Anti-Quorum Sensing Agents from South Florida Medicinal Plants and their Attenuation of Pseudomonas Aeruginosa Pathogenicity

Abstract

This dissertation, written by Allison L. Adonizio, and entitled Anti-quorum sensing agents from south Florida medicinal plants and their attenuation of Pseudomonas aeruginosa pathogenicity, having been approved in respect to style and intellectual content, is referred to you for judgment.We have read this dissertation and recommend that it be approved. Each plant presented a distinct profile of effect on QS genes and signaling molecules, suggesting varying modes of action. Virulence attenuation was observed with marginal reduction of bacterial growth, suggesting quorum quenching mechanisms unrelated to static or cidal effects. Extracts of these plants were also investigated for their effects on P. aeruginosa killing of the nematode Caenorhabditis elegans. Results were evaluated in both toxin-based and infection-based assays with P. aeruginosa strains PA01 and PA14. _____________________________Overall nematode mortality was reduced 50-90%. There was no indication of host toxicity, suggesting the potential for further development as anti-infectives. Using lowpressure chromatography and HPLC, two stereoisomeric ellagitannins, vescalagin and castalagin were isolated from an aqueous extract of C. erectus. Structures were confirmed via mass spectrometry and NMR spectroscopy. Both ellagitannins were shown to decrease signal production, QS gene expression, and virulence factor production in P.aeruginosa. This study introduces a potentially new therapeutic direction for the treatment of bacterial infections. In addition, this is the first report of vescalagin and castalagin being isolated from C. erectus, and the first report of ellagitannin activity on the QS system.

Inhibition of quorum sensing virulente factors of Pseudomonas aeruginosa PAO1 by Ferulago macedonica and Echinophora sibthorpiana extracts and essential oils

“…As previously mentioned, E. sibthorpina essential oil did not show potential in the reduction of biofilm synthesis, while F. macedonica oil expressed low activity. In our work, the anti-QS effects of tested extracts varied against different virulent factors, which is in agreement with the study of Adonizio (2008) where various plant extracts had different activity on P. aeruginosa. This bacterium uses the ability to form a biofilm controlled by gene expression, as a resistance to the antibiotics and as a protection from the host's immune system.…”

“…On the other hand, essential oils of Apium graveolens, Foeniculum vulgare, Petroselinum crispum and Trachyspermum ammi (Apiaceae) did not show anti-QS potential on C. violaceum CV12472 and CVO26 strains (Khan et al, 2009). Obtained differences in the activity of the samples recorded for anti-biofilm and anti-pyocyanin tests may originate from to the complex chemical composition of the extracts and essential oils and the possible synergism of various components (Adonizio, 2008). According to presented data in this work, ethanol extracts of E. sibthorpiana roots had moderate anti-QS activity and similar results were observed by Nagy (2010) for Eryngium aquaticum and Foeniculum vulgare root ethanol extracts.…”

“…These results may suggest a different polarity of ingredients active in the reduction of PAO1 virulence. The method used for extracts preparation and essential oils isolation also should be taken into consideration in results discussion (Adonizio, 2008).…”

Attenuation of quorum sensing-regulated behaviour by Tinospora cordifolia extract & identification of its active constituents

“…In a study by Adonizio22, among the plants tested, Conocarpus erectus and Bucida bucerus showed maximum inhibitory activity against QS in P. aeruginosa and were further tested for supression of virulence. Both plants showed significant decrease in LasA activity.…”

Assessment of Anti-Quorum Sensing Activity for Some Ornamental and Medicinal Plants Native to Egypt

“…Developing new, non-toxic, and broad-spectrum anti-quorum sensing drugs from both microorganisms and plants is of great interest in recent years. Plants produce diverse antimicrobial compounds such as simple phenolics, catechins, quinones, flavanones, polyphenolics, alkaloids, and terpenoids [2, 20, 21]. Hence, bioscreening plant extracts for antiquorum sensing activity, followed by isolating the compounds responsible for this activity, is rational [22].…”