Acanthamoeba castellanii is a ubiquitous organism found in environmental water. The amoeba is pathogenic to toward humans and is also a reservoir of bacteria of the genus Legionella, a causative ...agent of legionellosis. Oakmoss, a source of natural fragrance ingredients, and its components are antibacterial agents that are specifically active against the genus Legionella. In the present study, oakmoss and its components were investigated for their inhibitory effects on total (extra- and intracellular) Legionella pneumophila within A. castellanii and on L. pneumophila within A. castellanii. Among the oakmoss components, 3-hydroxy-5-methylphenyl 2,4-dihydroxy-6-methylbenzoate (1), 3-methoxy-5-methylphenyl 2,4-dihydroxy-6-methylbenzoate (2), and 8-(2,4-dihydroxy-6-(2-oxoheptyl)phenoxy)-6-hydroxy-3-pentyl-1H-isochromen-1-one (8) reduced the number of total bacteria (extra- and intracellular) in a test culture and also exhibited high amoebicidal activity against L. pneumophila within A. castellanii at concentrations lower than their IC50 values for A. castellanii. In contrast, 6,8-dihydroxy-3-pentyl-1H-isochromen-1-one (5) reduced the total number of L. pneumophila and, also that of total bacteria after 24 h of treatment (P < 0.05), whereas the compound did not exhibit amoebicidal activity against L. pneumophila within A. castellanii at concentrations lower than its IC50 value against A. castellanii. Thus, it is suggested that these oakmoss components could be good candidates for disinfectants to protect from Legionella infection.
Oakmoss is a natural fragrance ingredient exhibiting highly specific, potent antibacterial activity against Legionella pneumophila, a causative agent of severe water-bone pneumonia. In the present ...study, the antibacterial activity of individual compounds isolated from oakmoss was investigated against L. pneumophila and other Legionella spp. A total of 18 known compounds and two minor novel compounds (i.e., 3-methoxy-5-methylphenyl-2,4-dihydroxy-6-methylbenzoate (compound 9) and 8-(2,4-dihydroxy-6-(2-oxoheptyl)-phenoxy)-6-hydroxy-3-pentyl-1H-isochromen-1-one (compound 20)) were purified from oakmoss. The minimum inhibitory concentrations (MICs) against clinical and environmental isolates of L. pneumophila, L. bozemanii, L. micdadei, L. longbeachae, and L. dumoffii for 11 of the 20 compounds were less than 100 µg/mL (range 0.8-64.0 µg/mL). Novel compounds 9 and 20 exhibited potent antibacterial activity against L. pneumophila strains (MIC ranges of 1.3-8.0 µg/mL and 3.3-13.3 µg/mL, respectively) and also against four other Legionella species (MIC ranges of 0.8-8.0 µg/mL and 3.3-21.3 µg/mL, respectively). Time-kill assays indicated that compounds 9 and 20 kill bacteria at a concentration equivalent to 2×MIC after 1 h and 6 h co-incubations, respectively. While oakmoss and the purified components exhibited antibacterial activity against Legionella spp., they were not active against other Gram-negative and -positive bacteria such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus.
Oakmoss and its components are known as antibacterial agents, specifically against Legionella pneumophila. In the present study, we investigated the effects of oakmoss and its components (phenol, ...didepside and isochromen derivatives) on L. pneumophila biofilm formation, with particular reference to the bactericidal activity (minimum bactericidal concentration; MBC) of these components against the bacterial cells in the biofilm. Of the 20 compounds tested, two didepside derivatives and four phenol derivatives reduced biofilm formation by more than 50% of that observed for the control at their respective minimum inhibitory concentrations (1/2×MIC). The inhibitory activities of these compounds were either equivalent to or greater than that of the clarithromycin reference. Isochromen derivatives had no effect on biofilm formation. Analysis of bactericidal activity of didepside and isochromen derivatives revealed that three of four didepside derivatives and one of four isochromen derivatives exhibited high bactericidal activity (MBC: 32.0–74.7 µg/mL) against the L. pneumophila in the biofilm after 24 h or 48 h of co-incubation; the antibacterial activities of these compounds were almost equivalent to clarithromycin and chlorhexidine gluconate (MBC: 42.7–64.0 µg/mL) that were used as references. Thus, based on their anti-biofilm forming and bactericidal activities, didepside derivatives are considered to be good candidates for disinfectants against L. pneumophila.
Acanthamoeba castellanii, a ubiquitous organism in water environments, is pathogenic toward humans and also is a host for bacteria of the genus Legionella, a causative agent of legionellosis. ...Fragrance ingredients were investigated for their antibacterial activity against planktonic Legionella pneumophila, amoebicidal activity against A. castellanii, and inhibitory effect against L. pneumophila uptake into A. castellanii. Helional® exhibited relatively high antibacterial activity minimum inhibitory concentration (MIC) , 32.0 μg/mL . Anis aldehyde, canthoxal, helional® and vanillin exhibited amoebicidal activity (IC50 values, 58.4±2.0, 71.2±14.7, 66.8±8.3 and 49.1±2.5μg/mL, respectively) . L. pneumophila pretreatment with sub-MICs (0.25×MIC) of anis aldehyde, canthoxal, cortex aldehyde® 50 percent or vanillin evidently reduced L. pneumophila uptake into A. castellanii (p < 0.01) . Thus, fragrance ingredients were good candidates for disinfectant against L. pneumophila and A. castellanii.
ABSTRACT
Structural characterization studies have been carried out on the carbohydrate backbone of Vibrio parahaemolyticus serotype O6 lipopolysaccharides (LPS). The carbohydrate backbone isolated ...from O6 LPS by sequential derivatization, that is, dephosphorylation, O‐deacylation, pyridylamination, N‐deacylation and N‐acetylation, is a nonasaccharide consisting of 3 mol of D‐glucosamine (GlcN) (of which one is pyridylaminated), 2 mol of L‐glycero‐D‐manno‐heptose (Hep), and 1 mol each of D‐galactose (Gal), D‐glucose (Glc), D‐glucuronic acid (GlcA) and 3‐deoxy‐D‐manno‐oct‐2‐ulosonic acid (Kdo). Structural analyses by nuclear magnetic resonance spectroscopy and fast‐atom bombardment mass spectrometry demonstrated that the carbohydrate backbone is β‐Galp‐(1→2)‐α‐Hepp‐(1→3)‐α‐Hepp‐(1→5)‐α‐Kdop‐(2→6)‐β‐GlcpNAc‐(1→6)‐GlcNAc‐PA, in which the 3‐substituted α‐Hepp is further substituted by β‐GlcpNAc‐(1→4)‐β‐Glcp at position 4 and by β‐GlcpA at position 2. In native O6 LPS, an additional 1 mol of D‐galacturonic acid, which is liberated by dephosphorylation in hydrofluoric acid, is present at an unknown position. A previous study by the present authors reported that, of 13 O‐serotype LPS of V. parahaemolyticus, the only LPS from which Kdo was detected was from O6 LPS after mild acid hydrolysis. In the present study, we have demonstrated that only 1 mol of Kdo is present at the lipid A proximal position, a component which is common to the LPS in all serotypes of the bacterium, and that there is no additional Kdo in the carbohydrate backbone of O6 LPS. ELISA and ELISA inhibition analysis using antisera against O6 and Salmonella enterica Minnesota R595 and LPS of both strains further revealed that Kdo is not involved as an antigenic determinant of O6 LPS.
In the current study we investigated the antibacterial activity of fragrance ingredients against Legionella pneumophila, a causative agent of severe pneumonia. Among the 41 different fragrance ...ingredients tested, we found that the natural fragrance ingredients oakmoss (OM) and birch tar oil (BT), which contain many components, exhibit potent antibacterial activity. The minimum inhibitory concentration (MIC, % (v/v)) of OM and BT were 0.0020 and 0.0024, respectively and were lower than that of cinnamic aldehyde (0.0078), which has been previously shown to possess high antimicrobial activity. In a time–kill assay of OM and BT at MIC and two times MIC, the colony forming units (CFU) of the microbe were reduced to between 10−3 to 10−4 of the original CFU after 1 h co-incubation. After this time, the CFU gradually decreased in number, but remained above detection levels even after a 48-h co-incubation, except for BT at two times MIC. In contrast, at a concentration of 0.1% OM and BT (approximately 50 times MIC), CFU were not detected after co-incubation for 1 h. Another 18 fragrance ingredients including ketone, aldehyde, lactone, acid, phenol derivative, aliphatic alcohol and quinoline also exhibited a lesser degree of antibacterial activity against L. pneumophila at a MIC of less than 0.10.
The aim of the current study was to prepare a ternary complex of hinokitiol (HT), a metal ion (Cu (II)) and γ-cyclodextrin (γCD) via coprecipitation and to assess its physicochemical properties and ...the effects of complexation on the antimicrobial activity of HT.
Single-crystal X-ray structural analysis, powder X-ray diffraction (PXRD), near-infrared (NIR) absorption spectroscopy, and electron spin resonance (ESR) spectroscopy were performed to assess the complex in a solid state. Agar dilution was used to determine the minimum inhibitory concentration (MIC) of HT-Cu complex and the ternary inclusion complex with respect to Escherichia coli, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa.
A ternary HT-Cu/γCD inclusion complex formed as a result of coprecipitation. Results of an antimicrobial test revealed that the ternary HT-Cu/γCD inclusion complex had increased antimicrobial activity compared to that of HT alone. The level of antibacterial activity of ternary complex had action equivalent to that of an HT/γCD inclusion complex.
The antimicrobial action of HT can presumably be capitalized on by including HT in CD without a metal in certain applications. The current results should provide a basis for use of hinokitiol as a human and environmentally friendly antimicrobial.
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•・Coprecipitation resulted in the formation of a ternary HT-Cu/γCD inclusion complex.•・HT-Cu/γCD and 2-HT-Cu/γCD form complexes at different molar ratios.•・Ternary inclusion complex increased antibacterial activity in comparison HT alone.
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