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The antimicrobial activity of ursolic acid (UA) and oleanolic acid (OA), both triterpenoid compounds, against methicillin-resistant Staphylococcus aureus (MRSA) is controversial. We examined the antimicrobial effects of UA and OA against 19 strains of MRSA isolated from Koreans by determining minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The data showed that the methicillin-sensitive strain S. aureus KCTC 1621 T was more resistant to UA and OA than that of the MRSA strains. The MBC values of UA and OA against MRSA had broad ranges; 4 to 32 µg/ml and 16 to >256 µg/ml, respectively. It was difficult to understand the different antimicrobial activities of UA and OA among the MRSA strains, because UA and OA antimicrobial mechanisms are unknown. These results indicate that the antimicrobial effects of UA and OA against MRSA are dependent on resistance to UA and OA in each strain.

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A novel Gram-positive, anaerobic, and coccus-shaped bacterium, designated as strain ChDC B134(T), was isolated from a human postoperative infectious lesion in the right maxilla between the lateral incisor and canine and was characterized by polyphasic taxonomic analysis. 16S rRNA gene sequence analysis revealed that the strain ChDC B134(T) belonged to the genus Peptoniphilus, as it showed sequence similarities to Peptoniphilus indolicus KCTC 15023(T) (94.0 %) and Peptoniphilus asaccharolyticus KCTC 3321(T) (93.8 %). The prevalent fatty acids of of strain ChDC B134(T) were C16:0 (20.3 %), C18:1 cis 9 (34.3 %), and C18:0 (13.2 %). The DNA G+C content was 30.9 mol%. The cell wall diamino acid was D-ornithine, which is a property shared by other reference type strains of the genus Peptoniphilus. Based on the results of phenotypic, chemotaxonomic, and phylogenetic analysis, strain ChDC B134(T) (=KCOM 1628(T) = KCTC 15227(T) = JCM 30223(T)) should be classified as the type strain of a novel species of genus Peptoniphilus, for which the name Peptoniphilus mikwangii sp. nov. is proposed.

The aim of this study was to evaluate the antimicrobial effect of carvacrol against periodontopathic and cariogenic bacteria and its cytotoxicity in human oral tissue cells. We tested their antibacterial properties against mutans streptococci and five major periodontopathic bacterial species involved in periodontal disease. The antimicrobial activity was evaluated by the minimal inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The cell viability of carvacrol on normal human gingival fibroblast (NHGF) cells was tested by metyl thiazolyl tetrazolium assay. The data showed that carvacrol had remarkable antimicrobial effect on tested bacteria with a MIC and MBC values ranged from 16 to 128 µg/ml and from 32 to 128 µg/ml, respectively. In cell toxicity studies, carvacrol had significantly decreased cell viability when NHGF cells were treated at 128 µg/ml. These findings suggest that carvacrol has a strong antimicrobial activity against periodontopathic and cariogenic bacteria. However, in order to use it as a component of gargling solution or toothpaste, its concentration should be below 64 µg/ml and other compounds having an antimicrobial activity against periodontopathic and cariogenic bacteria should be used together.

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Purpose The purpose of this paper is to study the cause of severe corrosion of the galvanized lightning rods in a 220 kV transformer substation, and to seek the effective corrosion inhibition measures for the hollow lightning rods. Design/methodology/approach The corrosion morphology and rust component of lightning rod was analyzed, and the corrosion process of lightning rod was researched by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), ion chromatography and electrochemical tests. Findings The results indicated that the outer surface of hollow lightning rod was corroded slightly; however, its inner surface suffered severe corrosion because of a long time high-humidity environment inside the tube caused by the rainwater permeation. A rust layer consisted of Fe3O4 and a little FeOOH was accumulated on the inner surface of the hollow lightning rod. Moreover, Fe3O4 rust layer worked as a large cathode area which could promote the corrosion of metal substrate further. A self-accelerating corrosion process was formed on the inner surface, making the corrosion failure of lightning rod occurred and aggravated gradually. Originality/value The corrosion of inner surface of hollow lightning rod cannot be detected easily. More attention should be paid to the corrosion inhibition of lightning rod. The key of corrosion inhibition for the hollow lightning rod was to avoid the rainwater accumulation inside tube. The research results can provide guidelines on the corrosion inhibition measures selection of lightning rod in transformer substation.

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