Inhibitory effects of broccoli extract on Escherichia coli O157:H7 quorum sensing and in vivo virulence

An insight on the powerful of bacterial quorum sensing inhibition

Bacteria have their own language through which they communicate with one another like all higher organisms. So, many researchers are working hard to identify and comprehend the components of this bacterial communication, known as quorum sensing (QS). In quorum sensing, bacteria use signaling molecules called autoinducers (AIs) to exchange information. Many natural compounds and extraction techniques have been intensively studied to disrupt bacterial signaling and examine their effectiveness for bacterial pathogenesis control. Quorum sensing inhibitors can interfere with QS and block the action of AI signaling molecules. Recent research indicates that quorum sensing inhibitors (QSIs) and quorum quenching enzymes (QQEs) show great promise in reducing the pathogenicity of bacteria and inhibiting biofilm synthesis. In addition, the effectiveness of QQEs and QSIs in experimental animal models was demonstrated. These are taken into account in the development of innovative medical devices, such as dressings and catheters, to prevent bacterial infections. The present review highlights this aspect with a prospective vision for its development and application.

Antimicrobial and anti-biofilm properties of oleuropein against Escherichia coli and fluconazole-resistant isolates of Candida albicans and Candida glabrata

BACKGROUND

Side effects associated with antimicrobial drugs, as well as their high cost, have prompted a search for low-cost herbal medicinal substances with fewer side effects. These substances can be used as supplements to medicine or to strengthen their effects. The current study investigated the effect of oleuropein on the inhibition of fungal and bacterial biofilm in-vitro and at the molecular level.

MATERIALS AND METHODS

In this experimental study, antimicrobial properties were evaluated using microbroth dilution method. The effect of oleuropein on the formation and eradication of biofilm was assessed on 96-well flat bottom microtiter plates and their effects were observed through scanning electron microscopy (SEM). Its effect on key genes (Hwp1, Als3, Epa1, Epa6, LuxS, Pfs) involved in biofilm formation was investigated using the quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) method.

RESULTS

The minimum inhibitory concentration (MIC) and minimum fungicidal/bactericidal concentration (MFC/MBC) for oleuropein were found to be 65 mg/ml and 130 mg/ml, respectively. Oleuropein significantly inhibited biofilm formation at MIC/2 (32.5 mg/ml), MIC/4 (16.25 mg/ml), MIC/8 (8.125 mg/ml) and MIC/16 (4.062 mg/ml) (p < 0.0001). The anti-biofilm effect of oleuropein was confirmed by SEM. RT-qPCR indicated significant down regulation of expression genes involved in biofilm formation in Candida albicans (Hwp1, Als3) and Candida glabrata (Epa1, Epa6) as well as Escherichia coli (LuxS, Pfs) genes after culture with a MIC/2 of oleuropein (p < 0.0001).

CONCLUSIONS

The results indicate that oleuropein has antifungal and antibacterial properties that enable it to inhibit or destroy the formation of fungal and bacterial biofilm.

Caenorhabditis elegans as an In Vivo Model for the Discovery and Development of Natural Plant-Based Antimicrobial Compounds

Antimicrobial resistance (AMR) due to the prevalence of multidrug-resistant (MDR) pathogens is rapidly increasing worldwide, and the identification of new antimicrobial agents with innovative mechanisms of action is urgently required. Medicinal plants that have been utilised for centuries with minor side effects may hold great promise as sources of effective antimicrobial products. The free-living nematode Caenorhabditis elegans (C. elegans) is an excellent live infection model for the discovery and development of new antimicrobial compounds. However, while C. elegans has widely been utilised to explore the effectiveness and toxicity of synthetic antibiotics, it has not been used to a comparable extent for the analysis of natural products. By screening the PubMed database, we identified articles reporting the use of the C. elegans model for the identification of natural products endowed with antibacterial and antifungal potential, and we critically analysed their results. The studies discussed here provide important information regarding "in vivo" antimicrobial effectiveness and toxicity of natural products, as evaluated prior to testing in conventional vertebrate models, thereby supporting the relevance of C. elegans as a highly proficient model for their identification and functional assessment. However, their critical evaluation also underlines that the characterisation of active phytochemicals and of their chemical structure, and the unravelling of their mechanisms of action represent decisive challenges for future research in this area.

Antibacterial and anti-biofilm properties of carvacrol alone and in combination with cefixime against Escherichia coli

BACKGROUND

Plant-derived compounds can be used as antimicrobial agents in medicines and as food preservatives. These compounds can be applied along with other antimicrobial agents to strengthen the effect and/or reduce the required treatment dose.

RESULTS

In the present study, the antibacterial, anti-biofilm and quorum sensing inhibitory activity of carvacrol alone and in combination with the antibiotic cefixime against Escherichia coli was investigated. The MIC and MBC values for carvacrol were 250 μg/mL. In the checkerboard test, carvacrol showed a synergistic interaction with cefixime against E. coli (FIC index = 0.5). Carvacrol and cefixime significantly inhibited biofilm formation at MIC/2 (125 and 62.5 μg/mL), MIC/4 (62.5 and 31.25 μg/mL) and MIC/8 (31.25 and 15.625 μg/mL) for carvacrol and cefixime, respectively. The antibacterial and anti-biofilm potential effect of carvacrol confirmed by the scanning electron microscopy. Real-time quantitative reverse transcription PCR revealed significant down-regulation of the luxS and pfs genes following treatment with a MIC/2 (125 μg/mL) concentration of carvacrol alone and of only pfs gene following treatment with MIC/2 of carvacrol in combination with MIC/2 of cefixime (p < 0.05).

CONCLUSIONS

Because of the significant antibacterial and anti-biofilm activity of carvacrol, the present study examines this agent as an antibacterial drug of natural origin. The results indicate that in this study the best antibacterial and anti-biofilm properties are for the combined use of cefixime and carvacrol.

Research advances on the contamination of vegetables by Enterohemorrhagic Escherichia coli: pathways, processes and interaction

Enterohemorrhagic Escherichia coli is considered one of the primary bacterial pathogens that cause foodborne diseases because it can survive in meat, vegetables and so on. Understanding of the effect of vegetable characteristics on the adhesion and proliferation process of EHEC is necessary to develop control measures. In this review, the amount and methods of adhesion, the internalization pathway and proliferation process of EHEC have been described during the vegetable contamination. Types, cultivars, tissue characteristics, leaf age, and damage degree can affect EHEC adhesion on vegetables. EHEC cells contaminate the root surface of vegetables through soil and further internalize. It can also contaminate the stem scar tissue of vegetables by rain or irrigation water and internalize the vertical axis, as well as the stomata, necrotic lesions and damaged tissues of vegetable leaves. After EHEC adhered to the vegetables, they may further proliferate and form biofilms. Leaf and fruit tissues were more sensitive to biofilm formation, and shedding rate of biofilms on epidermis tissue was faster. Insights into the mechanisms of vegetable contamination by EHEC, including the role of exopolysaccharides and proteins responsible for movement, adhesion and oxidative stress response could reveal the molecular mechanism by which EHEC contaminates vegetables.

Medicinal plant extracts protect epithelial cells from infection and DNA damage caused by colibactin-producing Escherichia coli, and inhibit the growth of bacteria

AIMS

To investigate the biological activity of Thai medicinal plant extracts and their active substances on the inhibition of growth and the transcription of colibactin genes of colibactin-producing Escherichia coli, and effect on the pathogenesis from colibactin toxin including transient infections and colibactin-induced DNA damage.

METHODS AND RESULTS

Among 16 medicinal plants examined, aqueous extracts of Terminalia catappa, Psidium guajava and Sandoricum koetjape demonstrated the growth inhibition against E. coli ATCC 25922, which is known to produce colibactin toxin. These plant extracts contain the active phytochemical compounds, tannin and quercetin, which are able to inhibit the growth of E. coli ATCC 25922. Interestingly, the extracts of T. catappa, P. guajava and S. koetjape, and their compounds tannin and quercetin, protected the eukaryotic epithelial cells of Vero cells and Caco-2 cells from infection and DNA damage by E. coli ATCC 25922. Moreover, these plant extracts and compounds exhibited efficacy to downregulate the expression of five genes (clbA, clbB, clbM, clbN and clbP) that are required for colibactin biosynthesis.

CONCLUSIONS

The extracts of T. catappa, P. guajava and S. koetjape, and their compounds of tannin and quercetin had ability to inhibit the growth and transcription of colibactin genes of colibactin-producing Escherichia coli. Hence, these plant extracts and compounds could protect the transient infection and DNA damage of the eukaryotic epithelial cells.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study is the first of its kind to report on the enhancement of the biological properties of T. catappa, P. guajava and S. koetjape, and to support the exogenous compound usage of tannin and quercetin, which may be able to protect against the transient infection and DNA damage of eukaryotic cells from E. coli carrying colibactin toxin.

A randomized, double-blind, placebo-controlled pilot study to assess bacterial anti-adhesive activity in human urine following consumption of a cranberry supplement

Urinary tract infections (UTIs) are one of the common bacterial infections treated with antibiotics. The North American cranberry is recommended for prophylaxis in women with recurrent UTIs as a nutritional alternative. The ability of cranberry components and their metabolites to inhibit adhesion of uropathogenic Escherichia coli (E. coli) is an important mechanism by which cranberry mitigates UTIs. The objective of this study was to evaluate urinary anti-adhesion activity against type 1 and P-type uropathogenic E. coli after consumption of cranberry +health™ cranberry supplement (cranberry chew). In this randomized, double-blind, placebo-controlled, crossover design pilot trial (n = 20), subjects consumed two cranberry or placebo chews, one in the morning and one in the evening. Clean-catch urine samples collected at the baseline and post-intervention (0-3, 3-6, 6-9, 9-12, 12-24, 24-30, 30-36 h) were tested for anti-adhesion effects with a mannose-resistant human red blood cell hemagglutination assay specific for P-type E. coli, or a T24 cell line model for type 1 E. coli. Urinary anti-adhesion activity against P-type E. coli after consumption of the cranberry chew was significantly greater (p < 0.05) than that observed with placebo chew at all time points except 24-36 h. Ex vivo anti-adhesion effects on type 1 E. coli were greater (p < 0.05) after cranberry chew consumption than placebo chew at 3-6 and 6-9 h urine collections. In conclusion, consumption of cranberry +health™ cranberry supplement exhibited greater ex vivo urinary anti-adhesion activity compared to placebo, suggesting that it may have the potential to help promote urinary tract health.

Inhibitory Effect of Two Traditional Chinese Medicine Monomers, Berberine and Matrine, on the Quorum Sensing System of Antimicrobial-Resistant Escherichia coli

The quorum sensing (QS) system controls bacterial biofilm formation, which is highly related to the virulence and resistance of pathogens. In the present study, the effect of two traditional Chinese medicine (TCM) monomers, berberine and matrine, on biofilm formation and QS-related gene expression of antimicrobial-resistant (AMR) Escherichia coli strains was investigated by laser scanning confocal microscopy (LSCM) observation and real-time PCR. The results indicated a roughly positive relationship between biofilm formation ability and antimicrobial resistance. LSCM observation showed that berberine and matrine inhibited biofilm formation of AMR E. coli strains at 1/2 minimal inhibitory concentration (MIC) (1/2 MIC berberine at OD₆₃₀: 0.1020; 1/2 MIC matrine: OD₆₃₀: 0.1045); furthermore, abnormal cell morphology such as rounded and elongated cells was also observed. This finding was consistent with the downregulation of QS-related genes: luxS, pfS, sdiA, hflX, motA, and fliA. At 1/2 MIC and 1/4 MIC concentrations of berberine, a significant downregulation of luxS, pfS, hflX, ftsQ, and ftsE was observed. The results indicate that berberine and matrine can inhibit biofilm formation by inhibiting the QS system and that berberine is more effective than matrine.

Quorum sensing in food spoilage and natural-based strategies for its inhibition

Food can harbor a variety of microorganisms including spoilage and pathogenic bacteria. Many bacterial processes, including production of degrading enzymes, virulence factors, and biofilm formation are known to depend on cell density through a process called quorum sensing (QS), in which cells communicate by synthesizing, detecting and reacting to small diffusible signaling molecules - autoinducers (AI). The disruption of QS could decisively contribute to control the expression of many harmful bacterial phenotypes. Several quorum sensing inhibitors (QSI) have been extensively studied, being many of them of natural origin. This review provides an analysis on the role of QS in food spoilage and biofilm formation within the food industry. QSI from natural sources are also reviewed towards their putative future applications to prolong shelf life of food products and decrease foodborne pathogenicity.

[Prevent bacteria from communicating: Divide to cure]

Quorum Sensing (QS) is a communication system used by numerous bacteria to synchronize their behavior according to the cell density. In this way, bacteria secrete and sense small mediating molecules, called autoinducers (AI), which concentration increases in the environment proportionally to bacterial cell number. QS induces major physiological and phenotypic changes such as virulence induction and biofilm formation. Biofilm represents a physical barrier which shelters bacteria poorly sensitive to antimicrobial treatments and favors the apparition of resistance mechanisms. Disturbing QS is referred to as quorum quenching (QQ). This strategy is used by microorganisms themselves to prevent the development of specific group behaviors. Two strategies are mainly employed: the use of quorum sensing inhibitors (QSI) and of quorum quenching enzymes (QQE) that degrades AI. Many studies have been dedicated to identifying QSI (natural or synthetic) as well as QQE and demonstrating their anti-virulence and anti-biofilm effects on numerous bacterial species. Synergistic effects between QQ and traditional treatments such as antibiotherapy or with reemerging phage therapy have been put forward. The efficiency of numerous QSI and QQE was thereby demonstrated either with in vitro or in vivo animal models leading to the development of medical devices containing QSI and QQE to improve already existing treatments.

Interference in Bacterial Quorum Sensing: A Biopharmaceutical Perspective

Numerous bacteria utilize molecular communication systems referred to as quorum sensing (QS) to synchronize the expression of certain genes regulating, among other aspects, the expression of virulence factors and the synthesis of biofilm. To achieve this process, bacteria use signaling molecules, known as autoinducers (AIs), as chemical messengers to share information. Naturally occurring strategies that interfere with bacterial signaling have been extensively studied in recent years, examining their potential to control bacteria. To interfere with QS, bacteria use quorum sensing inhibitors (QSIs) to block the action of AIs and quorum quenching (QQ) enzymes to degrade signaling molecules. Recent studies have shown that these strategies are promising routes to decrease bacterial pathogenicity and decrease biofilms, potentially enhancing bacterial susceptibility to antimicrobial agents including antibiotics and bacteriophages. The efficacy of QSIs and QQ enzymes has been demonstrated in various animal models and are now considered in the development of new medical devices against bacterial infections, including dressings, and catheters for enlarging the therapeutic arsenal against bacteria.

Beyond Traditional Antimicrobials: A Caenorhabditis elegans Model for Discovery of Novel Anti-infectives

The spread of antibiotic resistance amongst bacterial pathogens has led to an urgent need for new antimicrobial compounds with novel modes of action that minimize the potential for drug resistance. To date, the development of new antimicrobial drugs is still lagging far behind the rising demand, partly owing to the absence of an effective screening platform. Over the last decade, the nematode Caenorhabditis elegans has been incorporated as a whole animal screening platform for antimicrobials. This development is taking advantage of the vast knowledge on worm physiology and how it interacts with bacterial and fungal pathogens. In addition to allowing for in vivo selection of compounds with promising anti-microbial properties, the whole animal C. elegans screening system has also permitted the discovery of novel compounds targeting infection processes that only manifest during the course of pathogen infection of the host. Another advantage of using C. elegans in the search for new antimicrobials is that the worm itself is a source of potential antimicrobial effectors which constitute part of its immune defense response to thwart infections. This has led to the evaluation of effector molecules, particularly antimicrobial proteins and peptides (APPs), as candidates for further development as therapeutic agents. In this review, we provide an overview on use of the C. elegans model for identification of novel anti-infectives. We highlight some highly potential lead compounds obtained from C. elegans-based screens, particularly those that target bacterial virulence or host defense to eradicate infections, a mechanism distinct from the action of conventional antibiotics. We also review the prospect of using C. elegans APPs as an antimicrobial strategy to treat infections.

Thiophenone Attenuates Enteropathogenic Escherichia coli O103:H2 Virulence by Interfering with AI-2 Signaling

Interference with bacterial quorum sensing communication provides an anti-virulence strategy to control pathogenic bacteria. Here, using the Enteropathogenic E. coli (EPEC) O103:H2, we showed for the first time that thiophenone TF101 reduced expression of lsrB; the gene encoding the AI-2 receptor. Combined results of transcriptional and phenotypic analyses suggested that TF101 interfere with AI-2 signalling, possibly by competing with AI-2 for binding to LsrB. This is supported by in silico docking prediction of thiophenone TF101 in the LsrB pocket. Transcriptional analyses furthermore showed that thiophenone TF101 interfered with expression of the virulence genes eae and fimH. In addition, TF101 reduced AI-2 induced E. coli adhesion to colorectal adenocarcinoma cells. TF101, on the other hand, did not affect epinephrine or norepinephrine enhanced E. coli adhesion. Overall, our results showed that thiophenone TF101 interfered with virulence expression in E. coli O103:H2, suggestedly by interfering with AI-2 mediated quorum sensing. We thus conclude that thiophenone TF101 might represent a promising future anti-virulence agent in the fight against pathogenic E. coli.

Network-assisted investigation of virulence and antibiotic-resistance systems in Pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative bacterium of clinical significance. Although the genome of PAO1, a prototype strain of P. aeruginosa, has been extensively studied, approximately one-third of the functional genome remains unknown. With the emergence of antibiotic-resistant strains of P. aeruginosa, there is an urgent need to develop novel antibiotic and anti-virulence strategies, which may be facilitated by an approach that explores P. aeruginosa gene function in systems-level models. Here, we present a genome-wide functional network of P. aeruginosa genes, PseudomonasNet, which covers 98% of the coding genome, and a companion web server to generate functional hypotheses using various network-search algorithms. We demonstrate that PseudomonasNet-assisted predictions can effectively identify novel genes involved in virulence and antibiotic resistance. Moreover, an antibiotic-resistance network based on PseudomonasNet reveals that P. aeruginosa has common modular genetic organisations that confer increased or decreased resistance to diverse antibiotics, which accounts for the pervasiveness of cross-resistance across multiple drugs. The same network also suggests that P. aeruginosa has developed mechanism of trade-off in resistance across drugs by altering genetic interactions. Taken together, these results clearly demonstrate the usefulness of a genome-scale functional network to investigate pathogenic systems in P. aeruginosa.

Antibacterial Flavonoids from Medicinal Plants Covalently Inactivate Type III Protein Secretion Substrates

Traditional Chinese Medicines (TCMs) have been historically used to treat bacterial infections. However, the molecules responsible for these anti-infective properties and their potential mechanisms of action have remained elusive. Using a high-throughput assay for type III protein secretion in Salmonella enterica serovar Typhimurium, we discovered that several TCMs can attenuate this key virulence pathway without affecting bacterial growth. Among the active TCMs, we discovered that baicalein, a specific flavonoid from Scutellaria baicalensis, targets S. Typhimurium pathogenicity island-1 (SPI-1) type III secretion system (T3SS) effectors and translocases to inhibit bacterial invasion of epithelial cells. Structurally related flavonoids present in other TCMs, such as quercetin, also inactivated the SPI-1 T3SS and attenuated S. Typhimurium invasion. Our results demonstrate that specific plant metabolites from TCMs can directly interfere with key bacterial virulence pathways and reveal a previously unappreciated mechanism of action for anti-infective medicinal plants.

Persistence of Indicator and Pathogenic Microorganisms in Broccoli following Manure Spreading and Irrigation with Fecally Contaminated Water: Field Experiment

In 2011 and 2012, trials consisting of experimental plots were carried out to evaluate the presence of pathogenic (Listeria monocytogenes, Salmonella) and prevalence of indicator (Escherichia coli) microorganisms in broccoli fertilized with liquid hog manure or mineral fertilizers and irrigated zero, one, or two times with E. coli-contaminated water. In 2011, results showed that E. coli contamination in broccoli heads was affected by the interval between irrigation and sampling (P = 0.0236), with a significant decrease between the first and third day following irrigation (P = 0.0064). In 2012, irrigation frequency significantly increased E. coli prevalence in broccoli samples (P = 0.0499). In 2012, E. coli counts in the soil were significantly influenced by the type of fertilizer applied, as plots receiving liquid hog manure showed higher bacterial counts (P = 0.0006). L. monocytogenes was recovered in one broccoli sample, but geno-serogrouping differentiated the isolate from those recovered in manure and irrigation water. The L. monocytogenes serogroup IIA, pulsotype 188 strain was found in six soil samples and in irrigation water applied 5 days before soil sampling. This study highlights the link between E. coli levels in irrigation water, irrigation frequency, and interval between irrigation and harvest on produce contamination. It also demonstrates that L. monocytogenes introduced into the soil following irrigation can persist for up to 5 days.

Extended longevity and robust early-stage development of Caenorhabditis elegans by a soil microbe, Lysinibacillus sphaericus

Caenorhabditis elegans, originally isolated from soil, is a nematode used in various fields of biological research including host–microbe interaction. While bacterial pathogens responsible for human infections have been actively studied in C. elegans, very few bacterial species that provide beneficial effects on C. elegans have been reported. Here, we tested several bacterial soil isolates and then characterized the effects of Lysinibacillus sphaericus on C. elegans growth-related phenotypes. Worms fed with L. sphaericus lived significantly longer than those growing with typical Escherichia coli OP50. Early- and juvenile-stage growth was also highly stimulated by L. sphaericus; body size at 28 h post-hatching was > 2 times larger than OP50-fed worms and L. sphaericus-fed worms moved through the larval stage development more rapidly than control worms. In addition, significantly elevated fertilization was observed in worms fed with L. sphaericus (∼ 8 h faster than the control group). Furthermore, growth with L. sphaericus resulted in the production of larger numbers of progeny than the control growth with OP50. Worms grown with L. sphaericus were highly resistant to oxidative, osmotic and infection stresses. Together, our results reveal a novel mode of growth that involves healthy ageing of nematodes.

Quorum quenching agents: resources for antivirulence therapy

The continuing emergence of antibiotic-resistant pathogens is a concern to human health and highlights the urgent need for the development of alternative therapeutic strategies. Quorum sensing (QS) regulates virulence in many bacterial pathogens, and thus, is a promising target for antivirulence therapy which may inhibit virulence instead of cell growth and division. This means that there is little selective pressure for the evolution of resistance. Many natural quorum quenching (QQ) agents have been identified. Moreover, it has been shown that many microorganisms are capable of producing small molecular QS inhibitors and/or macromolecular QQ enzymes, which could be regarded as a strategy for bacteria to gain benefits in competitive environments. More than 30 species of marine QQ bacteria have been identified thus far, but only a few of them have been intensively studied. Recent studies indicate that an enormous number of QQ microorganisms are undiscovered in the highly diverse marine environments, and these marine microorganism-derived QQ agents may be valuable resources for antivirulence therapy.

Development of a fluorometric microplate antiadhesion assay using uropathogenic Escherichia coli and human uroepithelial cells

A fluorometric microplate assay has been developed to determine Escherichia (E.) coli adhesion to uroepithelial cells (UEC). P-fimbriated E. coli were labeled with BacLight Green and preincubated 30 min with human urine or standard. Fluorescent-E. coli were added to UEC in mircoplates at a 400:1 ratio, incubated 1 h, and washed, and the fluorescence intensity was measured. Specific labeling and adherence were confirmed by flow cytometry. A myricetin (1) standard curve (0-30 μg/mL) was developed; the lower limit of detection was 0.1 μg/mL, and half-maximal inhibitory concentration was 0.88 μg/mL (intra- and interassay coefficients of variance were <10% and <15%, respectively). Vaccinium macrocarpon (cranberry) extracts, quercetin (2), and procyanidins B1 (3), B2 (4), and C1 (5) showed similar inhibition. Antiadhesion activity of urine samples from subjects (n = 12) consuming placebo or V. macrocarpon beverage determined using this assay was positively correlated (R(2) = 0.78; p < 0.01) with a radiolabeled-E. coli assay.

Thiophenone and furanone in control of Escherichia coli O103:H2 virulence

Escherichia coli are a mutual and foodborne pathogen, causing severe intestinal infections typically characterized by diarrhoea and vomiting. Biofilms are often a common source of pathogenic and nonpathogenic bacteria. Quorum sensing is a phenomenon where bacteria communicate and initiate the regulation of several virulence factors and biofilm formation. Thus, quorum sensing has been a new target in the fight against bacterial biofilms. In this study, we investigated the effect of two quorum-sensing inhibitors for preventing in vitro biofilm formation in wild-type E. coli O103:H2. Furanone F202 originates from the red algae Delisea pulchra, and thiophenone TF101 is a sulphur analogue of furanone. We also investigated the effect of thiophenone and furanone on virulence factors controlled by quorum sensing. Both TF101 and F202 interfered with biofilm formation, although TF101 was more effective. TF101 reduced motility presumably by interfering with flagella production, visualized by microscopic techniques. The expressions of flhd, which are involved in flagella synthesis, were affected by thiophenone. This is the first study exploring the effect of thiophenone on E. coli biofilm formation and virulence factors.

[Quorum sensing in bacteria and yeast]

Bacterial sets are complex dynamic systems, which interact with each other and through the interaction, bacteria coexist, collaborate, compete and share information in a coordinated manner. A way of bacterial communication is quorum sensing. Through this mechanism the bacteria can recognize its concentration in a given environment and they can decide the time at which the expression of a particular set of genes should be started for developing a specific and simultaneous response. The result of these interconnections raises properties that cannot be explained from a single isolated bacterial cell.

Extraction, chemical characterization and biological activity determination of broccoli health promoting compounds

Broccoli (Brassica oleracea L. var. Italica) contains substantial amount of health-promoting compounds such as vitamins, glucosinolates, phenolic compounds, and dietary essential minerals; thus, it benefits health beyond providing just basic nutrition, and consumption of broccoli has been increasing over the years. This review gives an overview on the extraction and separation techniques, as well as the biological activity of some of the above mentioned compounds which have been published in the period January 2008 to January 2013. The work has been distributed according to the different families of health promoting compounds discussing the extraction procedures and the analytical techniques employed for their characterization. Finally, information about the different biological activities of these compounds has been also provided.

Cis-9-octadecenoic acid from the rhizospheric bacterium Stenotrophomonas maltophilia BJ01 shows quorum quenching and anti-biofilm activities

Quorum quenching (QQ) is an effective approach for the prevention of bacterial infections involving biofilms. This study reports the QQ and anti-biofilm activities of a rhizospheric bacterium identified as Stenotrophomonas maltophilia BJ01. The QQ activity was demonstrated using Chromobacterium violaceum CV026 as a biosensor. A maximum of 95% reduction in violacein production, a quorum sensing-regulated behavior, was observed. Gas chromatography-mass spectroscopy of the extract showed that the active compound was cis-9-octadecenoic acid, which was confirmed by electronspray ionization-mass spectroscopy data. The extract also inhibited biofilm formation of Pseudomonas aeruginosa ATCC 9027 without affecting its growth. Scanning electron and atomic force microscopy showed architectural disruption of the biofilm when treated with the extract. This is the first report of the QQ and anti-biofilm activities of cis-9-octadecenoic acid isolated from any bacterium. It may have the potential to combat detrimental infections with P. aeruginosa. Further validation is required for any possible medical application.

Quorum sensing and phytochemicals

Most infectious diseases are caused by bacteria, which proliferate within quorum sensing (QS)-mediated biofilms. Efforts to block QS in bacteria and disrupt biofilms have enabled the identification of bioactive molecules that are also produced by plants. This mini review primarily focuses on natural QS inhibitors, which display potential for treating bacterial infections and also enhance the safety of food supply.