Myrtaceaes as antimicrobial agents against Staphylococcus aureus and Pseudomonas aeruginosa

Anti-microbial resistance causes more than 700,000 deaths annually, a figure that is predicted to grow to 10 million by 2050 and is one of the leading contributors to the Global Burden of Disease. The six leading contributors to the surge of antimicrobial resistance are named the ESKAPE pathogens. Staphylococcus aureus and Pseudomonas aeruginosa are two of these bacteria. More than 80% of the active ingredients in antimicrobial drugs are based on natural products. Botanical species are the largest contributors of these active ingredients, yet they remain largely unstudied. Our research aimed to explore the antimicrobial properties of the Myrtaceae family. We collected, dried, and extracted the flowers of six native Australian Myrtaceae species. We tested these crude extracts at ten different concentrations on S. aureus and P. aeruginosa, to determine percentage inhibition, which was used as an indicator of the efficiency of the crude extract in causing bacterial death. The minimum inhibitory concentration (MIC) determines the viability of an extract for further drug development. For S. aureus, all six tested Myrtaceae species exceeded MIC80 (concentration needed for 80% inhibition), with Corymbia ficifolia being the most potent, exceeding MIC80 at 0.04 mg/mL. For P. aeruginosa four out of the six tested Myrtaceae species reached MIC80. Xanthostemon chrysanthus was most effective against P. aeruginosa with a MIC80 of 5.00 mg/mL. Myrtaceae species were shown to be highly effective against S. aureus and even P. aeruginosa, suggesting that further investigation into Myrtaceae species, could be revolutionary in drug development for newer, more effective antimicrobial drugs.