The Antimicrobial Properties of a Traditional Medicinal Plant, Adenostoma fasciculatum

Overuse of antibiotics has selected new strains of bacterial pathogens that are resistant to the very antibiotics used to combat them. Many plants have been used for centuries by traditional healers and may have antibacterial properties. California Native Americans used the plant Adenostoma fasciculatum, chamise, to treat skin infections. Our hypothesis is A. fasciculatum will inhibit growth of bacterial skin pathogens. We collected A. fasciculatum and dehydrated it for 72 hours at 40°C. The leaves, stems, and flowers were separated and finely ground in acetone, ethanol, or methanol (0.5 g/mL). The Kirby-Bauer disk diffusion method was used to determine antimicrobial action against gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), gram-positive Staphylococcus aureus bacteria, and Saccharomyces cerevisiae yeast. Methanolic flower and stem extracts inhibited S. aureus. The average inhibition zones (control diameter subtracted from plant tissue diameter) were 3.1 mm (flowers) and 2.6 mm (leaves).  We are determining inhibition of other gram-positive pathogens: methicillin-resistant Sta. aureus, Streptococcus pyogenes, Str. mutans, and Mycobacterium phlei. We will investigate the method of action of the active compounds isolated. This plant may provide a source of new antibacterial agents against antibiotic-resistant bacteria.