• Korean journal of food and cookery science
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• v.26 no.2
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• pp.206-213
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• 2010

In this study, the antibacterial activities of essential oil from Zanthoxylum schinifolium against four Gram-positive bacteria and six Gram-negative bacteria were investigated. The antibacterial activity of the oils was determined using the agar-well diffusion assay, MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration). In particular, essential oil from Z. schinifolium showed higher antibacterial activity against Gram-positive bacteria than against Gram-negative bacteria. Essential oil from Z. schinifolium displayed large inhibition zones especially against Bacillus cereus (31 mm). At concentrations between 0 and $20\;{\mu}g/mL$ the oils showed an antibacterial effect against both Gram-negative and Gram-positive bacteria. The minimum inhibitory concentration (MIC) values against nine bacteria ranged from 1.25 to $5\;{\mu}g/mL$. The minimum bactericidal concentration (MBC) values against eight bacterial ranged from 2.5 to $20\;{\mu}g/mL$, except Shigella sonnei. Furthermore, our finding on the antibacterial activities of essential oils from Zanthoxylum schinifolium validated the use of this plant for medical purposes.

• International Journal of Oral Biology
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• v.43 no.3
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• pp.123-127
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• 2018

Polyphenon 60 refers to the mixture of catechins present in green tea. The aim of this study was to investigate the antimicrobial activities of polyphenon 60 against 4 strains of Streptococcus mutans and 2 strains of Streptococcus sorbrinus, which are the major causative bacteria of dental caries. The minimum bactericidal concentration (MBC) values of polyphenon 60 for S. mutans and S. sobrinus were determined and the effect of biofilm formation inhibition of that was evaluated. The MBC value of polyphenon 60 against the bacterial strains was 2.5 mg/ml except for one particular strain, S. mutans KCOM 1128 for which the value was 1.25 mg/ml. The results of biofilm formation inhibition assay revealed that polyphenon 60 inhibited biofilm formation more than 90% at a concentration of 2.5 mg/ml. It was apparent that polyphenon exhibited biofilm formation inhibition activity along with bactericidal effect against S. mutans and S. sobrinus. Therefore, it is proposed that polyphenon 60 as one of the components of bactericidal agents could be useful in developing oral hygiene products, toothpaste or gargling solution.

• Archives of Pharmacal Research
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• v.28 no.11
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• pp.1293-1301
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• 2005

Flavonoids, a group of low molecular weight phenylbenzopyrones, have various pharmacological properties including antioxidant, anticancer, bactericidal, and anti-inflammatory. We carried out anti-herpetic assays on 18 flavonoids in five classes and a virus-induced cytopathic effect (CPE) inhibitory assay, plaque reduction assay, and yield reduction assay were performed. When flavonoids were applied at various concentrations to Vero cells infected by HSV-1 and 2, most of the f1avonoids showed inhibitory effects on virus-induced CPE. Among the flavonoids, EC, ECG (flavanols), genistein (isoflavone), naringenin (flavanone), and quercetin (flavonol) showed a high level of CPE inhibitory activity. The antiviral activity of flavonoids were also examined by a plaque reduction assay. EC, ECG, galangin, and kaempferol showed a strong antiviral activity, and catechin, EGC, EGCG, naringenin, chrysin, baicalin, fisetin, myricetin, quercetin, and genistein showed moderate inhibitory effects against HSV-1. In these experiments, flavanols and flavonols appeared to be more active than flavones. Furthermore, treatment of Vero cells with ECG and galangin (which previously showed strong antiviral activities) before virus adsorption led to a slight enhancement of inhibition as determined by a yield reduction assay, indicating that an intracellular effect may also be involved.

• The Plant Pathology Journal
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• v.38 no.4
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• pp.334-344
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• 2022

Bacterial wilt is a re-emerging disease on dry bean and can affect many other crop species within the Fabaceae. The causal agent, Curtobacterium flaccumfaciens pv. flaccumfaciens (CFF), is a small, Gram-positive, rod-shaped bacterium that is seed-transmitted. Infections in the host become systemic, leading to wilting and economic loss. Clean seed programs and bactericidal seed treatments are two critical management tools. This study characterizes the efficacies of five bactericidal chemicals against CFF. It was hypothesized that this bacterium was capable of forming biofilms, and that the cells within biofilms would be more tolerant to bactericidal treatments. The minimum biocide eradication concentration assay protocol was used to grow CFF biofilms, expose the biofilms to bactericides, and enumerate survivors compared to a non-treated control (water). Streptomycin and oxysilver bisulfate had EC95 values at the lowest concentrations and are likely the best candidates for seed treatment products for controlling seed-borne bacterial wilt of bean. The results showed that CFF formed biofilms during at least two phases of the bacterial wilt disease cycle, and the biofilms were much more difficult to eradicate than their planktonic counterparts. Overall, biofilm formation by CFF is an important part of the bacterial wilt disease cycle in dry edible bean and antibiofilm bactericides such as streptomycin and oxysilver bisulfate may be best suited for use in disease management.

• Journal of Periodontal and Implant Science
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• v.53 no.2
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• pp.110-119
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• 2023

Purpose: This study aimed to investigate the proper wavelengths for safe levels of light-emitting diode (LED) irradiation with bactericidal and photobiomodulation effects in vitro. Methods: Cell viability tests of fibroblasts and osteoblasts after LED irradiation at 470, 525, 590, 630, and 850 nm were performed using the thiazolyl blue tetrazolium bromide assay. The bactericidal effect of 470-nm LED irradiation was analyzed with Streptococcus gordonii, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, and Tannerella forsythia. Levels of nitric oxide, a proinflammatory mediator, were measured to identify the anti-inflammatory effect of LED irradiation on lipopolysaccharide-stimulated inflammation in RAW 264.7 macrophages. Results: LED irradiation at wavelengths of 470, 525, 590, 630, and 850 nm showed no cytotoxic effect on fibroblasts and osteoblasts. LED irradiation at 630 and 850 nm led to fibroblast proliferation compared to no LED irradiation. LED irradiation at 470 nm resulted in bactericidal effects on S. gordonii, A. actinomycetemcomitans, F. nucleatum, P. gingivalis, and T. forsythia. Lipopolysaccharide (LPS)-induced RAW 264.7 inflammation was reduced by irradiation with 525-nm LED before LPS treatment and irradiation with 630-nm LED after LPS treatment; however, the effects were limited. Conclusions: LED irradiation at 470 nm showed bactericidal effects, while LED irradiation at 525 and 630 nm showed preventive and treatment effects on LPS-induced RAW 264.7 inflammation. The application of LED irradiation has potential as an adjuvant in periodontal therapy, although further investigations should be performed in vivo.

• Preventive Nutrition and Food Science
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• v.1 no.2
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• pp.269-277
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• 1996

Bacteriocins are proteins produced by a heterogeneous group of bacteria that have a bactericidal effect on closely related organisms. Recently, bacteriocins from lactic acid bacteria and other food-related organisms have been the subject of much research because of their potential as food biopreservatives. Various modifications of agar plate diffusion assays are the most widely used methods even though the limitations of such assays are generally recognized. The ability to obtain a concentrated crude preparation on bacteriocin by optimizing production parameters greatly simplifies recovery of bacteriocin on subsequent purification steps. Some studies performed to optimize bacteriocins have been purified to homogeneity, and the amino acid sequences of many of these purified bacteriocins have been determined. Obtaining characterization data on purified bacteriocin will minimize the risk of overlapping of research and confusion on identification of these compounds. Several me-chanisms leading to cell death have been hypothesized. These include depletion of the proton motive force(PMF) across the cell membrane: RNase and/or DNase activity within the sensitive cell; and pore formation and lysis of sensitive cells at the cell membrane.

• Journal of Microbiology and Biotechnology
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• v.27 no.10
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• pp.1837-1843
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• 2017

Knowledge of avian host responses to brucellosis is critical to understanding how birds resist this infection; however, this mechanism is not well established. On the other hand, temperature has a major involvement in the physiology of living organisms, and cell death induced by heat is attributed to protein denaturation. This study demonstrates the direct bactericidal effect of a high temperature ($41^{\circ}C$) on Brucella abortus that resulted in the gradual reduction of intracellular bacteria and inhibited bacterial growth within avian macrophage HD11 in an increasing period of time. On the other hand, this study also revealed that high temperature does not affect the rate of bacterial uptake, as confirmed by the bacterial adherence assay. No significant difference was observed in the expression of target genes between infected and uninfected cells for both temperatures. This study suggests the susceptibility of B. abortus to bacterial death under a high temperature with an increased period of incubation, leading to suppression of bacterial growth.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.7
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• pp.1052-1061
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• 2019

Objective: This study was conducted to identify duck liver-expressed antimicrobial peptide 2 (LEAP-2) and demonstrate its antimicrobial activity against various pathogens. Methods: Tissue samples were collected from 6 to 8-week-old Pekin ducks (Anas platyrhynchos domesticus), total RNA was extracted, and cDNA was synthesized. To confirm the duck LEAP-2 transcript expression levels, quantitative real-time polymerase chain reaction was conducted. Two kinds of peptides (a linear peptide and a disulfide-type peptide) were synthesized to compare the antimicrobial activity. Then, antimicrobial activity assay and fluorescence microscopic analysis were conducted to demonstrate duck LEAP-2 bactericidal activity. Results: The duck LEAP-2 peptide sequence showed high identity with those of other avian species (>85%), as well as more than 55% of identity with mammalian sequences. LEAP-2 mRNA was highly expressed in the liver with duodenum next, and then followed by lung, spleen, bursa and jejunum and was the lowest in the muscle. Both of LEAP-2 peptides efficiently killed bacteria, although the disulfide-type LEAP-2 showed more powerful bactericidal activity. Also, gram-positive bacteria was more susceptible to duck LEAP-2 than gram-negative bacteria. Using microscopy, we confirmed that LEAP-2 peptides could kill bacteria by disrupting the bacterial cell envelope. Conclusion: Duck LEAP-2 showed its antimicrobial activity against both gram-positive and gram-negative bacteria. Disulfide bonds were important for the powerful killing effect by disrupting the bacterial cell envelope. Therefore, duck LEAP-2 can be used for effective antibiotics alternatives.

• Journal of the Korea Society of Computer and Information
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• v.21 no.5
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• pp.135-139
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• 2016

Scrophularia ningpoensis hemsl has been traditionally used in China and Vietnam for treatment of bacteria, atopy, pimple, tonsillitis, angina and encephalitis for a long time. The main objectives of this study were to evaluate the antibacterial activity of the Scrophularia ningpoensis hemsl extract on biofilm formation of Klebsiella pneumoniae. Antibacterial activity was conducted using disc diffusion assay and minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were determined using the broth micro dilution method in accordance to Clinical and Laboratory Standards Institute guidelines(CLSI). Furthermore, cytotoxicity on L929 were assessed using animal cell culture for the proliferation test(MTT cell assay) and the biofilm forming capacity of the K. pneumoniae were determined using the colony forming unit (CFU) assay. The extract exhibited considerable antibacterial activity. K. pneumoniae was susceptible to the extract with the MIC and MBC of 0.1875 and $1.5mg/m{\ell}$ respectively. Cytoxicity test in L929 showed no sign of toxicity at the concentration of $0.75mg/m{\ell}$ and at the same concentration the extract caused inhibition of bacterial biofilm formation. The extract of Scrophularia ningpoensis hemsl possesses an in vitro antibacterial antibiofilm activities against K. pneumoniae, with no sign of cytoxicity on L929.

• Journal of Apiculture
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• v.34 no.2
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• pp.131-136
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• 2019

Recently, number of honeybees (Apis mellifera) has visibly decreased because they are vulnerable to some diseases like American foulbrood disease. American foulbrood disease, which is caused by Paenibacillus larvae, is emerged as great cause of decrease in number of honeybees. After antibiotic-resistant strain emerged, it is now more difficult to treat those pathogens successfully. Researches on finding alternative antibacterial compound are ongoing. In this study, we examined the antibacterial effect of honokiol on P. larvae. Honokiol showed great antibacterial effect with minimum inhibitory concentration of 12.5 ㎍/mL and minimum bactericidal concentration of 50 ㎍/mL. An agar diffusion test also confirmed the anti-Paenibacillus larvae activity of honokiol with an inhibitory zone of 9±0.5 mm. Since honokiol is known to interact membrane of some bacteria, we measured 260 nm absorbing particles, which could be induced by leakage of cells, and confirmed that the leakage of P. larvae occurred in dose-dependent manners. However, result of crystal violet assay suggested that honokiol has only mild anti-biofilm formation effect on P. larvae, which means honokiol controls the bacteria by inducing the bursting of membrane. Finally, an additive effect of honokiol with tetracycline and terramycin was found using a checkerboard assay with a fractional inhibitory concentration index value of 0.5.