Novel aqueous oil-in-water emulsions containing extracts of natural coniferous resins are strongly antimicrobial against enterobacteria, staphylococci and yeasts, as well as on bacterial biofilms.

AIMS: The aim of this study was to examine the antimicrobial properties of novel aqueous natural rapeseed oil/saline emulsions containing different soluble components of spruce resin. METHODS AND RESULTS: The composition of aqueous resin emulsions was analysed by GC-MS and their antimicrobial properties were studied with challenge tests and with turbidometric assays. The emulsions were strongly antimicrobial against common Gram-positive and Gram-negative bacteria (including MRSA) as well as common yeasts. Furthermore, they inhibited the biofilm formation and eradicated the microbial biofilms on tested microbes. Characteristic for the emulsions was the presence of oxidized resin acids. Other main components present in emulsions, such as lignans and coumaric acids, were not antimicrobial, when tested separately. CONCLUSIONS: The results indicated that the oxidized resin acids were the antimicrobial components in the emulsions. Also, there appears to be a stoichiometric relationship between the number of resin acid molecules and the number microbe cells in the antimicrobial action. SIGNIFICANCE AND IMPACT OF THE STUDY: The fact that these solutions do not contain abietic acid, which is the main allergenic compound in resins, suggests that these solutions would be suitable, well-tolerated antimicrobials for various medical applications. The aqueous formulation will also allow the expansion of the use of these emulsions in from medical applications to the food preservatives and disinfectants.

The colonization of a simulator of the human intestinal microbial ecosystem by a probiotic strain fed on a fermented oat bran product: effects on the gastrointestinal microbiota.

The effects of Lactobacillus-GG-fermented oat bran product on the microbiota and its metabolic activity in the human gut were investigated, using a simulator of the human intestinal microbial ecosystem (SHIME), by analysing the bacterial population, shortchain fatty acids and gas production. In addition, the effects of fermented oat bran supernatant and supernatant samples from reactors 4, 5 and 6 (large intestine) on the growth of Escherichia coli IHE 13047, Enterococcus faecalis VTT E-93203, Lactobacillus rhamnosus VTT E-94522 (Lactobacillus GG) and Lactococcus lactis subsp. lactis VTT E-90414 were monitored to ascertain possible stimulatory/inhibitory effects by an in vitro turbidometric method. Our experiments showed that Lactobacillus GG colonized the SHIME reactor and this colonization could be maintained for several weeks without extra supplementation. Oat bran feeding also favoured the growth of bifidobacteria and caused an increase in the production of acetic, propionic and butyric acid as well as CH4 and CO2. However, the effects of oat bran, either on bacterial populations or on their metabolic activity, were not directly dose-dependent. In turbidometric measurements, the supernatant of fermented oat bran exerted an inhibitory effect of Lactobacillus GG, but stimulated the growth of enterococci.

Influence of mutations at the rep gene on survival of Escherichia coli following ultraviolet light irradiation or 8-methoxypsoralen photosensitization: evidence for a recA+ rep+-dependent pathway for repair of DNA crosslinks.

Bacteria mutant at the rep gene (specifying a DNA-unwinding enzyme) were slightly more sensitive than rep+ bacteria to far ultraviolet light (ca. 254 nm; (FUV) and to monofunctional psoralen photoproducts produced with near ultraviolet light (ca. 360 nm; NUV). The enhanced sensitivity was shown in uvrA excision-deficient bacteria but not in those carrying the recA mutation. It is concluded that the rep unwinding enzyme has a small promoting effect on post-replication recombination repair. Rep- bacteria were rather more sensitive to the DNA cross-linking action f 8-methoxypsoralen (8-MOP) and NUV. This effect also was found in uvrA but not in recA bacteria. A cross-link repair pathway, dependent on both the recA+ and rep+ genes, therefore exists in addition to the pathway which depends upon the uvrAB endonuclease. Various lines of evidence suggest that the pathway operates at or after DNA replication. Exposure of rep+ bacteria to 8-MOP plus NUV did not induce any activity capable of repairing psoralen cross-links in infecting lambda phage. A possible model involving removal of the cross-link by glycosylase action at the replication fork is proposed.

The comparative mutagenicities of hydrazine and its mono- and di-methyl derivatives in bacterial test systems.

The mutagenic properties of hydrazine and its mono- and di-methyl derivatives were compared by direct microbial tests with the tryptophan auxotroph Escherichia coli as indicator organism. The methyl- and dimethyl-hydrazine were also tested with metabolic activation both by the Ames plate test and by the host-mediated assay with the histidine auxotroph Salmonella typhimurium tester strains. Only hydrazine and methylhydrazine were mutagenic in direct tests, hydrazine being a far more potent mutagen that methylhydrazine. Neither methylhydrazine nor dimethylhydrazines gave positive results in the Ames tests. In host-mediated assays, symmetrical dimethylhydrazine was clearly mutagenic, whereas methylhydrazine showed marginal mutagenic activity, and unsymmetrical dimethylhydrazine was negative. Evidently the mutagenic actions of different hydrazine derivatives, though these compounds are chemically closely related, depend on different reaction mechanisms.