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Bacterial growth curve indicating various phases. Stationary phase cultures have higher populations of persister cells.  

Bacterial growth curve indicating various phases. Stationary phase cultures have higher populations of persister cells.  

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Article
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Bacterial biofilms are surface-attached communities of slow- or non-replicating bacterial cells that display high levels of tolerance toward conventional antibiotic therapies. It is important to know that our entire arsenal of conventional antibiotics originated from screens used to identify inhibitors of bacterial growth, so it should be little su...

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... Both MBDC and MBEC (minimal biofilm-eradication concentration) actually have the same nature. The latter is commonly used to characterize biofilm-eradication activity of antibacterials through MBC/MBEC ratios that for the biofilm-eradicating agents typically have values in the range of 1 to 3 (Garrison and Huigens, 2017). Considering the high levels of the MBC/ MBDC ratios observed here (about 2 to 3), DMNP can be viewed as a biofilm-eradicating agent ( Figure 7C). ...
... We compared the results of the MBC/MBDC measurements with those for the MBC/MBEC ratios for WT that were conducted with the MBEC Biofilm Inoculator (Innovotech, Canada) for DMNP and the conventional antibiotics (Table S3). Although DMNP exhibited lower MBC/MBEC value (1.25) for WT strain as compared with MBC/MBDC (2.25), it still falls into the category of biofilm-eradicating agents, unlike the conventional antibiotics we tested (Garrison and Huigens, 2017). ...
... We showed here that DMNP used in combination with either streptomycin or rifampicin significantly enhanced their killing effect on M. smegmatis cells by interfering with persister cell formation ( Figure S3). Furthermore, DMNP, unlike the conventional antibiotics, can be viewed as a biofilm-eradicating agent characterized by a favorable MBC/MBDC ratio (about 2-3) ( Figure 7C) or MBC/MBEC ratio of 1.25 (Table S3) (Garrison and Huigens, 2017). Therefore, antipersistent substances elaborated on the basis of DMNP could be used potentially in combination with conventional antibiotics to eradicate chronic infections, including tuberculosis. ...
Article
Bacterial persistence coupled with biofilm formation is directly associated with failure of antibiotic treatment of tuberculosis. We have now identified 4-(4,7-DiMethyl-1,2,3,4-tetrahydroNaphthalene-1-yl)Pentanoic acid (DMNP), a synthetic diterpene analogue, as a lead compound that was capable of suppressing persistence and eradicating biofilms in Mycobacterium smegmatis. By using two reciprocal experimental approaches – Δ rel Msm and Δ relZ gene knockout mutations versus rel Msm and relZ overexpression technique – we showed that both Rel Msm and RelZ (p)ppGpp synthetases are plausible candidates for serving as targets for DMNP. In vitro, DMNP inhibited (p)ppGpp-synthesizing activity of purified Rel Msm in a concentration-dependent manner. These findings, supplemented by molecular docking simulation, suggest that DMNP targets the structural sites shared by Rel Msm, RelZ, and presumably by a few others as yet unidentified (p)ppGpp producers, thereby inhibiting persister cell formation and eradicating biofilms. Therefore, DMNP may serve as a promising lead for development of antimycobacterial drugs.
... With the 17 million new cases of biofilm infections in addition to >500 000 deaths each year in the United States that result from these infections, there is a critical need to identify compounds that effectively eradicate biofilms through growthindependent mechanisms ( Figure 2). 10,41 The current need for new and effective antibiotic therapies has motivated several research groups to initiate drug discovery programs inspired by various antibiotic natural products, which may be known or recently discovered. The Lewis group has created a new technology to facilitate isolation of novel antibiotics from previously inaccessible sources, while the Myers lab has developed novel total synthesis platforms for the discovery of new antibiotics. ...
Article
Bacteria utilize multiple mechanisms that enable them to gain, or acquire, resistance to antibiotic therapies during the treatment of infections. In addition, bacteria form biofilms which are surface-attached communities of enriched populations of persister cells encased within a protective extracellular matrix of biomolecules, leading to chronic and recurring antibiotic-tolerant infections. Antibiotic resistance and tolerance are major global problems that require innovative therapeutic strategies to address the challenges associated with pathogenic bacteria. Historically, natural products have played a critical role in bringing new therapies to the clinic to treat life-threatening bacterial infections. This review will discuss antibiotic resistance and tolerance in addition to highlighting recent advances (chemistry, biology, chemical biology, therapeutic development) from various research programs involved in the discovery of new antibacterial agents inspired by a diverse series of natural product antibiotics.
... Synthetically tunable antibacterial agents that operate through unique modes of action to target antibiotic-resistant and tolerant bacteria are of importance to human health. [1][2][3][4] Pathogenic bacteria present 2 distinct clinical problems: (1) acquired antibiotic resistance and (2) innate antibiotic tolerance. Bacteria acquire resistance to conventional antibiotics during therapy using one or more well-defined mechanism(s), including point mutations in antibiotic targets, enzyme-mediated antibiotic inactivation/degradation, and changes in membrane chemistry to impede drug penetration. ...
... Surface-attached bacterial communities, known as "biofilms," contain enriched nonreplicating persister cell populations that demonstrate high levels of tolerance to all classes of antibiotics. 1,6 Nearly 80% of bacterial infections are biofilm associated, which are credited as the underlying cause of persistent and chronic infections. ...
... It is important to note that all conventional antibiotic classes were initially discovered as bacterial growth-inhibiting agents in various microbiologic experiments involving planktonic bacteria and not biofilm communities. 1 To effectively identify compounds that can eradicate biofilms, new agents that operate through bacterial growth-independent mechanisms are required. Innovative discovery approaches are necessary to meet this clinical need and our group looked to nature's chemical inventory for inspiration, which has been the source of many therapeutic agents. ...
Article
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Antibiotic-resistant bacteria and surface-attached bacterial biofilms play a significant role in human disease. Conventional antibiotics target actively replicating free-floating, planktonic cells. Unfortunately, biofilm communities are endowed with nonreplicating persister cells that are tolerant to antibiotics. Innovative approaches are necessary to identify new molecules able to eradicate resistant and tolerant bacterial cells. Our group has discovered that select halogenated quinolines (HQs) can eradicate drug-resistant, gram-positive bacterial pathogens and their corresponding biofilms. Interestingly, the HQ scaffold is synthetically tunable and we have discovered unique antibacterial profiles through extensive analogue synthesis and microbiologic studies. We recently reported the synthesis of 14 new HQs to investigate the impact of ClogP values on antibacterial and biofilm eradication activities. We conducted diverse synthetic modifications at the 2-position of the HQ scaffold in an attempt to enhance water solubility and found new compounds that display enhanced activities against Staphylococcus epidermidis. In particular, HQ 2 (ClogP = 3.44) demonstrated more potent antibacterial activities against methicillin-resistant S epidermidis (MRSE) 35984 planktonic cells (minimum inhibitory concentration = 0.59 µM) compared with methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus isolates while demonstrating potent MRSE biofilm eradication activities (minimum biofilm eradication concentration = 2.35 µM). We believe that HQ could play a critical role in the development of next-generation antibacterial therapeutics.
... We have also demonstrated that HQs show bacterial targeting with minimal cytotoxicity against HeLa cells in addition to essentially no hemolytic activity when tested against red blood cells at high concentrations [17,18]. The collective activity profiles regarding HQ small molecules warrants further exploration and development as there are currently no biofilm-eradicating agents approved for clinical use [1]. ...
... Yield: 90% yield; 144 mg of 6 was isolated as a yellow solid. 1 ...
... The crude product was then purified via flash column chromatography using 100% dichloromethane to elute 9 as a white solid (98 mg, 69%). 1 ...
Article
Antibiotic-resistant bacteria and surface-attached biofilms continue to play a significant role in human health and disease. Innovative strategies are needed to identify new therapeutic leads to tackle infections of drug-resistant and tolerant bacteria. We synthesized a focused library of 14 new halogenated quinolines to investigate the impact of ClogP values on antibacterial and biofilm-eradication activities. During these investigations, we found select polar appendages at the 2-position of the HQ scaffold were more well-tolerated than others. We were delighted to see multiple compounds display enhanced activities against the major human pathogen S. epidermidis. In particular, HQ 2 (ClogP = 3.44) demonstrated enhanced activities against MRSE 35984 planktonic cells (MIC = 0.59 μM) compared to MRSA and VRE strains in addition to potent MRSE biofilm eradication activities (MBEC = 2.35 μM). Several of the halogenated quinolines identified here reported low cytotoxicity against HeLa cells with minimal hemolytic activity against red blood cells. We believe that halogenated quinoline small molecules could play an important role in the development of next-generation antibacterial therapeutics capable of targeting and eradicating biofilm-associated infections.
... Innovative discovery strategies must be implemented to identify compounds that effectively eradicate persistent, antibiotic-tolerant biofilms that operate via unconventional, growth-independent mechanisms. Considering the history of antibiotic discovery, which relies heavily on microbial warfare agents (i.e., penicillin, streptomycin, vancomycin), it stands to reason that alternative microbial warfare agents exist that include biofilm-eradicating agents we have yet to harness for therapeutic purposes 18 . Clinically effective biofilm-eradicating agents would significantly change bacterial treatments and enable the control of persistent biofilm infections. ...
Article
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Unlike individual, free-floating planktonic bacteria, biofilms are surface-attached communities of slow- or non-replicating bacteria encased within a protective extracellular polymeric matrix enabling persistent bacterial populations to tolerate high concentrations of antimicrobials. Our current antibacterial arsenal is composed of growth-inhibiting agents that target rapidly-dividing planktonic bacteria but not metabolically dormant biofilm cells. We report the first modular synthesis of a library of 20 halogenated phenazines (HP), utilizing the Wohl-Aue reaction, that targets both planktonic and biofilm cells. New HPs, including 6-substituted analogues, demonstrate potent antibacterial activities against MRSA, MRSE and VRE (MIC = 0.003–0.78 µM). HPs bind metal(II) cations and demonstrate interesting activity profiles when co-treated in a panel of metal(II) cations in MIC assays. HP 1 inhibited RNA and protein biosynthesis while not inhibiting DNA biosynthesis using ³H-radiolabeled precursors in macromolecular synthesis inhibition assays against MRSA. New HPs reported here demonstrate potent eradication activities (MBEC = 0.59–9.38 µM) against MRSA, MRSE and VRE biofilms while showing minimal red blood cell lysis or cytotoxicity against HeLa cells. PEG-carbonate HPs 24 and 25 were found to have potent antibacterial activities with significantly improved water solubility. HP small molecules could have a dramatic impact on persistent, biofilm-associated bacterial infection treatments.
... [6][7][8][9][10] High levels of antibiotic tolerance are prevalent in bacterial biofilms, or surface-attached bacterial communities encased in a slimy matrix of biological molecules that enables them to thrive in hostile environments, leading to chronic and recurring bacterial infections in humans. [11][12][13][14][15][16][17] In addition to bacteria, pathogenic fungi demonstrate resistance [18][19][20] and tolerance 21,22 to antifungal agents due to acquired resistance and fungal biofilm formation, respectively. ...
... Each of the antibiotic/antibacterial classes that are used to treat bacterial infections was initially discovered as growth inhibitors that target rapidly-dividing planktonic bacteria. 16 As a consequence, non-replicative bacteria within biofilms are tolerant to such agents, thus new small molecules operate through alternative mechanisms to eradicate tolerant bacteria have uses in several sectors in our society, including: medicine/biomedical applications (e.g., persistent biofilm infections, 13,17 hospital disinfectants 27,28 ), industry (e.g., oil/gas pipeline corrosion, 29,30 biofouling on ship hulls 31 ), and agriculture (e.g., crop disease 32,33 ). ...
... A small series of analogues (8)(9)(10)(11)21) were alkylation products that did not contain a benzyl group to determine if this moiety was critical/necessary for NH125's antimicrobial activities. Various benzylation reactions were carried out to probe the benzyl moiety on NH125 with various functional groups and substitution patterns (12)(13)(14)(15)(16)(17)(18)(19)(20), including two dimeric benzyl analogues (28,29). Truncated NH125 analogues 22 and 23 were also synthesized to determine the requirement for both imidazole nitrogen atoms to be substituted with carbon-containing groups. ...
Article
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During microbial infection, antimicrobial peptides are utilized by the immune response to rapidly eradicate microbial pathogens through the destruction of cellular membranes. Inspired by antimicrobial peptides, quaternary ammonium cationic (QAC) compounds have emerged as agents capable of destroying bacterial membranes leading to rapid bacterial death, including the eradication of persistent, surface-attached bacterial biofilms. NH125, an imidazolium cation with a sixteen membered fatty tail, was recently reported to eradicate persister cells and was our starting point for the development of novel antimicrobial agents. Here, we describe the design, chemical synthesis and biological investigations of a collection of 30 diverse NH125 analogues which provided critical insights into structural features that are important for antimicrobial activities in this class. From these studies, multiple NH125 analogues were identified to possess potent antibacterial and antifungal activities, eradicate both bacterial and fungal biofilms and rapidly eradicate MRSA persister cells in stationary phase. NH125 analogues also demonstrated more rapid persister cell killing activities against MRSA when tested alongside a panel of diverse membrane-active agents, including BAC-16 and daptomycin. NH125 analogues could have a significant impact on persister- and biofilm-related problems in numerous biomedical applications.
Thesis
Bien que la thérapie photodynamique a été découverte il y a plus d’un siècle par sa capacité à inactiver les microorganismes, elle a été développée principalement comme traitement thérapeutique anticancéreux. Récemment, avec le nombre croissant d'infections causées par des bactéries multirésistantes, la chimiothérapie photodynamique antimicrobienne (PACT) est considérée comme une approche antimicrobienne alternative prometteuse. La PACT est une stratégie thérapeutique non invasive, et a une action rapide. De plus, la PACT ne semble pas induire la mise en place de mécanismes de résistance par les bactéries, ce qui en fait une alternative attrayante, par exemple, aux traitements conventionnels des infections des plaies. Les photosensibilisateurs les plus utilisés dans le PACT sont les porphyrines et leurs dérivés. Cependant, ces composés souffrent d’une faible solubilité dans l'eau, d’auto-quenching et d’un manque de sélectivité contre les cellules bactériennes. Afin de pallier certains problèmes liés à l’utilisation des porphyrines en tant que photosensibilisateurs dans la PACT, nous nous sommes intéressés, au cours de ce travail, à deux stratégies pour l’optimisation de cette thérapie. La première consiste à coupler une porphyrine à deux dérivés de maltodextrines (maltohexaose ou maltotriose) utilisés récemment comme agent de ciblage bactérien pour l'imagerie médicale , afin d’améliorer la sélectivité de la porphyrine vis-à-vis les cellules bactériennes. L’évaluation biologique de ces conjugués a montré que l’association des porphyrines avec les maltooligosacharide augmente leur efficacité antibactérien Staphylococcus aureus et Staphylococcus epidermidis. La deuxième stratégie vise à incorporer des porphyrines dans des hydrogels à base de xylane. Pour cela, trois voies ont été explorées : dans une première approche, l’hydrogel a été synthétisé d’abord par réticulation de xylane avant de le chargé par une porphyrine cationique. Dans la deuxième, les porphyrines sont fixées d’abord par liaisons covalentes sur le xylane, puis les hydrogels ont été obtenus à partir de ces xylanes fonctionnalisés par un agent de réticulation. Dans la troisième méthode, l’hydrogel est obtenu directement par une réticulation directe du xylane par les porphyrines. Tous les hydrogels obtenus ont montré une bonne intégrité mécanique et un taux de gonflement élevé et une forte activité photoantibactérienne vis-à-vis des bactéries Gram positif et Gram négatif.
Thesis
Après l’âge d’or de la découverte des antibiotiques, les infections bactériennes représentent toujours un challenge considérable pour la santé publique mondiale. Le mode de croissance en biofilms est le principal responsable des infections chroniques pour lesquelles les thérapies antibiotiques sont en échec clinique, pointant la nécessité d’élaborer de nouvelles stratégies thérapeutiques. L’objectif de cette thèse a porté sur le développement d’une thérapie combinatoire à base d’agents anti-biofilms et de particules biodégradables d’acide poly-lactique pour la délivrance d’antibiotiques au cœur des biofilms bactériens. Une stratégie de formulation d’antibiotiques a été développée, aboutissant à des particules stables et fortement chargées en rifampicine. La charge de surface des particules a été inversée vers des valeurs positives par adsorption d’un peptide cationique, la poly-lysine. L’intérêt d’une telle formulation a été évalué in vitro sur des biofilms de Staphylococcus aureus. Capables d’interagir via des liaisons électrostatiques avec les biofilms et les bactéries, les particules cationiques sont retenues en plus grande quantité dans les biofilms que les particules anioniques qui peuvent être éliminées par lavage. Les particules permettant une délivrance progressive de l’antibiotique, l’inversion de leur charge de surface qui renforce ces interactions permet de réduire les quantités d’antibiotique nécessaires pour maintenir une efficacité anti-biofilm. La combinaison de ce traitement avec la DNase, une enzyme capable de dégrader la matrice de biofilms, permet de potentialiser la dégradation des biofilms sans toutefois augmenter l’activité bactéricide de l’antibiotique. Des évaluations in vivo de l’efficacité de cette stratégie thérapeutique permettraient de confirmer son intérêt pour le traitement des biofilms bactériens.
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https://singipedia.singidunum.ac.rs/izdanje/43755-osnove-tehnologije-zivotnih-namirnica