Proteomic Analysis of the Mode of Antibacterial Action ofTrans-Cinnamaldehyde AgainstCronobacter sakazakii415

Proteomic analysis of Staphylococcus aureus exposed to bacteriocin XJS01 and its bio-preservative effect on raw pork loins

Antibacterial mechanism of bacteriocins against foodborne S. aureus is still to be explored, particularly in proteomics, and a deep and comprehensive study on application of bacteriocins for preservation of raw pork is required. Here, proteomic mechanism of Lactobacillus salivarius bacteriocin XJS01 against foodborne S. aureus 2612:1606BL1486 (S. aureus_26) and its preservation effect on raw pork loins stored at 4 °C for 12 days was investigated. The results showed that 301 differentially abundant proteins (DAPs) were identified between XJS01-treated and -free groups (control group) using Tandem mass tag (TMT) quantitative proteomics technology, which were primarily involved in amino acids and carbohydrate metabolism, cytolysis, defense response, cell apoptosis, cell killing, adhesion, and oxygen utilization of S. aureus_26. Bacterial secretion system (SRP) and cationic antimicrobial peptide resistance may be key pathways to maintain protein secretion and counteract the deleterious effects on S. aureus_26 caused by XJS01. In addition, XJS01 could significantly improve the preservation of raw pork loins by the evaluation results of sensory and antibacterial activity on the meat surface. Overall, this study showed that XJS01 induced a complex organism response in S. aureus, and it could be potential pork preservative.

Proteomic Investigation of the Antibacterial Mechanism of trans-Cinnamaldehyde against Escherichia coli

Trans-Cinnamaldehyde (TC) is a widely used food additive, known for its sterilization, disinfection, and antiseptic properties. However, its antibacterial mechanism is not completely understood. In this study, quantitative proteomics was performed to investigate differentially expressed proteins (DEPs) in Escherichia coli in response to TC treatment. Bioinformatics analysis suggested aldehyde toxicity, acid stress, oxidative stress, interference of carbohydrate metabolism, energy metabolism, and protein translation as the bactericidal mechanism. E. coli BW25113ΔyqhD, ΔgldA, ΔbetB, ΔtktB, ΔgadA, ΔgadB, ΔgadC, and Δrmf were used to investigate the functions of DEPs through biochemical methods. The present study revealed that TC exerts its antibacterial effects by inducing the toxicity of its aldehyde group producing acid stress. These findings will contribute to the application of TC in the antibacterial field.

Exploration of Medicinal Plants as Sources of Novel Anticandidal Drugs

BACKGROUND

Human infections associated with skin and mucosal surfaces, mainly in tropical and sub-tropical parts of the world. During the last decade, there have been an increasing numbers of cases of fungal infections in immunocompromised patients, coupled with an increase in the number of incidences of drug resistance and toxicity to anti fungal agents. Hence, there is a dire need for safe, potent and affordable new antifungal drugs for the efficient management of candidal infections with minimum or no side effects.

INTRODUCTION

Candidiasis represents a critical problem to human health and a serious concern worldwide. Due to the development of drug resistance, there is a need for new antifungal agents. Therefore, we reviewed the different medicinal plants as sources of novel anticandidal drugs.

METHODS

The comprehensive and detailed literature on medicinal plants was carried out using different databases, such as Google Scholar, PubMed, and Science Direct and all the relevant information from the articles were analyzed and included.

RESULTS

Relevant Publications up to the end of November 2018, reporting anticandidal activity of medicinal plants has been included in the present review. In the present study, we have reviewed in the light of SAR and mechanisms of action of those plants whose extracts or phytomolecules are active against candida strains.

CONCLUSION

This article reviewed natural anticandidal drugs of plant origin and also summarized the potent antifungal bioactivity against fungal strains. Besides, mechanism of action of these potent active plant molecules was also explored for a comparative study. We concluded that the studied active plant molecules exhibit potential antifungal activity against resistant fungal strains.

Dietary Factors in Prevention of Pediatric Escherichia coli Infection: A Model Using Domestic Piglets

Enterotoxigenic Escherichia coli (ETEC) is the major etiological agent causing acute watery diarrhea that is most frequently seen in young children in lower-income countries. The duration of diarrheal symptom may be shortened by antibiotic treatment, but ETEC is relative refractory to common antibiotics. Burgeoning evidence suggests bioactive components that naturally occur in human milk (e.g., lysozyme and oligosaccharides) and plants (e.g., nondigestible carbohydrates and phytochemicals) contain antimicrobial functions are promising preventive measures to control ETEC infection. Although the exact protective mechanisms may vary for each compound and are still not completely understood, they generally act to (1) competitively inhibit the binding of pathogenic bacteria and toxins to gut epithelium; (2) directly kill pathogens; and (3) stimulate and/or enhance host mucosal and systemic immune defense against pathogenic microorganisms. An appropriate ETEC-challenge animal model is critical to evaluate the effect and unveil the mechanism of bioactive compounds in prevention of enteric infection. Despite wide application in biomedical research, rodents do not usually manifest typical clinical signs of enteric infections. The remarkable differences in digestive physiology, immune response, and gut microbiota between rodents and human beings necessitate the use of alternative animal models. Pigs are closely related to humans in terms of genomes, physiology, anatomy of gastrointestinal tracts, digestive enzymes, components of immune system, and gut microbiota. Like human infants and young children, nursing and nursery piglets are more susceptible to ETEC infection and reproduce the clinical signs as observed in humans. Hence, the ETEC-challenge piglet represents a valuable translational model to study pathogenesis and evaluate dietary factors (e.g., milk bioactive compounds, nondigestible carbohydrates, and phytochemicals) as preventive measures for ETEC infection in pediatrics.

Kinetics of complex formation of Fe(III) with syringic acid: Experimental and theoretical study

Kinetic study on the complexation of syringic acid with Fe(III) was described in aqueous solution at pH 9.0 together with a reappraisal of spectral evidence for chelate formation. The complexation reaction was found to be a first-order with rate constants for k₁ (formation) 3.67 × 10^-2 min^-1. Additionally, the effect of concentration and temperature on the complexation reaction was investigated. The gustatory properties of the isolated complex were investigated and complex showed no metallic taste. The isolated complex was stable at pH 9.0. The apparent activation energy of the complexation reaction was evaluated to be 168 kcal/mol. The total iron content was determined in the isolated complex by AAS technique and was found 0.0073/100 ml. The specific rotation of the complex was found at -85°.

Surface-modified nanoparticles as anti-biofilm filler for dental polymers

The objective of the study was to synthesis silica nanoparticles modified with (i) a tertiary amine bearing two t-cinnamaldehyde substituents or (ii) dimethyl-octyl ammonium, alongside the well-studied quaternary ammonium polyethyleneimine nanoparticles. These were to be evaluated for their chemical and mechanical properties, as well for antibacterial and antibiofilm activity. Samples were incorporated in commercial dental resin material and the degree of monomer conversion, mechanical strength, and water contact angle were tested to characterize the effect of the nanoparticles on resin material. Antibacterial activity was evaluated with the direct contact test and the biofilm inhibition test against Streptococcus mutans. Addition of cinnamaldehyde-modified particles preserved the degree of conversion and compressive strength of the base material and increased surface hydrophobicity. Quaternary ammonium functional groups led to a decrease in the degree of conversion and to low compressive strength, without altering the hydrophilic nature of the base material. In the direct contact test and the anti-biofilm test, the polyethyleneimine particles exhibited the strongest antibacterial effect. The cinnamaldehyde-modified particles displayed antibiofilm activity, silica particles with quaternary ammonium were ineffective. Immobilization of t-cinnamaldehyde onto a solid surface via amine linkers provided a better alternative to the well-known quaternary ammonium bactericides.

Chemistry, Antimicrobial Mechanisms, and Antibiotic Activities of Cinnamaldehyde against Pathogenic Bacteria in Animal Feeds and Human Foods

Cinnamaldehyde is a major constituent of cinnamon essential oils produced by aromatic cinnamon plants. This compound has been reported to exhibit antimicrobial properties in vitro in laboratory media and in animal feeds and human foods contaminated with disease-causing bacteria including Bacillus cereus, Campylobacter jejuni, Clostridium perfringens, Escherichia coli, Listeria monocytogenes, and Salmonella enterica. This integrated review surveys and interprets our current knowledge of the chemistry, analysis, safety, mechanism of action, and antibiotic activities of cinnamaldehyde in food animal (cattle, lambs, calves, pigs, poultry) diets and in widely consumed liquid (apple, carrot, tomato, and watermelon juices, milk) and solid foods. Solid foods include various fruits (bayberries, blueberries, raspberries, and strawberries), vegetables (carrots, celery, lettuce, spinach, cucumbers, and tomatoes), meats (beef, ham, pork, and frankfurters), poultry (chickens and turkeys), seafood (oysters and shrimp), bread, cheese, eggs, infant formula, and peanut paste. The described findings are not only of fundamental interest but also have practical implications for food safety, nutrition, and animal and human health. The collated information and suggested research needs will hopefully facilitate and guide further studies needed to optimize the use of cinnamaldehyde alone and in combination with other natural antimicrobials and medicinal antibiotics to help prevent and treat food animal and human diseases.

Membrane fatty acid composition as a determinant of Listeria monocytogenes sensitivity to trans-cinnamaldehyde

trans-Cinnamaldehyde, the major compound of cinnamon essential oil, is a potentially interesting natural antimicrobial food preservative. Although a number of studies have addressed its mode of action, the factors that determine bacterial sensitivity or tolerance to trans-cinnamaldehyde are poorly understood. We report the detailed characterization of a Listeria monocytogenes Scott A trans-cinnamaldehyde hypersensitive mutant defective in IlvE, which catalyzes the reversible transamination of branched-chain amino acids to the corresponding short-chain α-ketoacids. This mutant showed an 8.4 fold extended lag phase during growth in sublethal concentrations (4 mM), and faster inactivation in lethal concentrations of trans-cinnamaldehyde (6 mM). trans-Cinnamaldehyde hypersensitivity could be corrected by genetic complementation with the ilvE gene and supplementation with branched-chain α-ketoacids. Whole-cell fatty acid analyses revealed an almost complete loss of anteiso branched-chain fatty acids (BCFAs), which was compensated by elevated levels of unbranched saturated fatty acids and iso-BCFAs. Sub-inhibitory concentrations of trans-cinnamaldehyde induced membrane fatty acid adaptations predicted to reduce membrane fluidity, possibly as a response to counteract the membrane fluidizing effect of trans-cinnamaldehyde. These results demonstrate the role of IlvE in BCFA production and the role of membrane composition as an important determinant of trans-cinnamaldehyde sensitivity in L. monocytogenes.

Antimicrobial Activity of Ferulic Acid Against Cronobacter sakazakii and Possible Mechanism of Action

Cronobacter sakazakii is an opportunistic pathogen transmitted by food that affects mainly newborns, infants, and immune-compromised adults. In this study, the antibacterial activity of ferulic acid was tested against C. sakazakii strains. Minimum inhibitory concentration of ferulic acid against C. sakazakii strains was determined using the agar dilution method. Changes in intracellular pH, membrane potential and intracellular ATP concentration were measured to elucidate the possible antibacterial mechanism. Moreover, SYTO 9 nucleic acid staining was used to assess the effect of ferulic acid on bacterial membrane integrity. Cell morphology changes were observed under a field emission scanning electron microscope. The minimum inhibitory concentrations of ferulic acid against C. sakazakii strains ranged from 2.5 to 5.0 mg/mL. Addition of ferulic acid exerted an immediate and sustained inhibition of C. sakazakii proliferation. Ferulic acid affected the membrane integrity of C. sakazakii, as evidenced by intracellular ATP concentration decrease. Moreover, reduction of intracellular pH and cell membrane hyperpolarization were detected in C. sakazakii after exposure to ferulic acid. Reduction of green fluorescence indicated the injury of cell membrane. Electronic microscopy confirmed that cell membrane of C. sakazakii was damaged by ferulic acid. Our results demonstrate that ferulic acid has moderate antimicrobial activity against C. sakazakii. It exerts its antimicrobial action partly through causing cell membrane dysfunction and changes in cellular morphology. Considering its antimicrobial properties, together with its well-known nutritional functions, ferulic acid has potential to be developed as a supplement in infant formula or other foods to control C. sakazakii.

The Membrane Proteins Involved in Virulence of Cronobacter sakazakii Virulent G362 and Attenuated L3101 Isolates

Cronobacter sakazakii is an opportunistic foodborne pathogen and the virulence differences were previously documented. However, information about membranous proteins involved in virulence differences was not available. In this study, virulent characterization such as biofilm formation and flagella motility between virulent C. sakazakii isolate G362 and attenuated L3101 were determined. Then, two-dimensional gel electrophoresis (2-DE) technology was used to preliminarily reveal differential expression of membranous proteins between G362 and L3101. On the mass spectrometry (MS) analysis and MASCOT research results, fourteen proteins with differential expression were successfully identified. At the threshold of twofold changes, five out of eight membranous proteins were up-regulated in G362. Using RT-PCR, the expression abundance of the protein (enzV, ompX, lptE, pstB, and OsmY) genes at mRNA levels was consistent with the results by 2-DE method. The findings presented here provided novel information and valuable knowledge for revealing pathogenic mechanism of C. sakazakii.

Antimicrobial activity of syringic acid against Cronobacter sakazakii and its effect on cell membrane

Syringic acid (SA) has been reported to exhibit antibacterial ability against various microorganisms, but little work has been done on its effect on Cronobacter sakazakii. In this study, minimum inhibitory concentrations (MICs) of SA against various C. sakazakii strains were determined. Moreover, changes in intracellular ATP concentration, intracellular pH (pHin), membrane potential and membrane integrity were measured to evaluate the influence of SA on cell membrane. Finally, field emission scanning electron microscope (FESEM) was used to assess the morphological changes of bacterial cells caused by SA. It was shown that the MICs of SA against all tested C. sakazakii strains were 5mg/mL. SA retarded bacterial growth, and caused cell membrane dysfunction, which was evidenced by intracellular ATP concentration decrease, pHin reduction, cell membrane hyperpolarization and changes in cellular morphology. These findings indicated that SA has potential to be developed as a natural preservative to control C. sakazakii in foods associated with this pathogen and prevent related infections.

Effect of a VietnameseCinnamomum cassiaessential oil and its major componenttrans-cinnamaldehyde on the cell viability, membrane integrity, membrane fluidity, and proton motive force ofListeria innocua

The antibacterial mechanism of a Cinnamomum cassia essential oil from Vietnam and of its main component (trans-cinnamaldehyde, 90% (m/m) of C. cassia essential oil) against a Listeria innocua strain was investigated to estimate their potential for food preservation. In the presence of C. cassia essential oil or trans-cinnamaldehyde at their minimal bactericidal concentration (2700 μg·mL–1), L. innocua cells fluoresced green after staining with Syto9® and propidium iodide, as observed by epifluorescence microscopy, suggesting that the perturbation of membrane did not cause large pore formation and cell lysis but may have introduced the presence of viable but nonculturable bacteria. Moreover, the fluidity, potential, and intracellular pH of the cytoplasmic membrane were perturbed in the presence of the essential oil or trans-cinnamaldehyde. However, these membrane perturbations were less severe in the presence of trans-cinnamaldehyde than in the presence of multicomponent C. cassia essential oil. This indicates that in addition to trans-cinnamaldehyde, other minor C. cassia essential oil components play a major role in its antibacterial activity against L. innocua cells.

Sub-inhibitory concentrations of trans-cinnamaldehyde attenuate virulence in Cronobacter sakazakii in vitro

Cronobacter sakazakii is a foodborne pathogen, which causes a life-threatening form of meningitis, necrotizing colitis and meningoencephalitis in neonates and children. Epidemiological studies implicate dried infant formula as the principal source of C. sakazakii. In this study, we investigated the efficacy of sub-inhibitory concentrations (SIC) of trans-cinnamaldehyde (TC), an ingredient in cinnamon, for reducing C. sakazakii virulence in vitro using cell culture, microscopy and gene expression assays. TC significantly (p ≤ 0.05) suppressed C. sakazakii adhesion to and invasion of human and rat intestinal epithelial cells, and human brain microvascular endothelial cells. In addition, TC inhibited C. sakazakii survival and replication in human macrophages. We also observed that TC reduced the ability of C. sakazakii to cause cell death in rat intestinal cells, by inhibiting nitric oxide production. Results from gene expression studies revealed that TC significantly downregulated the virulence genes critical for motility, host tissue adhesion and invasion, macrophage survival, and LPS (Lipopolysaccharide) synthesis in C. sakazakii. The efficacy of TC in attenuating these major virulence factors in C. sakazakii underscores its potential use in the prevention and/or control of infection caused by this pathogen.

Cronobacter species (formerly known as Enterobacter sakazakii) in powdered infant formula: a review of our current understanding of the biology of this bacterium

Cronobacter species (formerly known as Enterobacter sakazakii) are opportunistic pathogens that can cause necrotizing enterocolitis, bacteraemia and meningitis, predominantly in neonates. Infection in these vulnerable infants has been linked to the consumption of contaminated powdered infant formula (PIF). Considerable research has been undertaken on this organism in the past number of years which has enhanced our understanding of this neonatal pathogen leading to improvements in its control within the PIF production environment. The taxonomy of the organism resulted in the recognition of a new genus, Cronobacter, which consists of seven species. This paper presents an up-to-date review of our current knowledge of Cronobacter species. Taxonomy, genome sequencing, current detection protocols and epidemiology are all discussed. In addition, consideration is given to the control of this organism in the manufacturing environment, as a first step towards reducing the occurrence of this pathogen in PIF.