• Korean Journal of Veterinary Research
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• v.21 no.1
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• pp.1-6
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• 1981

In order to observe the bactericidal effect of Ranunculus species on pathogenic bacteria, the minimal inhibitory concentration and bactericidal effect was tested Throughout the studies, the following experimental results were obtained and summarized. 1. Minimal inhibitory concentration of Ranunculus species extracts on E. coli was observed in the medium in which 1% Ranunculus species extracts added to brain heart infusion agar. 2. Minimal inhibitory concentration of Ranunculus species extracts on Salmonella species observed in the medium in which 1% Ranunculus species extracts added to brain heart infusion agar. 3. Minimal inhibitory concentration of Ranunculus species extracts on Staphylococcus and Streptococcus was observed in the medium in which 1.5% Ranunculus species extracts added to brain hrart infusion blood agar. 4. The Bactericidal effect of Ranunculus species extracts on E. coli and S. typhi was observed in 30 minutes. 5. The Bactericidal effect of Ranunculus species extracts on staphylococcus aureus was obserded in 40 minutes.

• Journal of Veterinary Clinics
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• v.20 no.1
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• pp.86-90
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• 2003

Little is known to data about the in vitro activity of antimicrobial agents aganist Brucella cams (B cams) isolated from Korea. Our study aimed at determining the in vitro activities of 15 antimicrobial agents against 3 isolates and 52 isolates of B cams from dogs in 1994 and 2002, respectively. In minimal inhibitory concentration (MIC) study, minocycline and doxycycline showed the lowest MICs ( < 0.06-0.5 ug/ml). Gentamicin, streptomycin, ciprofloxacin, norfloxacin and rifampin showed MICs in the range of less than 1 ug/ml. Lincomycin and sulfisox azole showed the highest MICs ( > 32 ug/ml). Interestingly, MICs of macrolides (erythromycin, spiramycin, tylosin) against 52 isolates in 2002 were 16-64 times higher than that of 3 isolates in 1994. In minimal bactericidal concentration (MBC) study, gentamicin, streptomycin, ciprofloxacin and norfloxacin showed the lowest MBCs [0.12-1 ug/ml (1-2 times higher than MIC)], but minocycline and doxycycline showed the highest MBCs [8-32 ug/ml (128 times higher than MIC)]. Rifampin showed the MBCs in the range from 2 to 4 ug/ml (2-4 times higher than MIC).

• International Journal of Oral Biology
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• v.40 no.4
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• pp.189-196
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• 2015

Minimal inhibitory concentration (MIC) is the lowest antibiotic concentration that inhibits the visible growth of bacteria. Sub-minimal inhibitory concentration (Sub-MIC) is defined as the concentration of an antimicrobial agent that does not have an effect on bacterial growth but can alter bacterial biochemistry, thus reducing bacterial virulence. Many studies have confirmed that sub-MICs of antibiotics can inhibit bacterial virulence factors. However, most studies were focused on Gram-negative bacteria, while few studies on the effect of sub-MICs of antibiotics on Gram-positive bacteria. In this study, we examined the influence of sub-MICs of doxycycline, tetracycline, penicillin and amoxicillin on biofilm formation and coaggregation of Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, and Actinomyces odontolyticus. In this study, incubation with sub-MIC of antibiotics had no effect on the biofilm formation of S. gordonii and A. naeslundii. However, S. mutans showed increased biofilm formation after incubation with sub-MIC amoxicillin and penicillin. Also, the biofilm formation of A. odontolyticus was increased after incubating with sub-MIC penicillin. Coaggregation of A. naeslundii with S. gordonii and A. odontolyticus was diminished by sub-MIC amoxicillin. These observations indicated that sub-MICs of antibiotics could affect variable virulence properties such as biofilm formation and coaggregation in Gram-positive oral bacteria.

• International Journal of Oral Biology
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• v.41 no.4
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• pp.209-215
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• 2016

Chlorhexidine has long been used in mouth washes for the control of dental caries, gingivitis and dental plaque. Minimal inhibitory concentration (MIC) is the lowest concentration of an antimicrobial substance to inhibit the growth of bacteria. Concentrations lower than the MIC are called sub minimal inhibitory concentrations (sub-MICs). Many studies have reported that sub-MICs of antimicrobial substances can affect the virulence of bacteria. The aim of this study was to investigate the effect of sub-MIC chlorhexidine on biofilm formation and coaggregation of oral early colonizers, such as Streptococcus gordonii, Actinomyces naeslundii and Actinomyces odontolyticus. The biofilm formation of S. gordonii, A. naeslundii and A. odontolyticus was not affected by sub-MIC chlorhexidine. However, the biofilm formation of S. mutans increased after incubation with sub-MIC chlorhexidine. In addition, cell surface hydrophobicity of S. mutans treated with sub-MIC of chlorhexidine, decreased when compared with the group not treated with chlorhexidine. However, significant differences were seen with other bacteria. Coaggregation of A. naeslundii with A. odontolyticus reduced by sub-MIC chlorhexidine, whereas the coaggreagation of A. naeslundii with S. gordonii remained unaffected. These results indicate that sub-MIC chlorhexidine could influence the binding properties, such as biofilm formation, hydrophobicity and coaggregation, in early colonizing streptococci and actinomycetes.

• YAKHAK HOEJI
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• v.38 no.6
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• pp.742-748
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• 1994

As part of our search for less toxic antimicrobial agents from natural resources, the carpophores of Elfvingia applanata$(P_{ers}.)K_{ARST}.$ was extracted with hot water. EA, the aqueous extract from the carpophores of E. applanata, was lyophilized and a dark brownish powder was obtained. Antimicrobial activity of EA was tested in vitro against Gram positive and Gram negative bacteria by serial broth dilution method, and the antimicrobial activity was expressed by minimal inhibitory concentration(MIC). Among fourteen species of bacteria tested, the antimicrobial activity of EA was the most potent against Proteus vulgaris showing MIC of 1.250 mg/ml. To investigate the effect of antimicrobial combinations of EA with four kinds of antibiotics(ampicillin, cefazolin, oxytetracycline and chloramphenicol), the fractional inhibitory concentration index(FICI) was determined by checkerboard assay for each strain. The antimicrobial combinations of EA with four kinds of antibiotics resulted in synergism in four instances, but no antagonism was observed. Four instances of synergism were observed when EA was combined with ampicillin against Micrococcus luteus, with cefazolin against Bacillus subtilis, with cefazolin against Micrococcus luteus and with oxytetracycline against Staphylococcus aureus.

• YAKHAK HOEJI
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• v.40 no.6
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• pp.653-658
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• 1996

As part of our search for less toxic antimicrobial agents from natural resources. rutin was isolated from Sophora japonica and then hydrolyzed to quercetin. Antimicrobial activity of quercetin was tested in vitro against five kinds of gram positive and ten kinds of gram negative bacteria by serial broth dilution method. Among fifteen kinds of bacteria tested, the antimicrobial activity of quercetin was the most potent against Proteus vulgaris showing minimal inhibitory concentration(MIC) of 125 ${\mu}$g/ml. To investigate the effect of antimicrobial combinations of quercetin with four kinds of antibiotics (ampicillin, cefazolin, oxytetracycline and chloramphenicol). the fractional inhibitory concentration index (FICI) was determined by checkerboard assay for each strain. The antimicrobial combinations of quercetin with four kinds of antibiotics resulted in synergism in one instance, additive effect in four instances, but no antagonism was observed.

• Journal of Food Hygiene and Safety
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• v.10 no.4
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• pp.205-211
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• 1995

To investigate the antimicrobial effect of polyphosphates as a food additive, the growth and structural change of Listeria monocytogentes Scott A were examined in relation to polyphosphates concentration and incubation temperature. Up to 10,000 ppm of polyphosphates, the growth rate of strain was gradually inhibited with increasing polyphosphates concentration and decreasting the incubation temperature. Minimal inhibitory concentration of polyphosphates to the growth of strain was about 12,000 ppm. It was observed , using both scanning electron microscopy(SEM) and transmission electron microscopy(TEM), that 0.9% polyphosphates treatment was resulted in the destruction of cell wall and outflow of cell ingredients. The antimicrobial effects of polyphosphates were more effective than those of dehydroacetate and potassium sorbate at 13$^{\circ}C$ and 4$^{\circ}C$. The growth rate the strain in beef was significantly inhibited by the treatment of 0.9% polyphosphates and storaged at cooling temperature.

• Journal of Pharmaceutical Investigation
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• v.31 no.1
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• pp.1-5
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• 2001

The aggregation behavior of nystatin (NYS) in the presence of pluronic F127, triblock copolymer of poly (ethylene oxide) (PEO) and poly (propylene oxide) (PPO), was measured and correlated with hemolytic activity. Antifungal activity was also studied using Saccharomyces cerevisiae as a model strain. The critical aggregation concentrations (CAC) of the drug were 50.1, 108.0, 134.2, 154.3, and $217.9\;{\mu}M$ at 0.1%, 0.5%, 1.0%, 1.5%, and 2.0% pluronic F127 solution, respectively. The levels of NYS required to start lysis of erythrocytes were about 80, 100, 125, 150, and $200\;{\mu}M$ at 0.1%, 0.5%, 1.0%, 1.5%, and 2.0% pluronic F127 solution, respectively. It was $50\;{\mu}M$ in the absence of the polymer. Minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) of NYS-pluronic F127 lyophilizate were same at $3\;{\mu}g/ml$, while MIC and MFC of pure NYS are $3\;{\mu}g/ml$ and $12\;{\mu}g/ml$, respectively. By modulating the aggregation behavior of NYS, pluronic F127 was able to reduce the toxicity of the drug without compromising the MIC and MFC.

• Journal of Ginseng Research
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• v.17 no.2
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• pp.148-152
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• 1993

One kind of microorganism was isolated and identified from Korean fresh, white and red ginseng, and the effect of a preservative, sodium benzoate on the microorganism and its thermal resistant propertues were studied. The results obtained were as follows. The predominant strain on ginseng and ginseng products was identified as Penicillium sp. The strain showed perithecium structure producing ascospores. The growth of the strain was slightly inhibited at 0.0571 concentration of sodium benzoate. The minimal inhibitory concentration (MIC) of sodium benzoate against the strain was 0.26%. The D value of the strain at 56, 59, $62^{\circ}C$ were 9.9, 5.0 and 4.5 min, respectively.

• International Journal of Oral Biology
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• v.40 no.1
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• pp.35-39
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• 2015

Minimal inhibitory concentration (MIC) is the lowest concentration of antibiotics that inhibits the visible growth of bacteria. It has been reported that sub-MIC of antibiotics may result in morphological alterations, along with the biochemical and physiological changes in bacteria. The purpose of this study was to examine morphological changes of Aggregatibacter actinomycetemcomitans, after the treatment with sub-MIC metronidazole and penicillin. The bacterial morphology was observed with scanning electron microscope, after incubating with sub-MIC antibiotics. The length of A. actinomycetemcomitans was increased after the incubation with sub-MIC metronidazole and penicillin. Sub-MIC metronidazole and penicillin inhibited bacterial division and induced long filaments. Our study showed that metronidazole and penicillin can induce the morphological changes in A. actinomycetemcomitans.