Rosa damascena extract mediated synthesis of silver nanoparticles with promising antibacterial synergy in combination with CM11 peptide against multidrug resistant and colistin resistant bacteria

The rise of pathogens exhibiting significant antibiotic resistance has severely limited treatment options, with multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains showing resistance even to last-resort antibiotics such as colistin. This growing resistance has compounded treatment challenges and intensified the need for alternative therapeutic strategies. This study aimed to synthesize silver nanoparticles (AgNPs) using Rosa damascena extract and to evaluate the antibacterial efficacy of this biogenic compound-both alone and in combination with the CM11 peptide-against antibiotic-resistant pathogens. The green-synthesized AgNPs were characterized using UV-Vis spectroscopy, Dynamic Light Scattering (DLS), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM). The antibacterial activities of both the AgNPs and the synthesized cationic CM11 peptide were determined using the broth microdilution assay. A checkerboard assay was then conducted to assess their combined effects. The AgNPs were successfully synthesized and confirmed using standard analytical techniques. Both the green-synthesized AgNPs and the CM11 peptide demonstrated inhibitory activity against MDR and colistin-resistant bacteria. The checkerboard results revealed that combining AgNPs with CM11 produced synergistic and partial synergistic effects against MDR Escherichia coli and Acinetobacter baumannii, respectively, and an additive effect against colistin-resistant Klebsiella pneumoniae and MDR Staphylococcus aureus. Our findings demonstrate that the green-synthesized AgNPs and CM11 peptide, whether applied independently or in combination, exhibit strong antibacterial activity against MDR and colistin-resistant isolates. These results suggest that such biogenic compounds could serve as promising alternatives for treating infections caused by resistant bacteria in the future.