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The widespread irrational use of antibiotics in recent years has resulted in an increase in the detection of multi-resistant bacterial strains, particularly methicillin-resistant Staphylococcus aureus (MRSA). The use of natural derivatives such as flavonoids is postulated as one of the most promising avenues to solve this emerging public health problem. The objective of the present study is to characterize the antimicrobial activity of icariin, a flavonoid compound isolated from a variety of plants of the Epimedium genus, against human and animal clinical MRSA isolates. Our study found that icariin alone did not have any antimicrobial effect on S. aureus or MRSA clinical isolates. However, icariin enhanced the effect of amoxycillin-clavulanate or ampicillin, whereas no effect was seen when used in combination with vancomycin. Specifically, co-incubation of S. aureus with amoxycillin-clavulanate plus icariin resulted in an increased proportion of dead cells, suggesting that this flavonoid potentially increases antimicrobial activity when used in combination with the beta-lactam antibiotic amoxycillin-clavulanate. Furthermore, we demonstrate that co-incubation of S. aureus with AmoxyClav plus icariin resulted in increased membrane disruption and growth inhibition. This study demonstrates the potential utility of icariin in permitting lower antibiotic therapeutic doses in alignment with strategies to reduce the spread of antibiotic resistance. Further research is required to determine the optimum concentration of icariin and to define clinically relevant combinations of flavonoid and antibiotic. Full article

Biofilm-associated tissue and device infection is a major threat to therapy. The present work aims to potentiate β-lactam antibiotics with biologically synthesized copper oxide nanoparticles. The synergistic combination of amoxyclav with copper oxide nanoparticles was investigated by checkerboard assay and time-kill assay against bacteria isolated from a burn wound and a urinary catheter. The control of biofilm formation and extracellular polymeric substance production by the synergistic combination was quantified in well plate assay. The effect of copper oxide nanoparticles on the viability of human dermal fibroblasts was evaluated. The minimum inhibitory concentration and minimum bactericidal concentration of amoxyclav were 70 μg/mL and 140 μg/mL, respectively, against Proteus mirabilis and 50 μg/mL and 100 μg/mL, respectively, against Staphylococcus aureus. The synergistic combination of amoxyclav with copper oxide nanoparticles reduced the minimum inhibitory concentration of amoxyclav by 16-fold against P. mirabilis and 32-fold against S. aureus. Above 17.5 μg/mL, amoxyclav exhibited additive activity with copper oxide nanoparticles against P. mirabilis. The time-kill assay showed the efficacy of the synergistic combination on the complete inhibition of P. mirabilis and S. aureus within 20 h and 24 h, respectively, whereas amoxyclav and copper oxide nanoparticles did not inhibit P. mirabilis and S. aureus until 48 h. The synergistic combination of amoxyclav with copper oxide nanoparticles significantly reduced the biofilm formed by P. mirabilis and S. aureus by 85% and 93%, respectively. The concentration of proteins, carbohydrates, and DNA in extracellular polymeric substances of the biofilm was significantly reduced by the synergistic combination of amoxyclav and copper oxide nanoparticles. The fibroblast cells cultured in the presence of copper oxide nanoparticles showed normal morphology with 99.47% viability. No cytopathic effect was observed. Thus, the study demonstrated the re-potentiation of amoxyclav by copper oxide nanoparticles. Full article