Antibacterial efficacy and adaptive proteomic strategies of antibiotic-resistant pathogens on nanostructured copper...

To evaluate the antibacterial activity of nanostructured copper oxide surfaces synthesized by hot water treatment (HWT) and to elucidate the underlying mechanisms of copper-induced stress responses in antibiotic-resistant Citrobacter freundii CF51 and Staphylococcus aureus HAR12.

Copper sheets were subjected to HWT to generate Cu₂O/CuO nanostructures. Antibacterial and antibiofilm activities were assessed using viability and biofilm assays. Cellular morphology was examined by FESEM. Whole-proteome and KEGG pathway analyses were performed to identify bacterial adaptive responses.

Nanostructured copper rapidly inactivated C. freundii and eliminated S. aureus with longer exposure. FESEM imaging showed membrane disruption, deformation, and lysis, with more severe damage on nanostructured surfaces. Proteomic analysis revealed species-specific regulation of pathways related to energy metabolism, transcription, ion transport, and cell envelope biogenesis. ABC transporters were upregulated in C. freundii but downregulated in S. aureus. The Staphylococcus aureus infection pathway was markedly suppressed. Efflux transporters (CorA, MdtF, YhiI) were consistently upregulated in both species, indicating conserved copper-detoxification mechanisms.

Nanostructured copper oxide surfaces demonstrate potent antibacterial and antibiofilm activity and induce distinct proteomic stress responses. These findings support the potential of nanostructured copper as an effective antimicrobial surface against antibiotic-resistant pathogens.