Synergistic Action between Copper Oxide (CuO) Nanoparticles and Anthraquinone-2-Carboxylic Acid (AQ) against Staphylococcus aureus

Infections linked to Staphylococcus spp. are difficult to treat with current antibiotic therapy, resulting in increased antibiotic resistance populations. One of the leading strategies to overcome this issue is the novel combination of antibacterial nanoparticles (NPs) and sustainable natural compounds. This study reported the identification of a new synergistic combination of copper oxide (CuO) NPs, a well-known antibacterial agent against Staphylococcus spp., and anthraquinone-2-carboxylic acid (AQ), a plant-derived antimicrobial compound, with a potent and specific fashion in killing Staphylococcus spp. CuO NPs were synthesized using the one-pot coprecipitation method and characterized by using X-ray diffraction and transmission electron microscopy. Further checkerboard analysis showed that CuO NPs and AQ increased the antibacterial activity of individual agents against Staphylococcus aureus among Staphylococcus spp. by four- to eightfold compared to individual materials. Additional mechanistic studies on the synergy revealed that the inhibition of biofilm formation and loss of cytoplasmic volume with cell shrinkage are the major actions of the combination in expressing the phenotype. This study clearly showed that the combination of CuO NPs and AQ would be a novel strategy to eradicate S. aureus infections.