Virulence of Mycobacterium tuberculosis Clinical Isolates Is Associated With Sputum Pre-treatment Bacterial Load, Lineage, Survival in Macrophages, and Cytokine Response

Mycobacterium tuberculosis complex molecular networks and their regulation: Implications of strain heterogeneity on epigenetic diversity and transcriptome regulation

Tuberculosis has been a public health crisis since the 1900, which has caused the highest mortalities due to a single bacterial infection worldwide, that was recently further complicated by the Coronavirus disease 2019 pandemic. The causative agent of Tuberculosis, Mycobacterium tuberculosis, belongs to a genetically well-characterized family of strains known as the Mycobacterium tuberculosis complex, which has complicated progress made towards eradicating Tuberculosis due to pathogen-specific phenotypic differences in the members of this complex. Mycobacterium tuberculosis complex strains are genetically diverse human- and animal-adapted pathogens belonging to 7 lineages (Indo-Oceanic, East-Asian, East-African Indian, Euro-American, M. africanum West Africa 1, M. africanum West Africa 2 and Ethopia), respectively and the recently identified Lineage 8 and M. africanum Lineage 9. Genomic studies have revealed that Mycobacterium tuberculosis complex members are ∼99 % similar, however, due to selective pressure and adaptation to human host, they are prone to mutations that have resulted in development of drug resistance and phenotypic heterogeneity that impact strain virulence. Furthermore, members of the Mycobacterium tuberculosis complex have preferred geographic locations and possess unique phenotypic characteristics that is linked to their pathogenicity. Due to the recent advances in development next generation sequencing platforms, several studies have revealed epigenetic changes in genomic regions combined with "unique" gene regulatory mechanisms through non-coding RNAs that are responsible for strain-specific behaviour on in vitro and in vivo infection models. The current review provides up to date epigenetic patterns, gene regulation through non-coding RNAs, together with implications of these mechanisms in down-stream proteome and metabolome, which may be responsible for "unique" responses to infection by members of the Mycobacterium tuberculosis complex. Understanding lineage-specific molecular mechanisms during infection may provide novel drug targets and disease control measures towards World Health organization END-TB strategy.

Genomic bacterial load associated with bacterial genotypes and clinical characteristics in patients with scrub typhus in Hainan Island, Southern China

Scrub typhus, caused by mite-borne Orientia tsutsugamushi (O. tsutsugamushi), is a major febrile disease in the Asia-Pacific region. The DNA load of O. tsutsugamushi in the blood was previously found to be significantly higher in patients with fatal disease than those with non-fatal disease and correlated with the duration of illness, presence of eschar, and hepatic enzyme levels. In this prospective observation study, we analyzed the association of bacterial DNA load with clinical features, disease severity, and genotype using real-time PCR targeting the 56 kDa TSA gene of O. tsutsugamushi in the blood samples of 117 surviving patients with scrub typhus who had not received appropriate antibiotic treatment. The median O. tsutsugamushi DNA load was 3.11×103 copies/mL (range, 44 to 3.3×106 copies/mL). The severity of patients was categorized as mild, moderate, and severe based on the number of dysfunctional organs, and no significant difference in O. tsutsugamushi DNA load was found among these groups. Patients infected with the Karp group showed a significantly higher O. tsutsugamushi DNA load than those in the Gilliam (P < 0.05) and TA763 (P < 0.01) groups. Patients belonging to the Li ethnic group showed a significantly higher DNA load than those in the Han ethnic groups. The blood bacterial DNA load of patients showed no significant difference between groups divided by gender, age, with or without eschar, or the season of disease onset. The highest body temperature recorded during fever onset was positively correlated with O. tsutsugamushi DNA load (ρ  =  0.272, P  =  0.022). Correlation analyses indicated that the serum total bilirubin level was positively correlated with O. tsutsugamushi DNA load. In conclusion, the findings in this study demonstrated the association of DNA load of O. tsutsugamushi with the severity and genotype in patients with scrub typhus in Hainan, China.

A Persistent Tuberculosis Outbreak in the UK Is Characterized by Hydrophobic fadB4-Deficient Mycobacterium tuberculosis That Replicates Rapidly in Macrophages

The genetic diversity of Mycobacterium tuberculosis can influence disease severity and transmissibility. To better understand how this diversity influences individuals and communities, we phenotyped M. tuberculosis that was causing a persistent outbreak in the East Midlands, United Kingdom. Compared to nonoutbreak isolates, bacilli had higher lipid contents and more hydrophobic cell surfaces. In macrophage infection models, the bacteria increased more rapidly, provoked the enhanced accumulation of macrophage lipid droplets and enhanced the secretion of IL-1β. Natural deletions in fadB4, nrdB, and plcC distinguished the outbreak isolates from other lineage 3 isolates in the region. fadB4 is annotated with a putative role in cell envelope biosynthesis, so the loss of this gene has the potential to alter the interactions of bacteria with immune cells. Reintroduction of fadB4 to the outbreak strain led to a phenotype that more closely resembled those of nonoutbreak strains. The improved understanding of the microbiological characteristics and the corresponding genetic polymorphisms that associate with outbreaks have the potential to inform tuberculosis control. IMPORTANCE Tuberculosis (TB) killed 1.5 million people in 2020 and affects every country. The extent to which the natural genetic diversity of Mycobacterium tuberculosis influences disease manifestation at both the individual and epidemiological levels remains poorly understood. Insights into how pathogen polymorphisms affect patterns of TB have the potential to translate into clinical and public health practice. Two distinct lineage 3 strains isolated from local TB outbreaks, one of which (CH) was rapidly terminated and the other of which (Lro) persistently transmitted for over a decade, provided us with an opportunity to study these issues. We compared genome sequences, microbiological characteristics, and early immune responses that were evoked upon infection. Our results indicate that the natural lack of fadB4 in the Lro strain contributes to its unique features.

Comparison of two mycobacterial strains in performance of the whole blood mycobacterial growth inhibition assay in Indian children

A major challenge in tuberculosis is identifying correlates of a protective immune response. The Mycobacterial Growth Inhibition Assay (MGIA) is a functional assay providing an integrated measure of the host immune response to mycobacteria. However, its feasibility is limited by reliance on biosafety level 3 facilities, and its performance has not been widely evaluated in TB-endemic settings. Here, we compared two mycobacterial strains (M. tuberculosis H37Rv versus attenuated M. bovis BCG) in the performance of whole-blood MGIA in 30 TB-exposed children (median age 2 years) in Chennai, India. The time-to-positivity in both assays was similar (5.7 days vs 6 days) and the mycobacterial growth of M. tuberculosis H37Rv and M. bovis BCG were correlated (r = 0.64, p<0.0001). In Bland-Altman analysis, the bias was -0.54 days (95% limit of agreement -2.08, 0.99). Collectively, our results indicate that M. tuberculosis H37Rv can be substituted with the less virulent M. bovis BCG strain to improve feasibility of the MGIA assay, particularly in low-income settings.

Does BCG vaccination protect against infection with M. tuberculosis?

BACKGROUND:

Protection against infection by the bacille Calmette-Guérin vaccine against Mycobacterium tuberculosis remains a subject of controversy. We investigated the association between BCG vaccination at birth and infection by M. tuberculosis.

MATERIAL AND METHODS:

This was a secondary analysis of data from tuberculin skin test (TST) surveys in Vietnamese schoolchildren between 1988 and 2001. We investigated whether a BCG scar was associated with a lower prevalence of TST positivity, adjusting for BCG-induced variation by varying cut-off values for a positive TST.

RESULTS:

We found a positive association between BCG scar and TST positivity. The strength of the association decreased with increasing TST cut-off values; however, it never inverted significantly, irrespective of geographic region and survey year.

CONCLUSION:

In Vietnam, BCG vaccination was not associated with reduced M. tuberculosis infection prevalence as measured using TST. This in contrary to a similar study conducted in Tanzania. These contradictory findings may be explained by geographical differences and the relatively high prevalence in Vietnam of the M. tuberculosis Beijing genotype, which is reported to be capable of circumventing BCG-induced immunity.

Macrophage: A Cell With Many Faces and Functions in Tuberculosis

Mycobacterium tuberculosis (Mtb) is the causative agent of human tuberculosis (TB) which primarily infects the macrophages. Nearly a quarter of the world's population is infected latently by Mtb. Only around 5%-10% of those infected develop active TB disease, particularly during suppressed host immune conditions or comorbidity such as HIV, hinting toward the heterogeneity of Mtb infection. The aerosolized Mtb first reaches the lungs, and the resident alveolar macrophages (AMs) are among the first cells to encounter the Mtb infection. Evidence suggests that early clearance of Mtb infection is associated with robust innate immune responses in resident macrophages. In addition to lung-resident macrophage subsets, the recruited monocytes and monocyte-derived macrophages (MDMs) have been suggested to have a protective role during Mtb infection. Mtb, by virtue of its unique cell surface lipids and secreted protein effectors, can evade killing by the innate immune cells and preferentially establish a niche within the AMs. Continuous efforts to delineate the determinants of host defense mechanisms have brought to the center stage the crucial role of macrophage phenotypical variations for functional adaptations in TB. The morphological and functional heterogeneity and plasticity of the macrophages aid in confining the dissemination of Mtb. However, during a suppressed or hyperactivated immune state, the Mtb virulence factors can affect macrophage homeostasis which may skew to favor pathogen growth, causing active TB. This mini-review is aimed at summarizing the interplay of Mtb pathomechanisms in the macrophages and the implications of macrophage heterogeneity and plasticity during Mtb infection.

Rv3737 is required for Mycobacterium tuberculosis growth in vitro and in vivo and correlates with bacterial load and disease severity in human tuberculosis

Background

Rv3737 is the sole homologue of multifunctional transporter ThrE in Mycobacterium tuberculosis (Mtb). In this study, we aimed to investigate whether this transporter participates in vitro and in vivo survival of Mtb.

Methods

To characterize the role of Rv3737, we constructed and characterized a Mtb H37RvΔRv3737. This strain was evaluated for altered growth rate and macrophage survival using a cell model of infection. In addition, the comparative analysis was conducted to determine the association between Rv3737 mRNA expression and disease severity in active pulmonary TB patients.

Results

The H37RvΔRv3737 strain exhibited significantly slow growth rate compared to H37Rv-WT strain in standard culture medium. Additionally, the survival rate of H37Rv-WT strain in macrophages was 2 folds higher than that of H37RvΔRv3737 at 72 h. A significantly higher level of TNF-α and IL-6 mRNA expression was observed in macrophages infected with H37RvΔRv3737 as compared to H37Rv-WT. Of note, Rv3737 expression was significantly increased in clinical Mtb isolates than H37Rv-WT. The relative expression level of Rv3737 was positively correlated with lung cavity number of TB patients. Similarly, the higher Rv3737 mRNA level resulted in lower C(t) value by Xpert MTB/RIF assay, demonstrating that a positive correlation between Rv3737 expression and bacterial load in TB patients.

Conclusions

Our data takes the lead in demonstrate that the threonine transporter Rv3737 is required for in vitro growth and survival of bacteria inside macrophages. In addition, the expression level of Rv3737 may be associated with bacterial load and disease severity in pulmonary tuberculosis patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06967-y.

Modulatory Impact of the sRNA Mcr11 in Two Clinical Isolates of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is a successful pathogen causing tuberculosis (TB) disease in humans. It has been shown, that some circulating strains of Mtb in TB endemic populations, are more virulent and more transmissible than others, which may be related to their evolved adaptations to modulate the host immune responses. Underlying these adaptations to the stressful conditions, different genetic regulatory networks involved sRNAs that are mostly unknown for Mtb. We have previously shown that Mcr11 is one of the main sRNAs that determine transcriptomic differences among the Colombian clinical isolates UT127 and UT205 compared to the laboratory strain H37Rv. We found that the knock-down of mcr11 using CRISPRi has a major impact on phenotypic traits, especially in the clinical isolate UT205. Through the analysis of RNA-seq during the knock-down of mcr11 in UT205, we found a downregulation of genes mainly involved in lipid synthesis, lipid metabolism, ribosomal proteins, transport systems, respiratory and energy systems, membrane and cell wall components, intermediary metabolism, lipoproteins and virulence genes. One of the most interesting genes showing transcriptomic changes is OprA (encoded by the gene rv0516c), which has been involved in the K⁺ regulation. Overall, our data may suggest that one of the prominent roles of the sRNA Mcr11 is to regulate genes that control Mtb growth and osmoregulation.

Bacterial Load Comparison of the Three Main Lineages of Mycobacterium tuberculosis Complex in West Africa

Studies have shown an association between bacterial load and virulence; however, not much is known about the diversity in this phenotypic characteristic of Mycobacterium tuberculosis complex (MTBC). This study was therefore aimed to determine the differences in bacterial load of the three most prevalent MTBC genotypes (L4, L5, and L6) in West Africa at the time of diagnosis. A total of 170 paired fresh sputum samples were collected; one part in guanidinium thiocyanate (GTC) was used for RNA extraction and tuberculosis molecular bacterial load assay (TB-MBLA), and the other part without GTC was confirmed for TB positivity using GeneXpert MTB/RIF, smear microscopy grading, and culture on Löwenstein-Jensen media slants. The 170 sputum samples comprised 155 new cases, three follow-up cases, and 12 TB negative sputum samples. The time-to-culture positivity (TTP) and degree of culture positivity (DCP) were recorded. All 122 isolates obtained were spoligotyped for lineage (L) classification, but spoligotypes were obtained from 120 isolates. Of the typed isolates, 70.0, 10.8, 10.8, 4.2, 2.5, 0.8, and 0.8% were lineages 4, 5, 6, 2, 3, 1, and Mycobacterium bovis, respectively. Further analysis of the three most prevalent lineages showed significantly shorter TTP and higher DCP by L4 compared to L5 and L6, respectively: TTP 20.8, vs. 26.5, and 28.2 days; p-value = 0.005 and DCP 1.27, vs. 0.81 and 0.29, p < 0.001. The average TB-MBLA measured bacterial load of L4 was 3.82 Log₁₀eCFU/ml which was not significantly different from 3.81 and 3.80 Log₁₀eCFU/ml of L5 and L6, respectively, p = 0.84. Degrees of smear microscopy L4 = 1.20, L5 = 1.20, and L6 = 0.92 and GeneXpert Cq values L4 = 17.08, L5 = 18.37, and L6 = 17.59 showed no significant difference between the lineages, p = 0.72 and p = 0.48, respectively. Retrospective analysis of a larger sample confirmed the difference in TTP, p < 0.001. In conclusion, the observed shorter TTP and high DCP of L4 could signify high growth rate in culture that is independent of total bacterial load at diagnosis.

Infection outcome needs two to tango: human host and the pathogen

Infectious diseases are potential drivers for human evolution, through a complex, continuous and dynamic interaction between the host and the pathogen/s. It is this dynamic interaction that contributes toward the clinical outcome of a pathogenic disease. These are modulated by contributions from the human genetic variants, transcriptional response (including noncoding RNA) and the pathogen’s genome architecture. Modern genomic tools and techniques have been crucial for the detection and genomic characterization of pathogens with respect to the emerging infectious diseases. Aided by next-generation sequencing (NGS), risk stratification of host population/s allows for the identification of susceptible subgroups and better disease management. Nevertheless, many challenges to a general understanding of host–pathogen interactions remain. In this review, we elucidate how a better understanding of the human host-pathogen interplay can substantially enhance, and in turn benefit from, current and future applications of multi-omics based approaches in infectious and rare diseases. This includes the RNA-level response, which modulates the disease severity and outcome. The need to understand the role of human genetic variants in disease severity and clinical outcome has been further highlighted during the Coronavirus disease 2019 (COVID-19) pandemic. This would enhance and contribute toward our future pandemic preparedness.

The Staphylococcus aureus toxin-antitoxin system YefM-YoeB is associated with antibiotic tolerance and extracellular dependent biofilm formation

The high antibiotic tolerance of Staphylococcus aureus biofilms is associated with challenges for treating periprosthetic joint infection. The toxin–antitoxin system, YefM–YoeB, is thought to be a regulator for antibiotic tolerance, but its physiological role is unknown. The objective of this study was to determine the biofilm and antibiotic susceptibility phenotypes associated with S. aureus yoeB homologs. We hypothesized the toxin–antitoxin yoeB homologs contribute to biofilm formation and antibiotic susceptibility. Disruption of yoeB1 and yoeB2 resulted in decreased biofilm formation in comparison to Newman and JE2 wild-type (WT) S. aureus strains. In comparison to yoeB mutants, both Newman and JE2 WT strains had higher polysaccharide intercellular adhesin (PIA) production. Treatment with sodium metaperiodate increased biofilm formation in Newman WT, indicating biofilm formation may be increased under conditions of oxidative stress. DNase I treatment decreased biofilm formation in Newman WT but not in the absence of yoeB1 or yoeB2. Additionally, WT strains had a higher extracellular DNA (eDNA) content in comparison to yoeB mutants but no differences in biofilm protein content. Moreover, loss of yoeB1 and yoeB2 decreased biofilm survival in both Newman and JE2 strains. Finally, in a neutropenic mouse abscess model, deletion of yoeB1 and yoeB2 resulted in reduced bacterial burden. In conclusion, our data suggest that yoeB1 and yoeB2 are associated with S. aureus planktonic growth, extracellular dependent biofilm formation, antibiotic tolerance, and virulence.

Characterisation of secretome-based immune responses of human leukocytes infected with various Mycobacterium tuberculosis lineages

Background

Differences in immune responses against different lineages of Mycobacterium tuberculosis (Mtb), and by different types of immune cell, are still poorly understood. We aimed to compare the secretome-based immune responses among three Mtb lineages and among immune-cell types. The immune responses were also investigated during infection and when the bacilli had been eliminated from the immune cells.

Methods

Human primary leukocytes were infected with strains representing three lineages of Mtb (East-Asian, Indo-Oceanic and Euro-American). Label-free GeLC MS/MS proteomic analysis of secretomes was performed. The response of each immune-cell type was compared with the appropriate interactome database for each.

Results

The expression pattern of proteins secreted by Mtb-infected leukocytes differed among Mtb lineages. The ancestral lineage (IO lineage) had a greater ability to activate MMP14 (associated with leukocyte migration) than did the more recent lineages (EA and EuA). During infection, proteins secreted by macrophages, dendritic cells, neutrophils and B-cells were associated with cell proliferation. Following clearance of Mtb, proteins associated with interferon signaling were found in macrophages, dendritic cells and neutrophils: proteins associated with antigen processing were found in B-cells and regulatory T-cells. Expression of immune response-related proteins from many immune-cell types might be suppressed by Mtb infection. Our study has provided a better insight into the host-pathogen interaction and immune response against different Mtb lineages.

Tuberculosis endotypes to guide stratified host-directed therapy

There is hope that host-directed therapy (HDT) for Tuberculosis (TB) can either shorten treatment duration, help cure drug resistant disease or limit the immunopathology. Many candidate HDT drugs have been proposed, however solid evidence only exists for a few select patient groups. The clinical presentation of TB is variable, with differences in severity, tissue pathology, and bacillary burden. TB clinical phenotypes likely determine the potential benefit of HDT. Underlying TB clinical phenotypes, there are TB "endotypes," defined as distinct molecular profiles, with specific metabolic, epigenetic, transcriptional, and immune phenotypes. TB endotypes can be characterized by either immunodeficiency or pathologic excessive inflammation. Additional factors, like comorbidities (HIV, diabetes, helminth infection), structural lung disease or Mycobacterial virulence also drive TB endotypes. Precise disease phenotyping, combined with in-depth immunologic and molecular profiling and multimodal omics integration, can identify TB endotypes, guide endotype-specific HDT, and improve TB outcomes, similar to advances in cancer medicine.

Harmful Effects of Granulocytic Myeloid-Derived Suppressor Cells on Tuberculosis Caused by Hypervirulent Mycobacteria

BACKGROUND

The role of myeloid-derived suppressor cells (MDSCs) in patients with severe tuberculosis who suffer from uncontrolled pulmonary inflammation caused by hypervirulent mycobacterial infection remains unclear.

METHODS

This issue was addressed using C57BL/6 mice infected with highly virulent Mycobacterium bovis strain MP287/03.

RESULTS

CD11b+GR1int population increased in the bone marrow, blood and lungs during advanced disease. Pulmonary CD11b+GR1int (Ly6GintLy6Cint) cells showed granularity similar to neutrophils and expressed immature myeloid cell markers. These immature neutrophils harbored intracellular bacilli and were preferentially located in the alveoli. T-cell suppression occurred concomitantly with CD11b+GR1int cell accumulation in the lungs. Furthermore, lung and bone marrow GR1+ cells suppressed both T-cell proliferation and interferon γ production in vitro. Anti-GR1 therapy given when MDSCs infiltrated the lungs prevented expansion and fusion of primary pulmonary lesions and the development of intragranulomatous caseous necrosis, along with increased mouse survival and partial recovery of T-cell function. Lung bacterial load was reduced by anti-GR1 treatment, but mycobacteria released from the depleted cells proliferated extracellularly in the alveoli, forming cords and clumps.

CONCLUSIONS

Granulocytic MDSCs massively infiltrate the lungs during infection with hypervirulent mycobacteria, promoting bacterial growth and the development of inflammatory and necrotic lesions, and are promising targets for host-directed therapies.

Mycobacterium tuberculosis Rv0341 Promotes Mycobacterium Survival in In Vitro Hostile Environments and within Macrophages and Induces Cytokines Expression

Mycobacterium tuberculosis represents an ancient deadly human pathogen that can survive and multiply within macrophages. The effectors are key players for the successful pathogenesis of this bacterium. M. tuberculosis open reading frame (ORF) Rv0341, a pathogenic mycobacteria-specific gene, was found to be upregulated in macrophages isolated from human tuberculosis granuloma and inside the macrophages during in vitro infection by M. tuberculosis. To understand the exact role of this gene, we expressed the Rv0341 gene in M. smegmatis, which is a non-pathogenic Mycobacterium. We found that Rv0341 expression can alter colony morphology, reduce the sliding capability, and decrease the cell wall permeability of M. smegmatis. Furthermore, Rv0341 remarkably enhanced M. smegmatis survival within macrophages and under multiple in vitro stress conditions when compared with the control strain. Ms_Rv0341 significantly induced expression of TNF-α, IL-1β, and IL-10 compared with M. smegmatis harboring an empty vector. In summary, these data suggest that Rv0341 is one of the M. tuberculosis virulence determinants that can promote bacilli survival in harsh conditions and inside macrophages.

Lineage-specific differences in lipid metabolism and its impact on clinical strains of Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tb) is the causative agent of TB and its incidences has been on the rise since 1993. Lipid metabolism is an imperative metabolic process, which grants M. tb the ability to utilize host-derived lipids as a secondary source of nutrition during infection. In addition to degrading host lipids, M. tb is proficient at using lipids, such as cholesterol, to facilitate its entry into macrophages. Mycolic acids, constituents of the mycobacterial cell wall, offer protection and aid in persistence of the bacterium. These are effectively synthesized using a complex fatty acid synthase system. Many pathogenesis studies have reported differences in lipid-metabolism of clinical strains of M. tb that belongs to diverse lineages of the Mycobacterium tuberculosis complex (MTBC). East-Asian and Euro-American lineages possess "unique" cell wall-associated lipids compared to the less transmissible Ethiopian lineage, which may offer these lineages a competitive advantage. Therefore, it is crucial to comprehend the complexities among the MTBC lineages with lipid metabolism and their impact on virulence, transmissibility and pathogenesis. Thus, this review provides an insight into lipid metabolism in various lineages of the MTBC and their impact on virulence and persistence during infection, as this may provide critical insight into developing novel therapeutics to combat TB.

The Interplay of Human and Mycobacterium Tuberculosis Genomic Variability

Tuberculosis (TB), caused by the human pathogens Mycobacterium tuberculosis (Mtb) and Mycobacterium africanum, has plagued humanity for millennia and remains the deadliest infectious disease in the modern world. Mycobacterium tuberculosis and M. africanum can be subdivided phylogenetically into seven lineages exhibiting a low but significant degree of genomic diversity and preferential geographic distributions. Human genetic variability impacts all stages of TB pathogenesis ranging from susceptibility to infection with Mtb, progression of infection to disease, and the development of distinct clinical subtypes. The genetic study of severe childhood TB identified strong inborn single-gene errors revealing crucial pathways of vulnerability to TB. However, the identification of major TB-susceptibility genes on the population level has remained elusive. In particular, the replication of findings from candidate and genome-wide association studies across distinct human populations has proven difficult, thus hampering the characterization of reliable host molecular markers of susceptibility. Among the possible confounding factors of genetic association studies is Mtb genomic variability, which generally was not taken into account by human genetic studies. In support of this possibility, Mtb lineage was found to be a contributing factor to clinical presentation of TB and epidemiological spread of Mtb in exposed populations. The confluence of pathogen and human host genetic variability to TB pathogenesis led to the consideration of a possible coadaptation of Mtb strains and their human hosts, which should reveal itself in significant interaction effects between Mtb strain and TB-susceptibility/resistance alleles. Here, we present some of the most consistent findings of genetic susceptibility factors in human TB and review studies that point to genome-to-genome interaction between humans and Mtb lineages. The limited results available so far suggest that analyses considering joint human–Mtb genomic variability may provide improved power for the discovery of pathogenic drivers of the ongoing TB epidemic.

Benzaldehyde thiosemicarbazone derivatives against replicating and nonreplicating Mycobacterium tuberculosis

In this article, we report a series of benzaldehyde thiosemicarbazone derivatives possessing high activity toward actively replicating Mycobacterium tuberculosis strain with minimum inhibitory concentration (MIC) values in the range from 0.14 to 2.2 μM. Among them, two compounds-2-(4-phenethoxybenzylidene)hydrazine-1-carbothioamide (13) and 2-(3-isopropoxybenzylidene)hydrazine-1-carbothioamide (20) also demonstrate submicromolar antimycobacterial activity against M. tuberculosis under hypoxia with MIC values of 0.68 and 0.74 μM, respectively. The activity of compounds 13 and 20 toward five investigated isoniazid-, rifampicin-, and fluoroquinolone-resistant M. tuberculosis isolates is similar to commercially available antituberculosis drugs. The compounds 13 and 20 possess good ADME properties and have low cytotoxicity toward human liver cells (HepG2). Therefore, 2-(4-phenethoxybenzylidene)hydrazine-1-carbothioamide (13) and 2-(3-isopropoxybenzylidene)hydrazine-1-carbothioamide (20) are valuable candidates for further preclinical studies.