• KSCE Journal of Civil and Environmental Engineering Research
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• v.1 no.1
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• pp.43-51
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• 1981

A model of substrate utilization witbin bacterial films has been developed and simulated for a better understanding of fixed film treatment processes. The model consists of two parts, a deep biofilm and a thin biofilm, which are classified based on substrate penetration into the biofilm. Substrate concentration and flux within a biofilm can be computed from the model. Three dimensionless parameters, ${\phi}_1$, ${\phi}_2$ and $\bar{S}_b$ were obtained during model construction, and the substrate concentration and flux can be expressed in terms of these parameters. It has been found that an. increase of ${\phi}_1$ or a decrease of ${\phi}_2$ results in an increase of treatment efficiencies. It has also been found that systems maintaining high efficiencies belong to a deep biofilm. Among the constants involved, the mass transfer coefficient is the only controllable term and it depends Largely on fluid velocity near the biofilm surface. Substrate removal efficiency may be increased with an increase of fluid velocity for a biofilm of fixed depth. However, film depth is decreased due to sloughing with increasing velocity, and the system reaches a new steady state. Because changes in film depth are not well defined quantitatively yet, the efficiency can not be clearly described at a new steady state.

• Journal of dental hygiene science
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• v.14 no.2
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• pp.87-93
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• 2014

Dental plaque resides passively at a site and makes an active contribution to the maintenance of health. The bacterial composition of plaque remains relatively stable despite regular exposure to minor environmental stress. This stability, homeostasis is due to a dynamic balance of microbial interactions. However, the homeostasis can break down, leading to shifts in the balance of the microflora. This change can be a sign of initial dental caries. It is proposed that disease can be prevented or treated not only by targeting the putative pathogens but also by interfering with the processes that drive the breakdown in homeostasis. It is essential to understand the plaque as a mixed species biofilm. In this essay I reviewed an extension of the caries ecological hypothesis to explain the relation between dynamic changes in the phenotypic/genotypic properties of plaque bacteria and the demineralization and remineralization balance of the dental caries process. We will have the strategies to impact significantly on clinical practice as understanding dental biofilm.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1558-1562
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• 2007

To elucidate the influence of pipe materials on the VBNC (viable but nonculturable) state and bacterial numbers in drinking water, biofilm and effluent from stainless steel, galvanized iron, and polyvinyl chloride pipe wafers were analyzed. Although no HPC (heterotrophic plate count) was detected in the chlorinated influent of the model system, a DVC (direct viable count) still existed in the range between 3- and 4-log cells/ml. Significantly high numbers of HPC and DVC were found both in biofilm and in the effluent of the model system. The pipe material, exposure time, and the season were all relevant to the concentrations of VBNC and HPC bacteria detected. These findings indicate the importance of determining the number of VBNC cells and the type of pipe materials to estimate the HPC concentration in water distribution systems and thus the need of determining a DVC in evaluating disinfection efficiency.

• Journal of Microbiology and Biotechnology
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• v.22 no.10
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• pp.1336-1342
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• 2012

In Burkholderia pseudomallei, the pathogen that causes melioidosis, the gene cluster encoding the capsular polysaccharide, is located on chromosome 1. Among the 19 capsular genes in this cluster, wzm has not been thoroughly studied. To study the function of wzm, we generated a deletion mutant and compared it with the wild-type strain. The mutant produced less biofilm in minimal media and was more sensitive to desiccation and oxidative stress compared with the wild-type strain, indicating that wzm is involved in biofilm formation and membrane integrity. Scanning electron microscopy showed that the bacterial cells of the mutant strain have more defined surfaces with indentations, whereas cells of the wild-type strain do not.

• Microbiology and Biotechnology Letters
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• v.51 no.1
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• pp.32-36
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• 2023

In this study, the effect of sodium hypochlorite on biofilm removal was evaluated using three bacterial strains; Aeromonas hydrophila, Streptococcus mutans, and Yersinia enterocolitica. For maximum biofilm removal in 10 min, sodium hypochlorite is required at 1.65, 0.83, and 0.41 g/l for A. hydrophila, S. mutans, and Y. enterocolitica, respectively. Resistance to sodium hypochlorite was increased by the biofilms of all three tested strains, while the change in bactericidal activity according to sodium hypochlorite concentration was strain-specific. Therefore, we aimed to determine the effective concentration of sodium hypochlorite required for hygiene, considering that higher concentrations are needed to remove biofilms than to kill cells.

• Journal of Veterinary Science
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• v.19 no.6
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• pp.808-816
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• 2018

Bacterial biofilms have been demonstrated to be closely related to clinical infections and contribute to drug resistance. Berberine, which is the main component of Coptis chinensis, has been reported to have efficient antibacterial activity. This study aimed to investigate the potential effect of a combination of berberine with ciprofloxacin (CIP) to inhibit Salmonella biofilm formation and its effect on expressions of related genes (rpoE, luxS, and ompR). The fractional inhibitory concentration (FIC) index of the combination of berberine with CIP is 0.75 showing a synergistic antibacterial effect. The biofilm's adhesion rate and growth curve showed that the multi-resistant Salmonella strain had the potential to form a biofilm relative to that of strain CVCC528, and the antibiofilm effects were in a dose-dependent manner. Biofilm microstructures were rarely observed at $1/2{\times}MIC/FIC$ concentrations (MIC, minimal inhibition concentration), and the combination had a stronger antibiofilm effect than each of the antimicrobial agents used alone at $1/4{\times}FIC$ concentration. LuxS, rpoE, and ompR mRNA expressions were significantly repressed (p< 0.01) at $1/2{\times}MIC/FIC$ concentrations, and the berberine and CIP combination repressed mRNA expressions more strongly at the $1/4{\times}FIC$ concentration. The results indicate that the combination of berberine and CIP has a synergistic effect and is effective in inhibiting Salmonella biofilm formation via repression of luxS, rpoE, and ompR mRNA expressions.

• Korean Journal of Food Science and Technology
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• v.54 no.2
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• pp.241-246
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• 2022

Antibiotic resistance is a serious problem to food safety as well as human healthcare. To avoid this, there are several approaches for a new class of antibiotic agents that target only production of virulence factors such as biofilm without bacterial growth defect. The objective of this study was to investigate the antibiofilm activity of tuberostemonine in Staphylococcus aureus. Tuberostemonine significantly reduced the biofilm formation (26.07-47.02%) in the crystal violet assay whereas there were no effect on S. aureus growth. The dispersion in preformed biofilm was also observed by confocal laser scanning microscopy (CLSM). Quantification real-time PCR revealed that the icaA and agrA expression having an important role in biofilm production of S. aureus were strongly affected with tuberostemonine. These results suggest that tuberostemonine has potential for controlling biofilm formation and dispersion by effect on virulence regulation of S. aureus.

• 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 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 Microbiology and Biotechnology
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• v.27 no.3
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• pp.542-551
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• 2017

Small phytochemicals have been successfully adopted as antibacterial chemotherapies and are being increasingly viewed as potential antibiofilm agents. Some of these molecules are known to repress biofilm and toxin production by certain bacterial and yeast pathogens, but information is lacking with regard to the genes allied with biofilm formation. The present study was performed to investigate the inhibitory effect of burdock root extract (BRE) and of chlorogenic acid (CGA; a component of BRE) on clinical isolates of Klebsiella pneumoniae. BRE and CGA exhibited significant antibiofilm activity against K. pneumoniae without inflicting any harm to its planktonic counterparts. In vitro assays supported the ${\beta}$-lactamase inhibitory effect of CGA and BRE while in silico docking showed that CGA bound strongly with the active sites of sulfhydryl-variable-1 ${\beta}$-lactamase. Furthermore, the mRNA transcript levels of two biofilm-associated genes (type 3 fimbriae mrkD and trehalose-6-phosphate hydrolase treC) were significantly downregulated in CGA- and BRE-treated samples. In addition, CGA inhibited biofilm formation by Escherichia coli and Candida albicans without affecting their planktonic cell growth. These findings show that BRE and its component CGA have potential use in antibiofilm strategies against persistent K. pneumoniae infections.