Repurposing a neurodegenerative disease drug to treat Gram-negative antibiotic-resistant bacterial sepsis

Abstract

The emergence of polymyxin resistance in carbapenem-resistant and extended-spectrum β-lactamase (ESBL)–producing bacteria is a critical threat to human health, and alternative treatment strategies are urgently required. We investigated the ability of the hydroxyquinoline analog ionophore PBT2 to restore antibiotic sensitivity in polymyxin-resistant, ESBL-producing, carbapenem-resistant Gram-negative human pathogens. PBT2 resensitized Klebsiella pneumoniae, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa to last-resort polymyxin class antibiotics, including the less toxic next-generation polymyxin derivative FADDI-287, in vitro. We were unable to select for mutants resistant to PBT2 + FADDI-287 in polymyxin-resistant E. coli containing a plasmid-borne mcr-1 gene or K. pneumoniae carrying a chromosomal mgrB mutation. Using a highly invasive K. pneumoniae strain engineered for polymyxin resistance through mgrB mutation, we successfully demonstrated the efficacy of PBT2 + polymyxin (colistin or FADDI-287) for the treatment of Gram-negative sepsis in immunocompetent mice. In comparison to polymyxin alone, the combination of PBT2 + polymyxin improved survival and reduced bacterial dissemination to the lungs and spleen of infected mice. These data present a treatment modality to break antibiotic resistance in high-priority polymyxin-resistant Gram-negative pathogens.

Rescuing Tetracycline Class Antibiotics for the Treatment of Multidrug-Resistant Acinetobacter baumannii Pulmonary Infection

“…PBT2 facilitates the direct permeation of zinc ions across biological membranes, independent of membrane protein-dependent transport pathways ( 19 ). PBT2 treatment of A. baumannii MS14413 increased the cellular content of zinc and copper and reduced magnesium.…”

“…Antibiotic potentiator molecules represent a promising avenue for rescuing the efficacy of existing antimicrobial therapies ( 48 ). In complex with zinc, ionophore compounds have been shown previously to potentiate polymyxin and amikacin activity against A. baumannii in vitro ( 19 , 49 ). Here, we demonstrate that the ionophore PBT2 breaks A. baumannii resistance to tetracycline class antibiotics in vivo .…”

“…RNA was isolated using a RNeasy Plus kit (Qiagen) as described previously ( 19 ). Briefly, A. baumannii MS14413 was grown to an OD 600 of 0.5 in CA-MHB.…”

“…RNA-seq analysis was performed at the Australian Genome Research Facility. The cDNA library was prepared and assessed as described previously ( 19 ). An average of 30 million reads per sample were generated, then trimmed using trimmomatic (v0.36), and mapped to the reference genome ( A. baumannii MS14413 accession number NZ_CP054302 ) using bowtie2 (v2.3.4.2) with default parameters (–local –very-sensitive-local).…”

“…We have reported previously that dysregulation of bacterial metal ion homeostasis breaks antibiotic resistance in select bacterial pathogens ( 19 – 21 ). Here, using the 8-hydroxyquinoline analog PBT2 [2-(dimethylamino) methyl-5,7-dichloro-8-hydroxyquinoline] ( 22 , 23 ), we demonstrate that the disruption of metal homeostasis breaks resistance to tetracycline class antibiotics in carbapenem-resistant, MDR, and XDR A. baumannii clinical isolates in vivo , using murine wound and pulmonary infection models.…”