• Proceedings of the Korean Society of Applied Pharmacology
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• 1997.04a
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• pp.40-47
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• 1997

New quinolones generally have a broad antibacterial spectrum against gram-positive, gram-negative, glucose-nonfermenting and anaerobic bacteria. Some of newly developed quinolones have potent activities against S. aureus including MRSA, S.pneumoniae including PRSP, B. fragilis, chlamydiae, mycoplasmas and mycobacteria as well, and show good activities against various strains resistant to antibacterial agents of other classes. Quinolones display postantibiotic effects in vitro and are bactericidal at concentrations similar to or twice that of the minimum inhibitory concentrations (MICs) for susceptible pathogens. In experimental murine infection models including systemic infections with various pathogens such as S. aureus, S. pyogenes, S. pneumoniae, E. coli and P. aeruginosa, quinolones have shown good oral efficacy as well as parenteral efficacy. Good oral absorption and good tissue penetration of quinolones account for good therapeutic effects in clinical settings. The target of quinolones are two structurally related type II topoisomerases, DNA gyrase and DNA topoisomerase IV. Quinolones are shown to stabilize the ternary quinolone-gyrase-DNA complex and inhibit the religation of the cleaved double-stranded DNA. Bacteria can acquire resistance to quinolones by mutations of these target enzymes. Mutation sites and amino acid changes in DNA gyrase and DNA topoisomerase IV are similar in the organisms examined, suggesting that the mechanism of quinolone resistance in the target enzymes is essentially the same among various organisms. Quinolones act on both the target enzymes to different degrees depending on the organisms or agents tested, and bacteria become highly resistant to quinolones in a step-wise fashion. Incomplete cross-resistance among quinolones in some strains of E. coli and S. aureus suggests the possibility of finding quinolones active against quinolone-resistant strains which are prevailing now. To find such quinolones, the potency toward two target enzymes and the membrane permeability including influx and/or efflux systems should be taken into account.

• Applied Chemistry for Engineering
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• v.7 no.6
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• pp.1096-1104
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• 1996

In order to synthesize a new antibacterial and antitumor agents, we have prepared new analogues pteroic acid(13a, 13b), which means C-9 position of pteroic acid has been replaced by norfloxacin(8) or ciprofloxacin(9) and amino group of C-2 position by $CH_3$. These derivatives were synthesized coupling at N-4 piperazine of norfloxacin and ciprofloxacin with 2-amino-3-cyano-5-chloromethylpyrazine(20) provided 1-alkyl(ethyl, cyclopropyl)-6-fluoro-1,4-dihydro-4-oxo-7-[[4-N-(2-amino-3-cyanopyrazin-5-yl)methyl]piperazin-1-yl]-3-quinoline-carboxylic acid(12a, 12b). It was then cyclized with acetamidine. HCI to obtain new analogues of C-2 desaminomethylpteroic acid(13a, 13b) in yield of 76.2% and 82.8 % respectively. These compounds were tested in vitro on antibacterial activity against Gram-positive and Gram-negative bacteria including Pseudomonas aeruginosa ATCC9027. In general, these synthesized compounds(13a, 13b) showed less potent activities than those of norfloxacin.

• Membrane Journal
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• v.32 no.1
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• pp.23-32
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• 2022

Bacteria grow biofilm on various surface such as separation membrane, food packaging film and biomedical device. Growth of biofilm is associated with the formation of a complex structure of exopolysaccharides. Effect of antibacterial effect reduce drastically once the biofilm developed due to the difficulties in mass transport of antimicrobial agent. In order to enhance the antibacterial activity, surface of the membrane is modified, coated or immobilized with functional materials with biocidal properties. One of the idea is to introduce positive charge on the membrane surface by the presence of quaternary ammonium group which might displace divalent metal ion such as magnesium or calcium present in the bacteria cell wall. Efficacy of cell membrane disruption depends on the mobility of the agents available directly on the surface environment. In this review, various biocidal agents like quaternary ammonium group, helamine or zwitter ion containing membrane are discussed.

• Journal of the Korean Society of Clothing and Textiles
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• v.20 no.3
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• pp.512-518
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• 1996

Microcapsules containing 2, 4, 4'-trichloro-2-hydroxydiphenyl ether and perfumes were prepared by the coacervation using poly (vinyl alcohol) and crosslinking agents. Effects of dispersing agents, core materials, agitating speed and crosslinking agents on microcapsule size were investigated. The mean and deviation of microcapsule diameters decreased with increasing agitation speed. The diameters of m;crocapsules decreased with increasing dispering agent concentration at 6, 000 rpm of agitation speed, but it was not changed at 10, 000 rpm. The dispering effect of PVA is better than that of gum arabic. The slight increase in the diameter of microcapsule was observed when the amount of core material was increased. As the amount of crosslinking agent was increased, the diameter of microcapsule was decreased.

• Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.241-247
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• 2015

In an effort to discover alternative phytotherapeutic antimicrobial agents to combat Streptococcus parauberis, a fish pathogenic bacterium, we evaluated the antibacterial activity of seaweed extracts in vitro. A methanolic extract of Ecklonia cava exhibited strong antibacterial activity against S. parauberis isolated from olive flounder Paralichthys olivaceus. Furthermore, the n-hexane soluble (Hexane) fraction of the E. cava methanolic extract exhibited the greatest antibacterial effect on S. parauberis strains with a minimum inhibitory concentration (MIC) ranging from 256 to $1,024{\mu}g/mL$. In addition, the MIC values of oxytetracycline against antibiotic-resistant S. parauberis were markedly reduced up to 64-fold in combination with the Hexane fraction, suggesting that the antibacterial activity of the antibiotic was restored when combined with the Hexane fraction. The interaction between both antibiotics and the Hexane fraction was assessed by the fractional inhibitory concentration (FIC) index. The Hexane fraction and oxytetracycline combination against antibiotic-resistant S. parauberis strains resulted in a median ${\sum}FIC$ range of 0.502 to 0.516. Thus, the synergistic ranges of median ${\sum}FIC$ < 1 were observed for all combinations of the Hexane fraction and oxytetracycline against S. parauberis. To the best of our knowledge, this is the first report indicating the efficacy of an E. cava extract against fish pathogenic bacterium S. parauberis.

• The Korea Journal of Herbology
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• v.30 no.5
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• pp.15-21
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• 2015

Objectives : Methicillin-resistantStaphylococcus aureus(MRSA) is a human pathogen. New antibacterial agents are needed to treat MRSA-related infections. This study investigated the antibacterial activity of EtOH 70% extracts ofTonghyeonipal-dan(THD) which prescription is composed of oriental medicine against MRSA.Methods : The antibacterial activity of THD was evaluated against MRSA strains by using the Disc diffusion method, broth microdilution method, Checkerboard dilution test, and Time-kill test; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors were used.Results : The minimum inhibitory concentration (MIC) of THD is 1,000~2,000 μg/mL against MRSA. In the checkerboard dilution test, fractional inhibitory concentration index (FICI) of THD in combination with antibiotics indicated synergy or partial synergism againstS. aureus. Furthermore, a time-kill assay showed that the growth of the tasted bacteria was considerably inhibited after 24 h of treatment with the combination of THD with selected antibiotics. For measurement of cell membrane permeability, THD 500 μg/mL along with concentration of Triton X-100 (TX) and Tris-(hydroxymethyl) aminomethane (TRIS) were used. In the other hand, N,N-dicyclohexylcarbodimide (DCCD) and Sodium azide (NaN3) were used as an inhibitor of ATPase. TX, TRIS, DCCD and NaN3 cooperation againstS. aureusshowed synergistic action.Conclusions : Accordingly, antimicrobial activity of THD was affected by cell membrane and inhibitor of ATPase were assessed. These results suggest that THD has antibacterial activity, and that THD extract offers great potential as a natural antibiotic against MRSA.

• Journal of Life Science
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• v.16 no.2 s.75
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• pp.297-301
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• 2006

For developing natural antibacterial agents from Houttuynia cordata Thunb., antibacterial effects of volatile flavor component using various bacterial sp. were tested. Extraction from Houttuynia cordata Thunb. by using SDE (Simultaneous steam Distillation-Extraction) showed strong antibacterial activities against Vibrio and Bacillus genus, such as Vibrio. cholerae, V. parahaemolyticus, V. vulnificus, Bacillus. cereus, and B. subtilis. Then chemical compositions of leaf and stem were analyzed. The contents of crude protein, lipid, and ash in stem were less than those of leaf, but fiber contents were higher than those of leaf. Among the amino acids, aspartic acid, glutamic acid, glycine, and arginine were higher than those of other amino acids. Linolenic acid, linoleic acid, oleic acid, and palmitic acid were major fatty acids. Major minerals of Houttuynia cordata Thunb. were potassium, calcium, phosphorus, magnesium, iron, zinc, and copper. Especially, in the case of potassium, it was highest.

• KSBB Journal
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• v.15 no.3
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• pp.226-231
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• 2000

Antibacterial activities of edible plant extracts were investigated to develop natural antimicrobial agents protecting horticultural products from spoiling-microorganisms during their storage. Crude extracts of Artemisa capillaris Allium tuberosum Ailanthus altissima Zanthoxylum pieperitum Pinus densiflora Morus alba lxeris dentata and Allium sativum showed remarkable antibacterial activities against Escherichia coli K 12 and Bacillus subtilis KCTC 1028 After solvent extraction of the crude extracts with n-hexane ethyl acetate chloroform and water in sequence each fractions was re-examined for the antbacterial activities. As results the ethyl acetate fractions of A. capillaris Aaltissima, P. densiflora and I. dentata and all fractions of Z. piperitum and A. sativium showed relatively strong antibacterial activities against E. coli and B. subtilis and the ethyl acetate fraction of A. altissima was the strongest(6mm and 7mm respectively) against two strawberry-spoiling bacteria isolated and identified at our laboratory as Staphylococcus sp. TG-101 and Staphylococcus sp. TG-102.

• Journal of Microbiology and Biotechnology
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• v.20 no.8
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• pp.1204-1209
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• 2010

We evaluated the antibacterial activities of selected edible Korean plant seeds against the food-borne pathogens Staphylococcus aureus KCTC1927, Escherichia coli KCTC2593, Salmonella typhimurium KCTC2054, and Bacillus cereus KCTC1014. While screening for antibacterial agents, we discovered that wheat germ extract contains 2,6-dimethoxy-1,4-benzoquinone (DMBQ) and is highly inhibitory to S. aureus and B. cereus. This is the first report of the antibacterial activity of wheat germ extract. We also investigated the antibacterial activities of the 1,4-benzoquinone standards 1,4-benzoquinone (BQ), hydroquinone (HQ), methoxybenzoquinone (MBQ), and 2,6-dimethoxy-1,4-benzoquinone (DMBQ). DMBQ and BQ were the most highly inhibitory to S. aureus and S. typhimurium, followed by MBQ and HQ. MICs for DMBQ and BQ ranged between 8 and 64 ${\mu}g/ml$ against the four foodborne pathogens tested. DMBQ and BQ showed significant antibacterial activity; the most sensitive organism was S. aureus with an MIC of 8 ${\mu}g/ml$. BQ exhibited good activity against S. typhimurium (32 ${\mu}g/ml$) and B. cereus (32 ${\mu}g/ml$). The results suggest that wheat germ extract has potential for the development of natural antimicrobials and food preservatives for controlling foodborne pathogens.

• Journal of Microbiology and Biotechnology
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• v.29 no.11
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• pp.1707-1716
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• 2019

The development of new antimicrobial agents is essential for the effective treatment of diseases such as sepsis. We previously developed a new short peptide, Pap12-6, using the 12 N-terminal residues of papiliocin, which showed potent and effective antimicrobial activity against multidrug-resistant Gram-negative bacteria. Here, we investigated the antimicrobial mechanism of Pap12-6 and a newly designed peptide, Pap12-7, in which the 12^th Trp residue of Pap12-6 was replaced with Val to develop a potent peptide with high bacterial selectivity and a different antibacterial mechanism. Both peptides showed high antimicrobial activity against Gram-negative bacteria, including multidrug-resistant Gram-negative bacteria. In addition, the two peptides showed similar anti-inflammatory activity against lipopolysaccharide-stimulated RAW 264.7 cells, but Pap12-7 showed very low toxicities against sheep red blood cells and mammalian cells compared to that showed by Pap12-6. A calcein dye leakage assay, membrane depolarization, and confocal microscopy observations revealed that the two peptides with one single amino acid change have different mechanisms of antibacterial action: Pap12-6 directly targets the bacterial cell membrane, whereas Pap12-7 appears to penetrate the bacterial cell membrane and exert its activities in the cell. The therapeutic efficacy of Pap12-7 was further examined in a mouse model of sepsis, which increased the survival rate of septic mice. For the first time, we showed that both peptides showed anti-septic activity by reducing the infiltration of neutrophils and the production of inflammatory factors. Overall, these results indicate Pap12-7 as a novel non-toxic peptide with potent antibacterial and anti-septic activities via penetrating the cell membrane.