Leniha LaGarde, Natalie Leon, Selene Lopez, Gaby Amador, Barbara Reque, Krisha Algoso, Professor Ashley McCarley, Dr. Isaac Quintanilla Salinas, & Dr. Caryl Ann Becerra
Antibiotic resistance is a prevalent global health threat. Due to the progressive ineffectiveness of antimicrobial drug treatments, there is a need for discovery of new antibiotics while also testing combinational therapy. Preliminary work shows that some native California plants used by the Chumash Native Americans have antimicrobial activity. Therefore, the aim of this research is to determine the synergistic effect of six plant extracts of indigenous plants (Lemonade Berry, White Sage, Manzanita, Coastal Sage, Yarrow, Rue). The plant extracts were tested for synergistic antimicrobial activity by combining two extracts using a 1:1 ratio. The susceptibility of Bacillus subtilis, Pseudomonas fluorescens, Escherichia coli to the plant extracts was tested using the Kirby-Bauer disk diffusion method. The zones of inhibition were examined by performing a needle inoculation to test for bactericidal/bacteriostatic properties. B. subtilis and P. fluorescens displayed higher susceptibility compared to E.coli plates. Lemonade Berry mixed with Manzanita Displayed higher zones of inhibition (greater susceptibility) compared to individual plant extracts tested against B. subtilis.