Altered expression of isoniazid-regulated genes in drug-treated dormant Mycobacterium tuberculosis (original) (raw)
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Antibiotics
Isoniazid (INH) is an antibiotic that is widely used to treat tuberculosis (TB). Adaptation to environmental stress is a survival strategy for Mycobacterium tuberculosis and is associated with antibiotic resistance development. Here, mycobacterial adaptation following INH treatment was studied using a multi-stress system (MS), which mimics host-derived stress. Mtb H37Rv (drug-susceptible), mono-isoniazid resistant (INH-R), mono-rifampicin resistant (RIF-R), and multidrug-resistant (MDR) strains were cultivated in the MS with or without INH. The expression of stress-response genes (hspX, tgs1, icl1, and sigE) and lipoarabinomannan (LAM)-related genes (pimB, mptA, mptC, dprE1, dprE2, and embC), which play important roles in the host–pathogen interaction, were measured using real-time PCR. The different adaptations of the drug-resistant (DR) and drug-susceptible (DS) strains were presented in this work. icl1 and dprE1 were up-regulated in the DR strains in the MS, implying their roles ...
Future Microbiology, 2016
Aim: To study the proteomic and morphological changes in Mycobacterium tuberculosis H37Rv exposed to subinhibitory concentration of isoniazid (INH). Materials & methods: The bacillus was exposed to ½ MIC of INH at 12, 24 and 48 h. The samples’ cells were submitted to scanning electron microscopy. The proteins were separated by 2D gel electrophoresis and identified by MS. Results: INH exposure was able to alter the format, the multiplication and causing a cell swelling in the bacillus. The major altered proteins were related to the virulence, detoxification, adaptation, intermediary metabolism and lipid metabolism. Conclusion: The protein and morphological changes in M. tuberculosis induced by ½ MIC INH were related to defense mechanism of the bacillus or the action of INH therein.
Journal of Biotechnology, 2015
Mycobacterium tuberculosis has the ability to persist within the host in a dormant stage. One important condition believed to contribute to dormancy is reduced access to oxygen known as hypoxia. However, the response of M. tuberculosis to such hypoxia condition is not fully characterized. Virtually all dormant models against tuberculosis tested in animals used laboratory strain H37Rv or Erdman strain. But major outbreaks of tuberculosis (TB) occur with the strains that have widely different genotypes and phenotypes compared to H37Rv. In this study, we used a custom oligonucleotide microarray to determine the overall transcriptional response of laboratory strain (H37Rv) and most prevalent clinical strains (S7 and S10) of M. tuberculosis from South India to hypoxia. Analysis of microarray results revealed that a total of 1161 genes were differentially regulated (≥1.5 fold change) in H37Rv, among them 659 genes upregulated and 502 genes down regulated. Microarray data of clinical isolates showed that a total of 790 genes were differentially regulated in S7 among which 453 genes were upregulated and 337 down regulated. Interestingly, numerous genes were also differentially regulated in S10 (total 2805 genes) of which 1463 genes upregulated and 1342 genes down regulated during reduced oxygen condition (Wayne's model). One hundred and thirty-four genes were found common and upregulated among all three strains (H37Rv, S7, and S10) and can be targeted for drug/vaccine development against TB.
International microbiology : the official journal of the Spanish Society for Microbiology, 2010
Major differences regarding the pathology and host immune response of the Beijing and Canettii genotypes of Mycobacterium tuberculosis have been reported; however, studies on the genetic expression of these genotypes during in vitro dormancy are scarce. This study examined the expression of five cell-cycle-related genes and two dormancy-related genes in M. canettii, M. tuberculosis H37Rv, and M. tuberculosis Beijing during the Wayne model of dormancy. The results showed that under hypoxic conditions the three tuberculosis genotypes were able to transcribe genes involved in DNA replication and cellular division. In addition, dosR was found to be up-regulated in M. tuberculosis Beijing during the exponential growth phase but down-regulated under hypoxic conditions. In this genotype, the replication-related gene dnaA was also strongly down-regulated. These latter two findings suggest that, compared to M. tuberculosis H37Rv and M. canettii, the Beijing genotype has a lower capacity to s...
Scientific Reports, 2021
Effective treatment reduces a tuberculosis patient's ability to infect others even before they test negative in sputum or culture. Currently, the basis of reduced infectiousness of the Mycobacterium tuberculosis (Mtb) with effective treatment is unclear. We evaluated changes in aerosolized bacteria expelled by patients through a transcriptomic approach before and after treatment initiation (up to 14 days) by RNA sequencing. A distinct change in the overall transcriptional profile was seen post-treatment initiation compared to pretreatment, only when patients received effective treatment. This also led to the downregulation of genes associated with cellular activities, cell wall assembly, virulence factors indicating loss of pathogenicity, and a diminished ability to infect and survive in new host cells. Based on this, we identified genes whose expression levels changed with effective treatment. The observations of the study open up avenues for further evaluating the changes in b...
Frontiers in Microbiology, 2018
The development of antibiotic tolerance is believed to be a major factor in the lengthy duration of current tuberculosis therapies. In the current study, we have modeled antibiotic tolerance in vitro by exposing Mycobacterium tuberculosis to two distinct stress conditions: progressive hypoxia and nutrient starvation [phosphate-buffered saline (PBS)]. We then studied the bacterial transcriptional response using RNA-seq and employed a bioinformatics approach to identify important transcriptional regulators, which was facilitated by a novel Regulon Enrichment Test (RET). A total of 17 transcription factor (TF) regulons were enriched in the hypoxia gene set and 16 regulons were enriched in the nutrient starvation, with 12 regulons enriched in both conditions. Using the same approach to analyze previously published gene expression datasets, we found that three M. tuberculosis regulons (Rv0023, SigH, and Crp) were commonly induced in both stress conditions and were also among the regulons enriched in our data. These regulators are worthy of further study to determine their potential role in the development and maintenance of antibiotic tolerance in M. tuberculosis following stress exposure.
Overview on mechanisms of isoniazid action and resistance in Mycobacterium tuberculosis
Infection, Genetics and Evolution, 2016
The tuberculosis (TB) is a disease caused by Mycobacterium tuberculosis (Mtb) and is considered a worldwide public health problem, classified as the leading cause of death by a single infectious agent. The conventional treatment is performed through the combination of drugs that exhibit precocious or sterilizing bactericidal activity. The commonly used drugs (knowing as first line drugs) are: izoniazide (INH), rifampicin (RIF), pyrazinamide (PZA) and ethambutol (ETH). However, the number of resistant TB cases (classified as RR-TB, MDR-TB and XDR-TB) to drugs has been growing in concern over the years. Of the total cases registered in 2016, about 600 thousand were resistant to one or more drugs used in the treatment. Resistance of Mtb strains to antituberculosis drugs is closely related to mutations in different bacillus genes. Multidrugresistant tuberculosis is a worldwide problem. A better understanding of the molecular mechanisms associated with the resistance to first-line drugs used in the TB treatment is of great importance for the development of new drugs, directly helping to reduce the number of resistant cases and bringing great benefits to public health. A review of the mechanisms of action of first-line drugs used in the treatment regimen to sensitive tuberculosis, as well as the main associated resistance mechanisms are.
Mycobacterium tuberculosis persistence mutants identified by screening in isoniazid-treated mice
Proceedings of the National Academy of Sciences, 2010
Tuberculosis (TB) is notoriously difficult to cure, requiring administration of multiple antibiotics for 6 mo or longer. Conventional anti-TB drugs inhibit biosynthetic processes involved in cell growth and division, such as DNA replication, RNA transcription, protein translation, and cell wall biogenesis. Although highly effective against bacteria cultured in vitro under optimal growth conditions, these antibiotics are less effective against bacteria grown in vivo in the tissues of a mammalian host. The factors that contribute to the antibiotic tolerance of bacteria grown in vivo are unknown, although altered metabolism and sluggish growth are hypothesized to play a role. To address this question, we identified mutations in Mycobacterium tuberculosis that impaired or enhanced persistence in mice treated with isoniazid (INH), a front-line anti-TB drug. Disruption of cydC , encoding a putative ATP-binding cassette transporter subunit, accelerated bacterial clearance in INH-treated mi...
Frontiers in Cellular and Infection Microbiology
Under unfavorable conditions such as host immune responses and environmental stresses, human pathogen Mycobacterium tuberculosis may acquire the dormancy phenotype characterized by "non-culturability" and a substantial decrease of metabolic activity and global transcription rates. Here, we found that the transition of M. tuberculosis from the dormant "non-culturable" (NC) cells to fully replicating population in vitro occurred not earlier than 7 days after the start of the resuscitation process, with predominant resuscitation over this time interval evidenced by shortening apparent generation time up to 2.8 h at the beginning of resuscitation. The early resuscitation phase was characterized by constant, albeit low, incorporation of radioactive uracil, indicating de novo transcription immediately after the removal of the stress factor, which resulted in significant changes of the M. tuberculosis transcriptional profile already after the first 24 h of resuscitation. This early response included transcriptional upregulation of genes encoding enzymes of fatty acid synthase system type I (FASI) and type II (FASII) responsible for fatty acid/mycolic acid biosynthesis, and regulatory genes, including whiB6 encoding a redox-sensing transcription factor. The second resuscitation phase took place 4 days after the resuscitation onset, i.e., still before the start of active cell division, and included activation of central metabolism genes encoding NADH dehydrogenases, ATP-synthases, and ribosomal proteins. Our results demonstrate, for the first time, that the resuscitation of dormant NC M. tuberculosis is characterized by immediate activation of de novo transcription followed by the upregulation of genes controlling key metabolic pathways and then, cell multiplication.
The Journal of infectious diseases, 2015
Treatment initiation rapidly kills most drug-susceptible Mycobacterium tuberculosis, but a bacterial sub-population tolerates prolonged drug exposure. We evaluated drug-tolerant bacilli in human sputum by comparing mRNA expression of drug-tolerant bacilli that survive the early bactericidal phase with treatment-naïve bacilli. M. tuberculosis gene expression was quantified via RT-PCR in serial sputa from 17 Ugandans treated for drug-susceptible pulmonary tuberculosis. Within four days, bacterial mRNA abundance declined >98%, indicating rapid killing. Thereafter, the rate of decline slowed >94%, indicating drug tolerance. After 14 days, 16S rRNA transcripts/genome declined 96%, indicating slow growth. Drug-tolerant bacilli displayed marked down-regulation of genes associated with growth, metabolism and lipid synthesis and up-regulation in stress responses and key regulatory categories - including stress-associated sigma factors, transcription factors, and toxin-antitoxin gene...