Bacterial infections present an enormous problem causing human suffering and cost burdens to healthcare systems worldwide. Here we present novel tunable antibacterial coatings which completely inhibit bacterial colonization by Staphylococcus epidermidis but allow normal adhesion and spreading of osteoblastic cells. The coatings are based on amine plasma polymer films loaded with silver nanoparticles. The method of preparation allows flexible control over the amount of loaded silver nanoparticles and the rate of release of silver ions.

A crude extract from the Australian desert plant Eremophila neglecta has recently been shown to possess antibacterial activity in a survey of candidate plants that may bear novel antimicrobial compounds. Bioassay-directed fractionation of the Et(2)O extract of E. neglecta using a broth microdilution assay led to the isolation of three new serrulatane-type diterpenoids, 2,19-diacetoxy-8-hydroxyserrulat-14-ene (2), 8,19-dihydroxyserrulat-14-ene (3), and 8-hydroxyserrulat-14-en-19-oic acid (4), and a known o-naphthoquinone commonly referred to as biflorin (5). The structures of 2-5 were determined using 1D and 2D NMR, FTIR, and high-resolution mass spectrometry. Compounds 3-5 showed antimicrobial activity against Gram-positive bacteria including Staphylococcus aureus, Streptococcus pyogenes, and S. pneumoniae. The minimum inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs) ranged from 6.5 to 101.6 microM and 12.7 to 202.9 microM, respectively. No activity was observed for these compounds against Gram-negative bacteria.

This paper presents a novel and facile method for the generation of efficient antibacterial coatings which can be applied to practically any type of substrate. Silver nanoparticles were stabilized with an adsorbed surface layer of polyvinyl sulphonate (PVS). This steric layer provided excellent colloidal stability, preventing aggregation over periods of months. PVS-coated silver nanoparticles were bound onto amine-containing surfaces, here produced by deposition of an allylamine plasma polymer thin film onto various substrates. SEM imaging showed no aggregation upon surface binding of the nanoparticles; they were well dispersed on amine surfaces. Such nanoparticle-coated surfaces were found to be effective in preventing attachment of Staphylococcus epidermidis bacteria and also in preventing biofilm formation. Combined with the ability of plasma polymerization to apply the thin polymeric binding layer onto a wide range of materials, this method appears promising for the fabrication of a wide range of infection-resistant biomedical devices.

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Plant species of the genus Eremophila (Myoporaceae) are native to Australia and are known to produce a diverse range of unusual secondary compounds. The purpose of this research was to examine the antimicrobial activity of 72 Eremophila species most of which had not been the subject of any previous pharmacological testing. Organic extracts of Eremophila species were screened for antimicrobial activity against Gram-positive and Gram-negative bacteria and yeasts of medical importance. Extracts of a number of Eremophila species showed selective activity against Gram-positive bacteria with MICs for the most active species in the range of 16 to 62 microg/ml for Streptococcus species, and 62 to 250 microg/ml for standard strains of Staphylococcus aureus. Extracts with the greatest activity against standard strains were tested against 68 clinical isolates of multi-resistant methicillin-resistant S. aureus (mMRSA). The majority of the clinical isolates were susceptible to concentrations below 62.5 microg/ml for the extracts of E. drummondii, E. linearis, E. serrulata, E. acrida, E. neglecta, E. virens and a new undescribed species affiliated with E. prolata. The extract of E. virens inhibited growth of all 68 clinical mMRSA isolates at the minimum tested concentration of 31 microg/ml. This study has shown for the first time that a number of different Eremophila species manifest selective antibacterial activity against Gram-positive organisms which are important causes of human disease. It shows that there are several Eremophila species possessing interesting antibacterial activity besides those that have published traditional use. These may yield novel antibacterial compounds with potential to be used in biomedical applications.