• Journal of Microbiology and Biotechnology
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• v.9 no.3
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• pp.276-281
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• 1999

In order to determine the functional region of the antifungal protein (AFP) isolated from Aspergillus giganteus responsible for growth inhibitory activity and the promotion of phospholipid vesicle aggregation, overlapping peptides covering the complete sequence of AFP were synthesized. The antibiotic activity against bacterial, fungal, and tumor cells, and the vesicle-aggregation activity of the synthetic peptides were investigated. The AFP functional sequence responsible for antibiotic and vesicle-aggregation activity was determined to be located within the region between AFP residues 19 to 32. AFP (19-32) exhibited an a-helical conformation in a cell membrane-like environment. AFP (19-32) displayed potent antibiotic activity against bacterial, fungal, and tumor cells without peptide toxicity as indicated by hemolysis. Accordingly, AFP (19-32) could be used as a good model for the design of effective antibiotic agents with powerful antibiotic activity yet without any cytotoxic effects against the host organism.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.12-19
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• 2009

The aim of this study is to assess the antibiotic activity of Actinomyces in plaque from black stained primary teeth to Streptococcus mutans. Samples were obtained from four children, 2-6 years of age, who had black stains on all erupted primary teeth. 16 different Actinomyces spp. were isolated, and antibiotic activity test with paper disc method was done. The results were as follows, 1. No.1 and No.5 Actinomyces spp. showed the antibiotic activity to Streptococcus mutans and the activity of No.5 Actinomyces spp. could compete with that of Oxacillin. 2. No.1 and No.5 Actinomyces spp. also exhibited the antibiotic activity to Bacillus cereus, Bacillus subtilis commonly used as experimental bacteria for testing antibiotic activity. 3. For identification of No.1 and No.5 spp., PCR analysis was done. No.5 spp. matched Actinomyces viscosus at 97% level but No.1 spp. didn't match.

• Journal of Microbiology and Biotechnology
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• v.20 no.1
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• pp.82-87
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• 2010

Biotransformation is often used to improve chemical activity. We evaluated the antimicrobial activity of rhapontigeuin, converted from rhapontin after treatment with Pectinex. Rhapontigenin showed 4-16 times higher antimicrobial activity than rhapontin. The activity was higher against Gram-positive strains than Gram-negative strains. Minimum inhibitory concentrations (MICs) of rhapontigenin, retinol, and five antibiotics were determined by the microbroth dilution method for antibiotic-sensitive and -resistant Propionibacterium acnes. We also investigated the in vitro antibacterial activity of rhapontigenin in combination with antibiotic against antibiotic-resistant P. acnes. The antibiotic combination effect against resistant P. acnes was studied by the checkerboard method. The combination formulations (rhapontigenin and clindamycin, retinol and clindamycin) showed synergistic effects on the inhibition of the growth of clindamycin-resistant P. acnes. It is predictable that the combination of antibiotics with rhapontigenin is helpful to treat acne caused by antibiotic-resistant P. acnes. The antibacterial activity of rhapontigenin was enhanced by biotransformation.

• Korean Journal of Pharmacognosy
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• v.41 no.1
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• pp.38-42
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• 2010

Curcumin content of butanol fraction from C. longa was found to be 22.4942% of the highest content. However, in DPPH radical scavenging ability and antibacterial activity against methicillin resistance Staphylococcus aureus(MRSA, CCARM3696), ethylacetate fraction contained 2.5791% of curcumin was exhibited highest activity. In comparison of enhancing antibiotic(ampicillin) effect against MRSA, ethanol extract contained 1.7838% of curcumin showed more strong activity. This indicates that the ethanol extract and some fractions from C. longa can have antibacterial activity and enhancing antibiotic effect possibly without curcumin. Appropriate use of antimicrobial agent was important point prior to the development of new antibiotics. And in that sence, extract and fractions of C. longa were worth using as synergist of antibiotics and natural antimicrobial agent.

• Bulletin of the Korean Chemical Society
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• v.20 no.9
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• pp.1078-1084
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• 1999

A synthetic cecropin A(1-13)-melittin(1-13) [CA-ME] hybrid peptide was known to be an antimicrobial peptide having strong antibacterial, antifungal and antitumor activity with minimal cytotoxic effect against human erythrocyte. Analogues were synthesized to investigate the influences of the flexible hinge region of CA-ME on the antibiotic activity. Antibiotic activity of the peptides was measured by the growth inhibition against bac-terial, fungal and tumor cells and vesicle-aggregating or disrupting activity. The deletion of Gln-Gly-Ile (P1) or Gly-Gln-Gly-Ile-Gly (P3) from CA-ME brought about a significant decrease on the antibiotic activities. In contrast, Gly-Ile-Gly deletion (P2) from CA-ME or Pro insertion (P5) instead of Gly-Gln-Gly-Ile-Gly of CA-ME retained antibiotic activity. This result indicated that the flexible hinge or β-bend structure provided by Gly-Gln-Gly-Ile-Gly, Gln-Gly, or Pro in the central region of the peptides is requisite for its effective antibiotic activity and may facilitate easily the hydrophobic C-terminal region of the peptide to penetrate the lipid bilayers of the target cell membrane. In contrast, P4 and P6 with Gly-Gln-Gly-Pro-Gly or Gly-Gln-Pro in the central region of the peptide caused a drastic reduction on the antibiotic activities. This result suggested that the con-secutive β-bend structure provided by Gly-Gln-Gly-Pro-Gly or Gly-Gln-Pro in the central hinge region of the peptide seems to interrupt the ion channel/pore formation on the target cell membranes.

• The Korean Journal of Mycology
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• v.9 no.2
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• pp.103-108
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• 1981

The antibiotic-producing Streptomyces strains were isolated from the soils of various localities in Yeang-Kwang and tested for the activity against some of gram positive and negative microorganisms, especially against Pseudomonas aeruginosa. The results are summarized as follows. 1. A total of 1464 Streptomyces strains were isolated from 336 soil samples. Of all the strains tested, 636 strains of the isolates showed antibiotic activity against either gram positive or negative test organisms. And 408 of the 636 strains were strongly active against one or all of those test­organisms. 2. Ninety-three of Streptomyces strains among the active isolates showed the antibiotic activity against Pseudomonas aeruginosa, and 24 of 93 strains showed the strong antibiotic activity against all of the test organisms i.e. Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Salmonella typhi and Shigella jlexneri. 3. Antibiotic-producing Streptomyces strains active against Pseudomonas aeruginosa were isolated from the soil samples taken from vegetable field, paddy field, sandy ground and roadway, but not isolated from the soil taken from dwelling area, grass field and piers.

• Natural Product Sciences
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• v.13 no.2
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• pp.164-168
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• 2007

To investigate natural antibiotics from plant essential oils and to evaluate their synergism with current antimicrobial drugs in inhibiting antibiotic-resistant strains of Streptococcus pneumoniae. The minimal inhibitory concentrations (MICs) of eleven plant essential oils and their main components were established for two antibiotic-susceptible and two antibiotic-resistant strains of S. pneumoniae, using broth microdilution tests. Potential synergism with oxacillin, norfloxacin, or erythromycin was evaluated using a checkerboard microtitre assay. Among the tested oils, Mentha piperita oil and its main component, menthol, exhibited the strongest inhibitory activities against all of the tested strains. The activity of antibiotics against antibiotic-resistant strains of S. pneumoniae was enhanced significantly by combination with Mentha piperita oils and its main component, menthol. In conclusion, the combination Mentha piperita essential oil or menthol with antibiotics could be used to reduce the effective dose of antibiotic and to modulate the resistance of S. pneumoniae strains.

• Korean Journal of Microbiology
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• v.5 no.2
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• pp.86-92
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• 1967

By cylinder-plate method was the antibiosis of 15 strains of Aspergilli examined, which were isolated from Korean "Meju" collected through all over South-Korea. The results are as follows; 1) Only two strains of Aspergilli (strain 1 and 9) sellected in screening test have antibiosis for the several gram positive and negative bacteria. 2) The activity of antibiotic produced by strain I was excellent, having been cultured at 25.deg.C in the Malt-infusion Czapek's medium of pH 3.5 to 7.5 for 6 days. 3) The activity of antibiotic produced by strain 9 was excellent, having been cultured at 25.deg.C in the Czapek's medium of pH 4.5 to 6.5 for 6 days. 4) When Aspergilli were cultured under optimum conditions which resulted, by experiments, the activity of antibiotic produced by Aspergilli was stronger than activity of 10.gamma./ml. streptomycin.eptomycin.

• Korean Journal of Medicinal Crop Science
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• v.25 no.6
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• pp.375-380
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• 2017

Background: The objective of this study were to determine the antibacterial activity and antibiotic activity-enhancing effect of 70% ethanol extract of the root of Rumex japonicus Houtt. and its fractions when used in combination with gentamicin against aerobic skin flora. Methods and Results: The antibacterial activity and antibiotic (gentamicin) activity enhancing effect against aerobic skin flora were determined using the disc diffusion assay. Chloroform fraction (CF) and ethyl acetate fraction (EF) showed higher activities against Staphylococcus aureus and Staphylococcus epidermidis than those shown by other fractions. Regarding the antibiotic (gentamicin) activity-enhancing effect against aerobic skin flora, the n-hexane fraction (HF) and CF showed strong activity. The combination of HF and CF with gentamicin was evaluated using the broth dilution assay to determine the inhibitory effect on the growth of aerobic skin flora. The combination of CF with gentamicin exhibited the highest inhibitory effect on the growth of S. aureus and S. epdermidis. MTT assay performed to determine the viability of L929 cells revealed that EF treatment resulted in viability of 33.96 - 116.76% at the tested concentration. The combination of 70% ethanol extract and its other fractions with gentamicin showed low cell toxicity. Conclusions: Appropriate use of antimicrobial agents is important prior to the development of new antibiotics. The 70% ethanol extract of the root of R. japonicus Houtt. and its fractions showed significant synergism with gentamicin when used in combination against S. aureus and S. epdermidis. Thus, R. japonicus Houtt. could be used as a functional materials in antimicrobial-related fields.

• Korean Journal of Pharmacognosy
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• v.15 no.1
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• pp.15-23
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• 1984

To find antimicrobial strains of the soil microorganisms in Korea, they were isolated from the soil samples of different locations and screened for antibiotic activity against several standard microbes. An isolate among them had an antibacterial activity against gram-positive bacteria. The examination of its morphological and biochemical characteristics according to the International Streptomyces Project methods showed that it belongs to the genus Streptomyces. The strain was named DMC-72. The strain appears to be a new strain when it was compared with the species within the genus which have been so far reported. The antibiotic metabolite of the strain was produced in submerged culture method. It was found to be a quinone compound and was named soulomycin. This strain was also found to produce an ${\alpha}-amylase$ inhibitor in the submerged culture.