Assay bacteria. Gram-negative

To compare the bactericidal efficacy of silver nanoparticles and silver ions, the minimum inhibitory concentration (MIC) assays were conducted for gram-negative bacterium E. coli, gram-positive bacteria S. aureus and B. subtilis and fungus P. phoeniceum. The data on MICs are summarized in Table 18.1. The results demonstrated that the antimicrobial activity of silver ions was superior to that of silver nanoparticles against all microbes tested. 

The plant was traditionally boiled in water to produce a medicinal tea that was used to accelerate childbirth. Reports of this use stimulated interest in characterising the bioactive component, which was subsequently found to be a 29 amino acid peptide referred to as kalata Bl.105 Cyclotides have also been reported to possess antimicrobial activity,106 and, for example, synthetic versions of the cyclotides circulin B and cyclopsychotride A are active against both Grampositive and Gram-negative bacteria.106 Impaired antimicrobial activity of cyclotides is observed at high salt concentration in the assay buffer and the phenomenon of activity linked to ionic strength has also been described for thionins and plant defensins and is an indicator of activity at membranes. 

DS-96 is the most active compound identified by us to date. The compound behaves in every in vitro and in vivo assay, at least equivalent to, if not better than, polymyxin B (Sil et al., 2007). Both DS-96 and PMB bind LPS with equal affinity (Sil et al., 2007), and inhibit LPS-induced NF-kB transactivation with an IC50 of 30 nM (Fig. 12.16a). DS-96 was also found to be active against LPS isolated from a broad range of Gram-negative bacteria (Fig. 12.16c). That the mechanism of action of DS-96 is that of a true LPS-sequestrant was confirmed not only by its specificity toward LPS in that non-LPS stimuli such as TNF-a, PMA and Tlr-2 agonists such... 

Parker, J.H., Fredrickson, H.L., Vestal, J.R. White, D.C. (1982) Sensitive assay, based on hydroxy-fatty acids lipopolysaccharide lipid A for gram negative bacteria in sediments. Applied and Environmental Microbiology 44, 1170-7. 

Both 39 and 39a inhibited phosphatidylinositol turnover in the A431 cell assay system, with IC50 = 10.0 pg/ml and 1.1 pg/ml, respectively[154], Piericidin B5 A-oxide was active against gram positive and some gram negative bacteria and fungi piericidin B5 was inactive [154]. 

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