Re-sensitization of Multidrug-Resistant and Colistin-Resistant Gram-Negative Bacteria to Colistin by Povarov/Doebner-Derived Compounds

Abstract

Colistin, typically viewed as the antibiotic of last resort to treat infections caused by multidrug-resistant (MDR) Gram-negative bacteria, had fallen out of favor due to toxicity issues. The recent increase in clinical usage of colistin has resulted in colistin-resistant isolates becoming more common. To counter this threat, we have investigated previously reported compounds, HSD07 and HSD17, and developed 13 compounds with more desirable drug-like properties for colistin sensitization against 16 colistin-resistant bacterial strains, three of which harbor the plasmid-borne mobile colistin resistance (mcr-1). Lead compound HSD1624, which has a lower LogDpH7.4 (2.46) compared to HSD07 (>5.58), reduces the minimum inhibitory concentration (MIC) of colistin against Pseudomonas aeruginosa strain TRPA161 to 0.03 μg/mL from 1024 μg/mL (34,000-fold reduction). Checkerboard assays revealed that HSD1624 and analogues are also synergistic with colistin against colistin-resistant strains of Escherichia coli, Acinetobacter baumannii, and Klebsiella pneumoniae. Preliminary mechanism of action studies indicate that HSD1624 exerts its action differently depending on the bacterial species. Time-kill studies suggested that HSD1624 in combination with 0.5 μg/mL colistin was bactericidal to extended-spectrum beta-lactamase (ESBL)-producing E. coli, as well as to E. coli harboring mcr-1, while against P. aeruginosa TRPA161, the combination was bacteriostatic. Mechanistically, HSD1624 increased membrane permeability in K. pneumoniae harboring a plasmid containing the mcr-1 gene but did not increase radical oxygen species (ROS), while a combination of 15 μM HSD1624 and 0.5 μg/mL colistin significantly increased ROS in P. aeruginosa TRPA161. HSD1624 was not toxic to mammalian red blood cells (up to 226 μM).

Using permeation guidelines to design new antibiotics—A PASsagE into Pseudomonas aeruginosa

“…These newly disclosed permeation rules can now be used to guide auxophore modification for enhanced P. aeruginosa accumulation. The eNTRy rules, put forth in 2017, have already accelerated gram‐negative antibacterial campaigns and delivered high accumulating and active antibiotics via modification of the auxophore in many different contexts 22–33 …”

“…The eNTRy rules, put forth in 2017, have already accelerated gram-negative antibacterial campaigns and delivered high accumulating and active antibiotics via modification of the auxophore in many different contexts. [22][23][24][25][26][27][28][29][30][31][32][33] Often, the eNTRy rules are used in campaigns that are centred around a small molecule that already possesses the necessary spatial parameters but lacks the amine required for gram-negative uptake. Although other ionizable nitrogen moieties can be beneficial for E. coli accumulation, 34 primary amines typically result in the largest accumulation increase and are thus typically preferred.…”