Aims: Because the Staphylococcus aureus is one of the most well-known pathogens associated with medical devices and nosocomial infections, the aim of the study was to examine antibiofilm potential of emodin against it.Methods and Results: Antibacterial activity was examined through microdilution assay. Antibiofilm testing included crystal violet staining of biofilm biomass and morphology analysis by Atomic force microscopy (AFM). Furthermore, aerobic respiration was monitored using the Micro-Oxymax respirometer. For investigation of gene expression qRT-PCR was performed. Emodin demonstrated strong antibacterial activity and ability to inhibit biofilm formation of all tested strains. The effect on preformed biofilms was spotted in few strains. AFM revealed that emodin affects biofilm structure and roughness. Monitoring of respiration under emodin treatment in planktonic and biofilm form revealed that emodin influenced aerobic respiration.Moreover, qRT-PCR showed that emodin modulates expression of icaA, icaD, srrA and srrB genes, as well as RNAIII, and that this activity was strain-specific. Conclusion:The results obtained in this study indicate the novel antibiofilm activity of emodin and its multiple pathways of action. Significance and Impact of Study:This is the first study that examined pathways through which emodin expressed its antibiofilm activity.
Acinetobacter baumannii is an emerging nosocomial pathogen resistant to a wide spectrum of antibiotics, with great potential to form a biofilm, which further aggravates treatment of infections caused by it. Therefore, searching for new potent agents that are efficient against A. baumannii seems to be a necessity. One of them, which has already been proven to possess a wide spectrum of biological activities, including antimicrobial effect, is cinnamon essential oil. Still, further increase of antibacterial efficacy and improvement of bioavailability of cinnamon oil is possible by emulsification process. The aim of this study was comparative analysis of cinnamon essential oil and its emulsion against biofilm forming A. baumannii clinical isolates. Furthermore, the investigation of toxicological aspects of possible applications of essential oil and emulsion was done as well. Gas chromatography–mass spectrometry of essential oil indicated trans-cinnamaldehyde as the most abundant component. The cinnamon emulsion was synthesized from cinnamon essential oil by combining modified low- and high- energy methods. Synthesized emulsion was characterized with Fourier-transform infrared spectroscopy and photon correlation spectroscopy. Both substances exhibited significant antibacterial (minimal inhibitory concentrations in the range 0.125–0.5 mg/ml) and antibiofilm effects (inhibitions of formation and reduction of pre-formed biofilm were 47–81 and 30–62%, respectively). Compared to essential oil, the efficacy of emulsion was even stronger considering the small share of pure oil (20%) in the emulsion. The result of biofilm eradication assay was confirmed by scanning electron microscopy. Even though the cytotoxicity was high especially for the emulsion, genotoxicity was not determined. In conclusion, strong antibacterial/antibiofilm effect against A. baumannii of the cinnamon essential oil and the fact that emulsification even potentiated the activity, seems to be of great significance. Observed cytotoxicity implicated that further analysis is needed in order to clearly determine active principles being responsible for obtained antibacterial/antibiofilm and cytotoxic properties.
Contamination by numerous food-borne pathogens is a major challenge facing the food industry daily. Even though there are many strategies in the fight against contamination, pathogens able to attach to different surfaces and form biofilms are the biggest concern. Staphylococcus aureus is a common food-borne pathogen capable of forming biofilms on foods and food contact surfaces. The prevalence of multidrug resistant S. aureus is high in raw products, high-protein foods and processed products. Bearing in mind S. aureus resistance to numerous antibacterial agents, the aim of this study was to investigate antibiofilm activity of an ethyl-acetate extract of the medicinal plant, Frangula alnus, against S. aureus ATCC 25923 and S. aureus ATCC 43300. It was demonstrated that extract reduced survival of both tested strains by up to 67%. Furthermore, quantification of biofilm biomass showed that extract possesses the extraordinary ability to inhibit biofilm formation of both tested strains (up to 91%). On the other hand, the effect on preformed biofilm was less pronounced and measured only for S. aureus ATCC 43300, wherein about 28% of preformed biofilm was eradicated. The results obtained in this study encourage further investigation of F. alnus as a novel antibiofilm agent or preservative in the food industry.
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