Decreased antimicrobial efficiency has become a global public health issue. The paucity of new antibacterial drugs is evident, and the arsenal against infectious diseases needs to be improved urgently. The selection of plants as a source of prototype compounds is appropriate, since plant species naturally produce a wide range of secondary metabolites that act as a chemical line of defense against microorganisms in the environment. Although traditional approaches to combat microbial infections remain effective, targeting microbial virulence rather than survival seems to be an exciting strategy, since the modulation of virulence factors might lead to a milder evolutionary pressure for the development of resistance. Additionally, anti-infective chemotherapies may be successfully achieved by combining antivirulence and conventional antimicrobials, extending the lifespan of these drugs. This review presents an updated discussion of natural compounds isolated from plants with chemically characterized structures and activity against the major bacterial virulence factors: quorum sensing, bacterial biofilms, bacterial motility, bacterial toxins, bacterial pigments, bacterial enzymes, and bacterial surfactants. Moreover, a critical analysis of the most promising virulence factors is presented, highlighting their potential as targets to attenuate bacterial virulence. The ongoing progress in the field of antivirulence therapy may therefore help to translate this promising concept into real intervention strategies in clinical areas.

Plants produce many compounds that are biologically active, either as part of their normal program of growth and development or in response to pathogen attack or stress. Traditionally, Anadenanthera colubrina, Commiphora leptophloeos and Myracrodruon urundeuva have been used by communities in the Brazilian Caatinga to treat several infectious diseases. The ability to impair bacterial adhesion represents an ideal strategy to combat bacterial pathogenesis, because of its importance in the early stages of the infectious process; thus, the search for anti-adherent compounds in plants is a very promising alternative. This study investigated the ability of stem-bark extracts from these three species to control the growth and prevent biofilm formation of Pseudomonas aeruginosa, an important opportunistic pathogen that adheres to surfaces and forms protective biofilms. A kinetic study (0–72 h) demonstrated that the growth of extract-treated bacteria was inhibited up to 9 h after incubation, suggesting a bacteriostatic activity. Transmission electron microscopy and fluorescence microscopy showed both viable and nonviable cells, indicating bacterial membrane damage; crystal violet assay and scanning electron microscopy demonstrated that treatment strongly inhibited biofilm formation during 6 and 24 h and that matrix production remained impaired even after growth was restored, at 24 and 48 h of incubation. Herein, we propose that the identified (condensed and hydrolyzable) tannins are able to inhibit biofilm formation via bacteriostatic properties, damaging the bacterial membrane and hindering matrix production. Our findings demonstrate the importance of this abundant class of Natural Products in higher plants against one of the most challenging issues in the hospital setting: biofilm resilience.

This study describes the first antibiofilm and antibacterial screening of Caatinga plants against S. epidermidis. The evaluation presented in this study confirms several ethnopharmacological reports and can be utilized to identify new antibiofilm and antibacterial products against S. epidermidis from traditional Brazilian medicine.

We report the isolation of a keratinolytic-producing Bacillus subtilis strain and the characterization of the exceptional dehairing properties of its subtilisin-like keratinase. This enzyme can be an alternative to sodium sulfide, the major pollutant from tanneries, and may completely replace it. Its unique nonactivity upon collagen enhances its industrial potential.Enzymatic dehairing in tanneries has been envisaged as an alternative to sulfides (4,6,9,22,23). Tanneries are constantly concerned about the obnoxious odor and pollution caused by the extremely toxic sodium sulfide used in the dehairing process step (24). Deaths due to this toxic chemical process have even been reported (2,8). Worldwide, it is estimated that 315 million bovine leathers are produced per year. Considering a waste treatment cost of $0.30 per m 2 of leather produced (A. Klein, personal communication), more than $1 million is spent per day to treat the waste from tanneries around the world. We report here a novel keratinase from Bacillus subtilis that has the potential to replace sodium sulfide in the dehairing process.Microorganism isolation. Bovine hair, skins wastes, and soil samples were suspended and cultivated in a feather-broth medium (composition in grams per liter: delipidated feather meal [the sole carbon and nitrogen source], 10.0; NaCl, 0.5; K 2 HPO 4 , 0.3; and KH 2 PO 4 , 0.4 [pH 7.5]).The best keratinase-producing organism was identified as a B. subtilis strain (named strain S14) after classification based on homology (99%) of its 16S fragment with sequences from the NCBI databank by use of BLASTN 2.2.6 (1) (accession number AY345856).Keratinase production. The microorganism was cultivated in a 14-liter bioreactor in a culture medium composed of whey milk (a dairy byproduct containing 94.0% water, 5% lactose, 0.9% protein, and 0.1% fat), pH 8.5, and bovine hair (40 g/liter). A crude extract (supernatant) was obtained after centrifugation of the culture. Keratinolytic, subtilisin, and collagenase activities were assayed by using azokeratin, as described elsewhere (15). One unit of enzyme activity was defined as the amount of enzyme that increases absorbance by 0.1 per hour in the conditions described above (15).Dehairing assay. A fresh fleshed bovine hide was washed with a commercial detergent solution and cut into 15-by 5-cm pieces. Two hundred grams of skin (usually two pieces) was processed in a drum flask at 4 rpm with crude extract or water (control) in a proportion of 1.0 ml of liquid per g of skin. When necessary, pH was adjusted with lime. At the end of the process, the skin pieces were gently scraped with fingers to remove loose hairs. This procedure was necessary because rubbing in this laboratory-scale process was not as vigorous as in industrial drums. Total skin depilation was observed in the pH range from 7 to 10, with 4.8 U/g of skin. A complete depilation was reached in 9 h at pH 9.0, 24°C, with 4.8 U/g of skin.Samples of bovine skin were kept in contact with the crude extract, and the skin fragments were fi...

Despite many advances, biomaterial-associated infections continue to be a major clinical problem. In order to minimize bacterial adhesion, material surface modifications are currently being investigated and natural products possess large potential for the design of innovative surface coatings. We report the bioguided phytochemical investigation of Pityrocarpa moniliformis and the characterization of tannins by mass spectrometry. It was demonstrated that B-type linked proanthocyanidins-coated surfaces, here termed Green coatings, reduced Gram-positive bacterial adhesion and supported mammalian cell spreading. The proposed mechanism of bacterial attachment inhibition is based on electrostatic repulsion, high hydrophilicity and the steric hindrance provided by the coating that blocks bacterium-substratum interactions. This work shows the applicability of a prototype Green-coated surface that aims to promote necessary mammalian tissue compatibility, while reducing bacterial colonization.