Mutations in Streptomycin Resistance Genes and Their Relationship to Streptomycin Resistance and Lineage of Mycobacterium tuberculosis Thai Isolates

The profile of genome-wide DNA methylation, transcriptome, and proteome in streptomycin-resistant Mycobacterium tuberculosis

Streptomycin-resistant (SM-resistant) Mycobacterium tuberculosis (M. tuberculosis) is a major concern in tuberculosis (TB) treatment. However, the mechanisms underlying streptomycin resistance remain unclear. This study primarily aimed to perform preliminary screening of genes associated with streptomycin resistance through conjoint analysis of multiple genomics. Genome-wide methylation, transcriptome, and proteome analyses were used to elucidate the associations between specific genes and streptomycin resistance in M. tuberculosis H37Rv. Methylation analysis revealed that 188 genes were differentially methylated between the SM-resistant and normal groups, with 89 and 99 genes being hypermethylated and hypomethylated, respectively. Furthermore, functional analysis revealed that these 188 differentially methylated genes were enriched in 74 pathways, with most of them being enriched in metabolic pathways. Transcriptome analysis revealed that 516 genes were differentially expressed between the drug-resistant and normal groups, with 263 and 253 genes being significantly upregulated and downregulated, respectively. KEGG analysis indicated that these 516 genes were enriched in 79 pathways, with most of them being enriched in histidine metabolism. The methylation level was negatively related to mRNA abundance. Proteome analysis revealed 56 differentially expressed proteins, including 14 upregulated and 42 downregulated proteins. Moreover, three hub genes (coaE, fadE5, and mprA) were obtained using synthetic analysis. The findings of this study suggest that an integrated DNA methylation, transcriptome, and proteome analysis can provide important resources for epigenetic studies in SM-resistant M. tuberculosis H37Rv.

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.

Whole-Genome Sequencing of Streptomycin-Resistant Mycobacterium tuberculosis Strain SBH145 from Sabah, Malaysia

This paper reports on the whole-genome sequencing of a streptomycin-resistant Mycobacterium tuberculosis strain that was isolated from a patient with pulmonary tuberculosis in Sabah state of Malaysian Borneo. The strain belongs to the EAI2-Manila family of lineage 1 and is clustered with M. tuberculosis strains from the Philippines, India, and Taiwan.

Whole genome sequencing of Mycobacterium tuberculosis for prediction of drug resistance

Whole-genome sequencing (WGS) has shown tremendous potential in rapid diagnosis of drug-resistant tuberculosis (TB). In the current study, we performed WGS on drug-resistant Mycobacterium tuberculosis isolates obtained from Shanghai (n = 137) and Russia (n = 78). We aimed to characterise the underlying and high-frequency novel drug-resistance-conferring mutations, and also create valuable combinations of resistance mutations with high predictive sensitivity to predict multidrug- and extensively drug-resistant tuberculosis (MDR/XDR-TB) phenotype using a bootstrap method. Most strains belonged to L2.2, L4.2, L4.4, L4.5 and L4.8 lineages. We found that WGS could predict 82.07% of phenotypically drug-resistant domestic strains. The prediction sensitivity for rifampicin (RIF), isoniazid (INH), ethambutol (EMB), streptomycin (STR), ofloxacin (OFL), amikacin (AMK) and capreomycin (CAP) was 79.71%, 86.30%, 76.47%, 88.37%, 83.33%, 70.00% and 70.00%, respectively. The mutation combination with the highest sensitivity for MDR prediction was rpoB S450L + rpoB H445A/P + katG S315T + inhA I21T + inhA S94A, with a sensitivity of 92.17% (0.8615, 0.9646), and the mutation combination with highest sensitivity for XDR prediction was rpoB S450L + katG S315T + gyrA D94G + rrs A1401G, with a sensitivity of 92.86% (0.8158, 0.9796). The molecular information presented here will be of particular value for the rapid clinical detection of MDR- and XDR-TB isolates through laboratory diagnosis.

Heterogeneous Streptomycin Resistance Level Among Mycobacterium tuberculosis Strains From the Same Transmission Cluster

Widespread and frequent resistance to the second-line tuberculosis (TB) medicine streptomycin, suggests ongoing transmission of low fitness cost streptomycin resistance mutations. To investigate this hypothesis, we studied a cohort of 681 individuals from a TB epidemic in Portugal. Whole-genome sequencing (WGS) analyses were combined with phenotypic growth studies in culture media and in mouse bone marrow derived macrophages. Streptomycin resistance was the most frequent resistance in the cohort accounting for 82.7% (n = 67) of the resistant Mycobacterium tuberculosis isolates. WGS of 149 clinical isolates identified 13 transmission clusters, including three clusters containing only streptomycin resistant isolates. The biggest cluster was formed by eight streptomycin resistant isolates with a maximum of five pairwise single nucleotide polymorphisms of difference. Interestingly, despite their genetic similarity, these isolates displayed different resistance levels to streptomycin, as measured both in culture media and in infected mouse bone marrow derived macrophages. The genetic bases underlying this phenotype are a combination of mutations in gid and other genes. This study suggests that specific streptomycin resistance mutations were transmitted in the cohort, with the resistant isolates evolving at the cluster level to allow low-to-high streptomycin resistance levels without a significative fitness cost. This is relevant not only to better understand transmission of streptomycin resistance in a clinical setting dominated by Lineage 4 M. tuberculosis infections, but mainly because it opens new prospects for the investigation of selection and spread of drug resistance in general.

Comprehensive review on mechanism of action, resistance and evolution of antimycobacterial drugs

Tuberculosis is one of the deadliest infectious diseases existing in the world since ancient times and still possesses serious threat across the globe. Each year the number of cases increases due to high drug resistance shown by Mycobacterium tuberculosis (Mtb). Available antimycobacterial drugs have been classified as First line, Second line and Third line antibiotics depending on the time of their discoveries and their effectiveness in the treatment. These antibiotics have a broad range of targets ranging from cell wall to metabolic processes and their non-judicious and uncontrolled usage in the treatment for years has created a significant problem called multi-drug resistant (MDR) tuberculosis. In this review, we have summarized the mechanism of action of all the classified antibiotics currently in use along with the resistance mechanisms acquired by Mtb. We have focused on the new drug candidates/repurposed drugs, and drug in combinations, which are in clinical trials for either treating the MDR tuberculosis more effectively or involved in reducing the time required for the chemotherapy of drug sensitive TB. This information is not discussed very adequately on a single platform. Additionally, we have discussed the recent technologies that are being used to discover novel resistance mechanisms acquired by Mtb and for exploring novel drugs. The story of intrinsic resistance mechanisms and evolution in Mtb is far from complete. Therefore, we have also discussed intrinsic resistance mechanisms of Mtb and their evolution with time, emphasizing the hope for the development of novel antimycobacterial drugs for effective therapy of tuberculosis.

Genome analyses of 174 strains of Mycobacterium tuberculosis provide insight into the evolution of drug resistance and reveal potential drug targets

Mycobacterium tuberculosis is a known human pathogen that causes the airborne infectious disease tuberculosis (TB). Every year TB infects millions of people worldwide. The emergence of multi-drug resistant (MDR), extensively drug resistant (XDR) and totally drug resistant (TDR) M. tuberculosis strains against the first- and second-line anti-TB drugs has created an urgent need for the development and implementation of new drug strategies. In this study, the complete genomes of 174 strains of M. tuberculosis are analysed to understand the evolution of molecular drug target (MDT) genes. Phylogenomic placements of M. tuberculosis strains depicted close association and temporal clustering. Selection pressure analysis by deducing the ratio of non-synonymous to synonymous substitution rates (dN/dS) in 51 MDT genes of the 174 M. tuberculosis strains led to categorizing these genes into diversifying (D, dN/dS>0.70), moderately diversifying (MD, dN/dS=0.35-0.70) and stabilized (S, dN/dS<0.35) genes. The genes rpsL, gidB, pncA and ahpC were identified as diversifying, and Rv0488, kasA, ndh, ethR, ethA, embR and ddn were identified as stabilized genes. Furthermore, sequence similarity networks were drawn that supported these divisions. In the multiple sequence alignments of diversifying and stabilized proteins, previously reported resistance mutations were checked to predict sensitive and resistant strains of M. tuberculosis. Finally, to delineate the potential of stabilized or least diversified genes/proteins as anti-TB drug targets, protein-protein interactions of MDT proteins with human proteins were analysed. We predict that kasA (dN/dS=0.29), a stabilized gene that encodes the most host-interacting protein, KasA, should serve as a potential drug target for the treatment of TB.

Molecular analysis of streptomycin-resistance associating genes in Mycobacterium tuberculosis isolates from Nepal

Mutation in rpsL (encoding ribosomal protein S12), rrs (encoding 16S ribosomal RNA) and gidB (encoding 7-methylguanosine methyltransferase) are associated with resistance to streptomycin (STR), which is used for the treatment of multi-drug resistant tuberculosis (MDR-TB) in Nepal. The aim of our study is to analyze the correlation between mutations in the target genes and STR-resistance in 197 Mycobacterium tuberculosis (MTB) isolates from Nepal. Mutations in rpsL was harbored by 65.9% of isolates, in which the most common mutation in rpsL is caused by K43R (58.8%) and were significantly associated with Beijing genotype (P < 0.001). About 13.2% of isolates harbored mutations in two highly mutable regions of rrs, the 530 loop and the 912 region. About 13.2% of gidB mutants do not show any mutation in rpsL and rrs, which might suggest the role of gidB mutations in STR-resistance in MTB. In addition, 5.6% of isolates do not show any mutations in three genes examined, suggesting the involvement of other mechanism in STR-resistance in MTB. Our findings can be implemented for the establishment of molecular STR-susceptibility testing, in which tuberculosis can be treated with appropriate drugs and can improve control strategies for DR-TB.

Comparison of the Wild-Type Obligate Methylotrophic Bacterium Methylophilus quaylei and its Isogenic Streptomycin-Resistant Mutant via Metal Nanoparticle Generation

Metal nanoparticles synthesized by green methods with the use of microorganisms are currently one of the most closely studied types of nanomaterials. It has accurately been shown that the characteristics of metal nanoparticles generated in the presence of different bacteria vary. For the two isogenic strains of obligate methylotrophic bacteria of the wild type (M. quaylei MT^T) and its streptomycin-resistant mutant (M. quaylei SM^R), the pleiotropic character of streptomycin resistance mutation in the SM^R cells has been revealed. It has been shown that both cultures can generate silver nanoparticles. There is a dramatic difference in the formation of palladium nanoparticles, which are formed only in the presence of cells of the streptomycin-resistant mutant M. quaylei SM^R. This study shows that closely related isogenic strains of obligate methylotrophic bacteria can be distinguished by the spectra of biogenic nanoparticles of two noble metals. While palladium nanoparticles are only generated by the cells of the streptomycin-resistant mutant M. quaylei SM^R, biogenic silver nanoparticles can be generated from both cultures. Thus, the assessment of the ability of microorganisms to form biogenic nanoparticles of different metals allows the revelation of subtle metabolic differences of even close cultures.

Phenotypic and Genotypic Characterization of Streptomycin-Resistant Multidrug-Resistant Mycobacterium tuberculosis Clinical Isolates in Southern China

Streptomycin (STR) is the first antibiotic used in the treatment of tuberculosis (TB) and the earliest antituberculosis drug with acquired resistance developed by Mycobacterium tuberculosis. The high prevalence of such resistance in many parts of the world limits its use for treating multidrug-resistant (MDR) TB. The aims of this study are to characterize of mutations in rpsL, rrs, and gidB genes in MDR M. tuberculosis isolates originating from southern China and to investigate possible relationship between mutations and strain genotypes for precise diagnosis and treatment. Sequences of rpsL, rrs, and gidB genes and the resistance profiles were analyzed for 218 MDR M. tuberculosis isolates. Our study showed that 68.35% of MDR M. tuberculosis isolates were resistant to STR and 89.91% of STR-resistant (STR^R) isolates were Beijing lineage strains. Mutations were observed in STR^R MDR M. tuberculosis isolates at the following rates: 72.48% in rpsL, 36.91% in rrs, and 15.44% in gidB. Compared with the phenotypic data, the combination of mutations in rpsL, rrs, and gidB has sensitivity and specificity of 96.64% and 100.00%, respectively. The most common mutations in STR^R isolates were rpsL128,263 and rrs514,1401, of which rpsL128 showed association with Beijing lineage (p < 0.001). It is noteworthy that a1401g mutation was present in rrs, while MDR M. tuberculosis isolates were resistant to both STR and amikacin. Twenty two novel mutations were found in STR^R isolates. These findings could be helpful to develop rapid molecular diagnostic methods and understand STR resistance in China for developing TB precision medicine and disturbance of drug-resistant TB transmission.

Single-nucleotide polymorphisms related to fluoroquinolone and aminoglycoside resistance in Mycobacterium avium isolates

Objective

The relationships between fluoroquinolone and aminoglycoside resistance and single-nucleotide polymorphisms (SNPs) in gyrA, gyrB, and rpsL genes were investigated in 95 clinical isolates of Mycobacterium avium from China.

Methods

Fluoroquinolone and aminoglycoside resistance were determined by the broth microdilution method. GyrA, gyrB, and rpsL were sequenced, SNPs were identified, and the corresponding amino acid mutations were recorded.

Results

The M. avium isolates displayed high levels of ofloxacin (93.68%), ciprofloxacin (92.63%), and streptomycin (65.26%) resistance. Moxifloxacin (18.95%) and amikacin (2.11%) were highly active against the strains. Fluoroquinolone resistance involving gyrA and gyrB gene mutations was identified. For gyrA, the most frequent SNPs were T→C (71/95, 74.74%), followed by A→G (64/95, 67.37%) and T→C (62/95, 65.26%). The amino acid mutations occurred mainly at Gly2444Asp (GGT→GAT) (20/95, 21.05%), Ala2445Ser (GCC→TCC) (20/95, 21.05%), Ala2447Val (GCC→GTC) (20/95, 21.05%), Val2449Ile (GTC→ATC) (20/95, 21.05%), and Glu2450Gln (GAA→CAA) (20/95, 21.05%). Prominent SNPs in gyrB included A→C (69/95, 72.63%), C→T (51/95, 53.68%), and T→G (29/95, 30.53%), and their amino acid substitutions were Ile2160Val (ATT→GTT) (21/95, 22.11%), Ile2160Met (ATT→ATG) (20/95, 21.05%), and Ile2273Leu (ATC→CTC) (11/95, 11.58%). Among the strains with aminoglycoside resistance, SNPs in rpsL were identified mostly at position G→A (73/95, 76.84%). G→C (21/95, 22.11%) was commonly seen. The amino acid mutations primarily involved Ala1539985Thr (GCC→ACC) (19/95, 20.00%), His1539992Asp (CAC→GAC) (19/95, 20.00%), and Gln-1539983Glu (CAG→GAG) (18/95, 18.95%).

Conclusion

Our study provides valuable information that could be used for the future diagnosis and treatment of M. avium disease.