A polymeric approach toward resistance-resistant antimicrobial agent with dual-selective mechanisms of action

Abstract

Antibiotic resistance is now a major threat to human health, and one approach to combating this threat is to develop resistance-resistant antibiotics. Synthetic antimicrobial polymers are generally resistance resistant, having good activity with low resistance rates but usually with low therapeutic indices. Here, we report our solution to this problem by introducing dual-selective mechanisms of action to a short amidine-rich polymer, which can simultaneously disrupt bacterial membranes and bind to bacterial DNA. The oligoamidine shows unobservable resistance generation but high therapeutic indices against many bacterial types, such as ESKAPE strains and clinical isolates resistant to multiple drugs, including colistin. The oligomer exhibited excellent effectiveness in various model systems, killing extracellular or intracellular bacteria in the presence of mammalian cells, removing all bacteria from Caenorhabditis elegans, and rescuing mice with severe infections. This “dual mechanisms of action” approach may be a general strategy for future development of antimicrobial polymers.

Multivalent Display of Lipophilic DNA Binders for Dual-Selective Anti-Mycobacterium Peptidomimetics with Binary Mechanism of Action

“…Such "binding moieties along a line" peptidomimetic design has already been successfully employed in pathogenic DNA/RNA binding, 33 and we indeed observed enhancement on DNA binding strength of PAPIs using PI fluorescent titration experiments (Figure 2a and Figure S13). The affinity of PAPI 1-2 toward M. smegmatis genomic DNA (K i = 2.8 μM against PI-DNA, per bisamidine moiety) were comparable to the oligoamidine we reported recently, 12 and were much higher than monomeric DAPI (K i = 94 μM), indicating the successful enhancement in DNA binding strength through a multivalent approach. Yet, similar to DAPI dye, PAPIs could also gain fluorescence upon binding to dsDNA (345 nm/455-510 nm, Figure S14), which would facilitate the observation of its intracellular binding behavior.…”

“…To enhancement peptidomimetics' effectiveness against mycobacteria, structural adjustments should be made to counter these bacteria's unique defensive fortifications: (1) mycobacteria have slow reproduction rate 15 and low sensitivity toward many antibiotics in "dormant state", 7 and (2) mycobacteria have thick and highly hydrophobic enclosures to protect themselves. As shown in Figure 1a, for the former we have already demonstrated that the "membrane-plus-DNA" dual-targeting strategy was effective for those "dormant persisters", 12 ; for the latter, a straightforward solution may be the preparation of more hydrophobic antimicrobial agents so that they can show higher affinity toward mycobacteria. Thus, our aim was narrowed down to the design of dual-mechanistic peptidomimetics with an emphasis on increased overall hydrophobicity.…”

“…This result clearly demonstrated that PAPI 1-2 was targeting bacterial DNA in a highly selective manner, presumably because the PAPI structure was large enough to be excluded from the membrane-protected eukaryotic nucleus and chromosomal DNA. 12,35 Thus, in eukaryotic cells such as RAW 264.7, gene expression levels of proteins, such as the key skeletal proteins Actin and Tubulin, were not significantly affected by the treatment with PAPI 1-2 at much higher concentrations than its MIC against mycobacteria (Figure 3b).…”

“…We have recently reported a resistance-resistant, oligoamidine-based antimicrobial peptidomimetic that could kill pathogenic bacteria with dual-selective mechanisms of actions, namely membrane disruption and DNA binding. 12 The compound also showed activity toward extracellular and intracellular Mycobacterium smegmatis (M. smegmatis), a non-pathogenic bacterium in the mycobacterium genus, despite that its inhibitory effect against M. tuberculosis was weaker. However, it is known that designed chemical structure alteration can be used to advantageously adjust the molecular properties of peptidomimetics irrespective of the actual chemical approach utilized.…”

Host Defense Peptide-Mimicking Polymers and Polymeric-Brush-Tethered Host Defense Peptides: Recent Developments, Limitations, and Potential Success

“…In addition to high therapeutic indices, the SNAPPs displayed low toxicity towards mammalian cells [115]. A recent study by Silei Bai et al [116] has also shown a short, amidine-rich antimicrobial polymer with dual-selective mechanisms of action against harmful "Superbugs", including disrupting bacterial membranes and binding to bacterial DNA. This so-called oligoamidine showed high therapeutic indices against many bacterial types, including the ESKAPE pathogens and clinical isolates resistant to multiple drugs, with no observable resistance generation.…”