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Validation of RelMtb as a target for Mycobacterium tuberculosis persisters

ABSTRACT: The lengthy and complicated multidrug therapy currently available to treat active tuberculosis (TB) infection has contributed to medical non-adherence and the emerging problems of multidrug-resistant (MDR)- and extensively drug-resistant (XDR)-TB, which are particularly deadly in the setting of HIV co-infection. The prolonged therapy required to eradicate TB infection is believed to reflect the ability of Mycobacterium tuberculosis (Mtb) to persist within host necrotic granulomas in a non-replicating state characterized by antibiotic tolerance to bactericidal drugs, which predominantly target actively dividing tubercle bacilli. The stringent response enzyme, RelMtb, is essential for Mtb survival under physiologically relevant stress conditions in vitro and in the lungs of mice and guinea pigs. A library of over 2 million compounds was screened in RelMtb-inhibition assays and whole-cell screens under conditions in which RelMtb is essential. A total of 178 RelMtb inhibitor candidates, representing 18 unique scaffolds, were identified and 39 compounds were tested against nutrient-starved wild-type Mtb. The antibiotic susceptibility of a relMtb deletion mutant (Δrel) was studied during nutrient starvation and chronic infection in mice, and isoniazid and RelMtb inhibitor candidates were tested for synergy against nutrient-starved wild-type Mtb and Δrel using checkerboard assays. The minimum bactericidal concentration of isoniazid was 500-fold lower against Δrel relative to wild type during nutrient starvation, and the potent bactericidal activity of isoniazid was maintained against Δrel during chronic infection in the lungs of mice. Inhibition of RelMtb appears to be a promising new approach to target Mtb persisters, with the potential to shorten the duration of treatment for drug-susceptible and drug-resistant TB. We used microarray to characterize the transcriptomic profiles of the wild type and Δrel during nutrient starvation. The RelMtb inhibitor, (E)-4-(3-methyl-4-(2-(4-methylthiazol-5-yl)ethoxy)styryl)benzoic acid, killed wild-type Mtb and prevented isoniazid tolerance during nutrient starvation. Treatment of nutrient-starved wild-type with the RelMtb inhibitor led to downregulation of the RelMtb regulon. Transcriptomic analysis revealed an altered gene expression in Δrel and wild-type treated with RelMtb inhibitor during nutrient starvation.

ORGANISM(S): Mycobacterium tuberculosis H37Rv

PROVIDER: GSE99710 | GEO | 2021/06/05

REPOSITORIES: GEO

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Project description:Introduction: Tuberculosis (TB) is a serious human disease caused by the bacterium Mycobacterium tuberculosis (Mtb). One third of the worldâs population is estimated to be latently infected with Mtb. Exact mechanisms and properties of latent TB infection (LTBI) are not fully elucidated. In essence, the pathogen can enter a dormant or latent state characterized by limited growth and metabolism, resulting in absence of clinical symptoms in the host, and most importantly by increased phenotypic tolerance to the commonly used medications, thereby allowing indefinite persistence in the human body. This persistence is the main reason why the current treatment of new-onset pulmonary TB is very long, consisting of a six months therapy of four antibiotics (rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months, and only rifampicin and isoniazid for the last four months). Current state of the art: To fight TB globally and more efficiently, it is essential to shorten the treatment for TB with new drugs that are efficient also against LTBI. To facilitate discovery of such drugs, in vitro models for LTBI can be used for high throughput screening of chemical libraries. Current in vitro models such as nutrient starvation (Betts et al. 2002), nutrient depletion (Hampshire et al. 2004; Rifat, Bishai, and Karakousis 2009), progressive hypoxia (Wayne and Hayes 1996), nitric oxide treatment (Martin I. Voskuil et al. 2003) and multiple stress (Deb et al. 2009) mimic the dormant state of Mtb, but the technical settings and equipment required for these models obstruct high throughput applications. Proposed model: The streptomycin (STR)-starved 18b model (SS18b) is a simple and drug discovery efficient Mtb latency model successfully applicable to both in vitro and in vivo settings (Zhang et al. 2012). It is based on the Mtb strain 18b, which is a STR-dependent mutant that enters a viable but nonreplicating state in the absence of STR (Hashimoto 1955). Despite the successful model, we know very little about 18b. How well does SS18b mimic the bacterial response to the complex host-pathogen interactions underlying LTBI, and how does the SS18b response compare to that of other dormancy models are still open questions. In this work we analyse the complete genome of 18b and describe the transcriptomic response of 18b to STR depletion. 12 samples were analyzed. Four biological replicates were sampled during the exponential growth phase, in presence of streptomycin. Four biological replicates derived after 2 weeks of streptomycin depletion, and two biological replicates derive after 4 weeks of streptomycin depletion. Two replicates derive from the resubmission of streptomycin after four weeks of depletion.

Project description:Introduction: Tuberculosis (TB) is a serious human disease caused by the bacterium Mycobacterium tuberculosis (Mtb). One third of the world’s population is estimated to be latently infected with Mtb. Exact mechanisms and properties of latent TB infection (LTBI) are not fully elucidated. In essence, the pathogen can enter a dormant or latent state characterized by limited growth and metabolism, resulting in absence of clinical symptoms in the host, and most importantly by increased phenotypic tolerance to the commonly used medications, thereby allowing indefinite persistence in the human body. This persistence is the main reason why the current treatment of new-onset pulmonary TB is very long, consisting of a six months therapy of four antibiotics (rifampicin, isoniazid, pyrazinamide, and ethambutol for the first two months, and only rifampicin and isoniazid for the last four months). Current state of the art: To fight TB globally and more efficiently, it is essential to shorten the treatment for TB with new drugs that are efficient also against LTBI. To facilitate discovery of such drugs, in vitro models for LTBI can be used for high throughput screening of chemical libraries. Current in vitro models such as nutrient starvation (Betts et al. 2002), nutrient depletion (Hampshire et al. 2004; Rifat, Bishai, and Karakousis 2009), progressive hypoxia (Wayne and Hayes 1996), nitric oxide treatment (Martin I. Voskuil et al. 2003) and multiple stress (Deb et al. 2009) mimic the dormant state of Mtb, but the technical settings and equipment required for these models obstruct high throughput applications. Proposed model: The streptomycin (STR)-starved 18b model (SS18b) is a simple and drug discovery efficient Mtb latency model successfully applicable to both in vitro and in vivo settings (Zhang et al. 2012). It is based on the Mtb strain 18b, which is a STR-dependent mutant that enters a viable but nonreplicating state in the absence of STR (Hashimoto 1955). Despite the successful model, we know very little about 18b. How well does SS18b mimic the bacterial response to the complex host-pathogen interactions underlying LTBI, and how does the SS18b response compare to that of other dormancy models are still open questions. In this work we analyse the complete genome of 18b and describe the transcriptomic response of 18b to STR depletion.

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Validation of RelMtb as a target for Mycobacterium tuberculosis persisters

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