Quorum Sensing Inhibiting Activity of Schinusterebinthifolius Radii (Anacardiaceae) Extracts Against MRSA
Morbidity and mortality estimates due to methicillin-resistant Staphylococcus aureus (MRSA) infections continue to rise . Therapeutic options are limited by antibiotic resistance. In our research, we aim to inhibit the pathways responsible for the production of virulence factors. This allows for the mediation of Staphylococcal pathogenesis without affecting growth, thus avoiding selective forces for drug-resistance. A cell-density dependent mechanism, known as quorum sensing (QS), is responsible for controlling protein expression in S. aureus. Staphylococcal QS is encoded by the agr locus and is responsible for the production of virulence factors such as the α-, β-, and δ-hemolysins. δ-Hemolysin is a translational protein product of RNAIII. Quantification of δ-hemolysin produced by S. aureus and found in the culture supernatants allows for the analysis of agr activity at the translational, rather than transcriptional, level. RP-HPLC techniques can be applied for the analysis of Staphylococcal culture filtrates . We applied this method in the analysis of anti-QS activity by extracts from Schinus terebinthifolius (Brazilian Pepper), an invasive plant found throughout southern Florida. Analyses of the ethanolic extracts of the stems and leaves of this species revealed a significant dose-dependent response (8–128 µg/ml) in the production of δ-hemolysin, indicating strong anti-QS activity in MRSA. Acknowledgements: This work was funded by NIH/NCCAM 1F31 AT004288-01A1 (PI: C.L. Quave), MBRS RISE – NIH/NIGMS R25GM061347, Botany in Action, Anne Chatham Fellowship in Medicinal Botany, USDA CSREES 20053842215940 and NIH/NCAAM 1T32AT01060-01 (PI: B.C. Bennett). We thank Dr. Michael Otto for guidance in the setup of the delta-hemolysin bioassay. We thank Dr. Horacio Preistap and Myron Georgiadis for technical support in the use of HPLC and LC/MS equipment. References:  Klevens RM, et al. (2006) Clin Infect Dis. 43: 387–388.  Otto M, Götz F (2000) Biotechniques 28: 1088–1096.