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Usnic Acid, a Natural Antimicrobial Agent Able To Inhibit Bacterial Biofilm Formation on Polymer Surfaces. I. Francolini, 2004.In modern medicine, artificial devices are used for repair or replacement of damaged parts of the body, delivery of drugs, and monitoring the status of critically ill patients . However, artificial surfaces are often susceptible to colonization by bacteria and fungi . Once microorganisms have adhered to the surface, they can form biofilms, resulting in highly resistant local or systemic infections . At this time, the evidence suggests that (+)-usnic acid, a secondary lichen metabolite, possesses antimicrobial activity against a number of planktonic gram-positive bacteria, including Staphylococcus aureus, Enterococcus faecalis, and Enterococcus faecium . Since lichens are surface-attached communities that produce antibiotics, including usnic acid, to protect themselves from colonization by other bacteria, we hypothesized that the mode of action of usnic acid may be utilized in the control of medical biofilms . We loaded (+)-usnic acid into modified polyurethane and quantitatively assessed the capacity of (+)-usnic acid to control biofilm formation by either S . aureus or Pseudomonas aeruginosa under laminar flow conditions by using image analysis . (+)-Usnic acid-loaded polymers did not inhibit the initial attachment of S . aureus cells, but killing the attached cells resulted in the inhibition of biofilm . Interestingly, although P . aeruginosa biofilms did form on the surface of (+)-usnic acid-loaded polymer, the morphology of the biofilm was altered, possibly indicating that (+)-usnic acid interfered with signaling pathways . A Colonization Factor (Production of Lateral Flagella) of Mesophilic Aeromonas spp . Is Inactive in Aeromonas salmonicida Strains. Susana Merino, 2003.The nine laf (lateral flagellum) genes of mesophilic aeromonads are in the Aeromonas salmonicida genome . The laf genes are functional, except for lafA (flagellin gene), which was inactivated by transposase 8 (IS3 family) . A pathogenic characteristic of mesophilic aeromonads (lateral flagella) is abolished in this specialized pathogen with a narrow host range . Degradation of Cross-Linked and Non-Cross-Linked Arabinoxylans by the Intestinal Microbiota in Children. Mark J. Hopkins, 2003.In humans, nonstarch polysaccharides (NSP), such as arabinoxylans (AX), are not digested in the upper gut and provide fermentable carbon sources for bacteria growing in the large bowel . Despite the ubiquity of AX in nature, the microbiologic and physiologic consequences of AX digestion in the gut are poorly understood . In this study, we investigated the breakdown of ferulic acid-cross-linked AX (AXF) and non-cross-linked AX in children's intestinal microbiotas, using starch as a readily fermentable polysaccharide for comparative purposes . The experiments were performed using pH-controlled fermentation vessels under anaerobic conditions . The results demonstrated that there was variation in the metabolism of these polysaccharides by colonic microbiotas . AX was always degraded more slowly than starch, while ferulic acid cross-linking reduced the rate of AX fermentation, as shown by fermentation product measurements . Starch digestion was associated with significant acetate and butyrate production, whereas AX breakdown resulted in increased propionate formation . In general, the presence of fermentable carbohydrate significantly increased the total anaerobe counts and eubacterial rRNA concentrations (P < 0.01), while non-cross-linked AX digestion was principally associated with increased viable counts of Bacteroides fragilis group organisms, which was supported by increases in Bacteroides-Porphyromonas-Prevotella group rRNA (P < 0.01) . Starch was considerably more bifidogenic than AX in these fermentations . In conclusion, in this study we found that the effects of AX and AXF on the microbial ecology and metabolism of intestinal microbiotas are similar in children and adults .
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