Membrane-active macromolecules kill antibiotic-tolerant bacteria and potentiate antibiotics towards Gram-negative bacteria

Abstract

Chronic bacterial biofilms place a massive burden on healthcare due to the presence of antibiotic-tolerant dormant bacteria. Some of the conventional antibiotics such as erythromycin, vancomycin, linezolid, rifampicin etc. are inherently ineffective against Gram-negative bacteria, particularly in their biofilms. Here, we report membrane-active macromolecules that kill slow dividing stationary-phase and antibiotic tolerant cells of Gram-negative bacteria. More importantly, these molecules potentiate antibiotics (erythromycin and rifampicin) to biofilms of Gram-negative bacteria. These molecules eliminate planktonic bacteria that are liberated after dispersion of biofilms (dispersed cells). The membrane-active mechanism of these molecules forms the key for potentiating the established antibiotics. Further, we demonstrate that the combination of macromolecules and antibiotics significantly reduces bacterial burden in mouse burn and surgical wound infection models caused by Acinetobacter baumannii and Carbapenemase producing Klebsiella pneumoniae (KPC) clinical isolate respectively. Colistin, a well-known antibiotic targeting the lipopolysaccharide (LPS) of Gram-negative bacteria fails to kill antibiotic tolerant cells and dispersed cells (from biofilms) and bacteria develop resistance to it. On the contrary, these macromolecules prevent or delay the development of bacterial resistance to known antibiotics. Our findings emphasize the potential of targeting the bacterial membrane in antibiotic potentiation for disruption of biofilms and suggest a promising strategy towards developing therapies for topical treatment of Gram-negative infections.

Usnic acid modifies MRSA drug resistance through down‐regulation of proteins involved in peptidoglycan and fatty acid biosynthesis

“…As evident from the results, UA could cause significant reduction of up to 16-fold in the MIC of norfloxacin with FICI ≤ 0.50 and thus it was selected for further studies. The clinical breakout point for the susceptibility of norfloxacin is ≤ 10 mgÁL À1 [47], and its MIC in combination with UA was observed to reach close to the susceptible limit as defined in the European Committee on Antimicrobial Susceptibility Testing guidelines (31.25 mgÁL À1 ).…”

Antibiotic killing of diversely generated populations of non-replicating bacteria

“…The results presented here illustrate that this is not the case for other antibiotics, and particularly some aminoglycosides and peptide antimicrobials kill stationary phase populations of E. coli and S. aureus. This observation is not new; it has been known for some time that the aminoglycosides and the cyclic peptides, daptomycin and colistin are capable of killing stationary phase bacteria (24,(61)(62)(63). Less seems to be known about the susceptibility to killing by bactericidal antibiotics of the other non-replicating states of bacteria considered here, persisters and bacteria with antibiotic-induced stasis.…”

Exogenous fatty acids alter phospholipid composition, membrane permeability, capacity for biofilm formation, and antimicrobial peptide susceptibility in Klebsiella pneumoniae

“…The importance of Lipid A to AMP resistance is well‐documented (Jeannot, Bolard, & Plesiat, ; Olaitan, Morand, & Rolain, ; Velkov et al., ) but the contributions of phospholipid fatty acyl constitution are largely unknown. Notably, the effectiveness of membrane‐active agents against Gram‐negative pathogens has reinforced bacterial membranes as prime targets for therapeutic attack (Uppu et al., ). We interpreted the MIC results as significant for those fatty acids that altered the MIC by at least fourfold as compared with the control.…”