A broad-spectrum bactericidal lipopeptide with anti-biofilm properties

Abstract

Previous studies of the oligoacyllysyl (OAK) series acyl-lysyl-lysyl-aminoacyl-lysine-amide, suggested their utility towards generating robust linear lipopeptide-like alternatives to antibiotics, although to date, none exhibited potent broad-spectrum bactericidal activity. To follow up on this premise, we produced a new analog (C14KKc12K) and investigated its properties in various media. Mechanistic studies suggest that C14KKc12K uses a non-specific membrane-disruptive mode of action for rapidly reducing viability of Gram-negative bacteria (GNB) similarly to polymyxin B (PMB), a cyclic lipopeptide used as last resort antibiotic. Indeed, C14KKc12K displayed similar affinity for lipopolysaccharides and induced cell permeabilization associated with rapid massive membrane depolarization. Unlike PMB however, C14KKc12K was also bactericidal to Gram-positive bacteria (GPB) at or near the minimal inhibitory concentration (MIC), as assessed against a multispecies panel of >50 strains, displaying MIC50 at 3 and 6 µM, respectively for GPB and GNB. C14KKc12K retained activity in human saliva, reducing the viability of cultivable oral microflora by >99% within two minutes of exposure, albeit at higher concentrations, which, nonetheless, were similar to the commercial gold standard, chlorhexidine. This equipotent bactericidal activity was also observed in pre-formed biofilms of Streptococcus mutans, a major periodontal pathogen. Such compounds therefore, may be useful for eradication of challenging poly-microbial infections.

Eliciting improved antibacterial efficacy of host proteins in the presence of antibiotics

“…However, data shown in Fig. 2B, as well as results from previous studies (18,28), argue against such a possibility. In fact, even less hydrophobic analogs (e.g., C 8 KKc 12 K) were able to damage the OM.…”

“…In this respect, membrane active compounds (MACs) having the ability to target multiple bacterial functions simultaneously has attracted increasing interest for their potential to overcome infections while avoiding diverse resistance mechanisms (4,(10)(11)(12). Unlike outright hydrophobic bactericidal MACs (13)(14)(15), borderline hydrophobic analogs tend to cause a variety of superficial impairments, ranging from barely detectable injuries to full-fledged compromising harms with bacteriostatic consequences (16)(17)(18). Being associated with rather high minimal inhibitory concentrations (MICs), borderline hydrophobic MACs can be transparent to many antibiotic screens while triggering damages of relatively high metabolic cost by altering membrane attributes such as bilayer thickness, charge, or fluidity.…”

Novel Miniature Membrane Active Lipopeptidomimetics against Planktonic and Biofilm Embedded Methicillin-Resistant Staphylococcus aureus

“…Along with slow growth under nutrient depletion conditions, biofilm-associated infections are complicated by the presence of extracellular polymeric substance (EPS) matrix which provides a physical barrier and allows bacterial populations to adhere together 7 . For a number of antibiotics and synthetic molecules, much higher concentrations have been reported to be effective towards eradication of biofilms 5 , 10 , 24 , 60 , 61 while sub-lethal concentrations of many antibiotics such as VAN and OXA are even known to promote staphylococcal biofilm formation on surfaces 62 . To evaluate the efficacy of designed peptidomimetics we next developed a 24 h biofilm formation inhibition model in a 96-well plate.…”

“…Additionally, matrix formation allows the creation of a microenvironment which promotes resistance and tolerance development in microbes along with providing protection from host immune surveillance 7 . Therefore, a lot of efforts are being directed towards optimization of novel molecules/strategies to eradicate clinically relevant biofilms 8 – 10 . Recently, the consensus is emerging that unlike single target capturing antibiotics; membrane disruptive, dual targeting antibiotics such as oritavancin and daptomycin can eradicate slow-growing, persister cells and thus are more effective against biofilm embedded cells 11 – 13 .…”

Effect of Disulfide Cyclization of Ultrashort Cationic Lipopeptides on Antimicrobial Activity and Cytotoxicity

“…To solve this problem, researchers have attempted to design molecules with beneficial properties to balance between toxicity and antimicrobial activity. Undoubtedly, ultrashort (up to 7 amino acid residues) cationic lipopeptides (USCLs) have been claimed to be effective antimicrobial agents [ 5 , 6 , 7 , 8 ]. These molecules have a detergent-like mode of action and their membrane—cation interactions partially rely on the electrostatic attraction between positively charged amino acid residues and negatively charged membrane components.…”