• Korean Journal of Plant Resources
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• v.24 no.6
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• pp.719-723
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• 2011

Antimicrobial activities of methanol, ethanol, water, and $CH_2Cl_2$ extracts from Fritillaria unibracteata Hsiao et K.C. Hsia and F. ussuriensis Maxim. were investigated by disk-agar diffusion method. The result showed comparatively strong antimicrobial activity against several microorganisms. The extracts from F. unibracteata and F. ussuriensis dosedependently increased the activity. However, water and $CH_2Cl_2$ extracts showed no antimicrobial activity against 7 microorganisms. Especially, against the most sensitive microorganism Staphylococcus epidermidis, methanol extracts at highest concentration of 20 mg/mL exhibited the largest clear zone on plate by 6-12 mm and ethanol extracts on plate by 6-10 mm.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.568-584
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• 1994

Bacteria have been regarded as major etiolgic factors in root canal infections. Infected root canal flora from thirteen patients who had visited to conservative department of Wonkwang dental hospital were cultured on blood agar plates. Cultued microorganisms were isolated and identified with Gram stain and biochemical tests using Vitek Systems(BioMeriux, MO, USA); Antibiotic susceptibillity was performed with disk diffusion and broth microdilution using Vitek Systems. Gram positive cocci(65 %) were predominant, which were composed of 6 Streptococcus viridans group, 5 Staph. spp., and 4 Enterococcus faecium, in the isolatd 23 strains. Gram negative rods (26 %) were the next common bacteria, which were composed of 5 non - fermentative Gram negative rods, and 1 Enterobacter cloacae. Most strains of S. viridans group and E. faecium were susceptible to antibiotics including penicillin. But strains of Staphylococcus spp. and non - fermentative Gram negative rods showed marked resistance to antibiotics except tetrancyclin and cefotaxime. Most results between disk diffusion and microdilution were all agreed, but the results of non - fermentative Gram negative rods were susceptible to cefotaxime in disk diffusion method but resistant in microdilution.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.1
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• pp.21-25
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• 2013

Acinetobacter baumannii is an aerobic, gram-negative and glucose-non-fermenting bacterium, which has emerged as a serious opportunistic pathogen. Many clinical microbiology laboratories use the Vitek 2 system for the routine antimicrobial susceptibility testing process, including testing on A. baumannii isolates. However, in case of amikacin, it is now recommended to perform additional antimicrobial susceptibility testing for A. baumannii strains due to the relatively lower minimum inhibitory concentration (MIC) in the Vitek 2 system compared to conventional reference methods. In our study, we assessed MIC for amikacin susceptibility testing of A. baumannii isolates in the Vitek 2 system, the agar dilution, Etest, and disk diffusion method. We collected 40 gentamicin-resistant, A. baumannii strains (amikacin MIC by Vitek 2:${\leq}2{\mu}g/mL$, 2 isolates; $4{\mu}g/mL$, 34 isolates; $8{\mu}g/mL$, 4 isolates) from a University hospital and compared the Vitek 2 system to other reference methods for testing susceptibility to amikacin. The Vitek 2 system showed major errors in all of the 40 isolates, yielding a low MIC. The results of our study strongly suggested that the Vitek 2 system was not a reliable method to test the MICs of gentamicin; ranging from ${\geq}16{\mu}g/mL$ for amikacin susceptibility. Other tests, such as agar dilution, Etest, or disk diffusion methods, should be paralleled to determine the MIC of amikacin in A. baumannii.

• Food Science and Biotechnology
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• v.15 no.5
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• pp.817-819
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• 2006

8-Quinolinol and other quinolinol derivatives were evaluated with regard to their growth-inhibitory effects against intestinal bacteria, using the paper disk-agar diffusion method. The observed growth responses varied according to the chemicals and dosages used, as well as the bacterial species tested. 8-Quinolinol showed a significant inhibitory effect against Clostridium difficile, C. perfringens, and Escherichia coli, at 5, 2, 1, and 0.5 mg/disk, and also exhibited a very strong inhibitory effect at 0.25 mg/disk. At low concentrations, 8-quinolinol had strong inhibitory effects against C. perfringens at 0.1 and 0.05 mg/disk; 8-quinolinol also manifested a moderate inhibitory effect against C. perfringens at 0.025 mg/disk. Furthermore, 8-quinolinol revealed moderate and weak growth inhibition against C. difficile and E. coli at concentrations of 0.1 and 0.05 mg/disk, respectively, but 2-quinolinol, 4-quinolinol, and 6-quinolinol evidenced no growth inhibition against B. bifidum, B. longum, C. difficile, C. perfringens, E. coli, or L. casei. The inhibitory effects of 8-quinolinol against C. difficile, C. perfringens, and E. coli lead to its consideration as a possible therapeutic modality for the treatment of diseases associated with harmful intestinal bacteria.

• KSBB Journal
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• v.9 no.5
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• pp.506-511
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• 1994

Antimicrobial activity of methanol extract and fraction from mugwort leaves(Artemisia princeps val. orientalis) was investigated for the screening of natural antiwucroblal components. By using agar diffusion method, ethyl acetate(EtOAc) layer fractionated from methanol extract of mugwort leaves showed the highest inhibitory effects against tested microorganisms. The ortho-coumaric acid(200∼600ppm) isolated from EtOAc layer showed strong antibacterial activities for Bacillus subtilis and Salmonella typhimurium. As derivatives of o-coumaric acid, antibacterial activity of para-coumaric acid was 1.2∼1.7 fold higher than that of o-coumaric acid. Three types of coumaric acids strong inhibited the growth of B. subtilis in the culture medium. Growth of S. tyhimurium, P. aeruginosa and S. aureus were effectively inhibited by o-, m- and p-coumaric acids, respectively. Minimum inhibitory dose of p-coumaric acid for B. subtilis was $\100∼200mu\textrm{g}$/paper disk.

• Microbiology and Biotechnology Letters
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• v.33 no.3
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• pp.236-239
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• 2005

Ethyl acetate extracts of traditional medicinal herbs were screened for their antifungal activity against Malassezia furfur through the liquid growth inhibition method with 96 well plate and the paper disk agar diffusion assay. Among the 91 kinds of herbal solvent extracts, borneolum (borneo-camphor, No. 56) was finally selected as the best antifungal effective medicinal herb. The MIC value of No. 56 against M. furfur was 0.3 mg/ml ($8.2{\times}10^6$ CFU/ml) and it was three times more efficient than midazole which is the known antifungal agent in clinical medicines.

• Microbiology and Biotechnology Letters
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• v.34 no.4
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• pp.342-351
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• 2006

The aim of this study was to survey susceptibilities of Escherichia coli and Klebsiella pneumoniae isolates against cefotaxime and to determine the prevalences of CTX-M type extended-spectrum $\beta$-lactamases (ESBLs) producing E. coli and K. pneumoniae in Korea. During the period of February to July, 2005, 153 E. coli and 52 K. neumoniae isolates were collected from 2 hospitals in Busan. Antimicrobial susceptibilities to cefotaxime were tested by the disk diffusion method. ESBL production of E. coli and K. pneumoniae was determined by the double disk synergy test. MICs of $\beta$-lactam antibiotics were determined by the agar dilution method. Blac$_{CTX-M}$ genes of the organism were detected by PCR. Among 153 isolates of E. coli and 52 isolates of K. neumoniae, 27 (17.6%) and 25 (48.0%) were intermediate or resistant to cefotaxime, respectively. Twenty-three (15.0%) isolates out of 153 E. coli and 13 (25.0%) out of 52 K. neumoniae isolates showed positive results for ESBL by the double disk synergy test. Twenty isolates out of 23 ESBL producing E. coli and 12 out of 13 ESBL producing K. neumoniae isolates harbored biacTx-M gene,11 of ESBL producing E. coli and 12 of ESBL producing K. neuinoniae isolates harbored bla$_{CTX-M}$ gene, 11 of the ESBL producing E. coli and 2 of ESBL producing K. neumoniae isolates harbored bla$_{TEM}$ gene, and 1 of the ESBL producing E. coli and 12 of ESBL producing K. neumoniae isolates harbored bla$_{SHV}$ gene. E. coli and K. neumoniae isolates producing CTX-M-type ESBLs were not uncommon in Korea. It is thought that continuous survey are necessary for inspecting the spread and novel variants of CTX-M-type ESBL genes. Further me]'e investigation and research on ESBL producing strains are needed in order to prevent the spread of resistant bacteria.

• Korean Journal of Veterinary Service
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• v.23 no.1
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• pp.19-28
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• 2000

There are several main antibacterial susceptibility tests, such as agar dilution method, broth dilution method and disk diffusion technique. Especially, for minimal inhibitory concentration (MIC) test, agar dilution method has been widely used. But that method is so complicated and bothering that it's difficult to treat a large amount of strains. On the other hand, modified broth dilution method(add 1% glucose and 0.018% phenol red as a pH indicator to broth) is fast and easy to perform. Most of all, it can visualize the result by color. The MICs of 22 antibiotics Including penicillins, aminoglycosides, cephalothin, chloramphenicol, lincomycin, ceftiofur, vancomycin and quinolones, erythromycin, colistin. sul-fadimethoxine, trimethoprim for arcanobacterium pyogenes 14 strains, actinobacillus pleuropneu-moniae 41 strains and pasteurella multocida 37 strains, which were collected from porcine during 1996 ∼ 1999, were determined by modified broth dilution method. Actinobacillus pleuropneumoniae was highly susceptible to all kinds of quinolones such as ciprofloxacin, enrofloxacin and norfloxacin and to all aminoglycosides, like gentamicin, apramycin, kanamycin and ampicillin, cephalothin and ceftiofur. But It was quite resistant to solfadimethoxin, colistin and vancomycin. Pasteurella multocida was found to have high susceptibility to ampicillin, cephalothin, chlorampenicol and gentamicin but had mid-degree susceptibility to other aminoglycosides. In addition, it was susceptible to norfloxacin and nalidixic acid, but not to newer fluoroquinolone like ciprofloxacin and enrofloxacin and it was resistant to colistin and kanamycin. Arcanobacterium pyogenes was highly susceptible to most of quinolones such as cipoofloxacin, enrofloxacin and norfloxacin and gentamicin and penicillin G. But it also obtained high resistance against the early quinolone, nalidixic acid and aminoglycosides such as amikacin, apramycin and kanamycin and erythromycin, chlorampenicol, tetracyclin and vancomycin.

• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.522-528
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• 2003

The growth responses of Phellodendron amurense root-derived materials against seven intestinal bacteria were examined, using an impregnated paper disk agar diffusion method and spectrometric method under $O_2$-free condition. The biologically active constituent of the P. amurense root extract was characterized as berberine chloride ($C_{20}H_{18}NO_{41}Cl$) using various spectroscopic analyses. The growth responses varied depending on the bacterial strain, chemicals, and dose tested. At 1 mg/disk, berberine chloride strongly inhibited the growth of Clostridium perfringens, and moderately inhibited the growth of Escherichia coli and Streptococcus mutans without any adverse effects on the growth of three lactic acid-bacteria (Bifidobacterium bifidum, B. longum, and Lactobacillus acidophilus). The structure-activity relationship revealed that berberine chloride exhibited more growth-inhibiting activity against C. perfringens, E. coli, and S. mutans than berberine iodide and berberine sulfate. These results, therefore, indicate that the growth-inhibiting activity of the three berberines was much more pronounced as chloridated analogue than iodided and sulphated analogues. As for the morphological effect caused by 1 mg/disk of berberine chloride, most strains of C. perfringens were damaged and killed, indicating that berberine chloride showed a strong inhibition against C. perfringens. As naturally occurring growth-inhibiting agents, the P. amurense root-derived materials described could be useful as a preventive agent against diseases caused by harmful intestinal bacteria such as clostridia.

• Korean Journal of Food Science and Technology
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• v.48 no.6
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• pp.560-564
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• 2016

The objective of this study was to investigate the anti-Bacillus cereus activity of actinonin. Actinonin inhibited the growth of B. cereus in a dose dependent manner. The growth-inhibitory activity of actinonin was evaluated using a broth micro-dilution method, and minimum inhibitory concentration (MIC) and agar disk diffusion tests. B. cereus showed high susceptibility to actinonin in a concentration-dependent manner and MIC was determined to be $0.192{\mu}g/mL$. Additionally, 1 and 2 mM actinonin induced formation of B. cereus inhibition zones. In addition, as compared to B. cereus alone, B. cereus added with $10{\mu}M$ actinonin showed a lower level of cytotoxicity in HeLa cells in vitro. Thus, this study revealed that actinonin could be a potential source of a natural antimicrobial agent or a pharmaceutical component against B. cereus.