Arbekacin, an aminoglycoside antibiotic, has antibacterial activity against both Gram-positive and Gram-negative bacteria and is stable in the presence of aminoglycoside-inactivating enzymes produced by methicillin-resistant Staphylococcus aureus (MRSA). In this report, the antibacterial activity of arbekacin was compared with that of vancomycin, a glycopeptide antibiotic that also has potent antibacterial activity against MRSA. Arbekacin showed concentration-dependent bactericidal activity against MRSA strain 1936 (0.5-2 x MIC), but vancomycin showed only slight bactericidal activity, even at high concentrations of 19 x MIC. Arbekacin showed a longer post-antibiotic effect (2.3-3.8 h) than vancomycin (0-1.3 h) against MRSA strain 1936. Arbekacin induced marked morphological changes at 0.5 x MIC and the changes remained for 2 h after removal of the agent. When exposed to 0.5 x MIC of vancomycin, no notable morphological change was observed in the treated cells. Since arbekacin has broad-spectrum activity, these findings suggest that it may be a useful agent against MRSA infection, especially for polymicrobial MRSA infection with Gram-negative bacilli, such as Pseudomonas aeruginosa.
INTRODUCTION Bacteria live on human skin surface and play crucial roles in various skin conditions 1. The microbiota on healthy skin surfaces contains many kinds of bacteria, such as Corynebacterium, Staphylococcus, and Propionibacteriaceae 2 4. Staphylococcal bacteria, including Staphylococcus aureus S. aureus and Staphylococcus epidermidis S. epidermidis are present in the nasal cavity or sebaceous glands. S. aureus causes inflammation of atopic dry skin as well as skin roughness and food poisoning 5, 6. In contrast, S. epidermidis enhances the innate barrier immunity 7 9. Therefore, many dermatologists and cosmetic
1,2-Alkanediol exhibits antibacterial activity against several bacteria and yeast. However, few studies have reported antimicrobial tests on skin microbiome. Bacterial microbiome on the skin surface include Staphylococcus aureus (S. aureus), which causes rough skin and inflammation in atopic dermatitis and Staphylococcus epidermidis (S. epidermidis), which enhances innate immunity. In this study, the minimal inhibitory concentration (MIC) was evaluated for 1,2-alkanediol comprising 4-12 carbon atoms against S. aureus and S. epidermidis. 1,2-Alkanediol comprising 6-12 carbon atoms exhibited antimicrobial activity against both species of Staphylococcus. The antibacterial activity depended on the alkyl chain length. In addition, the minimum bactericidal concentration (MBC) on agar was evaluated for 1,2-alkanediol comprising 6-12 carbon atoms. 1,2-Octanediol and 1,2-decanediol exhibited significant bactericidal activity.
Adding fatty acids to an oil-in-water (O/W) emulsion changes the stability of the emulsion. In this study, we prepared a series of O/W emulsions consisting of oil (triolein/fatty acid mixture), water and a range of surfactants (sucrose fatty acid esters) with varying hydrophilic-lipophilic balance (HLB) in order to determine the effects of alkyl chain length and the degree of unsaturation of the fatty acid molecules on the stability of the emulsions. As a result, sucrose fatty acid esters with HLB = 5-7 were suitable for obtaining O/W emulsions. In addition, the creaming phenomenon was inhibited for 30 days or more when fatty acids having a linear saturated alkyl chain with 14 or more carbon atoms were added. These findings are useful for designing stable O/W emulsions for food and cosmetic products.
A pot experiment confirmed that pigeonpea could efficiently utilize various sources of phosphorus (P) (aluminium phosphate, iron phosphate and apatite), irrespective of genotype. A qualitative assay method for iron (Fe)-P solubilizing activity showed that root exudates collected from P-deficient pigeonpea contained Fe-P solubilizing substances and that they were released mainly from root tips. Citric, malic, malonic, succinic and piscidic acids were identified in root exudates. Citric and piscidic acids release from roots was increased by low-P treatment in all the genotypes tested. The release rates of citric and piscidic acids were affected by the P concentration of shoots rather than that of roots. The pigeonpea roots released approximately 5-100 times more piscidic acid than citric acid depending on P stress status, plant age and genotype. When organic acids were added to Alfisols, citric acid was most capable of mobilizing P from the soil, followed by piscidic acid and malic acid. No correlation was found between genotypic variability in the release rates of citric and piscidic acids from the roots under low-P treatment at hydroponic culture and in the growth and P uptake of plants on Alfisols. Although citric and piscidic acids released from pigeonpea roots may play a partial role in solubilizing unavailable insoluble P in soils, the releases were thought to be an unsatisfactory strategy for explaining genotypic variation in low P availability of pigeonpea.
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