Isoxyl (ISO) and thiacetazone (TAC) are two antitubercular prodrugs formerly used in the clinical treatment of tuberculosis. Although both prodrugs have recently been shown to kill Mycobacterium tuberculosis through the inhibition of the dehydration step of the type II fatty acid synthase pathway, their detailed mechanism of inhibition, the precise number of enzymes involved in their activation, and the nature of their activated forms remained unknown. This paper demonstrates that both ISO and TAC specifically and covalently react with a cysteine residue (Cys61) of the HadA subunit of the dehydratase, thereby inhibiting HadAB activity. The results unveil for the first time the nature of the active forms of ISO and TAC and explain the basis for the structure–activity relationship of and resistance to these thiourea prodrugs. The results further indicate that the flavin-containing monooxygenase EthA is most likely the only enzyme required for the activation of ISO and TAC in mycobacteria.
Objective Activated alkaline glutaraldehyde remains one of the most widely used high-level disinfectant across the world. Yet, several reports have highlighted the potential for nontuberculous mycobacteria to develop high-level resistance to this product. Because aldehyde resistance may lead to cross-resistance to other biocides, we set out to investigate the susceptibility profile of glutaraldehyde-resistant Mycobacterium chelonae and Mycobacterium abscessus isolates to various disinfectant chemistries. Methods High-level disinfectants commonly used in the reprocessing of endoscopes and other heat-sensitive, semicritical medical equipment, including different formulations of aldehyde-based products and oxidizing agents, were tested against ten slow- and fast-growing, glutaraldehyde-susceptible and glutaraldehyde-resistant, Mycobacterium isolates in suspension and carrier tests at different temperatures. Results While peracetic acid- and hydrogen peroxide-based disinfectants (S40™, Resert™ XL, Reliance™ DG) efficiently killed all of the Mycobacterium isolates, glutaraldehyde- and ortho-phthalaldehyde-based products (Cidex®, Aldahol®, Cidex® OPA) showed variable efficacy against glutaraldehyde-resistant strains despite the ability of some formulations (Aldahol®) to overcome the resistance of some of these isolates, especially when the temperature was increased from 20 to 25°C. Conclusions Application permitting, oxidizing chemistries may provide a safe alternative to aldehyde-based products, particularly in the case of GTA-resistant mycobacterial outbreaks.
Detoxification, scavenging, and repair systems embody the archetypical antioxidant defenses of prokaryotic and eukaryotic cells. Metabolic rewiring also aids with the adaptation of bacteria to oxidative stress. Evolutionarily diverse bacteria combat the toxicity of reactive oxygen species (ROS) by actively engaging the stringent response, a stress program that controls many metabolic pathways at the level of transcription initiation via guanosine tetraphosphate and the α-helical DksA protein. Studies herein with Salmonella demonstrate that the interactions of structurally related, but functionally unique, α-helical Gre factors with the secondary channel of RNA polymerase elicit the expression of metabolic signatures that are associated with resistance to oxidative killing. Gre proteins both improve transcriptional fidelity of metabolic genes and resolve pauses in ternary elongation complexes of Embden–Meyerhof–Parnas (EMP) glycolysis and aerobic respiration genes. The Gre-directed utilization of glucose in overflow and aerobic metabolism satisfies the energetic and redox demands of Salmonella, while preventing the occurrence of amino acid bradytrophies. The resolution of transcriptional pauses in EMP glycolysis and aerobic respiration genes by Gre factors safeguards Salmonella from the cytotoxicity of phagocyte NADPH oxidase in the innate host response. In particular, the activation of cytochrome bd protects Salmonella from phagocyte NADPH oxidase-dependent killing by promoting glucose utilization, redox balancing, and energy production. Control of transcription fidelity and elongation by Gre factors represent important points in the regulation of metabolic programs supporting bacterial pathogenesis.
Salmonella invades host cells and replicates inside acidified, remodeled vacuoles that are exposed to reactive oxygen species (ROS) generated by the innate immune response. Oxidative products of the phagocyte NADPH oxidase mediate antimicrobial activity, in part, by collapsing the ΔpH of intracellular Salmonella .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.