Gram-negative synergy and mechanism of action of alkynyl bisbenzimidazoles

Abstract

Bisbenzimidazoles with terminal alkynyl linkers, selective inhibitors of bacterial topoisomerase I, have been evaluated using bacterial cytological profiling (BCP) to ascertain their mechanism of action and screened for synergism to improve Gram-negative bacterial coverage. Principal component analysis of high throughput fluorescence images suggests a dual-mechanism of action affecting DNA synthesis and cell membrane integrity. Fluorescence microscopy of bacteria challenged with two of the alkynyl-benzimidazoles revealed changes in the cellular ultrastructure that differed from topoisomerase II inhibitors including induction of spheroplasts and membrane lysis. The cytoskeleton recruitment enzyme inhibitor A22 in combination with one of the alkynyl-benzimidazoles was synergistic against Acinetobacter baumannii and Escherichia coli. Gram-positive coverage remained unchanged in the A22-alkynyl bisbenzimidazole combination. Efflux inhibitors were not synergistic, suggesting that the Gram-negative outer membrane was a significant barrier for alkynyl-bisbenzimidazole uptake. Time-kill assays demonstrated the A22-bisbenzimidazole combination had a similar growth inhibition curve to that of norfloxacin in E.coli. Bisbenzimidazoles with terminal alkynyl linkers likely impede bacterial growth by compromising cell membrane integrity and by interfering with DNA synthesis against Gram-positive pathogens and in the synergistic combination against Gram-negative pathogens including E. coli and multidrug-resistant A. baumanii.

Evaluation of Anticancer Activity of 1,3‐Oxazol‐4‐ylphosphonium Salts in Vitro

“…Specifically interacts with adenine and thymine of the minor groove of DNA, disrupting its synthesis. [45] …”

“…[44] TGI Pibenzimol Hydrochloride 0.47 Specifically interacts with adenine and thymine of the minor groove of DNA, disrupting its synthesis. [45] LC 50 Hycanthone 0.60 Intercalates into DNA and also targets topoisomerases and apurinic endonuclease 1, disrupting the nucleic acid synthesis. [46] Pyrazoloacridine 0.59 See above.…”

Type IA Topoisomerases as Targets for Infectious Disease Treatments

“…However, most of these derivatives still had cytotoxicity concerns, due to their DNA-binding activity [ 110 , 121 ]. DPA 154, shown in Figure 2 , was also reported to elicit changes in the cellular ultrastructure including induction of spheroplasts and membrane lysis, suggesting a dual mechanism of antibacterial action that includes compromising cell membrane integrity [ 122 ]. In vivo efficacy against E. coli was demonstrated in the mouse systemic infection model as well as the mouse neutropenic thigh model [ 111 ] for one of the bis-benzimidazoles, 2′-(4-ethoxyphenyl)-5-(4-propylpiperazin-1-yl)-1H,1′H-2,5′-bibenzo[ d ]imidazole (PPEF), shown in Figure 2 .…”

Onium- and Alkyl Amine-Decorated Protein Nanoparticles as Antimicrobial Agents and Carriers of Antibiotics to Promote Synergistic Antibacterial and Antibiofilm Activities

“…19 The activities of both antibiotics CiproF and Cefta are not membrane-oriented but by the inhibition of topoisomerase and cell wall synthesis inhibition, respectively. 29,30 This predicts that even a slight change in membrane integrity is enough to support the action of the antibiotic. A loss of membrane integrity could lead to a change in osmotic pressure, followed by membrane depolarization.…”