title: Characterization of a novel pyranopyridine inhibitor of the AcrAB efflux pump of Escherichia coli.
abstract: Members of the resistance-nodulation-division (RND) family of efflux pumps, such as AcrAB-TolC of Escherichia coli, play major roles in multidrug resistance (MDR) in Gram-negative bacteria. A strategy for combating MDR is to develop efflux pump inhibitors (EPIs) for use in combination with an antibacterial agent. Here, we describe MBX2319, a novel pyranopyridine EPI with potent activity against RND efflux pumps of the Enterobacteriaceae. MBX2319 decreased the MICs of ciprofloxacin (CIP), levofloxacin, and piperacillin versus E. coli AB1157 by 2-, 4-, and 8-fold, respectively, but did not exhibit antibacterial activity alone and was not active against AcrAB-TolC-deficient strains. MBX2319 (3.13 μM) in combination with 0.016 μg/ml CIP (minimally bactericidal) decreased the viability (CFU/ml) of E. coli AB1157 by 10,000-fold after 4 h of exposure, in comparison with 0.016 μg/ml CIP alone. In contrast, phenyl-arginine-β-naphthylamide (PAβN), a known EPI, did not increase the bactericidal activity of 0.016 μg/ml CIP at concentrations as high as 100 μM. MBX2319 increased intracellular accumulation of the fluorescent dye Hoechst 33342 in wild-type but not AcrAB-TolC-deficient strains and did not perturb the transmembrane proton gradient. MBX2319 was broadly active against Enterobacteriaceae species and Pseudomonas aeruginosa. MBX2319 is a potent EPI with possible utility as an adjunctive therapeutic agent for the treatment of infections caused by Gram-negative pathogens.
authors.affiliation: Microbiotix, Inc., Worcester, Massachusetts, USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Opperman
authors.forename: Steven M
authors.initials: SM
authors.lastname: Kwasny
authors.forename: Hong-Suk
authors.initials: HS
authors.lastname: Kim
authors.forename: Son T
authors.initials: ST
authors.lastname: Nguyen
authors.forename: Chad
authors.initials: C
authors.lastname: Houseweart
authors.forename: Sanjay
authors.initials: S
authors.lastname: D'Souza
authors.forename: Graham C
authors.initials: GC
authors.lastname: Walker
authors.forename: Norton P
authors.initials: NP
authors.lastname: Peet
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nikaido
authors.forename: Terry L
authors.initials: TL
authors.lastname: Bowlin
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002352:Carrier Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002939:Ciprofloxacin / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D004357:Drug Synergism; D004755:Enterobacteriaceae / Q000187:drug effects / Q000254:growth & development; D004926:Escherichia coli / Q000187:drug effects / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D064704:Levofloxacin / Q000494:pharmacology; D049990:Membrane Transport Modulators / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010878:Piperacillin / Q000494:pharmacology; D011714:Pyrans / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*
chemical_list: C573020:AcrAB-TolC protein, Enterobacter cloacae; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004151:Dipeptides; D029968:Escherichia coli Proteins; C000591634:MBX2319; D049990:Membrane Transport Modulators; D011714:Pyrans; D011725:Pyridines; C419365:phenylalanine arginine beta-naphthylamide; D002939:Ciprofloxacin; D064704:Levofloxacin; D010878:Piperacillin