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Objectives: We evaluated the efficacies of human-simulated regimens (HSRs) of two clinically utilized sulbactam regimens: 1 g q6h 0.5 h infusion (maximum FDA-approved dosage) and 3 g q8h 4 h infusion (high-dose, prolonged-infusion regimen), against Acinetobacter baumannii in a translational murine model., Methods: Thirty-two clinical A. baumannii isolates were investigated, of which 16 were sulbactam resistant (MIC ≥ 16 mg/L), 6 were sulbactam intermediate (MIC = 8 mg/L) and 10 were sulbactam susceptible (MIC ≤ 4 mg/L). Efficacies of the two sulbactam HSRs were assessed in the neutropenic murine pneumonia model. Changes in log10 cfu/lungs at 24 h compared with 0 h controls were measured, and efficacy was defined as achieving 1 log kill relative to baseline. WGS of the isolates and bioinformatics analysis were performed to explore potential associations between the genomic backgrounds and the in vivo responses., Results: Eleven isolates harboured blaOXA-23, of which 10 were sulbactam resistant, 1 was sulbactam intermediate while none was sulbactam susceptible. Both sulbactam HSRs achieved >1 log kill against sulbactam-susceptible isolates. Against sulbactam-intermediate and sulbactam-resistant isolates, lack of efficacy correlated with the presence of the blaOXA-23 gene; sulbactam 1 g HSR and 3 g HSR did not show efficacy against 11/11 and 9/11 blaOXA-23-positive isolates, respectively, while efficacy was observed against all 11 blaOXA-23-negative sulbactam-intermediate and sulbactam-resistant isolates (i.e. harbouring other resistance genes)., Conclusions: A sulbactam high-dose prolonged-infusion regimen provides comparable activity to the standard dose against isolates currently considered sulbactam susceptible. However, the activity against isolates with intermediate and resistant susceptibility could be predicted by the detection of blaOXA-23. Enhancing detection capabilities of common diagnostic modalities to include OXA-23 can improve patient outcome., (© The Author(s) 2024. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Background: Sulbactam dosing for Acinetobacter baumannii infections has not been standardized due to limited available pharmacokinetics/pharmacodynamics (PK/PD) data. Herein, we report a comprehensive PK/PD analysis of ampicillin-sulbactam against A. baumannii pneumonia., Methods: Twenty-one A. baumannii clinical isolates were tested in the neutropenic murine pneumonia model. For dose-ranging studies, groups of mice were administered escalating doses of ampicillin-sulbactam. Changes in log10cfu/lungs relative to 0 h were assessed. Dose-fractionation studies were performed. Estimates of the percentage of of time during which the unbound plasma sulbactam concentrations exceeded the MIC (%fT > MIC) required for different efficacy endpoints were calculated. The probabilities of target attainment (PTA) for the 1-log kill plasma targets were estimated following clinically utilized sulbactam regimens., Results: Dose-fractionation studies demonstrated time-dependent kill. Isolates resistant to both sulbactam and meropenem required three times the exposures to achieve 1-log kill; median [IQR] %fT > MIC of 60.37% [51.6-66.8] compared with other phenotypes (21.17 [16.0-32.9] %fT > MIC). Sulbactam standard dose (1 g q6h, 0.5 h infusion) provided >90% PTA up to MIC of 4 mg/L. Sulbactam 3 g q8h, 4 h inf provided greater PTA for isolates with sulbactam-intermediate susceptibility (8 mg/L, 100% versus 86% following the standard dose). Despite the higher exposure following 3 g q8h, 4 h inf, PTA was ≤57% among sulbactam-resistant/meropenem-resistant isolates., Conclusion: Sulbactam standard dose is a valuable regimen across sulbactam-susceptible isolates while the high-dose extended-infusion provides additional benefit against sulbactam-intermediate isolates. Given that most of the sulbactam-resistant A. baumannii isolates are meropenem-resistant, high-dose prolonged-infusion regimens are not expected to be effective as monotherapy against infections due to these isolates., (© The Author(s) 2024. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Purpose: Sulbactam/durlobactam is a combination antibiotic designed to target Acinetobacter baumannii, including carbapenem-resistant and multidrug-resistant strains. The objective of this study was to determine the physical compatibility of sulbactam/durlobactam solution during simulated Y-site administration with 95 intravenous (IV) drugs., Methods: Vials of sulbactam/durlobactam solution were diluted in 0.9% sodium chloride injection to a volume of 100 mL (the final concentration of both drugs was 15 mg/mL). All other IV drugs were reconstituted according to the manufacturer's recommendations and diluted with 0.9% sodium chloride injection to the upper range of concentrations used clinically or tested undiluted as intended for administration. Y-site conditions were simulated by mixing 5 mL of sulbactam/durlobactam with 5 mL of the tested drug solutions in a 1:1 ratio. Solutions were inspected for physical characteristics (clarity, color, and Tyndall effect), turbidity, and pH changes before admixture, immediately post admixture, and over 4 hours. Incompatibility was defined as any observed precipitation, significant color change, positive Tyndall test, or turbidity change of ≥0.5 nephelometric turbidity unit during the observation period., Results: Sulbactam/durlobactam was physically compatible with 38 out of 42 antimicrobials tested (90.5%) and compatible overall with 86 of 95 drugs tested (90.5%). Incompatibility was observed with albumin, amiodarone hydrochloride, ceftaroline fosamil, ciprofloxacin, daptomycin, levofloxacin, phenytoin sodium, vecuronium, and propofol., Conclusion: The Y-site compatibility of sulbactam/durlobactam with 95 IV drugs was described. These compatibility data will assist pharmacists and nurses to safely coordinate administration of IV medications with sulbactam/durlobactam., (© American Society of Health-System Pharmacists 2023. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives: We evaluated the in vivo efficacy of human-simulated regimens (HSRs) of cefiderocol, ceftazidime/avibactam, meropenem and ceftazidime/avibactam/meropenem combination against Guiana-extended spectrum (GES)-producing Pseudomonas aeruginosa isolates., Methods: Eighteen P. aeruginosa isolates producing GES-1 (n = 5), GES-5 (n = 5) or miscellaneous GESs (combinations of GES-19, GES-20 and/or GES-26; n = 8) were evaluated. In vitro MIC testing was determined using broth microdilution. In a validated murine thigh infection model, HSRs of cefiderocol 2 g q8h as a 3 h IV infusion, ceftazidime/avibactam 2.5 g q8h as a 2 h IV infusion, meropenem 2 g q8h as a 3 h IV infusion or ceftazidime/avibactam/meropenem were administered. Change in bacterial burden relative to baseline and the proportion of isolates in each genotypic group meeting 1-log10 kill endpoint were assessed., Results: Modal MICs (mg/L) ranged from 0.125 to 1 for cefiderocol, 4 to >64 for ceftazidime/avibactam and 2 to >64 for meropenem. Cefiderocol produced >1-log10 of kill against all 18 tested isolates. Meropenem was active against all GES-1 isolates whereas activity against GES-5 and miscellaneous GESs was lacking, consistent with the MICs. Ceftazidime/avibactam was active against all GES-1 and GES-5 isolates and retained activity against 62.5% of miscellaneous GESs including isolates with elevated MICs. For isolates where ceftazidime/avibactam failed, the addition of meropenem restored the in vivo efficacy., Conclusions: As monotherapy, cefiderocol was active in vivo against all tested isolates. The activities of meropenem or ceftazidime/avibactam alone were variable; however, a combination of both was active against all isolates. Cefiderocol and ceftazidime/avibactam/meropenem could be valuable therapeutic options for GES-producing P. aeruginosa infections. Clinical confirmatory data are warranted., (© The Author(s) 2023. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy.)

Objective: Tebipenem pivoxil hydrobromide is a novel oral carbapenem prodrug of tebipenem, the active moiety. We assessed tebipenem steady-state pharmacokinetics in the skin and soft tissue in healthy subjects and infected patients with diabetes using in vivo microdialysis., Methods: Six healthy subjects and six patients with an ongoing diabetic foot infection (DFI) received tebipenem pivoxil hydrobromide 600 mg orally every 8 h for three doses. A microdialysis probe was inserted in the thigh of healthy subjects or by the wound margin in patients. Plasma and dialysate samples were obtained immediately prior to the third dose and sampled over 8 h., Results: Tebipenem plasma protein binding (mean ± SD) was 50.2% ± 2.4% in healthy subjects and 53.5% ± 5.6% in infected patients. Mean ± SD tebipenem pharmacokinetic parameters in plasma for healthy subjects and infected patients were: maximum free concentration (fCmax), 3.74 ± 2.35 and 3.40 ± 2.86 mg/L, respectively; half-life, 0.88 ± 0.11 and 2.02 ± 1.32 h; fAUC0-8, 5.61 ± 1.64 and 10.01 ± 4.81 mg·h/L. Tebipenem tissue AUC0-8 was 5.99 ± 3.07 and 8.60 ± 2.88 mg·h/L for healthy subjects and patients, respectively. The interstitial concentration-time profile largely mirrored the free plasma profile within both populations, resulting in a penetration ratio of 107% in healthy subjects and 90% in infected patients., Conclusions: Tebipenem demonstrated excellent distribution into skin and soft tissue of healthy subjects and patients with DFI following oral administration of 600 mg of tebipenem pivoxil hydrobromide., (© The Author(s) 2022. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background: To date, no real-world data are available to describe cefiderocol use in carbapenem-resistant Acinetobacter baumannii (CRAB) meningitis. Furthermore, cefiderocol pharmacokinetic (PK) data to support CNS penetration in human subjects are limited. These gaps pose a significant concern for clinicians who are faced with treating such infections when considering cefiderocol use., Objectives: To describe cefiderocol CSF and plasma PK and pharmacodynamic (PD) data from two different dosing regimens [2 g IV q6h (regimen 1) and 2 g IV q8h (regimen 2)] during treatment of CRAB meningitis., Patients and Methods: A 61-year-old woman with CRAB meningitis was treated with cefiderocol and intraventricular gentamicin. Steady-state plasma and CSF cefiderocol concentrations were evaluated on Day 19 (regimen 1) and Day 24 (regimen 2) during the cefiderocol treatment course., Results: CSF AUC was 146.49 and 118.28 mg·h/L, as determined by the linear-log trapezoidal method for regimens 1 and 2, respectively. Penetration into CSF estimated as the AUCCSF/AUCfree plasma ratio was 68% and 60% for regimens 1 and 2, respectively. Estimated free plasma and CSF concentrations exceeded the MIC of the isolate for 100% of the dosing interval. Microbiological and clinical cure were achieved, and no cefiderocol-associated adverse effects were observed., Conclusions: Cefiderocol, when given as 2 g q8h and 2 g q6h, attained CSF concentrations that exceeded the organism-specific MIC and the CLSI susceptible breakpoint (≤4 mg/L) for 100% of the dosing interval., (© The Author(s) 2022. Published by Oxford University Press on behalf of British Society for Antimicrobial Chemotherapy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Bacterial biofilms are surface-attached communities of slow- or non-replicating cells embedded within a protective matrix of biomolecules. Unlike free-floating planktonic bacteria, biofilms are innately tolerant to conventional antibiotics and are prevalent in recurring and chronic infections. Nitroxoline, a broad-spectrum biofilm-eradicating agent, was used to probe biofilm viability. Transcript profiling (RNA-seq) showed that 452 of 2594 genes (17.4%) in methicillin-resistant Staphylococcus aureus (MRSA) biofilms were differentially expressed after a 2 h treatment of nitroxoline. WoPPER analysis and time-course validation (RT-qPCR) revealed that gene clusters involved in iron acquisition ( sbn , isd , MW2101, MW0695, fhu , and feo ) were rapidly up-regulated following nitroxoline treatment, which is indicative of iron starvation in MRSA biofilms. In addition, genes related to oligopeptide transporters and riboflavin biosynthesis were found to be up-regulated, while genes related to carotenoid biosynthesis and nitrate assimilation were down-regulated. RT-qPCR experiments revealed that iron uptake transcripts were also up-regulated in established Staphylococcus epidermidis and Acinetobacter baumannii biofilms following nitroxoline treatment. Overall, we show RNA-seq to be an ideal platform to define cellular pathways critical for biofilm survival, in addition to demonstrating the need these bacterial communities have for iron.

Pathogenic bacteria demonstrate incredible abilities to evade conventional antibiotics through the development of resistance and formation of dormant, surface-attached biofilms. Therefore, agents that target and eradicate planktonic and biofilm bacteria are of significant interest. We explored a new series of halogenated phenazines (HP) through the use of N -aryl-2-nitrosoaniline synthetic intermediates that enabled functionalization of the 3-position of this scaffold. Several HPs demonstrated potent antibacterial and biofilm-killing activities ( e.g. , HP 29 , against methicillin-resistant Staphylococcus aureus : MIC = 0.075 μM; MBEC = 2.35 μM), and transcriptional analysis revealed that HPs 3 , 28 , and 29 induce rapid iron starvation in MRSA biofilms. Several HPs demonstrated excellent activities against Mycobacterium tuberculosis (HP 34 , MIC = 0.80 μM against CDC1551). This work established new SAR insights, and HP 29 demonstrated efficacy in dorsal wound infection models in mice. Encouraged by these findings, we believe that HPs could lead to significant advances in the treatment of challenging infections.

Bacterial biofilms are surface-attached communities of slow-growing and non-replicating persister cells that demonstrate high levels of antibiotic tolerance. Biofilms occur in nearly 80 % of infections and present unique challenges to our current arsenal of antibiotic therapies, all of which were initially discovered for their abilities to target rapidly dividing, free-floating planktonic bacteria. Bacterial biofilms are credited as the underlying cause of chronic and recurring bacterial infections. Innovative approaches are required to identify new small molecules that operate through bacterial growth-independent mechanisms to effectively eradicate biofilms. One source of inspiration comes from within the lungs of young cystic fibrosis (CF) patients, who often endure persistent Staphylococcus aureus infections. As these CF patients age, Pseudomonas aeruginosa co-infects the lungs and utilizes phenazine antibiotics to eradicate the established S. aureus infection. Our group has taken a special interest in this microbial competition strategy and we are investigating the potential of phenazine antibiotic-inspired compounds and synthetic analogues thereof to eradicate persistent bacterial biofilms. To discover new biofilm-eradicating agents, we have established an interdisciplinary research program involving synthetic medicinal chemistry, microbiology and molecular biology. From these efforts, we have identified a series of halogenated phenazines (HPs) that potently eradicate bacterial biofilms, and future work aims to translate these preliminary findings into ground-breaking clinical advances for the treatment of persistent biofilm infections., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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 containing 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 Perspective provides an overview of antibiotic resistance and tolerance and highlights recent advances (chemistry, biology, drug discovery, and development) from various research programs involved in the discovery of new antibacterial agents inspired by a diverse series of natural product antibiotics.

While a number of disinfection techniques are employed in healthcare units, the eradication of drug-resistant microorganisms remains a challenge. We recently reported N -arylated NH125 analogue 1 , which demonstrated potent biofilm eradication and antibacterial activities against a panel of drug-resistant pathogens. The broad-spectrum activities observed for 1 along with its rapid eradication of MRSA persister cells suggested that this agent, and related analogues, can serve as disinfectants for antibiotic resistant pathogens in healthcare settings. Here, we report the rapid bactericidal activities of 1 against a panel of exponentially-growing, drug-resistant pathogens. Against MRSA, MRSE, VRE and MDR A. baumannii , 1 eradicated bacterial cells after five minutes when tested at 50 μM (3- to 6-log reduction of CFU per mL). We highlighted the rapid killing activities by demonstrating that 1 eradicates 99.99% of viable MRSA 1707 cells in one minute (50 μM, 4-log reduction of CFU per mL). In addition, 1 rapidly eradicated fungal pathogen C. neoformans in kill kinetic experiments. A solution of 1 demonstrated similar shelf stability to known disinfectant BAC-16 when tested up to 111 days after being stored. Collectively, our data highlights the potential of 1 to be used as a disinfecting agent to prevent healthcare-associated, drug-resistant infections.

Bacterial biofilms are surface-attached communities of non-replicating bacteria innately tolerant to antibiotics. Biofilms display differential gene expression profiles and physiologies as compared to their planktonic counterparts; however, their biology remains largely unknown. In this study, we used a halogenated phenazine (HP) biofilm eradicator in transcript profiling experiments (RNA-seq) to define cellular targets and pathways critical to biofilm viability. WoPPER analysis with time-course validation (RT-qPCR) revealed that HP-14 induces rapid iron starvation in MRSA biofilms, as evident by the activation of iron-acquisition gene clusters in 1 hour. Serine proteases and oligopeptide transporters were also found to be up-regulated, whereas glycolysis, arginine deiminase, and urease gene clusters were down-regulated. KEGG analysis revealed that HP-14 impacts metabolic and ABC transporter functional pathways. These findings suggest that MRSA biofilm viability relies on iron homeostasis., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., (Copyright © 2018 Elsevier Masson SAS. All rights reserved.)

Bacterial biofilms are surface-attached communities comprised of nonreplicating persister cells housed within a protective extracellular matrix. Biofilms display tolerance toward conventional antibiotics, occur in ∼80% of infections, and lead to >500000 deaths annually. We recently identified halogenated phenazine (HP) analogues which demonstrate biofilm-eradicating activities against priority pathogens; however, the synthesis of phenazines presents limitations. Herein, we report a refined HP synthesis which expedited the identification of improved biofilm-eradicating agents. 1-Methoxyphenazine scaffolds were generated through a Buchwald-Hartwig cross-coupling (70% average yield) and subsequent reductive cyclization (68% average yield), expediting the discovery of potent biofilm-eradicating HPs (e.g., 61: MRSA BAA-1707 MBEC = 4.69 μM). We also developed bacterial-selective prodrugs (reductively activated quinone-alkyloxycarbonyloxymethyl moiety) to afford HP 87, which demonstrated excellent antibacterial and biofilm eradication activities against MRSA BAA-1707 (MIC = 0.15 μM, MBEC = 12.5 μM). Furthermore, active HPs herein exhibit negligible cytotoxic or hemolytic effects, highlighting their potential to target biofilms.

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.

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 3 H-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.

Bacterial biofilms housing dormant persister cells are innately tolerant to antibiotics and disinfectants, yet several membrane-active agents are known to eradicate tolerant bacterial cells. NH125, a membrane-active persister killer and starting point for development, led to the identification of two N-arylated analogues (1 and 2) that displayed improved biofilm eradication potencies compared to the parent compound and rapid persister-cell-killing activities in stationary cultures of methicillin-resistant Staphylococcus aureus (MRSA). We found 1 and 2 to be superior to other membrane-active agents in biofilm eradication assays, with 1 demonstrating minimum biofilm eradication concentrations (MBEC) of 23.5, 11.7, and 2.35 μm against MRSA, methicillin-resistant Staphylococcus epidermidis (MRSE), and vancomycin-resistant Enterococcus faecium (VRE) biofilms, respectively. We tested our panel of membrane-active agents against MRSA stationary cultures and found 1 to rapidly eradicate MRSA stationary cells by 4 log units (99.99 %) in 30 min. The potent biofilm eradication and rapid persister-cell-killing activities exhibited by N-arylated NH125 analogues could have significant impact in addressing biofilm-associated problems., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Bacterial biofilms are surface-attached communities of slow-growing or non-replicating bacteria tolerant to conventional antibiotic therapies. Although biofilms are known to occur in ca. 80% of all bacterial infections, no therapeutic agent has been developed to eradicate bacteria housed within biofilms. We have discovered that nitroxoline, an antibacterial agent used to treat urinary tract infections, displays broad-spectrum biofilm-eradicating activities against major human pathogens, including drug-resistant Staphylococcus aureus and Acinetobacter baumannii strains. In this study, the effectiveness of nitroxoline to eradicate biofilms was determined using an in vitro [minimum biofilm eradication concentration (MBEC) = 46.9 µM against A. baumannii] and ex vivo porcine skin model (2-3 log reduction in viable biofilm cells). Nitroxoline was also found to eradicate methicillin-resistant S. aureus (MRSA) persister cells in non-biofilm (stationary) cultures, whereas vancomycin and daptomycin were found to be inactive. These findings could lead to effective, nitroxoline-based therapies for biofilm-associated infections., (Copyright © 2016 Elsevier B.V. and International Society of Chemotherapy. All rights reserved.)

Herein, we disclose the development of a catalyst- and protecting-group-free microwave-enhanced Friedländer synthesis which permits the single-step, convergent assembly of diverse 8-hydroxyquinolines with greatly improved reaction yields over traditional oil bath heating (increased from 34% to 72%). This rapid synthesis permitted the discovery of novel biofilm-eradicating halogenated quinolines (MBECs = 1.0-23.5 μM) active against MRSA, MRSE, and VRE. These small molecules exhibit activity through mechanisms independent of membrane lysis, further demonstrating their potential as a clinically useful treatment option against persistent biofilm-associated infections.

Agents capable of eradicating bacterial biofilms are of great importance to human health as biofilm-associated infections are tolerant to our current antibiotic therapies. We have recently discovered that halogenated quinoline (HQ) small molecules are: 1) capable of eradicating methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE) and vancomycin-resistant Enterococcus faecium (VRE) biofilms, and 2) synthetic tuning of the 2-position of the HQ scaffold has a significant impact on antibacterial and antibiofilm activities. Here, we report the chemical synthesis and biological evaluation of 39 HQ analogues that have a high degree of structural diversity at the 2-position. We identified diverse analogues that are alkylated and aminated at the 2-position of the HQ scaffold and demonstrate potent antibacterial (MIC≤0.39 μm) and biofilm eradication (MBEC 1.0-93.8 μm) activities against drug-resistant Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecium strains while demonstrating <5 % haemolysis activity against human red blood cells (RBCs) at 200 μm. In addition, these HQs demonstrated low cytotoxicity against HeLa cells. Halogenated quinolines are a promising class of antibiofilm agents against Gram-positive pathogens that could lead to useful treatments against persistent bacterial infections., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Persistent bacteria, including persister cells within surface-attached biofilms and slow-growing pathogens lead to chronic infections that are tolerant to antibiotics. Here, we describe the structure-activity relationships of a series of halogenated phenazines (HP) inspired by 2-bromo-1-hydroxyphenazine 1. Using multiple synthetic pathways, we probed diverse substitutions of the HP scaffold in the 2-, 4-, 7-, and 8-positions, providing critical information regarding their antibacterial and bacterial eradication profiles. Halogenated phenazine 14 proved to be the most potent biofilm-eradicating agent (≥99.9% persister cell killing) against MRSA (MBEC < 10 μM), MRSE (MBEC = 2.35 μM), and VRE (MBEC = 0.20 μM) biofilms while 11 and 12 demonstrated excellent antibacterial activity against M. tuberculosis (MIC = 3.13 μM). Unlike antimicrobial peptide mimics that eradicate biofilms through the general lysing of membranes, HPs do not lyse red blood cells. HPs are promising agents that effectively target persistent bacteria while demonstrating negligible toxicity against mammalian cells.

Conventional antibiotics are ineffective against non-replicating bacteria (for example, bacteria within biofilms). We report a series of halogenated phenazines (HP), inspired by marine antibiotic 1, that targets persistent bacteria. HP 14 demonstrated the most potent biofilm eradication activities to date against MRSA, MRSE, and VRE biofilms (MBEC = 0.2-12.5 μM), as well as the effective killing of MRSA persister cells in non-biofilm cultures. Frontline MRSA treatments, vancomycin and daptomycin, were unable to eradicate MRSA biofilms or non-biofilm persisters alongside 14. HP 13 displayed potent antibacterial activity against slow-growing M. tuberculosis (MIC = 3.13 μM), the leading cause of death by bacterial infection around the world. HP analogues effectively target persistent bacteria through a mechanism that is non-toxic to mammalian cells and could have a significant impact on treatments for chronic bacterial infections., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Small molecules capable of eradicating non-replicating bacterial biofilms are of great importance to human health as conventional antibiotics are ineffective against these surface-attached bacterial communities. Here, we report the discovery of several halogenated quinolines (HQs) identified through a reductive amination reaction that demonstrated potent eradication of MRSA (HQ-6; MBEC = 125 μM), MRSE (HQ-3; MBEC = 3.0 μM) and VRE (HQ-4, HQ-5 and HQ-6; MBEC = 1.0 μM) biofilms. HQs were evaluated using the Calgary Biofilm Device (CBD) and demonstrated near equipotent killing activities against planktonic and biofilm cells based on MBC and MBEC values. When tested against red blood cells, these HQ analogues demonstrated low haemolytic activity (3 to 21% at 200 μM) thus we conclude that these HQ analogues do not operate primarily through the destruction of bacterial membranes, typical of other biofilm-eradicating agents (i.e., antimicrobial peptides). HQ antibacterial agents are potent biofilm-eradicating compounds and could lead to useful treatments for biofilm-associated bacterial infections.

With the continued rise of drug-resistant bacterial infections coupled with the current discouraging state of the antibiotic pipeline, the need for new antibacterial agents that operate through unique mechanisms compared with conventional antibiotics and work in synergy with other agents is at an all-time high. We have discovered that gallic acid, a plant-derived phytochemical, dramatically potentiates the antibacterial activities of several halogenated quinolines (up to 11,800-fold potentiation against Staphylococcus aureus) against pathogenic bacteria, including drug-resistant clinical isolates. S. aureus demonstrated the highest sensitivity towards gallic acid-halogenated quinoline combinations, including one halogenated quinoline that demonstrated potentiation of biofilm eradication activity against a methicillin-resistant S. aureus (MRSA) clinical isolate. During our studies, we also demonstrated that these halogenated quionlines operate through an interesting metal(II) cation-dependent mechanism and display promising mammalian cytotoxicity., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Staphylococcus aureus and Staphylococcus epidermidis are recognized as the most frequent cause of biofilm-associated nosocomial and indwelling medical device infections. Biofilm-associated infections are known to be highly resistant to our current arsenal of clinically used antibiotics and antibacterial agents. To exacerbate this problem, no therapeutic option exists that targets biofilm-dependent machinery critical to Staphylococcal biofilm formation and maintenance. Here, we describe the discovery of a series of quinoline small molecules that demonstrate potent biofilm dispersal activity against methicillin-resistant S. aureus and S. epidermidis using a scaffold hopping strategy. This interesting class of quinolines also has select synthetic analogues that demonstrate potent antibacterial activity and biofilm inhibition against S. aureus and S. epidermidis., (Copyright © 2014 Elsevier Ltd. All rights reserved.)