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Updated: Jan 27, 2026
Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization
Published on: August 11, 2018
Structure⁻Activity Study, Characterization, and Mechanism of Action of an Antimicrobial Peptoid D2 and Its d- and
Ines Greco1, Johannes E Hansen2, Bimal Jana3
1Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen, Denmark. ines.greco@food.ku.dk.
Abstract:
Methicillin-resistant Staphylococcus pseudintermedius (MRSP) constitutes an emerging health problem for companion animals in veterinary medicine. Therefore, discovery of novel antimicrobial agents for treatment of Staphylococcus-associated canine infections is urgently needed to reduce use of human antibiotics in veterinary medicine. In the present work, we characterized the antimicrobial activity of the peptoid D2 against S. pseudintermedius and Pseudomonas aeruginosa, which is another common integumentary pathogen in dogs. Furthermore, we performed a structure⁻activity relationship study of D2, which included 19 peptide/peptoid analogs. Our best compound D2D, an all d-peptide analogue, showed potent minimum inhibitory concentrations (MICs) against canine S. pseudintermedius (2⁻4 µg/mL) and P. aeruginosa (4 µg/mL) isolates as well as other selected dog pathogens (2⁻16 µg/mL). Time⁻kill assays demonstrated that D2D was able to inhibit MRSP in 30 min at 1× MIC, significantly faster than D2. Our results suggest that at high concentrations D2D is rapidly lysing the bacterial membrane while D2 is inhibiting macromolecular synthesis. We probed the mechanism of action at sub-MIC concentrations of D2, D2D, the l-peptide analog and its retro analog by a macromolecular biosynthesis assay and fluorescence spectroscopy. Our data suggest that at sub-MIC concentrations D2D is membrane inactive and primarily works by cell wall inhibition, while the other compounds mainly act on the bacterial membrane.
Insights
Novel peptoids show potent antimicrobial activity against canine pathogens like methicillin-resistant Staphylococcus pseudintermedius (MRSP). The best compound, D2D, rapidly inhibits MRSP by targeting cell walls, offering a promising alternative for veterinary medicine.
Area of Science:
- Veterinary Microbiology
- Antimicrobial Peptides
- Drug Discovery
Background:
- Methicillin-resistant Staphylococcus pseudintermedius (MRSP) is a growing concern in companion animal health.
- There is an urgent need for new antimicrobials to treat canine infections and reduce human antibiotic use in veterinary medicine.
Purpose of the Study:
- To characterize the antimicrobial activity of peptoid D2 against Staphylococcus pseudintermedius and Pseudomonas aeruginosa.
- To conduct a structure-activity relationship study of D2 and its analogs.
- To investigate the mechanism of action of promising compounds.
Main Methods:
- Antimicrobial activity testing, including minimum inhibitory concentrations (MICs).
- Structure-activity relationship analysis of 19 peptide/peptoid analogs.
- Time-kill assays and macromolecular biosynthesis assays.
- Fluorescence spectroscopy to probe mechanism of action.
Main Results:
- The all-d-peptide analog D2D demonstrated potent MICs against canine S. pseudintermedius (2-4 µg/mL) and P. aeruginosa (4 µg/mL).
- D2D exhibited rapid inhibition of MRSP within 30 minutes at 1x MIC, faster than D2.
- At high concentrations, D2D rapidly lyses bacterial membranes, while D2 inhibits macromolecular synthesis.
- At sub-MIC concentrations, D2D primarily inhibits cell wall synthesis, whereas other analogs act on the bacterial membrane.
Conclusions:
- The peptoid D2D is a potent antimicrobial agent effective against key canine pathogens.
- D2D displays a distinct mechanism of action, primarily targeting cell wall synthesis at sub-inhibitory concentrations.
- These findings support the development of D2D as a novel therapeutic agent for canine bacterial infections.
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