The specific anti-biofilm effect of gallic acid on Staphylococcus aureus by regulating the expression of the ica operon

Staphylococcus aureus (S. aureus) biofilms are of considerable interest in food safety because biofilms can increase the risk of food contamination and enhance the pathogenicity of bacteria. The ica-encoded polysaccharide intercellular adhesin (PIA) plays an important role in biofilm formation. In this study, the MIC of gallic acid against S. aureus in suspension and in biofilms was 2 mg/mL and 4 mg/mL, respectively. Quantitative crystal violet staining of biofilms showed that 2 mg/mL gallic acid can effectively inhibit biofilm formation and the ESEM images clearly showed the three-dimensional biofilm morphology of the S. aureus and the resulting anti-biofilm effect. The determination of viable bacteria in the biofilm revealed that gallic acid penetrated the biofilm to kill S. aureus, the bactericidal effect on the biofilm bacteria was comparable to that of planktonic bacteria. We further explored the influence of gallic acid on ica family gene expression and polysaccharide slime formation in S. aureus biofilm formation. The results showed that icaR was significantly activated that; icaA and icaD were downregulated in a dose-dependent manner with increasing concentrations of gallic acid; however, the expression of icaB and icaC was not significantly affected. The polysaccharide slime formation was reduced as well. Based on these results, gallic acid, as a natural substance, may play an important role in the food industry.     

Antimicrobial and anti-biofilm effects of probiotic Lactobacillus plantarum KU200656 isolated from kimchi

Food Science and Biotechnology - The probiotic properties and anti-pathogenic effects of Lactobacillus plantarum KU200656 (KU200656) isolated from Korean fermented kimchi against Staphylococcus...     

Assessment of anti-biofilm activity and bifidogenic growth stimulator (BGS) effect of lyophilized exopolysaccharides (l-EPSs) from Lactobacilli strains

In the present study, a total of used six lactic acid bacterial strains that isolated from children’s feces and milk products. This study investigated the exopolysacch aride production of these strains. In the culture broth, highest exopolysaccharide production capacity was detected in GD-11, LB-69, and B-3 strains. Monosaccharide compositions of the exopolysaccharides that were purified and lyophilized in the culture medium were investigated and dominant monomer was found to be mannose in all strains. The biofilm-forming capacity of 13 pathogen bacteria was determined and four strains with the highest biofilm-forming capacity were selected as test bacteria for anti-biofilm studies. Different concentrations of l-exopolysaccharides of three lactic acid bacteria were tested for anti-biofilm effect. Highest anti-biofilm effects were exhibited by the L. fermentum LB-69 (90%) against B. cereus RSKK 863. In the statistical analyses performed using the available data, a strong correlation was found between the amount of mannose present in l-exopolysaccharides and the anti-biofilm activity exhibited by l-exopolysaccharides (p < 0.01). In this study, it was concluded that the l-exopolysaccharides of the L. fermentum LB-69 strain could be used as efficient agents with both bifidogenic growth stimulator effect and anti-biofilm effect. If these agents are taken via oral route, it would be possible to provide beneficial effects for the host by increasing the development of bifidobacteria present in the gastrointestinal tract as well as to prevent and treat the diseases by hindering the biofilm formation by harmful bacteria.     

The specific antibacterial effect of the Salvia oil nanoliposomes against Staphylococcus aureus biofilms on milk container

The Staphylococcus aureus (S. aureus) biofilm on container is the main source of microbial contamination in milk. In this study, the nanoliposomes encapsulating Salvia oil (SO) has been prepared. Based on the damage effect of pore-forming toxin on cell membrane, α-toxin secreted from S. aureus has been used to trigger the release of SO from nanoliposomes to achieve antibacterial effect on S. aureus biofilm on milk container. Firstly, the minimum biofilm eradication concentration (MBEC) and biofilms time-dependent killing of SO were tested. The results showed that the MBEC of SO against S. aureus biofilms was 0.2% and SO effectively eradicated the biofilms after treating for 4 h. Subsequently, SO was encapsulated into nanoliposomes in order to increase its stability. The particle size, poly dispersity index (PDI), zeta potential, pH, turbidity, and entrapment efficiency of SO nanoliposomes were analyzed systematically. Gas chromatography–mass spectrometry (GC–MS) has been utilized to observe the controlled release of SO form nanoliposomes incubated with S. aureus. The scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) images have also visually showed that SO nanoliposomes have high anti-biofilm activity against S. aureus biofilms on milk container.     

Enhanced antibacterial and anti-biofilm activities of silver nanoparticles against Gram-negative and Gram-positive bacteria

Silver nanoparticles (AgNPs) have been used as antibacterial, antifungal, antiviral, anti-inflammtory, and antiangiogenic due to its unique properties such as physical, chemical, and biological properties. The present study was aimed to investigate antibacterial and anti-biofilm activities of silver nanoparticles alone and in combination with conventional antibiotics against various human pathogenic bacteria. Here, we show that a simple, reliable, cost effective and green method for the synthesis of AgNPs by treating silver ions with leaf extract of Allophylus cobbe. The A. cobbe-mediated synthesis of AgNPs (AgNPs) was characterized by ultraviolet-visible absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Furthermore, the antibacterial and anti-biofilm activity of antibiotics or AgNPs, or combinations of AgNPs with an antibiotic was evaluated using a series of assays: such as in vitro killing assay, disc diffusion assay, biofilm inhibition, and reactive oxygen species generation in Pseudomonas aeruginosa, Shigella flexneri, Staphylococcus aureus, and Streptococcus pneumonia. The results suggest that, in combination with antibiotics, there were significant antimicrobial and anti-biofilm effects at lowest concentration of AgNPs using a novel plant extract of A. cobbe, otherwise sublethal concentrations of the antibiotics. The significant enhancing effects were observed for ampicillin and vancomycin against Gram-negative and Gram-positive bacteria, respectively. These data suggest that combining antibiotics and biogenic AgNPs can be used therapeutically for the treatment of infectious diseases caused by bacteria. This study presented evidence of antibacterial and anti-biofilm effects of A. cobbe-mediated synthesis of AgNPs and their enhanced capacity against various human pathogenic bacteria. These results suggest that AgNPs could be used as an adjuvant for the treatment of infectious diseases.     

Antioxidant properties of coriander essential oil and linalool and their potential to control Campylobacter spp.

Foodborne diseases remain common around the world with Campylobacteriosis being the most commonly reported zoonosis in the European Union in 2013. Campylobacter jejuni and Campylobacter coli are the main species associated with human illness. Furthermore, Campylobacter can develop biofilms which is becoming a major problem within the food industry. In addition to foodborne pathogens, oxidation is a non-microbial cause of deterioration of food causing loss of quality and safety. Thus, there is an urgent need in the food industry for new and effective strategies that can help prevent food contamination, spoilage and consequently, foodborne illnesses. Essential oils are known for their antimicrobial and antioxidant properties and are already widely used in the food industry. So, the aim of this work was to study the antimicrobial and anti-biofilm activity of coriander essential oil and its major compound linalool against C. jejuni and C. coli strains, as well as their effect in the quorum sensing (QS) system and their potential as antioxidants. Our results, demonstrated that both compounds have anti-Campylobacter activity, inhibited in vitro biofilm formation and promoted biofilm dispersion even at sub-MIC concentrations and interfered with the QS system through the inhibition of violacein production. Moreover, the essential oil and linalool were shown to have radical scavenging properties and lipid peroxidation inhibition ability which could make them potential alternatives to synthetic antioxidants. In sum, our results demonstrated the antibacterial, anti-biofilm, anti-QS and antioxidant potentials of the coriander essential oil and its major compound, linalool, suggesting that they could be used in the food industry to enhance shelf life of food products and increase food safety without requiring chemical additives or preservatives.