Anti-quorum sensing agents from south Florida medicinal plants and their attenuation of Pseudomonas aeruginosa pathogenicity

With the difficulty in treating recalcitrant infections and the growing resistance to antibiotics, new therapeutic modalities are becoming increasingly necessary. The interruption of bacterial quorum sensing (QS), or cell-cell communication is known to attenuate virulence, while limiting selective pressure toward resistance. This study initiates an ethnobotanically-directed search for QS inhibiting agents in south Florida medicinal plants. Fifty plants were screened for anti-QS activity using two biomonitor strains, Chromobacterium violaceum and Agrobacterium tumefaciens. Of these plants, six showed QS inhibition: Conocarpus erectus L. (Combretaceae), Chamaecyce hypericifolia (L.) Millsp. (Euphorbiaceae), Callistemon viminalis (Sol.ex Gaertn.) G. Don (Myrtaceae), Bucida burceras L. (Combretaceae), Tetrazygia bicolor (Mill.) Cogn. (Melastomataceae), and Quercus virginiana Mill. (Fagaceae). These plants were further examined for their effects on the QS system and virulence of Pseudomonas aeruginosa, an intractable opportunistic pathogen responsible for morbidity and mortality in the immunocompromised patient. C. erectus, B. buceras, and C. viminalis were found to significantly inhibit multiple virulence factors and biofilm formation in this organism. 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 low-pressure 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.

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

With the difficulty in treating recalcitrant infections and the growing resistance to antibiotics, new therapeutic modalities are becoming increasingly necessary. The interruption of bacterial quorum sensing (QS), or cell-cell communication is known to attenuate virulence, while limiting selective pressure toward resistance. This study initiates an ethnobotanically-directed search for QS inhibiting agents in south Florida medicinal plants. Fifty plants were screened for anti-QS activity using two biomonitor strains, Chromobacterium violaceum and Agrobacterium tumefaciens. Of these plants, six showed QS inhibition: Conocarpus erectus L. (Combretaceae), Chamaecyce hypericifolia (L.) Millsp. (Euphorbiaceae), Callistemon viminalis (Sol.ex Gaertn.) G. Don (Myrtaceae), Bucida burceras L. (Combretaceae), Tetrazygia bicolor (Mill.) Cogn. (Melastomataceae), and Quercus virginiana Mill. (Fagaceae). These plants were further examined for their effects on the QS system and virulence of Pseudomonas aeruginosa, an intractable opportunistic pathogen responsible for morbidity and mortality in the immunocompromised patient. C. erectus, B. buceras, and C. viminalis were found to significantly inhibit multiple virulence factors and biofilm formation in this organism. 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 low-pressure 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.

Proteomic Analysis of Wolbachia Symbiosis within the Drosophila

Wolbachia pipientis are bacterial endosymbionts of arthropods and in some filarial nematodes. Wolbachia are of particular interest because nematodeWolbachia have been shown to cause the diseases African river blindness and Lymphatic Filariasis. Doxycycline can be used to eliminate nematode Wolbachia, however, more efficient treatments are needed. Ideally, we would like to repurpose another FDA approved drug that helps to shorten treatment duration. Vitamins are one of the best classes of FDA approved compounds, generally recognized as safe. Interestingly, prior work by Serbus and colleagues found that dietary yeast, which is highly enriched in vitamins, dramatically reducesWolbachia titer in Drosophila melanogaster ovarian tissue. Imaging data indicated that the Wolbachia nucleoids were disrupted in response to yeast. This raised the possibility that yeast cells contain a bio-reactive, anti-Wolbachiacompound. Our close examination of yeast nutritional information identified which vitamins are most highly enriched in yeast. We then administered several of these to D. melanogaster, and saw that two of these led to reduced ovarianWolbachia titers, analogous to yeast-fed flies. This was especially interesting, as both vitamins are critical for functioning of the same biochemical pathway. We used retested effect of one of these vitamins in oogenesis by performing a dilution series, and achieved positive correlation from this dilution series. This opens up the avenue for clarifying the mechanism of how vitamins suppressWolbachia titer, and for testing enhancement of Doxycycline, to hopefully provide faster, more affordable treatment for millions of patients.

Proteomic Analysis of Wolbachia Symbiosis within the Drosophila

Wolbachia pipientis are bacterial endosymbionts of arthropods and in some filarial nematodes. Wolbachia are of particular interest because nematodeWolbachia have been shown to cause the diseases African river blindness and Lymphatic Filariasis. Doxycycline can be used to eliminate nematode Wolbachia, however, more efficient treatments are needed. Ideally, we would like to repurpose another FDA approved drug that helps to shorten treatment duration. Vitamins are one of the best classes of FDA approved compounds, generally recognized as safe. Interestingly, prior work by Serbus and colleagues found that dietary yeast, which is highly enriched in vitamins, dramatically reducesWolbachia titer in Drosophila melanogaster ovarian tissue. Imaging data indicated that the Wolbachia nucleoids were disrupted in response to yeast. This raised the possibility that yeast cells contain a bio-reactive, anti-Wolbachiacompound. Our close examination of yeast nutritional information identified which vitamins are most highly enriched in yeast. We then administered several of these to D. melanogaster, and saw that two of these led to reduced ovarianWolbachia titers, analogous to yeast-fed flies. This was especially interesting, as both vitamins are critical for functioning of the same biochemical pathway. We used retested effect of one of these vitamins in oogenesis by performing a dilution series, and achieved positive correlation from this dilution series. This opens up the avenue for clarifying the mechanism of how vitamins suppressWolbachia titer, and for testing enhancement of Doxycycline, to hopefully provide faster, more affordable treatment for millions of patients.