The antibiofilm potential of a heteropolysaccharide produced and characterized from the isolated marine bacterium Glutamicibacter nicotianae BPM30

Biofilms are the significant causes of 80% of chronic infections in the oral cavity, urinary tract, biliary tube, lungs, gastrointestinal tract, and so on to the general public. Treatment of pathogenic biofilm using bacterial exopolysaccharides (EPS) is an effective and promising strategy. In the present work, a marine bacterium was isolated, studied for exopolysaccharide production, and tested for its antibiofilm activity. Approximately 1.31 ± 0.07 g/L of a purified extracellular polysaccharide was produced and characterized from the isolated marine bacterium Glutamicibacter nicotianae BPM30. The hydrolyzed EPS contains multiple monosaccharides such as rhamnose, fructose, glucose, and galactose. The EPS demonstrated potential antibiofilm activity on four tested pathogens in a concentration-dependent mode. The antibiofilm activity of the purified EPS was studied by crystal violet assay and fluorescence staining method. Comparative inhibition results obtained for the tested strains are 93.25% ± 5.25 and 88.56% ± 2.25 for K. pneumoniae; 92.65% ± 7.6 and 98.33% ± 0.85 for P. aeruginosa; 90.36% ± 6.3 and 52.08% ± 7.74 for S. typhi; 84.62% ± 5.6 and 77.90% ± 5.90 for S. dysenteriae. The results of the present work demonstrated the antibiofilm potential of EPS, which could be helpful in the invention of novel curative approaches in battling bacterial biofilm-related medical complications.

A Guideline for Assessment and Characterization of Bacterial Biofilm Formation in the Presence of Inhibitory Compounds

Campylobacter jejuni, a zoonotic foodborne pathogen, is the worldwide leading cause of acute human bacterial gastroenteritis. Biofilms are a significant reservoir for survival and transmission of this pathogen, contributing to its overall antimicrobial resistance. Natural compounds such as essential oils, phytochemicals, polyphenolic extracts, and D-amino acids have been shown to have the potential to control biofilms formed by bacteria, including Campylobacter spp. This work presents a proposed guideline for assessing and characterizing bacterial biofilm formation in the presence of naturally occurring inhibitory molecules using C. jejuni as a model. The following protocols describe: i) biofilm formation inhibition assay, designed to assess the ability of naturally occurring molecules to inhibit the formation of biofilms; ii) biofilm dispersal assay, to assess the ability of naturally occurring inhibitory molecules to eradicate established biofilms; iii) confocal laser scanning microscopy (CLSM), to evaluate bacterial viability in biofilms after treatment with naturally occurring inhibitory molecules and to study the structured appearance (or architecture) of biofilm before and after treatment.

Environmental risk factors associated with the survival, persistence, and thermal tolerance of Cronobacter sakazakii during the manufacture of powdered infant formula

Cronobacter sakazakii is an opportunistic foodborne pathogen of concern for foods having low water activity such as powdered infant formula (PIF). Its survival under desiccated stress can be attributed to its ability to adapt effectively to many different environmental stresses. Due to the high risk to neonates and its sporadic outbreaks in PIF, C. sakazakii received great attention among the scientific community, food industry and health care providers. There are many extrinsic and intrinsic factors that affect C. sakazakii survival in low-moisture foods. Moreover, short- or long-term pre-exposure to sub-lethal physiological stresses which are commonly encountered in food processing environments are reported to affect the thermal resistance of C. sakazakii. Additionally, acclimation to these stresses may render C. sakazakii resistance to antibiotics and other antimicrobial agents. This article reviews the factors and the strategies responsible for the survival and persistence of C. sakazakii in PIF. Particularly, studies focused on the influence of various factors on thermal resistance, antibiotic or antimicrobial resistance, virulence potential and stress-associated gene expression are reviewed.

Bioactive Compounds from P. pertomentellum That Regulate QS, Biofilm Formation and Virulence Factor Production of P. aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen responsible for many nosocomial infections. This bacterium uses Quorum Sensing (QS) to generate antimicrobial resistance (AMR) so its disruption is considered a novel approach. The current study describes the antibiofilm and QS inhibitory potential of extract and chemical components from Piper pertomentellum. The methodo- logy included the phytochemical study on the aerial part of the species, the determination of QS inhibition efficacy on Chromobacterium violaceum and the evaluation of the effect on biofilm formation and virulence factors on P. aeruginosa. The phytochemical study led to the isolation and identification of a new piperamide (ethyltembamide 1), together with four known amides (tembamide acetate 2, cepharadione B 3, benzamide 4 and tembamide 5). The results indicated that the ethanolic extract and some fractions reduced violacein production in C. violaceum, however, only the ethanolic extract caused inhibition of biofilm formation of P. aeruginosa on polystyrene microtiter plates. Finally, the investigation determined that molecules (1-5) inhibited the formation of biofilms (50% approximately), while compounds 2-4 can inhibit pyocyanin and elastase production (30-50% approximately). In this way, the study contributes to the determination of the potential of extract and chemical constituents from P pertomentellum to regulate the QS system in P. aeruginosa.

"Multidimensional correlation analysis of temperature and contact time on eradication of biofilms of Cronobacter sakazakii on abiotic surfaces by combination of hypochlorite and malic acid"

AIM

In the present study, malic acid in combination with sodium hypochlorite is evaluated for eradication of biofilms formed by Cronobacter sakazakii strains individually and in a cocktail on different abiotic surfaces.

METHOD AND RESULTS

The biofilm formation by five strains of C. sakazakii and their cocktail culture on different substrates was studied in Tryptone Soy Broth (TSB) and reconstituted Powdered Infant Formula (PIF). Further, the effect of temperature (4, 27, 37 and 50°C) and contact time (10, 20, 30, 40, 50 and 60 min) on antibiofilm potential of test solution (0.0625 mol l-1 malic acid and 0.00004 mol l-1 sodium hypochlorite) against biofilm formed by C. sakazakii cocktail culture was investigated on these surfaces. The effect was evaluated in terms of viable cell count and biofilm texture using scanning electron microscopy (SEM). Principal Component Analysis (PCA) revealed that the maximum biofilm reduction was observed for stainless steel at 4°C after 60 min of contact whereas at 25, 37 and 50°C, maximum biofilm reduction was observed for polycarbonate. For glass and polyurethane, maximum log reductions were observed at 50°C. The SEM images revealed cell surface deformation and disruption in biofilms after treatment with the test solution.

CONCLUSIONS

The antibiofilm potential was observed to be greatly affected by contact time and temperature. These results indicated that the combination of malic acid NaOCl can effectively kill and remove C. sakazakii biofilms from food contact surfaces and enteral feeding tubes.

Extracellular c-di-GMP Plays a Role in Biofilm Formation and Dispersion of Campylobacter jejuni

Cyclic diguanosine monophosphate (c-diGMP) is a ubiquitous second messenger involved in the regulation of many signalling systems in bacteria, including motility and biofilm formation. Recently, it has been reported that c-di-GMP was detected in C. jejuni DRH212; however, the presence and the role of c-di-GMP in other C. jejuni strains are unknown. Here, we investigated extracellular c-di-GMP as an environmental signal that potentially triggers biofilm formation in C. jejuni NCTC 11168 using a crystal violet-based assay, motility-based plate assay, RT-PCR and confocal laser scanning microscopy (CLSM). We found that, in presence of extracellular c-di-GMP, the biofilm formation was significantly reduced (>50%) and biofilm dispersion enhanced (up to 60%) with no effect on growth. In addition, the presence of extracellular c-di-GMP promoted chemotactic motility, inhibited the adherence of C. jejuni NCTC 11168-O to Caco-2 cells and upregulated the expression of Cj1198 (luxS, encoding quarum sensing pathway component, autoinducer-2), as well as chemotaxis genes Cj0284c (cheA) and Cj0448c (tlp6). Unexpectedly, the expression of Cj0643 (cbrR), containing a GGDEF-like domain and recently identified as a potential diguanylate cyclase gene, required for the synthesis of c-di-GMP, was not affected. Our findings suggest that extracellular c-di-GMP could be involved in C. jejuni gene regulation, sensing and biofilm dispersion.

Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection

Due to the potent antibacterial properties of Cinnamomum and its derivatives, particularly cinnamaldehyde, recent studies have used these compounds to inhibit the growth of the most prevalent bacterial and fungal biofilms. By inhibiting flagella protein synthesis and swarming motility, Cinnamomum could suppress bacterial attachment, colonization, and biofilm formation in an early stage. Furthermore, by downregulation of Cyclic di‐guanosine monophosphate (c‐di‐GMP), biofilm-related genes, and quorum sensing, this compound suppresses intercellular adherence and accumulation of bacterial cells in biofilm and inhibits important bacterial virulence factors. In addition, Cinnamomum could lead to preformed biofilm elimination by enhancing membrane permeability and the disruption of membrane integrity. Moreover, this substance suppresses the Candida species adherence to the oral epithelial cells, leading to the cell wall deformities, damage, and leakages of intracellular material that may contribute to the established Candida’s biofilm elimination. Therefore, by inhibiting biofilm maturation and destroying the external structure of biofilm, Cinnamomum could boost antibiotic treatment success in combination therapy. However, Cinnamomum has several disadvantages, such as poor solubility in aqueous solution, instability, and volatility; thus, the use of different drug-delivery systems may resolve these limitations and should be further considered in future investigations. Overall, Cinnamomum could be a promising agent for inhibiting microbial biofilm-associated infection and could be used as a catheter and other medical materials surface coatings to suppress biofilm formation. Nonetheless, further in vitro toxicology analysis and animal experiments are required to confirm the reported molecular antibiofilm effect of Cinnamomum and its derivative components against microbial biofilm.

Microbiological Quality of Nuts, Dried and Candied Fruits, Including the Prevalence of Cronobacter spp

Cronobacter genus bacteria are food-borne pathogens. Foods contaminated with Cronobacter spp. may pose a risk to infants or immunocompromised adults. The aim of this study was to determine the microbiological quality of nuts, seeds and dried fruits with special emphasis on the occurrence of Cronobacter spp. Analyses were carried out on 64 samples of commercial nuts (20 samples), dried fruits (24), candied fruits (8), seeds (4), and mixes of seeds, dried fruits and nuts (8). The samples were tested for the total plate count of bacteria (TPC), counts of yeasts and molds, and the occurrence of Cronobacter spp. Cronobacter isolates were identified and differentiated by PCR-RFLP (Polymerase Chain Reaction - Restriction Fragments Length Polymorphism) and RAPD-PCR (Random Amplified Polymorphic DNA by PCR) analysis. TPC, and yeasts and molds were not detected in 0.1 g of 23.4%, 89.1%, and 32.8% of the analyzed samples. In the remaining samples, TPC were in the range of 1.2-5.3 log CFU g-1. The presence/absence of Cronobacter species was detected in 12 (18.8%) samples of: nuts (10 samples), and mixes (2 samples). The 12 strains of Cronobacter spp. included: C. sakazakii (3 strains), C. malonaticus (5), and C. turicensis (4). The results of this study contribute to the determination of the presence and species identification of Cronobacter spp. in products of plant origin intended for direct consumption.

The application of bacteriophage to control Cronobacter sakazakii planktonic and biofilm growth in infant formula milk

The goal was to identify the biofilm-forming ability of Cronobacter sakazakii on surfaces of stainless steel (SS) and silicone rubber (SR) in contact with infant formula milk. Two representative bacteriophages (PBES04 and PBES19) were used to control the growth of C. sakazakii as well as its biofilm forming ability on either SS or SR surfaces. Bacterial growth was confirmed at 20 °C when PBES04 and PBES19 were used, whereas C. sakazakii was not normally detected in infant formula milk treated with both bacteriophages for 6 h. In an additional biofilm reduction experiment, the biofilm on SS or SR surfaces were reduced by 3.07 and 1.92 log CFU cm^-2, respectively after PBES04 treatment, and 3.06 and 2.14 log CFU cm^-2, respectively, after PBES19 treatment. These results demonstrate that bacteriophages can be effective in inactivating C. sakazakii in biofilms which could potentially increase food safety in commercial facilities.

An innovative role for luteolin as a natural quorum sensing inhibitor in Pseudomonas aeruginosa

AIMS

The emergence of antibiotic tolerance was a tricky problem in the treatment of chronic Pseudomonas aeruginosa-infected cystic fibrosis and burn victims. The quorum sensing (QS) inhibitor may serve as a new tactic for the bacterial resistance by inhibiting the biofilm formation and the production of virulence factors. This study explored the potential of luteolin as a QS inhibitor against P. aeruginosa and the molecular mechanism involved.

MAIN METHODS

Crystal violet staining, CLSM observation, and SEM analysis were carried out to assess the effect of luteolin on biofilm formation. The motility assays and the production of virulence factors were determined to evaluate the QS-inhibitory activity of luteolin. Acyl-homoserine lactone, RT-PCR, and molecular docking assays were conducted to explain its anti-QS mechanisms.

KEY FINDINGS

The biofilm formation, the production of virulence factors, and the motility of P. aeruginosa could be efficiently inhibited by luteolin. Luteolin could also attenuate the accumulation of the QS-signaling molecules N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL) and N-butanoyl-L-homoserine lactone (BHL) (P < 0.01) and downregulate the transcription levels of QS genes (lasR, lasI, rhlR, and rhlI) (P < 0.01). Molecular docking analysis indicated that luteolin had a greater docking affinity with LasR regulator protein compared with OdDHL.

SIGNIFICANCE

This study is important as it reports the molecular mechanisms involved in the anti-biofilm formation activity of luteolin against P. aeruginosa. This study also indicated that luteolin could be helpful when used for the treatment of clinical drug-resistant infections of P. aeruginosa.

Bacteriophages for ESKAPE: role in pathogenicity and measures of control

INTRODUCTION

The quest to combat bacterial infections has dreaded humankind for centuries. Infections involving ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) impose therapeutic challenges due to the emergence of antimicrobial drug resistance. Recently, investigations with bacteriophages have led to the development of novel strategies against ESKAPE infections. Also, bacteriophages have been demonstrated to be instrumental in the dissemination of virulence markers in ESKAPE pathogens.

AREAS COVERED

The review highlights the potential of bacteriophage in and against the pathogenicity of antibiotic-resistant ESKAPE pathogens. The review also emphasizes the challenges of employing bacteriophage in treating ESKAPE pathogens and the knowledge gap in the bacteriophage mediated antibiotic resistance and pathogenicity in ESKAPE infections.

EXPERT OPINION

Bacteriophage infection can kill the host bacteria but in survivors can transfer genes that contribute toward the survival of the pathogens in the host and resistance toward multiple antimicrobials. The knowledge on the dual role of bacteriophages in the treatment and pathogenicity will assist in the prediction and development of novel therapeutics targeting antimicrobial-resistant ESKAPE. Therefore, extensive investigations on the efficacy of synthetic bacteriophage, bacteriophage cocktails, and bacteriophage in combination with antibiotics are needed to develop effective therapeutics against ESKAPE infections.

Synthesis, bioactivity and 3D-QSAR of azamacrolide compounds with a carbamate or urea moiety as potential fungicides and inhibitors of quorum sensing

Azamacrolides were synthesized and some azamacrolide compounds hold potential for the development of novel fungicides or inhibitors of quorum sensing.

Inhibition of Campylobacter jejuni Biofilm Formation by D-Amino Acids

The ability of bacterial pathogens to form biofilms is an important virulence mechanism in relation to their pathogenesis and transmission. Biofilms play a crucial role in survival in unfavorable environmental conditions, acting as reservoirs of microbial contamination and antibiotic resistance. For intestinal pathogen Campylobacter jejuni, biofilms are considered to be a contributing factor in transmission through the food chain and currently, there are no known methods for intervention. Here, we present an unconventional approach to reducing biofilm formation by C. jejuni by the application of D-amino acids (DAs), and L-amino acids (LAs). We found that DAs and not LAs, except L-alanine, reduced biofilm formation by up to 70%. The treatment of C. jejuni cells with DAs changed the biofilm architecture and reduced the appearance of amyloid-like fibrils. In addition, a mixture of DAs enhanced antimicrobial efficacy of D-Cycloserine (DCS) up to 32% as compared with DCS treatment alone. Unexpectedly, D-alanine was able to reverse the inhibitory effect of other DAs as well as that of DCS. Furthermore, L-alanine and D-tryptophan decreased transcript levels of peptidoglycan biosynthesis enzymes alanine racemase (alr) and D-alanine-D-alanine ligase (ddlA) while D-serine was only able to decrease the transcript levels of alr. Our findings suggest that a combination of DAs could reduce biofilm formation, viability and persistence of C. jejuni through dysregulation of alr and ddlA.

Natural Compounds With Antibacterial Activity Against Cronobacter spp. in Powdered Infant Formula: A Review

Bacteria from the genus Cronobacter are opportunistic foodborne pathogens capable of causing severe infections in neonates, the elderly and immunocompromised adults. The majority of neonatal infections have been linked epidemiologically to dehydrated powdered infant formulas (PIFs), the majority of which are manufactured using processes that do not ensure commercial sterility. Unfortunately, the osmotolerance, desiccation resistance, mild thermotolerance and wide-ranging minimum, optimum and maximum growth temperatures of Cronobacter spp. are conducive to survival and/or growth during the processing, reconstitution and storage of reconstituted PIFs. Consequently, considerable research has been directed at the development of alternative strategies for the control of Cronobacter spp. in PIFs, including approaches that employ antimicrobial compounds derived from natural sources. The latter include a range of phytochemicals ranging from crude extracts or essential oils derived from various plants (e.g., thyme, cinnamon, clove, marjoram, cumin, mint, fennel), to complex polyphenolic extracts (e.g., muscadine seed, pomegranate peel, olive oil, and cocoa powder extracts), purified simple phenolic compounds (e.g., carvacrol, citral, thymol, eugenol, diacetyl, vanillin, cinnamic acid, trans-cinnamaldehyde, ferulic acid), and medium chain fatty acids (monocaprylin, caprylic acid). Antimicrobials derived from microbial sources (e.g., nisin, other antibacterial peptides, organic acids, coenzyme Q0) and animal sources (e.g., chitosan, lactoferrin, antibacterial peptides from milk) have also been shown to exhibit antibacterial activity against the species. The selection of antimicrobials for the control of Cronobacter spp. requires an understanding of activity at different temperatures, knowledge about their mode of action, and careful consideration for toxicological and nutritional effects on neonates. Consequently, the purpose of the present review is to provide a comprehensive summary of currently available data pertaining to the antibacterial effects of natural antimicrobial compounds against Cronobacter spp. with a view to provide information needed to inform the selection of compounds suitable for control of the pathogen during the manufacture or preparation of PIFs by end users.

Lactobacillus gastricus BTM 7 prevents intestinal colonization by biofilm forming Cronobacter sakazakii in Caenorhabditis elegans model host

The study reports protective role of potential probiotic cultures against infection by biofilm forming Cronobacter sakazakii in Caenorhabditis elegans model system. Among the fifteen indigenous potential probiotics, the cell free supernatant of Lactobacillus gastricus BTM7 possessed highest antimicrobial action and biofilm inhibition against C. sakazakii. The competitive exclusion assays revealed that preconditioning with probiotics resulted in increased mean life span of the nematode to 12-13 days as compared to 5-6 days when the pathogen was administered alone. Enhanced expression of the marker genes (pmk-1, daf-16 and skn-1) was observed during the administration of probiotic cultures. The highest expression of pmk-1 (2.5 folds) was observed with administration of L. gastricus BTM7. The principal component analysis on selected variables revealed that L. gastricus BTM7 has the potential to limit the infection of C. sakazakii in C. elegans and enhance the expression of key genes involved in extending life span of the worm.

Impairment of Cronobacter sakazakii and Listeria monocytogenes biofilms by cell-free preparations of lactobacilli of goat milk origin

Biofilm-associated bacterial infections represent one of the major threats to modern medical treatments. Bacteria encased in biofilm matrix are more resistant towards antimicrobials and thus the capability of microbes to persist and nurture in a biofilm seems to be the foremost aspect of pathogenesis and therapeutic failure. Therefore, there is a pressing demand for new drugs active against microbial biofilms. In the current study, anti-biofilm potential of Lactobacillus spp. cell-free supernatants (CFSs) against Cronobacter sakazakii and Listeria monocytogenes was characterized using crystal violet staining and MTT assay. CFSs of goat milk origin lactobacilli not only prevented biofilm formation but also disrupted preformed biofilms. Neutralized and heat-treated preparations of Lactobacillus CFSs also inhibited biofilm formation by test pathogens. The results were quantitatively confirmed by light and fluorescent microscopy observations. Biofilms developed under static conditions displayed typical compact microcolonies with uniform distribution over the surface, while upon CFS challenge, biofilms were disrupted with presence of dead cells. These findings highlight the anti-biofilm potency of Lactobacillus spp. strains of goat milk origin and their potential application in food industries.

Evaluation of commercial probiotic lactic cultures against biofilm formation by Cronobacter sakazakii

BACKGROUND/AIMS

Cronobacter sakazakii, an emergent pathogen is considered as a major concern to infants and neonates fed on reconstituted powdered infant milk formula. In conjunction with many other factors, biofilm forming capacity adds to its pathogenic potential. In view of the facts that infants are at highest risk to C. sakazakii infections, and emerging antibiotic resistance among pathogens, it is imperative to evaluate probiotic cultures for their efficacy against C. sakazakii. Therefore, pure probiotic strains were isolated from commercial probiotic products and tested for their antimicrobial and anti-biofilm activities against C. sakazakii.

METHODS

A total of 6 probiotic strains were tested for their antibiotic susceptibility followed by antimicrobial activity using cell-free supernatant (CFS) against C. sakazakii. The inhibitory activity of CFS against biofilm formation by C. sakazakii was determined using standard crystal violet assay and microscopic observations.

RESULTS

All the probiotic strains were sensitive to ampicillin, tetracycline, vancomycin and carbenicillin whereas most of the strains were resistant to erythromycin and novobiocin. Four of the 6 probiotic derived CFS possessed antimicrobial activity against C. sakazakii at a level of 40 μL. A higher biofilm inhibitory activity (>80%) was observed at initial stages of biofilm formation with weaker activity during longer incubation upto 48 hours (50%-60%).

CONCLUSIONS

The study indicated the efficacy of isolated commercial probiotics strains as potential inhibitor of biofilm formation by C. sakazakii and could be further explored for novel bioactive molecules to limit the emerging infections of C. sakazakii.

A systematic review on black pepper (Piper nigrum L.): from folk uses to pharmacological applications

Considered as the "King of spices", black pepper (Piper nigrum L.) is a widely used spice which adds flavor of its own to dishes, and also enhances the taste of other ingredients. Piper nigrum has also been extensively explored for its biological properties and its bioactive phyto-compounds. There is, however, no updated compilation of these available data to provide a complete profile of the medicinal aspects of P. nigrum. This study endeavors to systematically review scientific data on the traditional uses, phytochemical composition, and pharmacological properties of P. nigrum. Information was obtained using a combination of keywords via recognized electronic databases (e.g., Science Direct and Google Scholar). Google search was also used. Books and online materials were also considered, and the literature search was restricted to the English language. The country with the highest number of traditional reports of P. nigrum for both human and veterinary medicine was India, mostly for menstrual and ear-nose-throat disorders in human and gastrointestinal disorders in livestock. The seeds and fruits were mostly used, and the preferred mode of preparation was in powdered form, pills or tablets, and paste. Piper nigrum and its bioactive compounds were also found to possess important pharmacological properties. Antimicrobial activity was recorded against a wide range of pathogens via inhibition of biofilm, bacterial efflux pumps, bacterial swarming, and swimming motilities. Studies also reported its antioxidant effects against a series of reactive oxygen and nitrogen species including the scavenging of superoxide anion, hydrogen peroxide, nitric oxide, DPPH, ABTS, and reducing effect against ferric and molybdenum (VI). Improvement of antioxidant enzymes in vivo has also been reported. Piper nigrum also exhibited anticancer effect against a number of cell lines from breast, colon, cervical, and prostate through different mechanisms including cytotoxicity, apoptosis, autophagy, and interference with signaling pathways. Its antidiabetic property has also been confirmed in vivo as well as hypolipidemic activity as evidenced by decrease in the level of cholesterol, triglycerides, and low-density lipoprotein and increase in high-density lipoprotein. Piper nigrum also has anti-inflammatory, analgesic, anticonvulsant, and neuroprotective effects. The major bioactive compound identified in P. nigrum is piperine although other compounds are also present including piperic acid, piperlonguminine, pellitorine, piperolein B, piperamide, piperettine, and (-)-kusunokinin, which also showed biological potency. Most pharmacological studies were conducted in vitro (n = 60) while only 21 in vivo and 1 clinical trial were performed. Hence, more in vivo experiments using a pharmacokinetic and pharmacokinetic approach would be beneficial. As a conclusive remark, P. nigrum should not only be regarded as "King of spices" but can also be considered as part of the kingdom of medicinal agents, comprising a panoply of bioactive compounds with potential nutraceutical and pharmaceutical applications.

Pathogenic features and characteristics of food borne pathogens biofilm: Biomass, viability and matrix

Biofilm is a ubiquitous growth pattern of bacterial species survival but is notorious for its threat on public health and food contamination. Extensive studies of the biofilm structure, formation, quantification, quorum sensing system and underlying control strategies have been reported during the past decades. Insightful elucidation of the pathogenic features and characteristic of bacterial biofilm can facilitate in devising appropriate control strategies for biofilm eradication. Therefore, this review mainly summarized the pathogenic features of biofilms from food borne microorganisms, including the biomass (which could be quantified using crystal violet and fluorogenic dye Syto9 assays), viability (which could be determined by tetrazolium salts, fluorescein diacetate, resazurin staining and alamar blue assays) and matrix (which are commonly detected by dimethyl methylene blue and wheat germ agglutinin assays). In addition, three features were further compared with its particular benefits in specific application.