Anti-swarming and -biofilm activities of rose phenolic extract during simulated in vitro gastrointestinal digestion

Changes of Bioactive Components and Antioxidant Capacity of Pear Ferment in Simulated Gastrointestinal Digestion In Vitro

Fruit ferment is rich in polyphenols, organic acids, enzymes, and other bioactive components, which contribute to their antioxidant ability. In this study, we investigated the effect of the simulated gastric and intestinal digestion in vitro on the total phenolic content (TPC), total flavonoid content (TFC), phenolic components content, organic acid content, protease activity, superoxide dismutase (SOD) activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (DPPH-RSA), hydroxyl (·OH) radical scavenging activity (·OH-RSA), and total reducing capacity in ‘Xuehua’ pear (Pyrus bretschneideri Rehd) ferment. The result showed that the TPC, TFC, protease activity, and phenolic components such as arbutin, protocatechuic acid, malic acid, and acetic acid showed a rising trend during the simulated gastric digestion in ‘Xuehua’ pear ferment, and these components might contribute to the increasing of ·OH-RSA and total reducing capacity. The SOD activity and epicatechin content showed an increasing trend at first and then a decreasing trend, which was likely associated with DPPH-RSA. During in vitro-simulated intestinal digestion, the majority of evaluated items reduced, except for protease activity, quercetin, and tartaric acid. The reason for the decreasing of bio-accessibility resulted from the inhibition of the digestive environment, and the transformation between substances, such as the conversion of hyperoside to quercetin. The correlation analysis indicated that the antioxidant capacity of ‘Xuehua’ pear ferment was mainly affected by its bioactive compounds and enzymes activity as well as the food matrices and digestive environment. The comparison between the digestive group with and without enzymes suggested that the simulated gastrointestinal digestion could boost the release and delay the degradation of phenolic components, flavonoids, and organic acid, protect protease and SOD activity, and stabilize DPPH-RSA, ·OH-RSA, and total reducing capacity in ‘Xuehua’ pear ferment; thus, the ‘Xuehua’ pear ferment could be considered as an easily digestible food.

Bacteriocin of Pediococcus acidilactici HW01 Inhibits Biofilm Formation and Virulence Factor Production by Pseudomonas aeruginosa

Pseudomonas aeruginosa is a potential source of food contamination that leads to food spoilage and infections as a result of the generation of biofilm and virulence factors. In the present study, we demonstrate that bacteriocin produced by Pediococcus acidilactici HW01 (HW01 bacteriocin) effectively inhibited the biofilm formation of Ps. aeruginosa (66.41, 45.77, and 21.73% of biofilm formation at 0.5, 1, and 2 mg/mL of HW01 bacteriocin, respectively) as well as the production of virulence factors. By means of a microtiter plate method and scanning electron microscopy, HW01 bacteriocin inhibited biofilm formation by Ps. aeruginosa in a dose-dependent manner. Although the viability of biofilm cells of Ps. aeruginosa was reduced in the presence of HW01 bacteriocin, the viability of planktonic cells of Ps. aeruginosa was not affected by HW01 bacteriocin (2.0 × 10⁹ CFU/mL vs. 2.4 × 10⁹ CFU/mL in the absence and the presence of HW01 bacteriocin, respectively). Additionally, HW01 bacteriocin decreased the twitching motility of Ps. aeruginosa as well as the production of virulence factors, such as pyocyanin, protease, and rhamnolipid. Furthermore, HW01 bacteriocin significantly inhibited Ps. aeruginosa biofilm formation on the surface of stainless steel (57% reduction at 24 h and 83% reduction at 72 h). These results indicate that HW01 bacteriocin is an effective antagonist of Ps. aeruginosa as a result of its ability to inhibit biofilm formation and the production of virulence factors.

Natural bioactive substances for the control of food-borne viruses and contaminants in food

Abstract

Food-borne viruses and contaminants, as an important global food safety problem, are caused by chemical, microbiological, zoonotic, and other risk factors that represent a health hazard. Natural bioactive substances, originating from plants, animals, or microorganisms, might offer the possibility of preventing and controlling food-borne diseases. In this contribution, the common bioactive substances such as polyphenols, essential oils, proteins, and polysaccharides which are effective in the prevention and treatment of food-borne viruses and contaminants are discussed. Meanwhile, the preventive effects of natural bioactive substances and the possible mechanisms involved in food protection are discussed and detailed. The application and potential effects of natural bioactive substances in the adjuvant treatment for food-borne diseases is also described.

Graphical abstract

Ethanol Extract of Campsis grandiflora Flower and Its Organic Acid Components Have Inhibitory Effects on Autoinducer Type 1 Quorum Sensing

Chinese herbs are a useful resource bank for natural drug development, and have attracted considerable attention to exploit quorum sensing inhibitors (QSIs). This study was designed to screen QSIs from raw Chinese herb materials. Of the 38 common herbs examined, the ethanol extract of Campsis grandiflora flower had the strongest QSI activity. The C. grandiflora flower ethanol extract (CFEE) was purified by HPD600, and the QSI activities were examined in further detail. CFEE inhibited violacein production of Chromobacterium violaceum 026 in a dose-dependent manner, and inhibit the swarming abilities of Escherichia coli K-12 and Pseudomonas aeruginosa PAO1. Furthermore, CFEE could inhibited biofilm formation and destroyed mature biofilms of E. coli K-12 and P. aeruginosa PAO1. The composition of CFEE was determined by UPLC-MS/MS to distinguish active QSI compounds, and 21 compounds were identified. In addition to gallic acid and caffeic acid, two organic acids, malic acid and succinic acid, were confirmed for the first time to have autoinducer type 1 QSI activities. Therefore, CFEE is a potential QSI that could be used as a novel antimicrobial agent and should be considered for medicinal development.

Current Challenges and Perspectives for the Use of Aqueous Plant Extracts in the Management of Bacterial Infections: The Case-Study of Salmonella enterica Serovars

Worldwide, foodborne diseases are a growing public health problem. Among the infectious bacteria, non-typhoidal Salmonella enterica serovars (NTS) are the major cause of hospitalization and death, and the emergence and spread of their antibiotic-resistance is becoming a worldwide health issue. This, coupled with the restrictions of antibiotics use in agriculture and animal production, calls for alternative approaches to solve this problem. Plant-derived aqueous extracts compounds could provide novel straightforward approaches to control pathogenic bacteria. This review discusses the antimicrobial activity of aqueous plant extracts against Salmonella serovars, the possible mechanisms of action involved, which components/structures might be responsible for such activity, and the current challenges for the use of these extracts/components in Salmonella infection management and their application perspectives.

Anti-quorum sensing activity of Pistacia atlantica against Pseudomonas aeruginosa PAO1 and identification of its bioactive compounds

Pseudomonas aeruginosa is a multidrug resistant opportunistic pathogen and an important cause of nosocomial infections. Quorum-sensing (QS) is a process in which bacterial cell-cell communication can regulates production of many virulence factors including pigment formation and the ability to form biofilm which is essential for establishment of chronic infections. We examined the inhibitory effect of Pistacia atlantica (Anacardiaceae) methanolic leaf extract and its bioactive components on biofilm formation and pigment production by P. aeruginosa PAO1. Fractionation of the methanolic leaf extract was carried out using HPLC based activity profiling. Identification of the active compounds was carried out by the integrated approach of HPLC-DAD and LC-MS followed by molecular docking analysis. Pistacia atlantica crude extract at 2 and 1 mg/mL, inhibited 92% and 79% biofilm formation, respectively. Minimum biofilm inhibitory concentration (MBIC) determined by microbroth dilution was 0.25 mg/mL with 39% inhibition. Pyocyanin production measured by spectrophotometry showed 100% and 83% inhibition at 2 and 1 mg/mL and minimum inhibitory concentration (MIC) was 0.5 mg/mL with 40% inhibition. Four active HPLC fractions (11, 15, 16 and 19) showed MBIC values of 0.06, 0.16, 0.10, 0.15 mg/mL, and MICs for pyocyanin production of 0.49, 0.31, 0.76, >0.30 mg/mL, respectively. The active compounds were identified as rutin (1), myricetin, 3-O-rutinoside (2) and kaempferol-3-O-rutinoside (4), all belonging to the flavonoid family. Molecular docking simulation of the active compounds showed that all had high affinity for LasR protein which is an important quorum-sensing signal receptor. The results of this study suggest that the active components of P. atlantica have high anti-QS activities and may have the potential for treatment of chronic infections caused by Pseudomonas aeruginosa.

The effect of burdock leaf fraction on adhesion, biofilm formation, quorum sensing and virulence factors of Pseudomonas aeruginosa

AIMS

This study aimed to evaluate the effect of a fraction of burdock (Arctium lappa L.) leaf on the initial adhesion, biofilm formation, quorum sensing and virulence factors of Pseudomonas aeruginosa.

METHODS AND RESULTS

Antibiofilm activity of the burdock leaf fraction was studied by the method of crystal violet staining. When the concentration of the burdock leaf fraction was 2·0 mg ml^-1 , the inhibition rates on biofilm formation of P. aeruginosa were 100%. The burdock leaf fraction was found to inhibit the formation of biofilm by reducing bacterial surface hydrophobicity, decreasing bacterial aggregation ability and inhibiting swarming motility. Interestingly, the burdock leaf fraction inhibited the secretion of quorum-sensing (QS) signalling molecule 3-oxo-C12-HSL and interfered quorum sensing. Moreover, the QS-regulated pyocyanin and elastase were also inhibited. Chemical composition analysis by UPLC-MS showed 11 active compounds in the burdock leaf fraction.

CONCLUSIONS

The burdock leaf fraction significantly inhibited the formation of biofilm and quorum sensing, as well as significantly decreased the content of virulence factors.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study introduces a natural and effective bacterial biofilm inhibitor, which could also significantly decrease the content of virulence factors and the drug resistance of P. aeruginosa.