Mutation profiling for detection of isoniazid resistance inMycobacterium tuberculosisclinical isolates
Tomasz JagielskiZofia BakułaKatarzyna RoeskeMichał KamińskiAgnieszka NapiórkowskaEwa Augustynowicz‐KopećZofia ZwolskaJacek Bielecki
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Progress in the detection of drug-resistant TB has been underpinned by the development and implementation of new, reliable and rapid diagnostic tools. These rely mostly on the detection of specific mutations conferring resistance to anti-TB drugs. The aim of this study was to search for mutations associated with isoniazid resistance among Mycobacterium tuberculosis clinical isolates. A collection of 150 M. tuberculosis strains, including 50 MDR, 50 isoniazid-monoresistant and 50 pan-susceptible strains, was used. For all the strains, seven structural genes (katG, inhA, ahpC, kasA, ndh, nat and mshA) and two regulatory regions (mabA-inhA promoter and oxyR-ahpC intergenic region) were PCR amplified and sequenced in their entirety. Sixty-six distinct mutations were detected at all nine loci investigated, accounting for 109 (72.7%) of the strains tested. The number of strains with any mutation among the MDR, isoniazid-monoresistant and pan-susceptible groups was 49 (98%), 37 (74%) and 23 (46%), respectively. Mutations in the katG gene predominated, with 29 different types distributed among 46 (92%) MDR, 31 (62%) isoniazid-monoresistant and 2 (4%) pan-susceptible strains. Twenty-nine and 19 mutations were found exclusively in MDR and isoniazid-monoresistant strains, respectively. This study revealed 17 mutations, previously unreported, that might be of potential use as new surrogate markers of isoniazid resistance. Their diagnostic accuracy needs to be confirmed on larger strain samples and from different geographical settings. For isoniazid resistance detection, molecular approaches should still be a complement to rather than a replacement for conventional drug susceptibility testing. This is supported by the lack of mutations in any of the nine genetic loci investigated in 18 isoniazid-resistant strains from this study.Objective To observe the mutations of katG in Mycobacterium tuberculosis isoniazid-resident isolates,to research their l value in isoniazid resistanceMethods Analyzing the mutations of katG in 72 Mycobacterium tuberculosis with PCR-SSCP.32 isoniazid susceptible Mycobacterium tuberculosis clinical isolates and 40 isoniazid resistant isolates with Mycobacterium tuberculosis H37RV reference strains as control group.Results Amplification was abserved all of isoniazid susceptible Mycobacterium tuberculosis clinical isolates.Among 40 isoniazid resistant chinial isolates,15 isolates diaplayed the same patterns as H37RV and 25 isolates showed PCR-SSCP diffirent from that of H37RV.About 62.5 percent isoniazid-resident isolates showed mutation or deletion of katG gene.Conclusion The changes of katG gene are associated with isoniazid residenance.PCR-SSCP technique will be useful to rapidly screen gene mutation of isoniazid resistant Mycobacterium tuberculosis.
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ABSTRACT Background Studies on human intraocular tuberculosis (IOTB) are extremely challenging. For understanding the pathogenesis of IOTB, it is important to investigate the mycobacterial transcriptional changes in ocular environment. Methods Mice were challenged intravenously with Mycobacterium tuberculosis H37Rv and at 45 days post-infection, experimental IOTB was confirmed based on bacteriological and molecular assays. M. tuberculosis transcriptome was analyzed in the infected eyes using microarray technology. The identified M. tuberculosis signature genes were further validated and investigated in human IOTB samples using real-time polymerase chain reaction. Results Following intravenous challenge with M. tuberculosis, 45% (5/12) mice showed bacilli in the eyes with positivity for M. tuberculosis ribonucleic acid in 100% (12/12), thus confirming the paucibacillary nature of IOTB similar to human IOTB. M. tuberculosis transcriptome in these infected eyes showed significant upregulation of 12 M. tuberculosis genes and five of these transcripts (Rv0962c, Rv0984, Rv2612c, Rv0974c and Rv0971c) were also identified in human clinically confirmed cases of IOTB. Conclusions Differentially expressed mycobacterial genes identified in an intravenously challenged paucibacillary mouse IOTB model and presence of these transcripts in human IOTB samples highlight the possible role of these genes for survival of M. tuberculosis in the ocular environment, thus contributing to pathogenesis of IOTB.
Pathogenesis
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Isoniazid,the first line drug of anti-Mycobacterium tuberculosis,is one of the most extensively used anti-tuberculosis drugs.Since its application in clinical practice in 1952,isoniazid had become a basic drug for treatment of tuberculosis and potential infections.Some reports considered that the resistance to isoniazid has become the top problem in China.The molecule mechanisms of Mycobacterium tuberculosis resistance to isoniazid are very complicated,involving multiple genes including katG,inhA,kasA,ndh and axyR.The article reviewed some researches on this issue.
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Isoniazid resistance in Mycobacterium tuberculosis is associated with lack of catalase-peroxidase activity. A recent study showed that some isoniazid-resistant M. tuberculosis strains have a complete deletion of the gene (katG) encoding this enzyme. To examine what proportion of clinical isolates of M. tuberculosis have katG deletion, katG sequences in 80 randomly selected isolates from New York City were analyzed. Polymerase chain reaction was used to amplify a 282-bp segment of M. tuberculosis katG and showed that 35 (90%) of 39 isoniazid-sensitive and 31 (76%) of 41 isoniazid-resistant strains contained katG sequences (P > .1). Ten multidrug and high-level isoniazid-resistant strains with identical restriction fragment length polymorphism patterns were also analyzed. All were found to have katG sequences. These findings suggest that mechanisms other than complete deletion of katG are involved in isoniazid resistance among most clinical isolates of M. tuberculosis from New York City.
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ObjectivesDespite having potent activity against actively replicating Mycobacterium tuberculosis, isoniazid has very limited activity against dormant bacilli. In order to investigate the lack of bactericidal activity of this drug under conditions leading to mycobacterial dormancy, we studied the transcriptional pattern of M. tuberculosis in different physiological states following exposure to isoniazid.
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SUMMARY Exposure of growing Mycobacterium tuberculosis bcg to 1 µ g. isoniazid/ml. inhibited the incorporation of 14C from [U-14C] and [2-14C]glycerol and [1-14C]- glutamate into its walls by about 50 % over 12 h. because 14C incorporation into the mycolic acids of the walls was prevented. Isoniazid, 0·5 µ g. / ml. with M. tuberculosis bcg or 0·1 µ g./ml. with M. tuberculosis H37 Ra, inhibited incorporation of 14C from [U-14C] glycerol into total mycolic acids by about 90 % over 6 h., indicating that inhibition began within 1 h. of the addition of the drug. There was no effect on mycolic acid synthesis in an isoniazid- resistant strain of M. tuberculosis bcg. The primary inhibitory action of isoniazid in sensitive mycobacteria is probably on mycolic acid synthesis, and this leads to formation of defective boundary layers of the bacteria.
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Transcriptional Biomarkers of Differentially Detectable Mycobacterium tuberculosis in Patient Sputum
Certain populations of Mycobacterium tuberculosis go undetected by standard diagnostics but can be enumerated using limiting dilution assays. These differentially detectable M. tuberculosis (DD M. tuberculosis) populations may have relevance for persistence due to their drug tolerance. It is unclear how well DD M. tuberculosis from patients is modeled by a recently developed
Tuberculosis diagnosis
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Isoniazid is one of the most important first-line drugs of anti-tuberculosis strategy. In the past 50 years, isoniazid played a very important role in anti-tuberculosis treatment. However, with the emergence of isoniazid-resistant Myeobacterium tuberculosis, the efficacy is decreasing. Herein, this article discusses the mechanism of isoniazid action against Mycobacterium tuberculosis, and reviews the molecular mechanism of isoniazid resistance in Myeobacterium tuberculosis.
Key words:
Isoniazid; Mycobacterium tuberculosis; Drug-resistant
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Introduction. Relapses of tuberculosis are fairly rare nowdays and they represent the onset of tuberculosis two, or more than two years after completion of previous treatment. Material and Methods. In the previous period, relapses of tuberculosis occurred in 141 patients (87 male and 54 female). Their mean age was 46.2 years. Results. Relapses of tuberculosis occurred after 11.3 years, on average. All patients presented with pulmonary tuberculosis, and two patients also had pulmonary and extrapulmonary tuberculosis(bones). Resistance was one of the statistically significant factors for relapse of tuberculosis. Resistance to one antituberculotic agent was most common - 8 patients, resistance to two drugs - 4 patients, resistance to three drugs - 4 patients, resistance to four drugs in 5 patients. Due to these findings on resistant strains of mycobacterium tuberculosis, a huge number of patients with relapses of tuberculosis had full recovery and completed the treatment. Conclusion. The importance of resistant strains of mycobacterium tuberculosis is really huge in our conditions. The findings of these resistant strains of mycobacterium tuberculosis and adequate medical treatment are obligatory nowadays. .
Mycobacterium tuberculosis complex
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There is considerable variability in the outcome of Mycobacterium tuberculosis infection. We hypothesized that Mycobacterium africanum was less likely than M. tuberculosis to transmit and progress to tuberculosis disease.In a cohort study of patients with tuberculosis and their household contacts in The Gambia, we categorized 1808 HIV-negative tuberculosis contacts according to exposure to M. tuberculosis or M. africanum. Positive skin test results indicated transmission, and development of tuberculosis during 2 years of follow-up indicated progression to disease.Transmission rates were similar, but rates of progression to disease were significantly lower in contacts exposed to M. africanum than in those exposed to M. tuberculosis (1.0% vs. 2.9%; hazard ratio [HR], 3.1 [95% confidence interval {CI}, 1.1-8.7]). Within M. tuberculosis sensu stricto, contacts exposed to a Beijing family strain were most likely to progress to disease (5.6%; HR relative to M. africanum, 6.7 [95% CI, 2.0-22]).M. africanum and M. tuberculosis transmit equally well to household contacts, but contacts exposed to M. africanum are less likely to progress to tuberculosis disease than those exposed to M. tuberculosis. The variable rate of progression by lineage suggests that tuberculosis variability matters in clinical settings and should be accounted for in studies evaluating tuberculosis vaccines and treatment regimens for latent tuberculosis infection.
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