with East African-Indian strains.

CONCLUSIONS

Mutations associated with high levels of drug resistance without/with low fitness costs (rpoB_Ser450Leu and katG_Ser315Thr) along with compensatory mutations linked to rifampicin resistance were strongly associated with multidrug-resistant M. tuberculosis Beijing strains in Vietnam.

Ecology, global diversity and evolutionary mechanisms in the Mycobacterium tuberculosis complex

With the COVID-19 pandemic receding, tuberculosis (TB) is again the number one cause of human death to a single infectious agent. TB is caused by bacteria that belong to the Mycobacterium tuberculosis complex (MTBC). Recent advances in genome sequencing have provided new insights into the ecology and evolution of the MTBC. This includes the discovery of new phylogenetic lineages within the MTBC, a deeper understanding of the host tropism among the various animal-adapted lineages, enhanced knowledge on the evolutionary dynamics of antimicrobial resistance and transmission, as well as a better grasp of the within-host MTBC diversity. Moreover, advances in long-read sequencing are increasingly highlighting the relevance of structural genomic variation in the MTBC. These findings not only shed new light on the biology and epidemiology of TB, but also give rise to new questions and research avenues. The purpose of this Review is to summarize these new insights and discuss their implications for global TB control.

Clinical epidemiology, genetic diversity, and drug susceptibility patterns by whole genome sequencing of Mycobacterium tuberculosis complex isolates in Gabon from 2012 to 2022

Objectives

This study aimed to investigate genotypic characteristics and drug resistance profiles of Mycobacterium tuberculosis complex (Mtbc) strains isolated from patients with suspected tuberculosis (TB) in Gabon.

Methods

We performed whole genome sequencing of 430 Mtbc strains cultured between 2012 and 2022. Phylogenetic strain classification, genomic resistance prediction, and cluster analysis were also performed.

Results

Strains from four major Mtbc lineages, L4 (n = 372; 65%), L5 (n = 46; 11%), L2 (n = 6; 1,4%), and L6 (n = 3; 0,7%), were observed. Interestingly, more than 10% of the strains were represented by Mycobacterium africanum strains (L5 and L6), with L4 strains being dominant. The subclassification of L4 strains showed that L4.6.2.2 (Cameroon, n = 116) was the most prevalent. The proportion of resistance (any resistance to first-line TB drugs) was 30%, with 12% (n = 52) being at least multidrug-resistant (MDR) and six showing additional fluoroquinolone resistance. The overall cluster rate was 64% in non-MDR and MDR Mtbc strains.

Conclusion

Although most Mtbc infections are caused by L4 M. tuberculosis strains, M. africanum strains also contribute to TB epidemiology in Gabon. The MDR epidemic is mainly driven by one dominant L4 Haarlem outbreak clone that has been spreading for approximately a century in the country.

Analysis of complete genomes of Mycobacterium tuberculosis sublineage 2.1 (Proto-Beijing) revealed the presence of three pe_pgrs3-pe_pgrs4-like genes

Mycobacterium tuberculosis Complex (MTBC), the etiological agent of tuberculosis (TB), demonstrates considerable genotypic diversity with distinct geographic distributions and variable virulence profiles. The pe-ppe gene family is especially noteworthy for its extensive variability and roles in host immune response modulation and virulence enhancement. We sequenced an Mtb genotype L2.1 isolate from Chiangrai, Northern Thailand, using second and third-generation sequencing technologies. Comparative genomic analysis with two additional L2.1 isolates and two L2.2.AA3 (Asia Ancestral 3 Beijing) isolates revealed significant pe-ppe gene variations. Notably, all L2.1 isolates harbored three copies of pe_pgrs3-pe_pgrs4-like genes (pe_pgrs3*, pe_pgrs4*, and pe_pgrs4), different from L2.2.AA3 and H37Rv strains. Additionally, ppe53 was duplicated in all but H37Rv, and ppe50 was deleted in L2.1 isolates, contrasting with an extended ppe50 in an L2.2 isolate (Mtb 18b), which contains an additional SVP motif. Complete deletion of ppe66 and loss of wag22 were observed in L2.1 isolates. These findings highlight the high structural variability of the pe-ppe gene family, emphasizing its complex roles in Mtb-host immune interactions. This genetic complexity offers potentially critical insights into mycobacterial pathogenesis, with significant implications for vaccine development and diagnostics.

Increasing circulation of multi-drug resistant tuberculosis strains in Buryatia, high-burden and ethnically diverse region in the Russian Far East

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.

Antimicrobial Resistance Surveillance in Post-Soviet Countries: A Systematic Review

BACKGROUND

Antimicrobial resistance (AMR) is a global health threat. AMR surveillance is crucial for understanding and controlling the spread of AMR. Surveillance systems can inform clinicians, guide health policymakers, and support effective AMR interventions. AMR surveillance data from former Soviet region countries are often limited, resulting in gaps in up-to-date knowledge.

METHODS

This systematic review was registered under the PROSPERO protocol CRD42024537799 and followed the PRISMA guidelines. Data from five databases (PubMed, MEDLINE, Embase, CINAHL, and CyberLeninka) and official sources were searched according to the inclusion criteria.

RESULTS

In total, 30 publications describing AMR surveillance and National Action Plans (NAPs) were included. Among the 15 countries, 14 (93.3%) have either developed a NAP or are in the process of implementing one; and 7 (46.7%) countries have a standardized AMR surveillance system. Almost all countries have reference laboratory centers, but nine (60%) countries have established standard testing methods in all sites. Only three (20%) countries have fully implemented quality assessment. There is an increasing tendency to involve and report AMR data to international networks, and countries will strengthen their AMR systems by adhering to international standards. The subgroup analysis revealed that Central and Western Asian countries are less developed in terms of AMR surveillance, which may encourage proactive engagement in AMR governance in these regions.

CONCLUSIONS

This review is crucial for understanding the current efforts and improving AMR surveillance in former Soviet countries. The findings are promising and indicate that AMR surveillance is established in all reviewed countries, although at different levels.

Rifaximin prophylaxis causes resistance to the last-resort antibiotic daptomycin

Multidrug-resistant bacterial pathogens like vancomycin-resistant Enterococcus faecium (VREfm) are a critical threat to human health1. Daptomycin is a last-resort antibiotic for VREfm infections with a novel mode of action2, but for which resistance has been widely reported but is unexplained. Here we show that rifaximin, an unrelated antibiotic used prophylactically to prevent hepatic encephalopathy in patients with liver disease3, causes cross-resistance to daptomycin in VREfm. Amino acid changes arising within the bacterial RNA polymerase in response to rifaximin exposure cause upregulation of a previously uncharacterized operon (prdRAB) that leads to cell membrane remodelling and cross-resistance to daptomycin through reduced binding of the antibiotic. VREfm with these mutations are spread globally, making this a major mechanism of resistance. Rifaximin has been considered 'low risk' for the development of antibiotic resistance. Our study shows that this assumption is flawed and that widespread rifaximin use, particularly in patients with liver cirrhosis, may be compromising the clinical use of daptomycin, a major last-resort intervention for multidrug-resistant pathogens. These findings demonstrate how unanticipated antibiotic cross-resistance can undermine global strategies designed to preserve the clinical use of critical antibiotics.

The innate memory response of macrophages to Mycobacterium tuberculosis is shaped by the nature of the antigenic stimuli

Innate immune cells, such as macrophages, mount an immune response upon exposure to antigens and pathogens. Emerging evidence shows that macrophages exposed to an antigen can generate a "memory-like" response (a.k.a. trained immunity), which confers a non-specific and enhanced response upon subsequent stimulation with a second antigen/microbe. This trained immunity has been implicated in the enhanced response of macrophages against several invading pathogens. However, the association between the nature of the antigen and the corresponding immune correlate of elicited trained immunity is not fully understood. Similarly, the response of macrophages trained and restimulated with homologous stimulants to subsequent infection by pathogenic Mycobacterium tuberculosis (Mtb) remains unexplored. Here, we report the immune and metabolic profiles of trained immunity in human THP-1-derived macrophages after homologous training and restimulation with BCG, LPS, purified protein Derivative (PPD), heat-killed Mtb strains HN878 (hk-HN), and CDC1551 (hk-CDC). Furthermore, the impact of training on the autophagic and antimicrobial responses of macrophages with or without subsequent infection by clinical Mtb isolates HN878 and CDC1551 was evaluated. Results show that repeated stimulation of macrophages with different antigens displays distinct pro-inflammatory, metabolic, antimicrobial, and autophagy induction profiles. These macrophages also induce a differential antimicrobial response upon infection with clinical Mtb HN878 and CDC1551 isolates. A significantly reduced intracellular bacterial load was noted in the stimulated macrophages, which was augmented by the addition of rapamycin, an autophagy inducer. These observations suggest that the nature of the antigen and the mode of stimulation shape the magnitude and breadth of macrophage innate memory response, which impacts subsequent response to Mtb infection.

IMPORTANCE

Trained immunity (a.k.a. innate memory response) is a novel concept that has been rapidly emerging as a mechanism underpinning the non-specific immunity of innate immune cells, such as macrophages. However, the association between the nature of the stimuli and the corresponding immune correlate of trained immunity is not fully understood. Similarly, the kinetics of immunological and metabolic characteristics of macrophages upon "training" by the same antigen as primary and secondary stimuli (homologous stimulation) are not fully characterized. Furthermore, the ability of antigens such as purified protein derivative (PPD) and heat-killed-Mtb to induce trained immunity remains unknown. Similarly, the response of macrophages primed and trained by homologous stimulants to subsequent infection by pathogenic Mtb is yet to be reported. In this study, we evaluated the hypothesis that the nature of the stimuli impacts the depth and breadth of trained immunity in macrophages, which differentially affects their response to Mtb infection.

Genomic evolution of ST228 SCCmec-I MRSA 10 years after a major nosocomial outbreak

In this study, we investigated the genomic changes in a major methicillin-resistant Staphylococcus aureus (MRSA) clone following a significant outbreak at a hospital. Whole-genome sequencing of MRSA isolates was utilized to explore the genomic evolution of post-outbreak MRSA strains. The epidemicity of the clone declined over time, coinciding with the introduction of multimodal infection control measures. A genome-wide association study (GWAS) identified multiple genes significantly associated with either high or low epidemic success, indicating alterations in mobilome, virulence, and defense mechanisms. Random Forest models pinpointed a gene related to fibrinogen binding as the most influential predictor of epidemicity. The decline of the MRSA clone may be attributed to various factors, including the implementation of new infection control measures, single nucleotide polymorphisms accumulation, and the genetic drift of a given clone. This research underscores the complex dynamics of MRSA clones, emphasizing the multifactorial nature of their evolution. The decline in epidemicity seems linked to alterations in the clone's genetic profile, with a probable shift towards decreased virulence and adaptation to long-term carriage. Understanding the genomic basis for the decline of epidemic clones is crucial to develop effective strategies for their surveillance and management, as well as to gain insights into the evolutionary dynamics of pathogen genomes.

Genetic diversity, evolution and drug resistance of Mycobacterium tuberculosis lineage 2

Mycobacterium tuberculosis causes a chronic infectious disease called tuberculosis. Phylogenetic lineage 2 (L2) of M. tuberculosis, also known as the East Asian lineage, is associated with high virulence, increased transmissibility, and the spread of multidrug-resistant strains. This review article examines the genomic characteristics of the M. tuberculosis genome and M. tuberculosis lineage 2, such as the unique insertion sequence and spoligotype patterns, as well as MIRU-VNTR typing, and SNP-based barcoding. The review describes the geographical distribution of lineage 2 and its history of origin. In addition, the article discusses recent studies on drug resistance and compensatory mechanisms of M. tuberculosis lineage 2 and its impact on the pathogen's transmissibility and virulence. This review article discusses the importance of establishing a unified classification for lineage 2 to ensure consistency in terminology and criteria across different studies and settings.

The recent rapid expansion of multidrug resistant Ural lineage Mycobacterium tuberculosis in Moldova

The projected trajectory of multidrug resistant tuberculosis (MDR-TB) epidemics depends on the reproductive fitness of circulating strains of MDR M. tuberculosis (Mtb). Previous efforts to characterize the fitness of MDR Mtb have found that Mtb strains of the Beijing sublineage (Lineage 2.2.1) may be more prone to develop resistance and retain fitness in the presence of resistance-conferring mutations than other lineages. Using Mtb genome sequences from all culture-positive cases collected over two years in Moldova, we estimate the fitness of Ural (Lineage 4.2) and Beijing strains, the two lineages in which MDR is concentrated in the country. We estimate that the fitness of MDR Ural strains substantially exceeds that of other susceptible and MDR strains, and we identify several mutations specific to these MDR Ural strains. Our findings suggest that MDR Ural Mtb has been transmitting efficiently in Moldova and poses a substantial risk of spreading further in the region.

Molecular determinants of multidrug-resistant tuberculosis in Sierra Leone

Multidrug-resistant tuberculosis (MDR-TB) management has become a serious global health challenge. Understanding its epidemic determinants on the regional level is crucial for developing effective control measures. We used whole genome sequencing data of 238 of Mycobacterium tuberculosis complex (MTBC) strains to determine drug resistance profiles, phylogeny, and transmission dynamics of MDR/rifampicin-resistant (RR) MTBC strains from Sierra Leone. Forty-two strains were classified as RR, 196 as MDR, 5 were resistant to bedaquiline (BDQ) and clofazimine (CFZ), but none was found to be resistant to fluoroquinolones. Sixty-one (26%) strains were resistant to all first-line drugs, three of which had additional resistance to BDQ/CFZ. The strains were classified into six major MTBC lineages (L), with strains of L4 being the most prevalent, 62% (n = 147), followed by L6 (Mycobacterium africanum) strains, (21%, n = 50). The overall clustering rate (using ≤d12 single-nucleotide polymorphism threshold) was 44%, stratified into 31 clusters ranging from 2 to 16 strains. The largest cluster (n = 16) was formed by sublineage 2.2.1 Beijing Ancestral 3 strains, which developed MDR several times. Meanwhile, 10 of the L6 strains had a primary MDR transmission. We observed a high diversity of drug resistance mutations, including borderline resistance mutations to isoniazid and rifampicin, and mutations were not detected by commercial assays. In conclusion, one in five strains investigated was resistant to all first-line drugs, three of which had evidence of BDQ/CFZ resistance. Implementation of interventions such as rapid diagnostics that prevent further resistance development and stop MDR-TB transmission chains in the country is urgently needed.

IMPORTANCE

A substantial proportion of MDR-TB strains in Sierra Leone were resistant against all first line drugs; however this makes the all-oral-six-month BPaLM regimen or other 6-9 months all oral regimens still viable, mainly because there was no FQ resistance.Resistance to BDQ was detected, as well as RR, due to mutations outside of the hotspot region. While the prevalence of those resistances was low, it is still cause for concern and needs to be closely monitored.

Emergence of bedaquiline-resistant tuberculosis and of multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis strains with rpoB Ile491Phe mutation not detected by Xpert MTB/RIF in Mozambique: a retrospective observational study

BACKGROUND

In 2021, an estimated 4800 people developed rifampicin-resistant tuberculosis in Mozambique, 75% of which went undiagnosed. Detailed molecular data on rifampicin-resistant and multidrug-resistant (MDR) tuberculosis are not available. Here, we aimed at gaining precise data on the determinants of rifampicin-resistant and MDR tuberculosis in Mozambique.

METHODS

In this retrospective observational study, we performed whole-genome sequencing of 704 rifampicin-resistant Mycobacterium tuberculosis complex (Mtbc) strains submitted to the National Tuberculosis Reference Laboratory (NTRL) in Maputo, Mozambique, between 2015 and 2021. Phylogenetic strain classification, genomic resistance prediction, and cluster analysis were performed.

FINDINGS

Between Jan 1, 2015, and July 31, 2021, 2606 Mtbc isolates with an isoniazid or rifampicin resistance were identified in the NTRL biobank, of which, 1483 (56·9%) were from men, 1114 (42·7%) from women, and nine (0·4%) were unknown. Genome-based drug-resistant prediction classified 704 Mtbc strains as rifampicin resistant. 628 (89%) of the 704 Mtbc strains were classified MDR; of those, 146 (23%) were pre-extensively drug resistant (pre-XDR; additional fluoroquinolone resistance), and 24 (4%) extensively drug resistant (XDR; combined fluoroquinolone and bedaquiline resistance). Overall, 61 (9%) of 704 strains revealed resistance to bedaquiline: five (7%) of 76 rifampicin resistant plus bedaquiline resistant, 32 (7%) of 458 MDR plus bedaquiline resistant, and 24 (100%) of 24 XDR. Prevalence of bedaquiline resistance increased from 3% in 2016 to 14% in 2021. The cluster rate (12 single-nucleotide polymorphism threshold) was 42% for rifampicin-resistant strains, 78% for MDR strains, 94% for pre-XDR strains, and 96% for XDR Mtbc strains. 31 (4%) of 704 Mtbc strains, belonging to a diagnostic escape outbreak strain previously described in Eswatini (group_56), had an rpoB Ile491Phe mutation which is not detected by Xpert MTB/RIF (no other rpoB mutation). Of these, 23 (74%) showed additional resistance to bedaquiline, 13 (42%) had bedaquiline and fluoroquinolone resistance, and two (6%) were bedaquiline, fluoroquinolone, and delamanid resistant.

INTERPRETATION

Pre-XDR resistance is highly prevalent among MDR Mtbc strains in Mozambique and so is bedaquiline resistance; and the frequency of bedaquiline resistance quadrupled over time and was found even in Mtbc strains without fluoroquinolone resistance. Importantly, strains with Ile491Phe mutation were frequent, accounting for 31% (n=10) of MDR plus bedaquiline-resistant strains and 54% (n=13) of XDR Mtbc strains. Given the current diagnostic algorithms and treatment regimens, both the emergence of rifampicin resistance due to Ile491Phe and bedaquiline resistance might jeopardise MDR tuberculosis prevention and care unless sequencing-based technology is rolled out. The potential cross border spread of diagnostic escape strains needs further investigation.

FUNDING

The German Ministry of Health through the Seq_MDRTB-Net project, the Deutsche Forschungsgemeinschaft under Germany's Excellence Strategy Precision Medicine in Inflammation and the Research Training Group 2501 TransEvo, the Leibniz Science Campus Evolutionary Medicine of the Lung, and the German Ministry of Education and Research via the German Center for Infection Research.

Prison as a driver of recent transmissions of multidrug-resistant tuberculosis in Callao, Peru: a cross-sectional study

Background

We sought to identify resistance patterns and key drivers of recent multidrug-resistant tuberculosis (MDR-TB) transmission in a TB-prevalent area in Peru.

Methods

Cross-sectional study including MDR Mycobacterium tuberculosis complex (Mtbc) strains identified in Callao-Peru between April 2017 and February 2019. Mtbc DNA was extracted for whole genome sequencing which was used for phylogenetic inference, clustering, and resistance mutation analyses. Clusters indicative of recent transmission were defined based on a strain-to-strain distance of ≤5 (D5) single nucleotide polymorphisms (SNPs). Epidemiologic factors linked to MDR-TB clustering were analyzed using Poisson regression.

Findings

171 unique MDR-Mtbc strains were included; 22 (13%) had additional fluoroquinolone resistance and were classified as pre-XDR. Six strains (3.5%) harboured bedaquiline (BDQ) resistance mutations and were classified as MDR + BDQ. 158 (92%) Mtbc strains belonged to lineage 4 and 13 (8%) to lineage 2. Using a cluster threshold of ≤5 SNPs, 98 (57%) strains were grouped in one of the 17 D5 clusters indicative of recent transmission, ranging in size from 2 to the largest cluster formed by 53 4.3.3 strains (group_1). Lineage 4.3.3 strains showed the overall highest cluster rate (43%). In multivariate analyses, current or previous imprisonment was independently associated with being part of any MDR-TB transmission clusters (adjusted prevalence ratio [aPR], 1.45; 95% CI, 1.09-1.92).

Interpretation

Pre-XDR-TB emerged in more than 10% of the MDR-TB strains investigated. Transmission of 4.3.3 Mtbc strains especially of the dominant group_1 clone is a major driver of the MDR-TB epidemic in Callao. Current or previous imprisonment was linked to recent MDR-TB transmissions, indicating an important role of prisons in driving the MDR-TB epidemic.

Funding

This work was supported in part by the ERANet-LAC Network of the European Union, Latin America and the Caribbean Countries on Joint Innovation and Research Activities, and FONDECYT. Additional support was received from Leibniz Science Campus Evolutionary Medicine of the Lung, the Deutsche Forschungsgemeinschaft (German Research Foundation, under Germany's Excellence Strategy-EXC 2167 Precision Medicine in Inflammation), and the Research Training Group 2501 TransEvo.

Implementation of Whole Genome Sequencing of Tuberculosis Isolates in a Referral Center in Rome: Six Years' Experience in Characterizing Drug-Resistant TB and Disease Transmission

Over the past years, Tuberculosis (TB) control strategies have been effective in reducing drug-resistant (DR) TB globally; however, a wider implementation of new diagnostic strategies, such as Whole genome sequencing (WGS), would be critical for further improvement. The aim of this study, based on WGS of Mycobacterium tuberculosis (MTB) strains isolated in a TB referral center over 6 years, was to evaluate the efficacy of this methodology in improving therapy guidance for clinicians and in improving the understanding of the epidemiology of TB transmission. WGS was performed in addition to pDST on 1001 strains consecutively isolated between January 2016 and December 2021; the results allowed us to improve the quality of data on resistance and to identify possible clusters of transmission. Prediction of rifampicin-resistant (RR) or multi-drug-resistant TB strains (MDR-TB, defined as resistance to at least rifampicin and isoniazid) was obtained for 50 strains (5%). Mutations predictive of an MDR isolate were further characterized, and Ser450Leu and Ser315Thr were found to be the most frequent mutations in rpoB and katG genes, respectively. Discordances between WGS and phenotypic drug susceptibility testing (pDST) were found in few strains, and their impact on clinical decisions and outcome was addressed. The introduction of WGS in our Institute improved our diagnostic routine, allowing accurate patient management, and was a valid instrument for epidemiological investigations and infection control.

Tandem gene duplications contributed to high-level azole resistance in a rapidly expanding Candida tropicalis population

Invasive diseases caused by the globally distributed commensal yeast Candida tropicalis are associated with mortality rates of greater than 50%. Notable increases of azole resistance have been observed in this species, particularly within Asia-Pacific regions. Here, we carried out a genetic population study on 1571 global C. tropicalis isolates using multilocus sequence typing (MLST). In addition, whole-genome sequencing (WGS) analysis was conducted on 629 of these strains, comprising 448 clinical invasive strains obtained in this study and 181 genomes sourced from public databases. We found that MLST clade 4 is the predominant azole-resistant clone. WGS analyses demonstrated that dramatically increasing rates of azole resistance are associated with a rapid expansion of cluster AZR, a sublineage of clade 4. Cluster AZR isolates exhibited a distinct high-level azole resistance, which was induced by tandem duplications of the ERG11A395T gene allele. Ty3/gypsy-like retrotransposons were found to be highly enriched in this population. The alarming expansion of C. tropicalis cluster AZR population underscores the urgent need for strategies against growing threats of antifungal resistance.

Evolution and transmission of antibiotic resistance is driven by Beijing lineage Mycobacterium tuberculosis in Vietnam

IMPORTANCE

Drug-resistant tuberculosis (TB) infection is a growing and potent concern, and combating it will be necessary to achieve the WHO's goal of a 95% reduction in TB deaths by 2035. While prior studies have explored the evolution and spread of drug resistance, we still lack a clear understanding of the fitness costs (if any) imposed by resistance-conferring mutations and the role that Mtb genetic lineage plays in determining the likelihood of resistance evolution. This study offers insight into these questions by assessing the dynamics of resistance evolution in a high-burden Southeast Asian setting with a diverse lineage composition. It demonstrates that there are clear lineage-specific differences in the dynamics of resistance acquisition and transmission and shows that different lineages evolve resistance via characteristic mutational pathways.

Towards the reconstruction of a global TB history using a new pipeline "TB-Annotator"

Mycobacterium tuberculosis complex (MTBC) has a population structure consisting of 9 human and animal lineages. The genomic diversity within these lineages is a pathogenesis factor that affects virulence, transmissibility, host response, and antibiotic resistance. Hence it is important to develop improved information systems for tracking and understanding the spreading and evolution of genomes. We present results obtained thanks to a new informatics platform for computational biology of MTBC, that uses a convenience sample from public/private SRAs, designated as TB-Annotator. Version 1 was a first interactive graphic-based web tool based on 15,901 representative genomes. Version 2, still interactive, is a more sophisticated database, developed using the Snakemake Workflow Management System (WMS) that allows an unsupervised global and scalable analysis of the content of the USA National Center for Biotechnology Information Short Read Archives database. This platform analyzes nucleotide variants, the presence/absence of genes, known regions of difference and detect new deletions, the insertion sites of mobile genetic elements, and allows phylogenetic trees to be built, imported in a graphical interface and interactively analyzed between the data and the tree. The objective of TB-Annotator is triple: detect recent epidemiological links, reconstruct distant phylogeographical histories as well as perform more complex phenotypic/genotypic Genome-Wide Association Studies (GWAS). In this paper, we compare the various taxonomic SNPs-based labels and hierarchies previously described in recent reference papers for L1, and present a comparative analysis that allows identification of alias and thus provides the basis of a future unifying naming scheme for L1 sublineages. We present a global phylogenetic tree built with RAxML-NG, and one on L2; at the time of writing, we characterized about 200 sublineages, with many new ones; a detail tree for Modern L2 and a hierarchical scheme allowing to facilitate L2 lineage assignment are also presented.

In vitro activities of contezolid (MRX-I) against drug-sensitive and drug-resistant Mycobacterium tuberculosis

A novel oxazolidinone for the treatment of Mycobacterium tuberculosis has been developed, but the activity of contezolid (MRX-I) still needs to be clarified. In this study, we isolated Mycobacterium tuberculosis from 48 clinical patients with pulmonary tuberculosis. Roche drug susceptibility tests identified drug-sensitive and 39 drug-resistant M. tuberculosis isolates. Drug susceptibility assays indicated that MRX-I exhibited anti-Mycobacterium tuberculosis activity against both drug-sensitive and drug-resistant isolates, with an advantage against drug-resistant isolates. The results also showed that the anti-Mycobacterium tuberculosis activity was comparable to that of linezolid. IMPORTANCE Currently, Mycobacterium tuberculosis has exhibited increased drug resistance, leading to ineffective drug treatment in many patients with tuberculosis. Among the anti-Mycobacterium tuberculosis drugs, oxazolidinones have been gradually developed. Contezolid (MRX-I) has been newly developed in China with advantages versus the first oxazolidinone antibiotic approved by the Food and Drug Administration for clinical use, but the anti-M. tuberculosis activity needs to be further clarified. In this study, in vitro activities of MRX-I against M. tuberculosis were tested. The drug susceptibility assays indicated that MRX-I exhibited anti-M. tuberculosis activity comparable to that of linezolid, with an advantage against drug-resistant isolates.

Insight into the drug-resistant characteristics and genetic diversity of multidrug-resistant Mycobacterium tuberculosis in China

Multidrug-resistant tuberculosis (MDR-TB) has a severe impact on public health. To investigate the drug-resistant profile, compensatory mutations and genetic variations among MDR-TB isolates, a total of 546 MDR-TB isolates from China underwent drug-susceptibility testing and whole genome sequencing for further analysis. The results showed that our isolates have a high rate of fluoroquinolone resistance (45.60%, 249/546) and a low proportion of conferring resistance to bedaquiline, clofazimine, linezolid, and delamanid. The majority of MDR-TB isolates (77.66%, 424/546) belong to Lineage 2.2.1, followed by Lineage 4.5 (6.41%, 35/546), and the Lineage 2 isolates have a strong association with pre-XDR/XDR-TB (P < 0.05) in our study. Epidemic success analysis using time-scaled haplotypic density (THD) showed that clustered isolates outperformed non-clustered isolates. Compensatory mutations happened in rpoA, rpoC, and non-RRDR of rpoB genes, which were found more frequently in clusters and were associated with the increase of THD index, suggesting that increased bacterial fitness was associated with MDR-TB transmission. In addition, the variants in resistance associated genes in MDR isolates are mainly focused on single nucleotide polymorphism mutations, and only a few genes have indel variants, such as katG, ethA. We also found some genes underwent indel variation correlated with the lineage and sub-lineage of isolates, suggesting the selective evolution of different lineage isolates. Thus, this analysis of the characterization and genetic diversity of MDR isolates would be helpful in developing effective strategies for treatment regimens and tailoring public interventions. IMPORTANCE Multidrug-resistant tuberculosis (MDR-TB) is a serious obstacle to tuberculosis prevention and control in China. This study provides insight into the drug-resistant characteristics of MDR combined with phenotypic drug-susceptibility testing and whole genome sequencing. The compensatory mutations and epidemic success analysis were analyzed by time-scaled haplotypic density (THD) method, suggesting clustered isolates and compensatory mutations are associated with MDR-TB transmission. In addition, the insertion and deletion variants happened in some genes, which are associated with the lineage and sub-lineage of isolates, such as the mpt64 gene. This study offered a valuable reference and increased understanding of MDR-TB in China, which could be crucial for achieving the objective of precision medicine in the prevention and treatment of MDR-TB.

The Global Success of Mycobacterium tuberculosis Modern Beijing Family Is Driven by a Few Recently Emerged Strains

Strains of the Mycobacterium tuberculosis complex (MTBC) Beijing family aroused concern because they were often found in clusters and appeared to be exceptionally transmissible. However, it was later found that strains of the Beijing family were heterogeneous, and the transmission advantage was restricted to sublineage L2.3 or modern Beijing. In this study, we analyzed the previously published genome sequences of 7,896 L2.3 strains from 51 different countries. Using BEAST software to approximate the temporal emergence of L2.3, our calculations suggest that L2.3 initially emerged in northern East Asia during the early 15th century and subsequently diverged into six phylogenetic clades, identified as L2.3.1 through L2.3.6. Using terminal branch length and genomic clustering as proxies for transmissibility, we found that the six clades displayed distinct population dynamics, with the three recently emerged clades (L2.3.4 to L2.3.6) exhibiting significantly higher transmissibility than the older three clades (L2.3.1 to L2.3.3). Of the Beijing family strains isolated outside East Asia, 83.1% belonged to the clades L2.3.4 to L2.3.6, which were also associated with more cross-border transmission. This work reveals the heterogeneity in sublineage L2.3 and demonstrates that the global success of Beijing family strains is driven by the three recently emerged L2.3 clades. IMPORTANCE The recent population dynamics of the global tuberculosis epidemic are heavily shaped by Mycobacterium tuberculosis complex (MTBC) strains with enhanced transmissibility. The infamous Beijing family strain stands out because it has rapidly spread throughout the world. Identifying the strains responsible for the global expansion and tracing their evolution should help to understand the nature of high transmissibility and develop effective strategies to control transmission. In this study, we found that the L2.3 sublineage diversified into six phylogenetic clades (L2.3.1 to L2.3.6) with various transmission characteristics. Clades L2.3.4 to L2.3.6 exhibited significantly higher transmissibility than clades L2.3.1 to L2.3.3, which helps explain why more than 80% of Beijing family strains collected outside East Asia belong to these three clades. We conclude that the global success of L2.3 was not caused by the entire L2.3 sublineage but rather was due to the rapid expansion of L2.3.4 to L2.3.6. Tracking the transmission of L2.3.4 to L2.3.6 strains can help to formulate targeted TB prevention and control.

Drug resistance prediction for Mycobacterium tuberculosis with reference graphs

Tuberculosis is a global pandemic disease with a rising burden of antimicrobial resistance. As a result, the World Health Organization (WHO) has a goal of enabling universal access to drug susceptibility testing (DST). Given the slowness of and infrastructure requirements for phenotypic DST, whole-genome sequencing, followed by genotype-based prediction of DST, now provides a route to achieving this. Since a central component of genotypic DST is to detect the presence of any known resistance-causing mutations, a natural approach is to use a reference graph that allows encoding of known variation. We have developed DrPRG (Drug resistance Prediction with Reference Graphs) using the bacterial reference graph method Pandora. First, we outline the construction of a Mycobacterium tuberculosis drug resistance reference graph. The graph is built from a global dataset of isolates with varying drug susceptibility profiles, thus capturing common and rare resistance- and susceptible-associated haplotypes. We benchmark DrPRG against the existing graph-based tool Mykrobe and the haplotype-based approach of TBProfiler using 44 709 and 138 publicly available Illumina and Nanopore samples with associated phenotypes. We find that DrPRG has significantly improved sensitivity and specificity for some drugs compared to these tools, with no significant decreases. It uses significantly less computational memory than both tools, and provides significantly faster runtimes, except when runtime is compared to Mykrobe with Nanopore data. We discover and discuss novel insights into resistance-conferring variation for M. tuberculosis - including deletion of genes katG and pncA - and suggest mutations that may warrant reclassification as associated with resistance.

Effect of compensatory evolution in the emergence and transmission of rifampicin-resistant Mycobacterium tuberculosis in Cape Town, South Africa: a genomic epidemiology study

BACKGROUND

Experimental data show that drug-resistance-conferring mutations are often associated with a decrease in the replicative fitness of bacteria in vitro, and that this fitness cost can be mitigated by compensatory mutations; however, the role of compensatory evolution in clinical settings is less clear. We assessed whether compensatory evolution was associated with increased transmission of rifampicin-resistant tuberculosis in Khayelitsha, Cape Town, South Africa.

METHODS

We did a genomic epidemiological study by analysing available M tuberculosis isolates and their associated clinical data from individuals routinely diagnosed with rifampicin-resistant tuberculosis in primary care and hospitals in Khayelitsha, Cape Town, South Africa. Isolates were collected as part of a previous study. All individuals diagnosed with rifampicin-resistant tuberculosis and with linked biobanked specimens were included in this study. We applied whole-genome sequencing, Bayesian reconstruction of transmission trees, and phylogenetic multivariable regression analysis to identify individual and bacterial factors associated with the transmission of rifampicin-resistant M tuberculosis strains.

FINDINGS

Between Jan 1, 2008, and Dec 31, 2017, 2161 individuals were diagnosed with multidrug-resistant or rifampicin-resistant tuberculosis in Khayelitsha, Cape Town, South Africa. Whole-genome sequences were available for 1168 (54%) unique individual M tuberculosis isolates. Compensatory evolution was associated with smear-positive pulmonary disease (adjusted odds ratio 1·49, 95% CI 1·08-2·06) and a higher number of drug-resistance-conferring mutations (incidence rate ratio 1·38, 95% CI 1·28-1·48). Compensatory evolution was also associated with increased transmission of rifampicin-resistant disease between individuals (adjusted odds ratio 1·55; 95% CI 1·13-2·12), independent of other patient and bacterial factors.

INTERPRETATION

Our findings suggest that compensatory evolution enhances the in vivo fitness of drug-resistant M tuberculosis genotypes, both within and between patients, and that the in vitro replicative fitness of rifampicin-resistant M tuberculosis measured in the laboratory correlates with the bacterial fitness measured in clinical settings. These results emphasise the importance of enhancing surveillance and monitoring efforts to prevent the emergence of highly transmissible clones capable of rapidly accumulating new drug resistance mutations. This concern becomes especially crucial at present, because treatment regimens incorporating novel drugs are being implemented.

FUNDING

Funding for this study was provided by a Swiss and South Africa joint research award (grant numbers 310030_188888, CRSII5_177163, and IZLSZ3_170834), the European Research Council (grant number 883582), and a Wellcome Trust fellowship (to HC; reference number 099818/Z/12/Z). ZS-D was funded through a PhD scholarship from the South African National Research Foundation and RMW was funded through the South African Medical Research Council.

Insight into Population Structure and Drug Resistance of Pediatric Tuberculosis Strains from China and Russia Gained through Whole-Genome Sequencing

This study aimed to determine phenotypic and genotypic drug resistance patterns of Mycobacterium tuberculosis strains from children with tuberculosis (TB) in China and Russia, two high-burden countries for multi/extensively-drug resistant (MDR/XDR) TB. Whole-genome sequencing data of M. tuberculosis isolates from China (n = 137) and Russia (n = 60) were analyzed for phylogenetic markers and drug-resistance mutations, followed by comparison with phenotypic susceptibility data. The Beijing genotype was detected in 126 Chinese and 50 Russian isolates. The Euro-American lineage was detected in 10 Russian and 11 Chinese isolates. In the Russian collection, the Beijing genotype and Beijing B0/W148-cluster were dominated by MDR strains (68% and 94%, respectively). Ninety percent of B0/W148 strains were phenotypically pre-XDR. In the Chinese collection, neither of the Beijing sublineages was associated with MDR/pre-XDR status. MDR was mostly caused by low fitness cost mutations (rpoB S450L, katG S315T, rpsL K43R). Chinese rifampicin-resistant strains demonstrated a higher diversity of resistance mutations than Russian isolates (p = 0.003). The rifampicin and isoniazid resistance compensatory mutations were detected in some MDR strains, but they were not widespread. The molecular mechanisms of M. tuberculosis adaptation to anti-TB treatment are not unique to the pediatric strains, but they reflect the general situation with TB in Russia and China.

Evolution and epidemic success of Mycobacterium tuberculosis in eastern China: evidence from a prospective study

BACKGROUND

Lineage distribution of Mycobacterium tuberculosis (Mtb) isolates is strongly associated with geographically distinct human populations, and its transmission can be further impacted by the bacterial genome. However, the epidemic success of Mtb isolates at an individual level was unknown in eastern China. Knowledge regarding the emergence and transmission of Mtb isolates as well as relevant factors may offer a new solution to curb the spread of the disease. Thus, this study aims to reveal the evolution and epidemic success of Mtb isolates in eastern China.

RESULTS

Of initial 1040 isolates, 997 were retained after removing duplicates and those with insufficient sequencing depth. Of the final samples, 733 (73.52%) were from Zhejiang Province, and 264 (26.48%) were from Shanghai City. Lineage 2 and lineage 4 accounted for 80.44% and 19.56%, with common ancestors dating around 7017 years ago and 6882 years ago, respectively. Sub-lineage L2.2 (80.34%) contributed the majority of total isolates, followed by L4.4 (8.93%) and L4.5 (8.43%). Additionally, 51 (5.12%) isolates were identified to be multidrug-resistant (MDR), of which 21 (29.17%) were pre-extensively drug-resistant (pre-XDR). One clade harboring katG S315T mutation may date back to 65 years ago and subsequently acquired mutations conferring resistance to another five antibiotic drugs. The prevalence of compensatory mutation was the highest in pre-XDR isolates (76.19%), followed by MDR isolates (47.06%) and other drug-resistant isolates (20.60%). Time-scaled haplotypic density analyses suggested comparable success indices between lineage 2 and lineage 4 (P = 0.306), and drug resistance did not significantly promote the transmission of Mtb isolates (P = 0.340). But for pre-XDR isolates, we found a higher success index in those with compensatory mutations (P = 0.025). Mutations under positive selection were found in genes associated with resistance to second-line injectables (whiB6) and drug tolerance (prpR) in both lineage 2 and lineage 4.

CONCLUSIONS

Our study demonstrates the population expansion of lineage 2 and lineage 4 in eastern China, with comparable transmission capacity, while accumulation of resistance mutations does not necessarily facilitate the success of Mtb isolates. Compensatory mutations usually accompany drug resistance and significantly contribute to the epidemiological transmission of pre-XDR strains. Prospective molecular surveillance is required to further monitor the emergence and spread of pre-XDR/XDR strains in eastern China.

The relative transmission fitness of multidrug-resistant Mycobacterium tuberculosis in a drug resistance hotspot

Multidrug-resistant tuberculosis (MDR-TB) is among the most frequent causes of death due to antimicrobial resistance. Although only 3% of global TB cases are MDR, geographical hotspots with up to 40% of MDR-TB have been observed in countries of the former Soviet Union. While the quality of TB control and patient-related factors are known contributors to such hotspots, the role of the pathogen remains unclear. Here we show that in the country of Georgia, a known hotspot of MDR-TB, MDR Mycobacterium tuberculosis strains of lineage 4 (L4) transmit less than their drug-susceptible counterparts, whereas most MDR strains of L2 suffer no such defect. Our findings further indicate that the high transmission fitness of these L2 strains results from epistatic interactions between the rifampicin resistance-conferring mutation RpoB S450L, compensatory mutations in the RNA polymerase, and other pre-existing genetic features of L2/Beijing clones that circulate in Georgia. We conclude that the transmission fitness of MDR M. tuberculosis strains is heterogeneous, but can be as high as drug-susceptible forms, and that such highly drug-resistant and transmissible strains contribute to the emergence and maintenance of hotspots of MDR-TB. As these strains successfully overcome the metabolic burden of drug resistance, and given the ongoing rollout of new treatment regimens against MDR-TB, proper surveillance should be implemented to prevent these strains from acquiring resistance to the additional drugs.

Mycobacterium tuberculosis - atpE gene profile of bedaquiline-treated pulmonary tuberculosis patients at the referral hospital Dr. Soetomo, Indonesia

Background

The atpE gene is a target for bedaquiline (Bdq)-activating drug action and mutations in the gene are fixed to cause resistance. However, changes in the amino acid of ATPase have been little reported from a clinical setting since it was first used in 2015 in Indonesia. This study aims to observe the sequence of nucleotide and amino acid from rifampicin-resistant (RR) pulmonary tuberculosis (TB) patients, both new and relapse cases treated with Bdq.

Methods

This is an observational descriptive study performed in the referral hospital Dr Soetomo, Indonesia, at August 2022-November 2022. We performed Sanger sequencing and comparison of the atpE gene from the patient's sputum from August to November 2022 to wild-type Mycobacterium tuberculosis H37Rv and species of mycobacteria using BioEdit version 7.2 and BLAST NCBI software. We also conducted an epidemiological study on patients' characteristics. This study uses a descriptive statistic to show the percentage of data.

Results

The total of 12 M. tuberculosis isolates showed that the atpE gene sequence was 100% similar to the wild-type M. tuberculosis H37Rv. No single-nucleotide polymorphisms or mutations were found, and no change in the amino acid structure at position 28 (Asp), 61 (Glu), 63 (Ala), and 66 (Ile). The percentage identity of atpE to M. tuberculosis H37Rv and M. tuberculosis complex was 99%-100%, while the similarity with the other mycobacteria species other than TB (Mycobacterium avium complex, Mycobacterium abscessus, and Mycobacterium lepraemurium) was 88%-91%.

Conclusions

This study revealed M. tuberculosis -atpE gene sequence profile of RR-TB patients had no mutations, as the specific gene region, and no change in the amino acid structure. Therefore, Bdq can be continually trusted as an effective anti-tubercular drug in RR-TB patients.

The Evolution and Transmission Dynamics of Multidrug-Resistant Tuberculosis in an Isolated High-Plateau Population of Tibet, China

On the Tibetan Plateau, most tuberculosis is caused by indigenous Mycobacterium tuberculosis strains with a monophyletic structure and high-level drug resistance. This study investigated the emergence, evolution, and transmission dynamics of multidrug-resistant tuberculosis (MDR-TB) in Tibet. The whole-genome sequences of 576 clinical strains from Tibet were analyzed with the TB-profiler tool to identify drug-resistance mutations. The evolution of the drug resistance was then inferred based on maximum-likelihood phylogeny and dated trees that traced the serial acquisition of mutations conferring resistance to different drugs. Among the 576 clinical M. tuberculosis strains, 346 (60.1%) carried at least 1 resistance-conferring mutation and 231 (40.1%) were MDR-TB. Using a pairwise distance of 50 single nucleotide polymorphisms (SNPs), most strains (89.9%, 518/576) were phylogenetically separated into 50 long-term transmission clusters. Eleven large drug-resistant clusters contained 76.1% (176/231) of the local multidrug-resistant strains. A total of 85.2% of the isoniazid-resistant strains were highly transmitted with an average of 6.6 cases per cluster, of which most shared the mutation KatG Ser315Thr. A lower proportion (71.6%) of multidrug-resistant strains were transmitted, with an average cluster size of 2.9 cases. The isoniazid-resistant clusters appear to have undergone substantial bacterial population growth in the 1970s to 1990s and then subsequently accumulated multiple rifampicin-resistance mutations and caused the current local MDR-TB burden. These findings highlight the importance of detecting and curing isoniazid-resistant strains to prevent the emergence of endemic MDR-TB. IMPORTANCE Emerging isoniazid resistance in the 1970s allowed M. tuberculosis strains to spread and form into large multidrug-resistant tuberculosis clusters in the isolated plateau of Tibet, China. The epidemic was driven by the high risk of transmission as well as the potential of acquiring further drug resistance from isoniazid-resistant strains. Eleven large drug-resistant clusters consisted of the majority of local multidrug-resistant cases. Among the clusters, isoniazid resistance overwhelmingly evolved before all the other resistance types. A large bacterial population growth of isoniazid-resistant clusters occurred between 1970s and 1990s, which subsequently accumulated rifampicin-resistance-conferring mutations in parallel and accounted for the local multidrug-resistant tuberculosis burden. The results of our study indicate that it may be possible to restrict MDR-TB evolution and dissemination by prioritizing screening for isoniazid (INH)-resistant TB strains before they become MDR-TB and by adopting measures that can limit their transmission.

Genetic Diversity and Primary Drug Resistance of Mycobacterium tuberculosis Beijing Genotype Strains in Northwestern Russia

The Beijing genotype is the main family of Mycobacterium tuberculosis in Russia. We analyzed its diversity and drug resistance in provinces across Northwestern Russia to identify the epidemiologically relevant Beijing strains. The study collection included 497 isolates from newly-diagnosed tuberculosis (TB) patients. Bacterial isolates were subjected to drug-susceptibility testing and genotyping. The Beijing genotype was detected in 57.5% (286/497); 50% of the Beijing strains were multidrug-resistant (MDR). Central Asian/Russian and B0/W148 groups included 176 and 77 isolates, respectively. MDR was more frequent among B0/W148 strains compared to Central Asian/Russian strains (85.7% vs. 40.3%, p < 0.0001). Typing of 24 minisatellite loci of Beijing strains revealed 82 profiles; 230 isolates were in 23 clusters. The largest Central Asian/Russian types were 94-32 (n = 75), 1065-32 (n = 17), and 95-32 (n = 12). B0/W148 types were 100-32 (n = 59) and 4737-32 (n = 5). MDR was more frequent in types 1065-32 (88.2%), 100-32 (83.1%), and 4737-32 (100%). In contrast, type 9391-32 (n = 9) included only drug-susceptible strains. To conclude, M. tuberculosis Beijing genotype is dominant in Northwestern Russia, and an active transmission of overwhelmingly MDR B0/W148 types explains the reported increase of MDR-TB. The presence of MDR-associated minor variants (type 1071-32/ancient Beijing and Central Asia Outbreak strain) in some of the studied provinces also requires attention.

In Silico Design and Investigation of Novel Thiazetidine Derivatives as Potent Inhibitors of PrpR in Mycobacterium tuberculosis

Tuberculosis is one of the most life-threatening acute infectious diseases diagnosed in humans. In the present investigation, a series of 16 new disubstituted 1,3-thiazetidines derivatives is designed, and investigated via various in silico methods for their potential as anti-tubercular agent by evaluating their ability to block the active site of PrpR transcription factor protein of Mycobacterium tuberculosis. The efficacy of the molecules was initially assessed with the help of AutoDock Vina algorithm. Further Glide module is used to redock the previously docked complexes. The binding energies and other physiochemical properties of the designed molecules were evaluated using the Prime-MM/GBSA and the QikProp module, respectively. The results of docking revealed the nature, site of interaction and the binding affinity between the proposed candidates and the active site of PrpR. Further the inhibitory effect of the scaffolds was predicted and evaluated employing a machine learning-based algorithm and was used accordingly. Further, the molecular dynamics simulation studies ascertained the binding characteristics of the unique 13, when analysed across a time frame of 100 ns with GROMACS software. The results show that the proposed 1,3-thiazetidine derivatives such as 10, 11, 13 and 14 could be potent and selective anti-tubercular agents as compared to the standard drug Pyrazinamide. Finally, this study concludes that designed thiazetidines can be employed as anti-tubercular agents. Undeniably, the results may guide the experimental biologists to develop safe and non-toxic drugs against tuberculosis by demanding further in vivo and in vitro analyses.

Evolutionary history and spread of the Mycobacterium tuberculosis Latin American and Mediterranean (L4.3/LAM) sublineage, Tunisia

BACKGROUND

To infer the origin and spread of the Mycobacterium tuberculosis Latin American and Mediterranean (L4.3/LAM) sublineage in a Mediterranean country, Tunisia, where it predominates.

METHODS

We combined Bayesian (STRUCTURE) and maximum likelihood (MIGRAINE) estimation approaches based on a global 24-loci mycobacterial interspersed repetitive units-variable numbers of tandem repeats (MIRU-VNTR24) genotyping dataset consisting of 1573 L4.3/LAM clinical strains from four continents, including 252 isolates originating from Tunisia.

RESULTS

Phylogenetic analyses coupled with Bayesian estimations suggested that the most predominant L4.3/LAM subpopulation in Tunisia (65.07%), which is dominated by a single clonal complex, TUN4.3_CC1 (94.51%), has evolved from an ancestral pool that is restricted to Europe and Africa, contrasting with the remaining L4.3/LAM subpopulations whose ancestry was traced all over the word. Maximum likelihood analysis revealed that TUN4.3_CC1 has been undergoing a demographic expansion since 131 years ago (CI95%: 90.7-205), thus explaining its preponderance relative to the second most predominant CC, TUN4.3_CC2, whose population was found under contraction.

CONCLUSIONS

The preponderance of L4.3/LAM in Tunisia stems from a 130-year expansion process of a locally evolved clone.

Mycobacterium tuberculosis Transmission in High-Incidence Settings-New Paradigms and Insights

Tuberculosis has affected humankind for thousands of years, but a deeper understanding of its cause and transmission only arose after Robert Koch discovered Mycobacterium tuberculosis in 1882. Valuable insight has been gained since, but the accumulation of knowledge has been frustratingly slow and incomplete for a pathogen that remains the number one infectious disease killer on the planet. Contrast that to the rapid progress that has been made in our understanding SARS-CoV-2 (the cause of COVID-19) aerobiology and transmission. In this Review, we discuss important historical and contemporary insights into M. tuberculosis transmission. Historical insights describing the principles of aerosol transmission, as well as relevant pathogen, host and environment factors are described. Furthermore, novel insights into asymptomatic and subclinical tuberculosis, and the potential role this may play in population-level transmission is discussed. Progress towards understanding the full spectrum of M. tuberculosis transmission in high-burden settings has been hampered by sub-optimal diagnostic tools, limited basic science exploration and inadequate study designs. We propose that, as a tuberculosis field, we must learn from and capitalize on the novel insights and methods that have been developed to investigate SARS-CoV-2 transmission to limit ongoing tuberculosis transmission, which sustains the global pandemic.