{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T02:37:17Z","timestamp":1790649437098,"version":"4.1.0"},"reference-count":54,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2021,12,28]],"date-time":"2021-12-28T00:00:00Z","timestamp":1640649600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antibiotics"],"abstract":"<jats:p>The ability to rescue the activity of antimicrobials that are no longer effective against bacterial pathogens such as Pseudomonas aeruginosa is an attractive strategy to combat antimicrobial drug resistance. Herein, novel efflux pump inhibitors (EPIs) demonstrating strong potentiation in combination with levofloxacin against wild-type P. aeruginosa ATCC 27853 are presented. A structure activity relationship of aryl substituted heterocyclic carboxamides containing a pentane diamine side chain is described. Out of several classes of fused heterocyclic carboxamides, aryl indole carboxamide compound 6j (TXA01182) at 6.25 \u00b5g\/mL showed 8-fold potentiation of levofloxacin. TXA01182 was found to have equally synergistic activities with other antimicrobial classes (monobactam, fluoroquinolones, sulfonamide and tetracyclines) against P. aeruginosa. Several biophysical and genetic studies rule out membrane disruption and support efflux inhibition as the mechanism of action (MOA) of TXA01182. TXA01182 was determined to lower the frequency of resistance (FoR) of the partner antimicrobials and enhance the killing kinetics of levofloxacin. Furthermore, TXA01182 demonstrated a synergistic effect with levofloxacin against several multidrug resistant P. aeruginosa clinical isolates.<\/jats:p>","DOI":"10.3390\/antibiotics11010030","type":"journal-article","created":{"date-parts":[[2021,12,28]],"date-time":"2021-12-28T06:55:03Z","timestamp":1640674503000},"page":"30","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":16,"title":["Evaluation of Heterocyclic Carboxamides as Potential Efflux Pump Inhibitors in Pseudomonas aeruginosa"],"prefix":"10.3390","volume":"11","author":[{"given":"Yi","family":"Yuan","sequence":"first","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jesus D.","family":"Rosado-Lugo","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yongzheng","family":"Zhang","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pratik","family":"Datta","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yangsheng","family":"Sun","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yanlu","family":"Cao","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anamika","family":"Banerjee","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ajit K.","family":"Parhi","sequence":"additional","affiliation":[{"name":"TAXIS Pharmaceuticals, Inc., 9 Deer Park Drive, Suite J-15, Monmouth Junction, NJ 08852, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,12,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"168","DOI":"10.3389\/fphar.2013.00168","article-title":"Efflux pumps of Gram-negative bacteria: What they do, how they do it, with what and how to deal with them","volume":"4","author":"Amaral","year":"2014","journal-title":"Front. Pharmacol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"159","DOI":"10.2165\/00003495-200464020-00004","article-title":"Efflux-mediated drug resistance in bacteria","volume":"64","author":"Li","year":"2004","journal-title":"Drugs"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"340","DOI":"10.1111\/j.1574-6976.2011.00290.x","article-title":"Broad-specificity efflux pumps and their role in multidrug resistance of Gram-negative bacteria","volume":"36","author":"Nikaido","year":"2012","journal-title":"FEMS Microbiol. Rev."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"143","DOI":"10.2217\/fmb-2019-0235","article-title":"RND efflux pumps in Gram-negative bacteria; regulation, structure and role in antibiotic resistance","volume":"15","author":"Colclough","year":"2020","journal-title":"Future Microbiol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"10731","DOI":"10.1038\/ncomms10731","article-title":"Tripartite assembly of RND multidrug efflux pumps","volume":"7","author":"Daury","year":"2016","journal-title":"Nat. Commun."},{"key":"ref_6","first-page":"255","article-title":"Multidrug efflux pumps and antimicrobial resistance in Pseudomonas aeruginosa and related organisms","volume":"3","author":"Poole","year":"2001","journal-title":"J. Mol. Microbiol. Biotechnol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"59","DOI":"10.2174\/1568026013395605","article-title":"Multidrug efflux in Pseudomonas aeruginosa: Components, mechanisms and clinical significance","volume":"1","author":"Poole","year":"2001","journal-title":"Curr. Top. Med. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"366","DOI":"10.3389\/fmicb.2019.00366","article-title":"MexXY Multidrug Efflux System Is More Frequently Overexpressed in Ciprofloxacin Resistant French Clinical Isolates Compared to Hospital Environment Ones","volume":"10","author":"Serra","year":"2019","journal-title":"Front. Microbiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"582","DOI":"10.1128\/CMR.00040-09","article-title":"Antibacterial-resistant Pseudomonas aeruginosa: Clinical impact and complex regulation of chromosomally encoded resistance mechanisms","volume":"22","author":"Lister","year":"2009","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"919","DOI":"10.1080\/17460441.2018.1514386","article-title":"The development of efflux pump inhibitors to treat Gram-negative infections","volume":"13","author":"Blanco","year":"2018","journal-title":"Expert Opin. Drug Discov."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"702","DOI":"10.2174\/1389450116666151001103948","article-title":"Efflux Pump Inhibitors: A Novel Approach to Combat Efflux-Mediated Drug Resistance in Bacteria","volume":"17","author":"Wang","year":"2016","journal-title":"Curr. Drug Targets"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"382","DOI":"10.1016\/j.molmed.2005.06.006","article-title":"Inhibitors of efflux pumps in Gram-negative bacteria","volume":"11","author":"Pages","year":"2005","journal-title":"Trends Mol. Med."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1128\/AAC.45.1.105-116.2001","article-title":"Identification and characterization of inhibitors of multidrug resistance efflux pumps in Pseudomonas aeruginosa: Novel agents for combination therapy","volume":"45","author":"Lomovskaya","year":"2001","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2755","DOI":"10.1016\/S0960-894X(03)00556-0","article-title":"Conformationally-restricted analogues of efflux pump inhibitors that potentiate the activity of levofloxacin in Pseudomonas aeruginosa","volume":"13","author":"Renau","year":"2003","journal-title":"Bioorg. Med. Chem. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"7087","DOI":"10.1016\/j.bmc.2007.07.039","article-title":"MexAB-OprM specific efflux pump inhibitors in Pseudomonas aeruginosa. Part 7: Highly soluble and in vivo active quaternary ammonium analogue D13-9001, a potential preclinical candidate","volume":"15","author":"Yoshida","year":"2007","journal-title":"Bioorg. Med. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"722","DOI":"10.1128\/AAC.01866-13","article-title":"Characterization of a novel pyranopyridine inhibitor of the AcrAB efflux pump of Escherichia coli","volume":"58","author":"Opperman","year":"2014","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"910","DOI":"10.1016\/j.bcp.2005.12.008","article-title":"Practical applications and feasibility of efflux pump inhibitors in the clinic\u2014A vision for applied use","volume":"71","author":"Lomovskaya","year":"2006","journal-title":"Biochem. Pharmacol."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"2284","DOI":"10.1093\/jac\/dky208","article-title":"Revitalizing the drug pipeline: AntibioticDB, an open access database to aid antibacterial research and development","volume":"73","author":"Farrell","year":"2018","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"337","DOI":"10.1128\/CMR.00117-14","article-title":"The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria","volume":"28","author":"Li","year":"2015","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1062","DOI":"10.2174\/0929867323666160304150522","article-title":"Current Advances in Developing Inhibitors of Bacterial Multidrug Efflux Pumps","volume":"23","author":"Mahmood","year":"2016","journal-title":"Curr. Med. Chem."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"633","DOI":"10.1517\/17460441.2012.688949","article-title":"Understanding efflux in Gram-negative bacteria: Opportunities for drug discovery","volume":"7","author":"Schweizer","year":"2012","journal-title":"Expert Opin. Drug Discov."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"e00181-19","DOI":"10.1128\/CMR.00181-19","article-title":"Antimicrobial Resistance in ESKAPE Pathogens","volume":"33","author":"Forde","year":"2020","journal-title":"Clin. Microbiol. Rev."},{"key":"ref_23","unstructured":"TAXIS Pharmaceuticals, Inc (2020). Tackling resistance in multidrug-resistant bacterial infections. Biopharma Deal., 14, Available online: www.nature.com\/articles\/d43747-020-00935-2."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"30","DOI":"10.1016\/j.ejmech.2019.05.075","article-title":"Structure-activity relationships of potentiators of the antibiotic activity of clarithromycin against Escherichia coli","volume":"178","author":"Blankson","year":"2019","journal-title":"Eur. J. Med. Chem."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"3254","DOI":"10.1016\/j.bmc.2019.06.003","article-title":"Advances in the structural studies of antibiotic potentiators against Escherichia coli","volume":"27","author":"Blankson","year":"2019","journal-title":"Bioorg. Med. Chem."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"124","DOI":"10.1186\/s13756-020-00793-8","article-title":"Development of in vitro resistance to fluoroquinolones in Pseudomonas aeruginosa","volume":"9","author":"Zhao","year":"2020","journal-title":"Antimicrob. Resist. Infect. Control"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1093\/jac\/dki171","article-title":"Efflux-mediated antimicrobial resistance","volume":"56","author":"Poole","year":"2005","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1046\/j.1365-2958.1997.2281594.x","article-title":"Characterization of MexE-MexF-OprN, a positively regulated multidrug efflux system of Pseudomonas aeruginosa","volume":"23","author":"Kohler","year":"1997","journal-title":"Mol. Microbiol."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3322","DOI":"10.1128\/AAC.44.12.3322-3327.2000","article-title":"Substrate specificities of MexAB-OprM, MexCD-OprJ, and MexXY-oprM efflux pumps in Pseudomonas aeruginosa","volume":"44","author":"Masuda","year":"2000","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1093\/jac\/48.4.549","article-title":"Fluoroquinolone susceptibilities of efflux-mediated multidrug-resistant Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Burkholderia cepacia","volume":"48","author":"Zhang","year":"2001","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_31","first-page":"26","article-title":"RND efflux pumps in P. aeruginosa: An underestimated resistance mechanism","volume":"26321","author":"Avrain","year":"2013","journal-title":"Antibiot. Susceptibility"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"972","DOI":"10.1128\/AAC.47.3.972-978.2003","article-title":"Efflux-mediated resistance to tigecycline (GAR-936) in Pseudomonas aeruginosa PAO1","volume":"47","author":"Dean","year":"2003","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1636","DOI":"10.1128\/AAC.49.4.1636-1638.2005","article-title":"Presence of tetracycline resistance determinants and susceptibility to tigecycline and minocycline","volume":"49","author":"Fluit","year":"2005","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"738","DOI":"10.1128\/AAC.43.4.738","article-title":"In vitro and in vivo antibacterial activities of a novel glycylcycline, the 9-t-butylglycylamido derivative of minocycline (GAR-936)","volume":"43","author":"Petersen","year":"1999","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"2288","DOI":"10.1128\/AAC.40.10.2288","article-title":"Multidrug efflux in intrinsic resistance to trimethoprim and sulfamethoxazole in Pseudomonas aeruginosa","volume":"40","author":"Kohler","year":"1996","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1732","DOI":"10.1128\/AAC.38.8.1732","article-title":"Role of efflux pump(s) in intrinsic resistance of Pseudomonas aeruginosa: Resistance to tetracycline, chloramphenicol, and norfloxacin","volume":"38","author":"Li","year":"1994","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"424","DOI":"10.1128\/AAC.43.2.424","article-title":"Carbapenem activities against Pseudomonas aeruginosa: Respective contributions of OprD and efflux systems","volume":"43","author":"Kohler","year":"1999","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"48","DOI":"10.1128\/AAC.26.1.48","article-title":"Compounds which increase the permeability of the Pseudomonas aeruginosa outer membrane","volume":"26","author":"Hancock","year":"1984","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"1361","DOI":"10.1128\/AAC.01581-12","article-title":"Quantitative contributions of target alteration and decreased drug accumulation to Pseudomonas aeruginosa fluoroquinolone resistance","volume":"57","author":"Bruchmann","year":"2013","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"275","DOI":"10.2147\/IDR.S147581","article-title":"Mutations in the gyrA, parC, and mexR genes provide functional insights into the fluoroquinolone-resistant Pseudomonas aeruginosa isolated in Vietnam","volume":"11","author":"Nguyen","year":"2018","journal-title":"Infect. Drug Resist."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1093\/jac\/dkh505","article-title":"Reduction of the fitness burden of quinolone resistance in Pseudomonas aeruginosa","volume":"55","author":"Kugelberg","year":"2005","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_42","doi-asserted-by":"crossref","unstructured":"Braz, V.S., Furlan, J.P., Fernandes, A.F., and Stehling, E.G. (2016). Mutations in NalC induce MexAB-OprM overexpression resulting in high level of aztreonam resistance in environmental isolates of Pseudomonas aeruginosa. FEMS Microbiol. Lett., 363.","DOI":"10.1093\/femsle\/fnw166"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"493","DOI":"10.1038\/ismej.2011.122","article-title":"Quorum quenching quandary: Resistance to antivirulence compounds","volume":"6","author":"Maeda","year":"2012","journal-title":"ISME J."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"565","DOI":"10.1007\/s00203-016-1215-7","article-title":"Overexpression of MexAB-OprM efflux pump in carbapenem-resistant Pseudomonas aeruginosa","volume":"198","author":"Pan","year":"2016","journal-title":"Arch. Microbiol."},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Choudhury, D., Ghose, A., Dhar Chanda, D., Das Talukdar, A., Dutta Choudhury, M., Paul, D., Maurya, A.P., Chakravarty, A., and Bhattacharjee, A. (2016). Premature Termination of MexR Leads to Overexpression of MexAB-OprM Efflux Pump in Pseudomonas aeruginosa in a Tertiary Referral Hospital in India. PLoS ONE, 11.","DOI":"10.1371\/journal.pone.0151308"},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"480","DOI":"10.1128\/AAC.45.2.480-484.2001","article-title":"Carbapenem resistance mechanisms in Pseudomonas aeruginosa clinical isolates","volume":"45","author":"Pai","year":"2001","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1251","DOI":"10.1126\/science.288.5469.1251","article-title":"High frequency of hypermutable Pseudomonas aeruginosa in cystic fibrosis lung infection","volume":"288","author":"Oliver","year":"2000","journal-title":"Science"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1410","DOI":"10.1128\/JB.182.5.1410-1414.2000","article-title":"Influence of mutations in the mexR repressor gene on expression of the MexA-MexB-oprM multidrug efflux system of Pseudomonas aeruginosa","volume":"182","author":"Srikumar","year":"2000","journal-title":"J. Bacteriol."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"1847","DOI":"10.1128\/JB.188.5.1847-1855.2006","article-title":"Antibiotic inducibility of the MexXY multidrug efflux system of Pseudomonas aeruginosa: Involvement of the antibiotic-inducible PA5471 gene product","volume":"188","author":"Morita","year":"2006","journal-title":"J. Bacteriol."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"2058","DOI":"10.1099\/mic.0.069286-0","article-title":"Functional characterization of the NfxB repressor of the mexCD-oprJ multidrug efflux operon of Pseudomonas aeruginosa","volume":"159","author":"Purssell","year":"2013","journal-title":"Microbiology"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"508","DOI":"10.1128\/AAC.00830-10","article-title":"mexEF-oprN multidrug efflux operon of Pseudomonas aeruginosa: Regulation by the MexT activator in response to nitrosative stress and chloramphenicol","volume":"55","author":"Fetar","year":"2011","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"18","DOI":"10.1186\/1754-1611-3-18","article-title":"Fluorometric determination of ethidium bromide efflux kinetics in Escherichia coli","volume":"3","author":"Paixao","year":"2009","journal-title":"J. Biol. Eng."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"1699","DOI":"10.1016\/j.bcp.2013.10.010","article-title":"Pharmacokinetics and in vivo antistaphylococcal efficacy of TXY541, a 1-methylpiperidine-4-carboxamide prodrug of PC190723","volume":"86","author":"Kaul","year":"2013","journal-title":"Biochem. Pharmacol."},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"5297","DOI":"10.1128\/AAC.02894-14","article-title":"Bactericidal activity, absence of serum effect, and time-kill kinetics of ceftazidime-avibactam against beta-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa","volume":"58","author":"Keepers","year":"2014","journal-title":"Antimicrob. Agents Chemother."}],"container-title":["Antibiotics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-6382\/11\/1\/30\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:54:51Z","timestamp":1760169291000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-6382\/11\/1\/30"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,12,28]]},"references-count":54,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2022,1]]}},"alternative-id":["antibiotics11010030"],"URL":"https:\/\/doi.org\/10.3390\/antibiotics11010030","relation":{},"ISSN":["2079-6382"],"issn-type":[{"value":"2079-6382","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,12,28]]}}}