Supreme activity of gramicidin S against resistant, persistent and biofilm cells of staphylococci and enterococci

Abstract

Three promising antibacterial peptides were studied with regard to their ability to inhibit the growth and kill the cells of clinical strains of Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium. The multifunctional gramicidin S (GS) was the most potent, compared to the membranotropic temporin L (TL), being more effective than the innate-defence regulator IDR-1018 (IDR). These activities, compared across 16 strains as minimal bactericidal and minimal inhibitory concentrations (MIC), are independent of bacterial resistance pattern, phenotype variations and/or biofilm-forming potency. For S. aureus strains, complete killing is accomplished by all peptides at 5 × MIC. For E. faecalis strains, only GS exhibits a rapid bactericidal effect at 5 × MIC, while TL and IDR require higher concentrations. The biofilm-preventing activities of all peptides against the six strains with the largest biofilm biomass were compared. GS demonstrates the lowest minimal biofilm inhibiting concentrations, whereas TL and IDR are consistently less effective. In mature biofilms, only GS completely kills the cells of all studied strains. We compare the physicochemical properties, membranolytic activities, model pharmacokinetics and eukaryotic toxicities of the peptides and explain the bactericidal, antipersister and antibiofilm activities of GS by its elevated stability, pronounced cell-penetration ability and effective utilization of multiple modes of antibacterial action.

The DNA Damage Inducible SOS Response Is a Key Player in the Generation of Bacterial Persister Cells and Population Wide Tolerance

“…Pretreatment with sublethal concentations of antibiotics substantially increased the levels of persister cells (Johnson and Levin, 2013). Furthermore, in planktonic bacteria, exposure to subinhibitory concentrations of antibiotics induced switching to a biofilm lifestyle (Berditsch et al, 2019). SOS induction has also been shown to enhance the expression of fibronectin-binding protein (Bisognano et al, 2004) that facilitates attachment to host cells and biofilm formation (McCourt et al, 2014).…”

Gramicidin‐S‐Inspired Cyclopeptidomimetics as Potent Membrane‐Active Bactericidal Agents with Therapeutic Potential

“…Bacterial cells were then fixed with 2.5 % (w/v) glutaraldehyde at 4°C for 6 h. Before centrifugation at 8000 × g for 3 min, the cells were mixed by gently inverting the tube up and down for several minutes to prevent clumping of the cells. After three washes with PBS, the bacterial pellets were dehydrated for 15 min with a series of graded ethanol solutions (30,50,70,80, 90 and 100 %), the cells were mixed and centrifuged at 8000 × g for 3 min. Following dehydration, the dried bacterial cells were transferred to dry alcohol.…”

“…[10,21,28] The aforementioned GS, a well-known AMP obtained from bacteria, is active against a wide range of Gram-positive and Gram-negative bacteria, as well as viruses, fungi and tumors. [10,[29][30][31] Structurally, it is a cyclodecapeptide with the primary sequence cyclo-(VOL D FP) 2 (where O stands for ornithine), which adopts a rigid C 2 -symmetric β-hairpin structure (Figure 1, left panel). The global conformation is constrained by four intra-molecular H-bonds with four hydrophobic side-chains (Val and Leu) positioned on the opposite face from the two Orn cationic side chains, resulting in a strong amphiphilicity.…”

Engineering DNA templated nonribosomal peptide synthesis

“…Gramicidin S is a well-investigated cyclic decapeptide antibiotic with the sequence cyclo-(fPVOL)2. [22][23][24] Mono-modular GrsA (f) and tetramodular GrsB (PVOL) concatenate two molecules of pentapeptide fPVOL into gramicidin S. Here, in addition to the standard abbreviation of amino acids, letters in small case designate D-amino acids, "O" ornithine, and "O*" cyclized ornithine. Interruption of the gramicidin S assembly process leads to shunt products, for instance cyclo-(fP) 25 and fPVO* (Figure 1).…”