Antibacterial Activity and Toxicity of Zinc Oxide Nanoparticles Combined with Supernatants of Lactobacillus spp. Against ESKAPE Bacteria: A Novel Mixture

Background: The emergence of multidrug resistance among nosocomial pathogens has prompted researchers to look for new antibacterial sources. Metal nanoparticles and probiotic products have attracted the attention of researchers. However, combination therapy is an attractive alternative in this field. Objectives: This study evaluated the antibacterial activity and toxicity of Zinc Oxide nanoparticles (ZnO-NPs) combined with Cell-free Supernatant (CFS) of Lactobacillus plantarum (L. plantarum) and Lactobacillus acidophilus (L. acidophilus) alone and in a novel mixture. Methods: Antibacterial effects and cytotoxic properties of ZnO-NPs, CFS of L. plantarum (SLP), and CFS of L. acidophilus (SLA) were determined alone and in a mixture against ESKAPE strains. In addition, the viability percentage of the cells was evaluated after exposure to these agents. Results: Antibacterial mixtures (ZnO-NPs with SLP or ZnO-NPs with SLA) demonstrated synergistic and additive effects against Pseudomonas aeruginosa (FIC≤0.75), Acinetobacter baumannii (FIC = 1), and Escherichia coli (FIC≤0.75). The viability percentage of the cells after 24 h of exposure to a mixture of ZnO-NPs and SLA (about 50%) was more than when the cells were exposed to ZnO-NPs alone (about 30%) at the same concentration. Conclusions: A mixture of ZnO-NPs and CFS of probiotics can be an alternative to antibiotics, with more effectiveness and fewer side effects.