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  • 1.
    Cairns, Andrew G.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sarkar, Souvik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Larsson, Andreas
    FOI, Swedish Defence Research Agency, CBRN Defence & Security, Umeå, Sweden.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    An efficient and scalable synthesis of thiazolo ring fused 2-pyridones using flow chemistry2021In: ARKIVOC, ISSN 1551-7004, E-ISSN 1551-7012, Vol. 2020, no 7, p. 365-378Article in journal (Refereed)
    Abstract [en]

    Thiazolino ring fused 2-pyridones are a valuable scaffold with varied and substitution dependent biological activity, accessed primarily by an acyl ketene-imine cycloaddition and rearrangement. Although powerful, some aspects of this chemistry such as the requirement for excess starting material and the production of gas can make larger scale synthesis challenging. Here we describe the development, application and scaling of a continuous flow process allowing larger scale synthesis, with better handling of hazards and more reliable scaling. Optimisation and control of conditions allows for a more efficient synthesis, with a lower equivalence of the acyl ketene precursor required.

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  • 2.
    Harrison, Gregory A.
    et al.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Wang, Erin R.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Cho, Kevin
    Department of Chemistry, Washington University in St. Louis, MO, St. Louis, United States; Department of Medicine, Washington University School of Medicine, MO, St. Louis, United States; Center for Metabolomics and Isotope Tracing, Washington University in St. Louis, MO, St. Louis, United States.
    Mreyoud, Yassin
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Sarkar, Souvik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Patti, Gary J.
    Department of Chemistry, Washington University in St. Louis, MO, St. Louis, United States; Department of Medicine, Washington University School of Medicine, MO, St. Louis, United States; Center for Metabolomics and Isotope Tracing, Washington University in St. Louis, MO, St. Louis, United States.
    Stallings, Christina L.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Inducing vulnerability to InhA inhibition restores isoniazid susceptibility in drug-resistant Mycobacterium tuberculosis2024In: mBio, ISSN 2161-2129, E-ISSN 2150-7511, Vol. 15, no 3Article in journal (Refereed)
    Abstract [en]

    Of the approximately 10 million cases of Mycobacterium tuberculosis (Mtb) infections each year, over 10% are resistant to the frontline antibiotic isoniazid (INH). INH resistance is predominantly caused by mutations that decrease the activity of the bacterial enzyme KatG, which mediates the conversion of the pro-drug INH to its active form INH-NAD. We previously discovered an inhibitor of Mtb respiration, C10, that enhances the bactericidal activity of INH, prevents the emergence of INH-resistant mutants, and re-sensitizes a collection of INH-resistant mutants to INH through an unknown mechanism. To investigate the mechanism of action of C10, we exploited the toxicity of high concentrations of C10 to select for resistant mutants. We discovered two mutations that confer resistance to the disruption of energy metabolism and allow for the growth of Mtb in high C10 concentrations, indicating that growth inhibition by C10 is associated with inhibition of respiration. Using these mutants as well as direct inhibitors of the Mtb electron transport chain, we provide evidence that inhibition of energy metabolism by C10 is neither sufficient nor necessary to potentiate killing by INH. Instead, we find that C10 acts downstream of INH-NAD synthesis, causing Mtb to become particularly sensitive to inhibition of the INH-NAD target, InhA, without changing the concentration of INH-NAD or the activity of InhA, the two predominant mechanisms of potentiating INH. Our studies revealed that there exists a vulnerability in Mtb that can be exploited to render Mtb sensitive to otherwise subinhibitory concentrations of InhA inhibitor. IMPORTANCE Isoniazid (INH) is a critical frontline antibiotic to treat Mycobacterium tuberculosis (Mtb) infections. INH efficacy is limited by its suboptimal penetration of the Mtb-containing lesion and by the prevalence of clinical INH resistance. We previously discovered a compound, C10, that enhances the bactericidal activity of INH, prevents the emergence of INH-resistant mutants, and re-sensitizes a set of INH-resistant mutants to INH. Resistance is typically mediated by katG mutations that decrease the activation of INH, which is required for INH to inhibit the essential enzyme InhA. Our current work demonstrates that C10 re-sensitizes INH-resistant katG-hypomorphs without enhancing the activation of INH. We furthermore show that C10 causes Mtb to become particularly vulnerable to InhA inhibition without compromising InhA activity on its own. Therefore, C10 represents a novel strategy to curtail the development of INH resistance and to sensitize Mtb to sub-lethal doses of INH, such as those achieved at the infection site.

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  • 3.
    Nye, Taylor M.
    et al.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University, School of Medicine, MO, St. Louis, United States.
    Tükenmez, Hasan
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Flores-Mireles, Ana L.
    Department of Biological Sciences, University of Notre Dame, Notre Dame, India.
    Obernuefemann, Chloe L.P.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University, School of Medicine, MO, St. Louis, United States.
    Pinkner, Jerome S.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University, School of Medicine, MO, St. Louis, United States.
    Sarkar, Souvik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Bonde, Mari
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Lindgren, Anders E. G.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Dodson, Karen W.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University, School of Medicine, MO, St. Louis, United States.
    Johansson, Jörgen
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Caparon, Michael G.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University, School of Medicine, MO, St. Louis, United States.
    Hultgren, Scott J.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University, School of Medicine, MO, St. Louis, United States.
    Ring-fused 2-pyridones effective against multidrug-resistant Gram-positive pathogens and synergistic with standard-of-care antibiotics2022In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 119, no 43, article id e2210912119Article in journal (Refereed)
    Abstract [en]

    The alarming rise of multidrug-resistant Gram-positive bacteria has precipitated a healthcare crisis, necessitating the development of new antimicrobial therapies. Here we describe a new class of antibiotics based on a ring-fused 2-pyridone backbone, which are active against vancomycin-resistant enterococci (VRE), a serious threat as classified by the Centers for Disease Control and Prevention, and other multidrug-resistant Gram-positive bacteria. Ring-fused 2-pyridone antibiotics have bacteriostatic activity against actively dividing exponential phase enterococcal cells and bactericidal activity against nondividing stationary phase enterococcal cells. The molecular mechanism of drug-induced killing of stationary phase cells mimics aspects of fratricide observed in enterococcal biofilms, where both are mediated by the Atn autolysin and the GelE protease. In addition, combinations of sublethal concentrations of ring-fused 2-pyridones and standard-of-care antibiotics, such as vancomycin, were found to synergize to kill clinical strains of VRE. Furthermore, a broad range of antibiotic resistant Gram-positive pathogens, including those responsible for the increasing incidence of antibiotic resistant healthcare-associated infections, are susceptible to this new class of 2-pyridone antibiotics. Given the broad antibacterial activities of ring-fused 2-pyridone compounds against Gram-positive (GmP) bacteria we term these compounds GmPcides, which hold promise in combating the rising tide of antibiotic resistant Gram-positive pathogens.

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  • 4.
    Sarkar, Souvik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mayer Bridwell, Anne E.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Good, James A. D.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wang, Erin R.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    McKee, Samuel R.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Valenta, Joy
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Harrison, Gregory A.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Flentie, Kelly N.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Henry, Frederick L.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Wixe, Torbjörn
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Demirel, Peter
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vagolu, Siva K.
    Department of Microbiology, University of Oslo, Oslo, Norway.
    Chatagnon, Jonathan
    University Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Center for Infection and Immunity of Lille, Lille, France.
    Machelart, Arnaud
    University Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Center for Infection and Immunity of Lille, Lille, France.
    Brodin, Priscille
    University Lille, CNRS, INSERM, CHU Lille, Institut Pasteur de Lille, U1019-UMR 9017-CIIL-Center for Infection and Immunity of Lille, Lille, France.
    Tønjum, Tone
    Department of Microbiology, University of Oslo, Oslo, Norway; Oslo University Hospital, Oslo, Norway.
    Stallings, Christina L.
    Department of Molecular Microbiology, Center for Women’s Infectious Disease Research, Washington University School of Medicine, MO, St. Louis, United States.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Design, synthesis, and evaluation of novel Δ2-thiazolino 2-pyridone derivatives that potentiate isoniazid activity in an isoniazid-resistant mycobacterium tuberculosis mutant2023In: Journal of Medicinal Chemistry, ISSN 0022-2623, E-ISSN 1520-4804, Vol. 66, no 16, p. 11056-11077Article in journal (Refereed)
    Abstract [en]

    Mycobacterium tuberculosis (Mtb) drug resistance poses an alarming threat to global tuberculosis control. We previously reported that C10, a ring-fused thiazolo-2-pyridone, inhibits Mtb respiration, blocks biofilm formation, and restores the activity of the antibiotic isoniazid (INH) in INH-resistant Mtb isolates. This discovery revealed a new strategy to address INH resistance. Expanding upon this strategy, we identified C10 analogues with improved potency and drug-like properties. By exploring three heterocycle spacers (oxadiazole, 1,2,3-triazole, and isoxazole) on the ring-fused thiazolo-2-pyridone scaffold, we identified two novel isoxazoles, 17h and 17j. 17h and 17j inhibited Mtb respiration and biofilm formation more potently with a broader therapeutic window, were better potentiators of INH-mediated inhibition of an INH-resistant Mtb mutant, and more effectively inhibited intracellular Mtb replication than C10. The (−)17j enantiomer showed further enhanced activity compared to its enantiomer and the 17j racemic mixture. Our potent second-generation C10 analogues offer promise for therapeutic development against drug-resistant Mtb.

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  • 5.
    Sarkar, Souvik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edin, Simon
    Centre for Analysis and Synthesis, Lund University, Lund, Sweden.
    Wendt, Ola F.
    Centre for Analysis and Synthesis, Lund University, Lund, Sweden.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Synthesis of three-dimensional ring fused heterocycles by a selective [4 + 2] cycloaddition between bicyclic thiazolo 2-pyridones and arynes2024In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 89, no 1, p. 731-739Article in journal (Refereed)
    Abstract [en]

    A selective [4 + 2] cycloaddition reaction of thiazolo-2-pyridones with arynes has been demonstrated. The developed protocol allows rapid access to highly functionalized, structurally complex thiazolo-fused bridged isoquinolones in high yields, which are susceptible to further late-stage functionalization.

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  • 6.
    Tyagi, Mohit
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Adolfsson, Dan E.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ådén, Jörgen
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Jayaweera, Sanduni Wasana
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Gharibyan, Anna
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Bharate, Jaideep B.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kiss, Anita
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sarkar, Souvik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Olofsson, Anders
    Umeå University, Faculty of Medicine, Department of Medical Biochemistry and Biophysics.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Tandem Ring Opening/Intramolecular [2 + 2] Cycloaddition Reaction for the Synthesis of Cyclobutane Fused Thiazolino-2-Pyridones2021In: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 86, no 23, p. 16582-16592Article in journal (Refereed)
    Abstract [en]

    Reaction of thiazoline fused 2-pyridones with alkyl halides in the presence of cesium carbonate opens the thiazoline ring via S-alkylation and generates N-alkenyl functionalized 2-pyridones. In the reaction with propargyl bromide, the thiazoline ring opens and subsequently closes via a [2 + 2] cycloaddition between an in situ generated allene and the α,β-unsaturated methyl ester. This method enabled the synthesis of a variety of cyclobutane fused thiazolino-2-pyridones, of which a few analogues inhibit amyloid β1–40 fibril formation. Furthermore, other analogues were able to bind mature α-synuclein and amyloid β1−40 fibrils. Several thiazoline fused 2-pyridones with biological activity tolerate this transformation, which in addition provides an exocyclic alkene as a potential handle for tuning bioactivity.

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  • 7.
    Tükenmez, Hasan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Sarkar, Souvik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Anoosheh, Saber
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Kruchanova, Anastasiia
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Edström, Isabel
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Harrison, Gregory A.
    Department of Molecular Microbiology, Washington University School of Medicine, MO, St. Louis, United States.
    Stallings, Christina L.
    Department of Molecular Microbiology, Washington University School of Medicine, MO, St. Louis, United States.
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Larsson, Christer
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Mycobacterium tuberculosis Rv3160c is a TetR-like transcriptional repressor that regulates expression of the putative oxygenase Rv3161c2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 1523Article in journal (Refereed)
    Abstract [en]

    Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is a major health threat listed among the top 10 causes of death worldwide. Treatment of multidrug-resistant Mtb requires use of additional second-line drugs that prolong the treatment process and result in higher death rates. Our team previously identified a 2-pyridone molecule (C10) that blocks tolerance to the first-line drug isoniazid at C10 concentrations that do not inhibit bacterial growth. Here, we discovered that the genes rv3160c and rv3161c are highly induced by C10, which led us to investigate them as potential targets. We show that Rv3160c acts as a TetR-like transcriptional repressor binding to a palindromic sequence located in the rv3161c promoter. We also demonstrate that C10 interacts with Rv3160c, inhibiting its binding to DNA. We deleted the rv3161c gene, coding for a putative oxygenase, to investigate its role in drug and stress sensitivity as well as C10 activity. This Δrv3161c strain was more tolerant to isoniazid and lysozyme than wild type Mtb. However, this tolerance could still be blocked by C10, suggesting that C10 functions independently of Rv3161c to influence isoniazid and lysozyme sensitivity.

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  • 8.
    Tükenmez, Hasan
    et al.
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). QureTech Bio, Umeå, Sweden.
    Singh, Pardeep
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sarkar, Souvik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Çakır, Melike
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Oliveira, Ana H.
    Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    Lindgren, Cecilia
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Vaitkevicius, Karolis
    Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS).
    Bonde, Mari
    QureTech Bio, Umeå, Sweden.
    Sauer-Eriksson, A. Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Almqvist, Fredrik
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR).
    Johansson, Jörgen
    Umeå University, Faculty of Medicine, Molecular Infection Medicine Sweden (MIMS). Umeå University, Faculty of Medicine, Umeå Centre for Microbial Research (UCMR). Umeå University, Faculty of Medicine, Department of Molecular Biology (Faculty of Medicine).
    A highly substituted ring-fused 2-pyridone compound targeting PrfA and the efflux regulator BrtA in listeria monocytogenes2023In: mBio, ISSN 2161-2129, E-ISSN 2150-7511, Vol. 14, no 3, article id e0044923Article in journal (Refereed)
    Abstract [en]

    Listeria monocytogenes is a facultative Gram-positive bacterium that causes listeriosis, a severe foodborne disease. We previously discovered that ring-fused 2-pyridone compounds can decrease virulence factor expression in Listeria by binding and inactivating the PrfA virulence activator. In this study, we tested PS900, a highly substituted 2-pyridone that was recently discovered to be bactericidal to other Gram-positive pathogenic bacteria, such as Staphylococcus aureus and Enterococcus faecalis. We show that PS900 can interact with PrfA and reduce the expression of virulence factors. Unlike previous ring-fused 2-pyridones shown to inactivate PrfA, PS900 had an additional antibacterial activity and was found to potentiate sensitivity toward cholic acid. Two PS900-tolerant mutants able to grow in the presence of PS900 carried mutations in the brtA gene, encoding the BrtA repressor. In wild-type (WT) bacteria, cholic acid binds and inactivates BrtA, thereby alleviating the expression of the multidrug transporter MdrT. Interestingly, we found that PS900 also binds to BrtA and that this interaction causes BrtA to dissociate from its binding site in front of the mdrT gene. In addition, we observed that PS900 potentiated the effect of different osmolytes. We suggest that the increased potency of cholic acid and osmolytes to kill bacteria in the presence of PS900 is due to the ability of the latter to inhibit general efflux, through a yet-unknown mechanism. Our data indicate that thiazolino 2-pyridones constitute an attractive scaffold when designing new types of antibacterial agents.

    IMPORTANCE: Bacteria resistant to one or several antibiotics are a very large problem, threatening not only treatment of infections but also surgery and cancer treatments. Thus, new types of antibacterial drugs are desperately needed. In this work, we show that a new generation of substituted ring-fused 2-pyridones not only inhibit Listeria monocytogenes virulence gene expression, presumably by inactivating the PrfA virulence regulator, but also potentiate the bactericidal effects of cholic acid and different osmolytes. We identified a multidrug repressor as a second target of 2-pyridones. The repressor–2-pyridone interaction displaces the repressor from DNA, thus increasing the expression of a multidrug transporter. In addition, our data suggest that the new class of ring-fused 2-pyridones are efficient efflux inhibitors, possibly explaining why the simultaneous addition of 2-pyridones together with cholic acid or osmolytes is detrimental for the bacterium. This work proves conclusively that 2-pyridones constitute a promising scaffold to build on for future antibacterial drug design.

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