Diverse Effects of Natural and Synthetic Surfactants on the Inhibition of Staphylococcus aureus Biofilm

A major challenge in the biomedical field is the creation of materials and coating strategies that effectively limit the onset of biofilm-associated infections on medical devices. Biosurfactants are well known and appreciated for their antimicrobial/anti-adhesive/anti-biofilm properties, low toxicity, and biocompatibility. In this study, the rhamnolipid produced by Pseudomonas aeruginosa 89 (R89BS) was characterized by HPLC-MS/MS and its ability to modify cell surface hydrophobicity and membrane permeability as well as its antimicrobial, anti-adhesive, and anti-biofilm activity against Staphylococcus aureus were compared to two commonly used surfactants of synthetic origin: Tween® 80 and TritonTM X-100. The R89BS crude extract showed a grade of purity of 91.4% and was composed by 70.6% of mono-rhamnolipids and 20.8% of di-rhamnolipids. The biological activities of R89BS towards S. aureus were higher than those of the two synthetic surfactants. In particular, the anti-adhesive and anti-biofilm properties of R89BS and of its purified mono- and di-congeners were similar. R89BS inhibition of S. aureus adhesion and biofilm formation was ~97% and 85%, respectively, and resulted in an increased inhibition of about 33% after 6 h and of about 39% after 72 h when compared to their chemical counterparts. These results suggest a possible applicability of R89BS as a protective coating agent to limit implant colonization

Determination of melatonin content of different varieties of hemp (Cannabis sativa L.) by liquid chromatography tandem mass spectrometry

Melatonin (N-acetyl-5-methoxytryptamine), was first isolated in the bovine pineal gland, and then was discovered in bacteria, algae and higher plants. Melatonin concentrations in plants differ from species to species, among varieties within the same species and also within different organs or tissues of a given plant as roots, leaves, fruits, flowers, and seeds. Although the presence of melatonin in plants seems to be a universal trait, there is still lack of information on its occurrence in several plants, in particular in hemp (Cannabis sativa L.). The aim of this study was to develop a method to quantitate melatonin in the aerial parts of the plant, constituted of leaves and flower heads, and in the seeds, of four different hemp varieties using liquid chromatography- tandem mass spectrometry (LC–ESI/MS/MS). A sample preparation procedure with methanol extraction followed by solid-phase clean-up protocol was set up for melatonin extraction and a LC-ESI/MS/MS method in single reaction monitoring (SRM) was used for its determination. Chromatographic separation was achieved on a C18 column using a gradient elution with acetonitrile– buffer ammonium formate/ formic acid system. The developed method, validated as per International Conference on Harmonization guidelines, was successfully applied to analyze hemp samples varieties belonging to fiber-type or drug-type chemotypes. The melatonin was found to accumulate highly in seeds in the range 13.43-30.40 ng g-1while the content in the aerial parts was assessed in the range 1.16-4.85 ng g-1. No correlation was found between the melatonin levels detected in aerial parts and seeds in each hemp variety and the concentration of specific cannabinoids in the same variety

Biosurfactants

Biosurfactants are structurally diverse and heterogeneous groups of surface-active amphipathic molecules. Owing to their capability to reduce surface and interfacial tension, they have a wide range of industrial and environmental applications. The present chapter reviews the most recent results obtained in the production technologies, optimization methods, recovery of biosurfactants, and their many different application fields

Lipopeptides from Bacillus subtilis AC7 inhibit adhesion and biofilm formation of Candida albicans on silicone

Candida albicans is the major fungus that colonises medical implants, causing device-associated infections with high mortality. Antagonistic bacterial products with interesting biological properties, such as biosurfactants, have recently been considered for biofilm prevention. This study investigated the activity of lipopeptide biosurfactant produced by Bacillussubtilis AC7 (AC7 BS) against adhesion and biofilm formation of C. albicans on medical-grade silicone elastomeric disks (SEDs). Chemical analysis, stability, surface activities of AC7 BS crude extract and physicochemical characterisation of the coated silicone disk surfaces were also carried out. AC7 BS showed a good reduction of water surface tension, low critical micelle concentration, good emulsification activity, thermal resistance and pH stability. Co-incubation with 2 mg ml−1 AC7 BS significantly reduced adhesion and biofilm formation of three C. albicans strains on SEDs in a range of 67-69 % and of 56-57 %, respectively. On pre-coated SEDs, fungal adhesion and biofilm formation were reduced by 57-62 % and 46-47 %, respectively. Additionally, AC7 BS did not inhibit viability of C. albicans strains in both planktonic and sessile form. Chemical analysis of the crude extract revealed the presence of two families of lipopeptides, principally surfactin and a lower percentage of fengycin. The evaluation of surface wettability indicated that AC7 BS coating of SEDs surface was successful although uneven. AC7 BS significantly prohibits the initial deposition of C. albicans and slows biofilm growth, suggesting a potential role of biosurfactant coatings for preventing fungal infection associated with silicone medical device