P3-164 Antimicrobial Efficacy of Syzygium antisepticum Plant Extract against Staphylococcus aureus and Methicillin-resistant S. aureus and Its Application Potential with Cooked Chicken

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Wenqian Yuan , National University of Singapore , Singapore , Singapore
Hyun Gyun Yuk , Korea National University of Transportation , Chungju , South Korea
Hyun-Jung Chung , Inha University , Incheon , South Korea
Introduction: Medicinal plants have been used for disease treatment for centuries, and many have recently been reported to possess good antimicrobial properties. However, thr majority of them remain unexplored

Purpose: This study aimed at identifying a novel plant extract with potential antimicrobial activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA), to validate efficacy in a food model, and to elucidate the major volatile composition and antimicrobial mechanism.

Methods: The minimum inhibitory and bactericidal concentrations of four plant extracts (Atuna racemosa AR, Xanthostemon verticillatus XV, Syzygium antisepticum leaf SA-L, and Syzygium antisepticum stem SA-S) were determined against S. aureus and MRSA, using the microdilution method. Anti-staphylococcal activity of SA-L was validated in cooked chicken at 4, 10, and 25°C. SA-L extract volatile composition was determined using GC-MS. The antimicrobial mechanism of the crude extract and its major compound was studied using transmission electron microscopy and flow cytometry, respectively.

Results: Among the four extracts evaluated, SA-L showed the most potent antimicrobial activity against S. aureus and MRSA, with an MIC of 0.13 mg/mL. In a food study, higher SA-L concentration (32 mg/mL) was needed to inhibit or reduce growth of S. aureus and MRSA in cooked chicken, but this caused a color change on meat surface. By GC-MS, caryophyllene (9.19%) was found to be the most abundant volatile compound in SA-L extract. Both crude extract and caryophyllene induced membrane damage in S. aureus. Caryophyllene, alone, showed weaker antimicrobial activities.

Significance: These results demonstrated the antimicrobial properties of S. antisepticum leaf extract against S. aureus and MRSA, identified its major volatile composition, and its membrane-damaging antimicrobial mechanism. However, further work is needed to enhance its antimicrobial activity in food matrices.