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. 2015 Feb 19;22(2):196-205.
doi: 10.1016/j.chembiol.2015.01.002.

D-enantiomeric peptides that eradicate wild-type and multidrug-resistant biofilms and protect against lethal Pseudomonas aeruginosa infections

César de la Fuente-Núñez  1 , Fany Reffuveille  1 , Sarah C Mansour  1 , Shauna L Reckseidler-Zenteno  2 , Diego Hernández  2 , Gilles Brackman  3 , Tom Coenye  3 , Robert E W Hancock  4
Affiliations

D-enantiomeric peptides that eradicate wild-type and multidrug-resistant biofilms and protect against lethal Pseudomonas aeruginosa infections

César de la Fuente-Núñez et al. Chem Biol. .

Erratum in

  • Chem Biol. 2015 Sep 17;22(9):1280-2

Abstract

In many infections, bacteria form surface-associated communities known as biofilms that are substantially more resistant to antibiotics than their planktonic counterparts. Based on the design features of active antibiofilm peptides, we made a series of related 12-amino acid L-, D- and retro-inverso derivatives. Specific D-enantiomeric peptides were the most potent at inhibiting biofilm development and eradicating preformed biofilms of seven species of wild-type and multiply antibiotic-resistant Gram-negative pathogens. Moreover, these peptides showed strong synergy with conventional antibiotics, reducing the antibiotic concentrations required for complete biofilm inhibition by up to 64-fold. As shown previously for 1018, these D-amino acid peptides targeted the intracellular stringent response signal (p)ppGpp. The most potent peptides DJK-5 and DJK-6 protected invertebrates from lethal Pseudomonas aeruginosa infections and were considerably more active than a previously described L-amino acid peptide 1018. Thus, the protease-resistant peptides produced here were more effective both in vitro and in vivo.

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Figures

Figure 1
Figure 1. D-enantiomeric peptides completely prevented biofilm formation and eradicated P. aeruginosa biofilms
Sub-MIC concentrations (2.5 μg/ml) of peptides DJK-5 and DJK-6 were used. Inhibition of biofilm development was tested by immediately adding peptide into the flow-through medium of the flow cell apparatus and then monitoring biofilm formation for 3 days. Eradication conditions involved waiting two days before addition of either peptide into the flow-through medium. After 3 days, bacteria were stained green with the all bacteria stain Syto-9 and red with the dead-bacteria stain propidium iodide (merge shows as yellow to red) prior to confocal imaging. Each panel shows reconstructions from the top in the large panel and sides in the right and bottom panels (xy, yz and xz dimensions).
Figure 2
Figure 2. D-enantiomer peptides DJK-5 (A) and DJK-6 (B) exhibited anti-biofilm activity in flow cells and synergized with conventional antibiotics in preventing biofilm formation by different bacterial species
Sub-inhibitory concentrations of peptides DJK-5 and DJK-6 in combination with antibiotics prevented biofilm development of Gram-negative bacteria. Inhibition of biofilm development was tested by immediately (at the beginning of biofilm growth at day 0) adding peptide plus antibiotic into the flow-through medium of the flow cell apparatus and then monitoring biofilm formation for 3 days. After 3 days, bacteria were stained green with the all bacteria stain Syto-9 and red with the dead-bacteria stain propidium iodide (merge shows as yellow to red) prior to confocal imaging. Each panel shows reconstructions from the top in the large panel and sides in the right and bottom panels (xy, yz and xz dimensions). The top FIC combinations of peptide + antibiotic (determined in checkerboard assays) were used.
Figure 3
Figure 3. Synergistic interactions of D-enantiomer peptides DJK-5 (A) and DJK-6 (B) with different classes of antibiotics in treating mature biofilms
Bacteria were grown in flow cells and treated at day 2 of biofilm formation with peptide, antibiotic, or the combination of both. The top FIC combinations of peptide + antibiotic (determined in checkerboard assays) were used (as in Figure 2). In some cases, at the concentrations selected, the activity of the peptides led to complete eradication of the flow cell biofilms. Thus, we decreased the levels of peptide used, which lowered the FIC values (see on the right hand side of panels) compared to the checkerboard assay results shown in Table 2. Specifically, in (A) 0.8 (μg/ml of DJK-5 (instead of 6.4 (μg/ml) was used in combination with tobramycin vs A. baumannii. In (B), 0.5 (μg/ml of DJK-6 were used instead of 2 (μg/ml combined with imipenem vs. A. baumannii, 1 (μg/ml of DJK-6 (as opposed to 2 (μg/ml) was used in conjunction with ciprofloxacin vs S. enterica, and 0.5 (μg/ml of DJK-6, instead of 2 (μg/ml, was used in combination with tobramycin vs K. pneumoniae. After 3 days, bacteria were stained green with the all bacteria stain Syto-9 and red with the dead-bacteria stain propidium iodide (merge shows as yellow to red) prior to confocal imaging. Each panel shows reconstructions from the top in the large panel and sides in the right and bottom panels (xy, yz and xz dimensions).
Figure 4
Figure 4. D-enantiomeric peptides prevented (p)ppGpp accumulation and led to disappearance of (p)ppGpp in vivo.
(A) Anti-biofilm peptides DJK-5 and DJK-6 at 1 (μg/ml led to the absence of (p)ppGpp accumulation as revealed by TLC separation of guanine nucleotides extracted from intact cells as described in Experimental Procedures. (B) D-enantiomeric peptides RI-1018 and DJK-5 led to complete disappearance of (p)ppGpp more potently than L-peptide 1018. (C) D-enantiomeric peptide DJK-6 exhibited increased ability to trigger the degradation of pre-formed (p)ppGpp compared to RI-1018 and RI-JK6. Twenty (μg/ml of each of the three peptides were used.
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