• Journal of Microbiology and Biotechnology
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• v.31 no.1
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• pp.115-122
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• 2021

Phenol-soluble modulins (PSMs) are responsible for regulating biofilm formation, persister cell formation, pmtR expression, host cell lysis, and anti-bacterial effects. To determine the effect of psm deletion on methicillin-resistant Staphylococcus aureus, we investigated psm deletion mutants including Δpsmα, Δpsmβ, and Δpsmαβ. These mutants exhibited increased β-lactam antibiotic resistance to ampicillin and oxacillin that was shown to be caused by increased N-acetylmannosamine kinase (nanK) mRNA expression, which regulates persister cell formation, leading to changes in the pattern of phospholipid fatty acids resulting in increased anteiso-C15:0, and increased membrane hydrophobicity with the deletion of PSMs. When synthetic PSMs were applied to Δpsmα and Δpsmβ mutants, treatment of Δpsmα with PSMα1-4 and Δpsmβ with PSMβ1-2 restored the sensitivity to oxacillin and slightly reduced the biofilm formation. Addition of a single fragment showed that α1, α2, α3, and β2 had an inhibiting effect on biofilms in Δpsmα; however, β1 showed an enhancing effect on biofilms in Δpsmβ. This study demonstrates a possible reason for the increased antibiotic resistance in psm mutants and the effect of PSMs on biofilm formation.

• Restorative Dentistry and Endodontics
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• v.46 no.2
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• pp.20.1-20.11
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• 2021

Objectives: The aim of this study was to evaluate bacterial nanocellulose (BNC) membranes incorporated with antimicrobial agents regarding cytotoxicity in fibroblasts of the periodontal ligament (PDLF), antimicrobial activity, and inhibition of multispecies biofilm formation. Materials and Methods: The tested BNC membranes were BNC + 1% clindamycin (BNC/CLI); BNC + 0.12% chlorhexidine (BNC/CHX); BNC + nitric oxide (BNC/NO); and conventional BNC (BNC; control). After PDLF culture, the BNC membranes were positioned in the wells and maintained for 24 hours. Cell viability was then evaluated using the MTS calorimetric test. Antimicrobial activity against Enterococcus faecalis, Actinomyces naeslundii, and Streptococcus sanguinis (S. sanguinis) was evaluated using the agar diffusion test. To assess the antibiofilm activity, BNC membranes were exposed for 24 hours to the mixed culture. After sonicating the BNC membranes to remove the remaining biofilm and plating the suspension on agar, the number of colony-forming units (CFU)/mL was determined. Data were analyzed by 1-way analysis of variance and the Tukey, Kruskal-Wallis, and Dunn tests (α = 5%). Results: PDLF metabolic activity after contact with BNC/CHX, BNC/CLI, and BNC/NO was 35%, 61% and 97%, respectively, compared to BNC. BNC/NO showed biocompatibility similar to that of BNC (p = 0.78). BNC/CLI showed the largest inhibition halos, and was superior to the other BNC membranes against S. sanguinis (p < 0.05). The experimental BNC membranes inhibited biofilm formation, with about a 3-fold log CFU reduction compared to BNC (p < 0.05). Conclusions: BNC/NO showed excellent biocompatibility and inhibited multispecies biofilm formation, similarly to BNC/CLI and BNC/CHX.

• Journal of Pharmacopuncture
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• v.26 no.4
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• pp.307-318
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• 2023

Objectives: Bacterial biofilm is regarded as a significant threat to the production of safe food and the arise of antibiotic-resistant bacteria. The objective of this investigation is to evaluate the quorum sensing inhibitory effect of Nepeta curviflora methanolic extract. Methods: The effectiveness of the leaves at sub-inhibitory concentrations of 2.5, 1.25, and 0.6 mg/mL on the virulence factors and biofilm formation of P. aeruginosa was evaluated. The effect of N. curviflora methanolic extract on the virulence factors of P. aeruginosa, including pyocyanin, rhamnolipid, protease, and chitinase, was evaluated. Other tests including the crystal violet assay, scanning electron microscopy (SEM), swarming motility, aggregation ability, hydrophobicity and exopolysaccharide production were conducted to assess the effect of the extract on the formation of biofilm. Insight into the mode of antiquorum sensing action was evaluated by examining the effect of the extract on the activity of N-Acyl homoserine lactone (AHL) and the expression of pslA and pelA genes. Results: The results showed a significant attenuation in the production of pyocyanin and rhamnolipid and in the activities of protease and chitinase enzymes at 2.5 and 1.25 mg/mL. In addition, N. curviflora methanolic extract significantly inhibited the formation of P. aeruginosa biofilm by decreasing aggregation, hydrophobicity, and swarming motility as well as the production of exopolysaccharide (EPS). A significant reduction in AHL secretion and pslA gene expression was observed, indicating that the extract inhibited quorum sensing by disrupting the quorum-sensing systems. The quorum-sensing inhibitory effect of N. curviflora extract appears to be attributed to the presence of kaempferol, quercetin, salicylic acid, rutin, and rosmarinic acid, as indicated by LCMS analysis. Conclusion: The results of the present study provide insight into the potential of developing anti-quorum sensing agents using the extract and the identified compounds to treat infections resulting from quorum sensing-mediated bacterial pathogenesis.

• Journal of Life Science
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• v.20 no.3
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• pp.321-325
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• 2010

Among endogenous oral microflora, Streptococcus mutans plays a critical role in dental plaque formation, which mainly contributes to the development of caries and periodontal disease. Phytochemicals are plant-derived chemical compounds that have been studied as beneficial nutrients to human health. The purpose of this study was to determine the effects of phytochemicals against S. mutans. Among them, oleanolic acid (OA) and 5-(hydroxymethyl)-2-furfural (HF) from Thomson seedless raisins were tested for anti-microbial effects against various clinically important bacteria. OA inhibited the growth of Gram-positive bacteria, but not Gram-negative bacteria. However, HF did not display any antibacterial effect against any of the strains tested. OA also exhibited inhibitory effects in surface adherence and biofilm formation of S. mutans. The results suggest that OA can be utilized as a potential anti-plaque and anti-caries agent by controlling the physiological characteristics of S. mutans on teeth.

• Microbiology and Biotechnology Letters
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• v.32 no.1
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• pp.1-10
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• 2004

Many bacteria monitor their population density and control the expression of specialized gene sets in response to bacterial cell density based on a mechanism referred to as quorum sensing. In all cases, quorum sensing involves the production and detection of extracellular signaling molecules, auto inducers, as which Gram-negative and Gram-positive bacteria use most prevalently acylated homoserine lactones and processed oligo-peptides, respectively. Through quorum-sensing communication circuits, bacteria regulate a diverse array of physiological functions, including virulence, symbiosis, competence, conjugation, antibiotic production, motility, sporulation, and biofilm formation. Many pathogens have evolved quorum-sensing mechanisms to mount population-density-dependent attacks to over-whelm the defense responses of plants, animals, and humans. Since these AHL-mediated signaling mechanisms are widespread and highly conserved in many pathogenic bacteria, the disruption of quorum-sensing system might be an attractive target for novel anti-infective therapy. To control AHL-mediated pathogenicity, several promising strategies to disrupt bacterial quorum sensing have been reported, and several chemicals and enzymes have been also investigated for years. These studies indicate that anti-quorum sensing strategies could be developed as possible alternatives of antibiotics.

• Journal of the korean academy of Pediatric Dentistry
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• v.42 no.4
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• pp.302-311
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• 2015

The purpose of this study was to evaluate the antibacterial properties of a sealant containing S-PRG filler compared to those of two contemporary commercial sealants to determine the inhibition of bacterial growth in broth culture and biofilm formation using the CDC Biofilm Reactor. The BeautiSealant containing S-PRG filler, the fluoride releasing Clinpro$^{TM}$ sealant, which are known to have higher antibacterial effects, and the non-fluoride releasing Concise$^{TM}$ sealant were selected for this study. A Streptococcus mutans culture in BHI broth without sealant served as a negative control in the planktonic growth inhibition test. As a result, bacterial growth was inhibited in all three sealant groups compared to that in the control. The Clinpro$^{TM}$ sealant showed a significantly reduced number of CFUs compared to those of the BeautiSealant and Concise$^{TM}$ sealants. However, no significant difference was detected between the BeautiSealant and Concise$^{TM}$ sealants. The Clinpro$^{TM}$ sealant significantly decreased biofilm formation compared to that by the BeautiSealant and Concise$^{TM}$ sealants. No significant difference was observed between the BeautiSealant and Concise$^{TM}$ sealants. In conclusion, the sealant containing S-PRG filler had a less potent anti-bacterial property and increased biofilm formation capacity compared to those of the fluoride releasing Clinpro$^{TM}$ sealant.

• Journal of Life Science
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• v.29 no.6
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• pp.712-723
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• 2019

Chemically synthesized compounds are widely used in oral hygiene products. However, excessively long-term use of these chemicals can cause undesirable side effects such as bacterial tolerance, allergy, and tooth discoloration. To solve these issues, significant effort is put into the search for natural antibacterial agents. The aim of this study was to assess the extracts of foreign native plants that inhibit the growth and biofilm formation of Streptococcus mutans. Among the 300 foreign plant extracts used in this study, Chesneya nubigena (D. Don) Ali extract had the highest antimicrobial activity relatively against S. mutans with a clear zone of 9 mm when compared to others. This plant extract also showed anti-biofilm activity and bacteriostatic effect (minimal bactericidal concentration [MBC], 1.5 mg/ml). In addition, the plant extracts of 19 species decreased the ability of S. mutans to form biofilm at least a 6-fold in proportion to the tested concentrations. Of particular note, C. nubigena (D. Don) Ali extract was found to inhibit biofilm formation at the lowest concentration tested effectively. Therefore, our results reveal that C. nubigena (D. Don) Ali extract is a potential candidate for the development of antimicrobial substitutes, which might be effective for caries control as well, as demonstrated by its inhibitory effect on the persistence and pathogenesis of S. mutans.

• Journal of Life Science
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• v.26 no.12
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• pp.1487-1497
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• 2016

Bacterial cell to cell communication strategies called quorum sensing (QS) using small diffusible signaling molecules (auto-inducers) govern the expression of various genes dependent on their population density manner. As a consequence of synthesis and response to the signaling molecules, individual planktonic cells synchronized group behaviors to control a diverse array of phenotypes such as maturation of biofilm, production of extra-polymeric substances (EPS), virulence, bioluminescence and antibiotic production. Many studies indicated that biofilm formations are associated with QS signaling molecules such as acyl-homoserine lactones (AHLs) mainly used by several Gram negative bacteria. The biofilm maturation causes undesirable biomass accumulation in various surface environments anywhere water is present called biofouling, which results in serious eco-technological problems. Numerous molecules that interfere the bacterial QS called quorum quenching (QQ), have been discovered from various microorganisms, and their functions and mechanisms associated with QS have also been elucidated. To resolve biofouling problems related to various industries, the novel approach based on QS interference has been emerged attenuating multi-drug resisting bacteria appearance and environmental toxicities, which may provide potential advantages over the conventional anti-biofouling approaches. Therefore this paper presents recent information related to bacterial quorum sensing system, quorum quenching enzymes that can control the QS signaling, and lastly discuss the anti-biofouling approaches using the quorum quenching.

• Korean Journal of Pharmacognosy
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• v.52 no.1
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• pp.41-48
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• 2021

This research was conducted to investigate the antibacterial and anti-inflammatory effects of MeOH Ex. of Salvia miltiorrhiza (MESM) against oral pathogenic bacteria. Minimum inhibitory concentration (MIC), removal effect of biofilm produced by Streptococcus mutans, effect of gene expression of proinflammatory cytokines and effect of production of proinflammatory cytokine of MESM were tested. MESM showed moderated antibacterial activity against oral pathogenic bacteria. About 89±8% of biofilms produced by S. mutans were removed by MESM at a concentration of 1 mg/mL. Gene expression of IL-1β and TNF-α induced by Porphyromonas gingivalis were 8~9 folds reduced by MESM. Gene expression of IL-8 induced by Fusobacterium nucelatum were 12 folds reduced by MESM. Production of IL-1β, TNF-α and IL-8 were significantly suppressed by MESM. Conclusively, MESM showed potent antibacterial and anti-inflammatory effect against oral pathogenic bacteria.

• Korean Journal of Food Science and Technology
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• v.50 no.4
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• pp.414-419
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• 2018

Escherichia coli O157:H7 is one of the most common foodborne pathogens responsible for outbreaks of hemorrhagic colitis, which can lead to the life-threatening hemolytic-uremic syndrome. In this study, we identified phytochemicals that specifically inhibit the expression of LEE operon in E. coli O157:H7. Among phytochemicals, diosmin decreased the adherence of E. coli O157:H7 towards Caco-2 cells in vitro (p<0.01) and its biofilm formation activity (p<0.05). Quantitative RT-PCR analysis revealed that the transcripts of Ler-regulated genes and genes related to curli production were significantly reduced in the presence of diosmin. However, diosmin does not affect bacterial viability, indicating that the resistance rate to diosmin was remarkably low. Overall, these results provide significant insights into the development of a novel anti-infective agent that is different from conventional antibiotics.