• Archives of Pharmacal Research
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• v.19 no.5
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• pp.400-405
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• 1996

In vitro studies were conducted to dertermine the frequency rate of spontaneous resistance to LB20304 and to dertermine whether cross-resistance to other antimicrobial agents develops. In eight strains of bacteria, the frequency of mutation to LB20304 at the concentrations of four and eight times the minimal inhibitory concentration(MIC) ranaged from less than 4.0 ${\times}$ $10^{-10}$ to 2.2 $\{times}$ $10^{-10}$ . These results were similar to those founf for other new fluoroquinolones. THe development of stepwise resistance was determined by repeated subculture in broth in the presence of increasing concentration of the compounds. Exposure of bacteria to increasing concentrations of LB20304 resulted in the selection of organisms with higher MICs. There were 4- to 128-fold increases in the MIC of LB20304 for bacterial strains of Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli and Pseudomonas aeruginosa. However, those strains selected after repeated exposure were well within the susceptibility range for LB20304 except for Pseudomonas aeruginosa. The resistant isolates selected with LB20304 showed cross-resistance when tested against ciprofloxacin and vice versa.

• International Journal of Oral Biology
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• v.38 no.2
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• pp.51-54
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• 2013

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the important causative microbes for nosocomial infection and has been isolated from the dental environment. The purpose of this study was to investigate the antimicrobial activity of linalool and ${\alpha}$-terpineol against MRSA isolates from a Korean population. In the experiments, we determined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of these two compounds against 18 strains of MRSA. The data revealed that the $MIC_{90}/MBC_{90}$ values of linalool and ${\alpha}$-terpineol against MRSA were >12.8 mg/ml and 6.4 mg/ml, respectively. These results indicate that ${\alpha}$-terpineol has more potent antimicrobial activity against MRSA than linalool and may have utility as an anti-MRSA cleansing agent for dental instruments and dental unit chairs.

• Journal of Microbiology and Biotechnology
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• v.17 no.5
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• pp.858-864
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• 2007

This study investigated the antibacterial activities of sophoraflavanone G from Sophora flavescens in combination with two antimicrobial agents against oral bacteria. The combined effect of sophoraflavanone G and the antimicrobial agents was evaluated using the checkerboard method to obtain a fractional inhibitory concentration(FIC) index. The sophoraflavanone G+ampicillin(AM) combination was found to have a synergistic effect against S. mutans, S. sanguinis, S. sobrinus, S. gordonii, A. actinomycetemcomitans, F nucleatum, P. intermedia, and P. gingivalis, whereas the sophoraflavanone G+gentamicin(GM) combination had a synergistic effect against S. sanguinis, S. criceti, S. anginosus, A. actinomycetemcomitans, F nucleatum, P. intermedia, and P. gingivalis. Neither combination exhibited any antagonistic interactions(FIC index>4). In particular, the MICs/MBCs for all the bacteria were reduced to one-half$\sim$one-sixteenth as a result of the drug combinations. A synergistic interaction was also confirmed by time-kill studies for nine bacteria where the checkerboard suggested synergy. Thus, a strong bactericidal effect was exerted through the drug combinations, plus in vitro data suggested that sophoraflavanone G combined with other antibiotics may be microbiologically beneficial rather than antagonistic.

• Korean Journal of Medicinal Crop Science
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• v.18 no.5
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• pp.315-322
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• 2010

This study was carried out to investigate the antimicrobial activities of organic extracts obtained from the fruit of Thuja orientalis L. The native fruits in Korea were collected and extracted by 80% ethanol, and the extract was sequentially fractionated with n-hexane, chloroform, ethylacetate, and butanol. The fraction yields of n-hexane, chloroform, ethylacetate, butanol and water of ethanol extract were 10.15%, 10.05%, 1.45%, 45.35% and 27.55%, respectively. n-Hexane-soluble fraction showed the highest antibacterial activity against gram positive bacteria, while the chloroform, ethylacetate, butanol and aqueous fractions did not show any antibacterial activity. Minimum inhibitory concentration (MICs) on Staphyloycoccus aureus, Bacillus subtilis and Sateptococcus pneumoniae, n-hexane-soluble fraction were $100\;{\mu}g$, $500\;{\mu}g$ and $50\;{\mu}g$/disc, respectively. The antibacterial activity was not destroyed by heating at 80, 100, $120^{\circ}C$ for 30 min and was not affected by pH. In the inhibitory test against the Staphylococcus aureus, Bacillus subtilis and Sateptococcus pneumoniae, n-hexane-soluble fraction showed potent growth inhibition at the concentration of 0.1 and $0.5\;{\mu}g/mL$ for 12~24 hours and n-hexane-soluble fraction did not show any mutagenic activity.

• Preventive Nutrition and Food Science
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• v.6 no.4
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• pp.230-234
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• 2001

The extract of Ulmus davidiana var. japonica cortex has known as natural anti-inflammatory substance in East Asia. For the identification of antimicrobial substance, it was extracted by using methanol and fractionated by using different organic solvents. The fraction of butanol was represented the highest antimicrobial activities. Therefore, the butanol fraction was purified and identified the chemical structure by $^1$H and $^{13}$ C-NMR spectra, FT-IR and EI/MS spectroscopies. The isolated antimicrobial substance was identified as cis-2-[3,4-dihydroxy phenyl]-3,4-dihydro-2H-1-benzopyran-3,5,7-triol, which has commonly known as (-)epicatechin. Its minimum inhibitory concentrations (MICs) against Staphylococcus aureus and Listeria monocytogenes were shown as 100 $\mu\textrm{g}$/mL, respectively.

• YAKHAK HOEJI
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• v.52 no.3
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• pp.219-224
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• 2008

Clinically isolated methicillin-resistant Staphylococcus aureus strains were exposed to subinhibitory concentration of DW286, DW-224a, gemifloxacin, trovafloxacin, sparfloxacin and ciprofloxacin during 26- to 39-days period. Subculturing led to resistance development, and most of the selected mutants were above susceptible breakpoints. Selected mutants had broad cross resistance to other quinolone antibiotics and only one mutant was completely susceptible to all fluoroquinolones. Twenty five among 42 mutants revealed mutations on DNA gyrase and topoisomerase IV by sequencing. Also 16 mutants had fluoroquinolones MICs that were 4-32 times lower in the presence of reserpine. In conclusion, alterations in DNA gyrase or topoisomerase IV and action of efflux pumping out system are the resistance mechanisms of DW-224a.

• YAKHAK HOEJI
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• v.42 no.1
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• pp.89-94
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• 1998

Propionibacterium acnes is the pharmacological target site of antiacne drugs. We have examined the antiacne activity of ninety seven natural products which have been used as Korean traditional medicines in various skin disorders. The antibacterial activity of extracts from the natural products were evaluated against P. acnes ATCC 9616 by disc method. Twelve natural products showed the potent antibacterial activity against P. acnes, and were, selected for the minimal inhibitory concentration(MC) against P. acnes. MICs of nine extracts were below 0.3% (w/v) and Sophora flavescens showed the most potent activity with a MIC of less than 0.008%(w/v) against P. acnes. Thus, the results suggest that nine natural products including S. flavescens can be developed as sources of promising potent antiacne agents.

• Natural Product Sciences
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• v.25 no.1
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• pp.11-15
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• 2019

Lauraceae is a family medicinal plant whose tubers possesses antimicrobial, and cytotoxic, such as antiparasitic and anti-inflammatory special effects and has been used for the medicine in the cure of hepatitis and rheumatism. The antimicrobial activities of bioactive compounds including one neolignan; kunstlerone (1) and two alkaloids include isocaryachine (2) and noratherosperminine (3) as well as crude hexane, methanol and dichloromethane extracts were evaluated. Additionally, the effect of compounds 1, 2 and 3 were evaluated on A549, PC-3, A375, HT-29 and WRL-68 cell lines. In conclusion, kunstlerone 1 showed moderate cytotoxicity against various cancer cell lines such as A549, PC-3, A375, HT-29 and WRL-68, respectively with $EC_{50}$ values of 28.02, 26.78, 33.78, 33.65 and $16.46{\mu}g/mL$. The crude methanol extract showed antigrowth activity against S. pyogenes II and B. cereus, with MICs of $256{\mu}g/mL$. The compounds kunstlerone (1), isocaryachine (2) and noratherosperminine (3) showed complete inhibition against P. shigelloides, with MIC ${\leq}60{\mu}g/mL$ compare to ampicillin, as a positive control, which showed antigrowth activity against P. shigelloides at MIC $10{\mu}g/mL$.

• Natural Product Sciences
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• v.25 no.2
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• pp.172-180
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• 2019

Infections with Pseudomonas aeruginosa are difficult to treat not only because it is often associated with multidrug-resistant infections but also it is able to form biofilm. The aim of this study was to evaluate the antibiofilm and anti-Quorum Sensing (QS) activities of Thymbra capitata essential oils (EOs) against Beta Lactamase (BL) producing P. aeruginosa and the reference strain P. aeruginosa 10145. GC/MS analysis showed that thymol (23.25%) is the most dominant compound in T. capitata EOs. The MICs of T. capitata EOs against P. aeruginosa (BL) and P. aeruginosa 10145 were 1.11%. At sub MIC (0.041, 0.014 and 0.0046%), the EOs of T. capitata remarkably inhibited the biofilm formation of both strains tested and complete inhibition of the biofilm formation was reported at 0.041%. The EOs of T. capitata were found to inhibit the swarming motility, aggregation ability and hydrophobic ability of P. aeruginosa (BL) and P. aeruginosa 10145. Interestingly, the EOs of T. capitata reduce the production of three secreted virulence factors that regulated by QS system including pyocyanin, rhamnolipids and LasA protease. The potent antibiofilm and anti-QS activities of T. capitata EOs can propose it as a new antibacterial agent to control pseudomonas infections.

• Journal of Microbiology and Biotechnology
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• v.32 no.8
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• pp.1003-1010
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• 2022

The purpose of this study was to examine the phytochemical compounds and antibacterial activity of Coffea robusta leaf extract (RLE). The results indicated that chlorogenic acid (CGA) is a major component of RLE. The minimum inhibitory concentrations (MICs) of RLE against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Salmonella Typhimurium were 6.25, 12.5, 12.5, and 12.5 mg/ml, respectively. RLE effectively damages the bacterial cell membrane integrity, as indicated by the high amounts of proteins and nucleic acids released from the bacteria, and disrupts bacterial cell membrane potential and permeability, as revealed via fluorescence analysis. Cytotoxicity testing showed that RLE is slightly toxic toward HepG2 cells at high concentration but exhibited no toxicity toward Caco2 cells. The results from the present study suggest that RLE has excellent potential applicability as an antimicrobial in the food industry.