Inhibition Of Escherichia coli Growth In Food By Arctostaphylos glauca

Native Americans have traditionally used Arctostaphylos glauca berries to treat urinary tract infections. Most urinary tract infections are caused by Escherichia coli, therefore the purpose of our work is to determine whether an extract of A. glauca berries can be used to inhibit E. coli survival and growth in food. This could help prevent foodborne infections. Antibacterial effects of A. glauca were determined against E. coli, Pseudomonas aeruginosa, and Staphylococcus aureus bacteria using an agar diffusion assay. Acetonic and ethanolic extracts (<250 mg/mL) inhibited growth of all three bacteria. The minimum inhibitory concentration of the ethanolic extract is 25 mg/mL and the minimum bactericidal concentration is 2.5 mg/mL against E. coli. Heterotrophic plate counts were performed to determine the effect of the extract on E. coli growth and survival in food. Lettuce or berries inoculated with E. coli were treated with the ethanolic extract (4.0 mg/mL). E. coli survival in the treated produce was decreased by 90% compared to the untreated controls. We are determining the optimum pH for antimicrobial activity. We conclude that an A. glauca berry extract has potential for use as an antimicrobial to kill E. coli bacteria in fresh produce.