BACKGROUND AND OBJECTIVE

Orthodontic brackets predispose dental biofilm accumulation causing caries and gingivitis. Chlorhexidine is an adjunct to mechanical plaque removal, but has side-effects (tooth staining, bacterial resistance) due to long term use. This study tested the efficacy of Photodynamic Therapy, which produces reactive oxygen species, to reduce Streptococcus mutans in dental biofilm on orthodontic brackets.

A 5-day S. mutans biofilm was grown on forty enamel-bracket specimens. Thirty-nine specimens were randomized to three treatment groups: A. Distilled Water; B. 0.12% Chlorhexidine (CHX); C. Photodynamic Therapy (PDT) using Toluidine Blue O (TBO) as a photosensitizer, activated by red LED (630nm). After treatment, one random specimen from each group was viewed under Environmental Scanning Electron Microscopy (ESEM); the other 12 specimens, biofilms were collected, weighed, and cultured onto BHI agar plates to determine the number of CFU/mg. For baseline evaluation, one clean and one untreated specimens were preserved for ESEM.

Based on Tukey HSD test, group A had the most S. mutans (37.0573 CFU/mg) and was significantly different (p < 0.05) from groups B (0.1712 CFU/mg) and C (1.1193 CFU/mg), where both showed less bacteria than group A. The statistical difference between groups B and C was insignificant. ESEM images showed specimen A covered with more abundant and denser S. mutans biofilm than specimens B and C, with almost similar morphology showing sparse, less dense, and disintegrated biofilm with unclear cellular walls and presence of amorphous masses.

Both Photodynamic Therapy and 0.12% Chlorhexidine showed a significant reduction of S. mutans in dental biofilm on orthodontic brackets. However, there is no significant difference between them in reducing S. mutans CFU/mg. Photodynamic therapy could be an alternative adjunctive tool to mechanical removal of plaque adhered to orthodontic brackets.

OBJECTIVE: CRISPR-Cas protects bacteria from exogenous DNA invasion and is associated with bacterial biofilm formation and pathogenicity. METHODS: We analyzed the type I-F CRISPR-Cas system of Legionella pneumophila WX48, including Cas1, Cas2-Cas3, Csy1, Csy2, Csy3, and Cas6f, along with downstream CRISPR arrays. We explored the effects of the CRISPR-Cas system on the in vitro growth, biofilm-forming ability, and pathogenicity of L. pneumophila through constructing gene deletion mutants. RESULTS: The type I-F CRISPR-Cas system did not affect the in vitro growth of wild-type or mutant strains. The biofilm formation and intracellular proliferation of the mutant strains were weaker than those of the wild type owing to the regulation of type IV pili and Dot/Icm type IV secretion systems. In particular, Cas6f deletion strongly inhibited these processes. CONCLUSION The type I-F CRISPR-Cas system may reduce biofilm formation and intracellular proliferation in L. pneumophila.
Legionella pneumophila/pathogenicity* ; CRISPR-Cas Systems ; Biofilms/growth & development* ; Phenotype ; Bacterial Proteins/metabolism* ; Gene Deletion

OBJECTIVES: This study aims to investigate the impact of glutathione S-transferase (GST) on the environmental adaptability of Streptococcus mutans (S. mutans). METHODS: A GST knockout strain ΔgsT was constructed. Transcriptomic sequencing was performed to analyze the gene expression differences between the wild-type S. mutans UA159 and its GST knockout strain ΔgsT. Comprehensive functional assessments, including acid tolerance assays, hydrogen peroxide challenge assays, nutrient limitation growth assays, and fluorescence in situ hybridization, were conducted to evaluate the acid tolerance, antioxidant stress resistance, growth kinetics, and interspecies competitive ability of ΔgsT within plaque biofilms. RESULTS: Compared with the wild-type S. mutans, 198 genes in ΔgsT were significantly differentially expressed and enriched in pathways related to metabolism, stress response, and energy homeostasis. The survival rate of ΔgsT in acid tolerance assays was markedly reduced (P<0.01). After 15 min of hydrogen peroxide challenge, the survival rate of ΔgsT decreased to 38.12% (wild type, 71.75%). Under nutrient-limiting conditions, ΔgsT exhibited a significantly lower final OD₆₀₀ value than the wild-type strain (P<0.05). In the biofilm competition assays, the proportion of S. mutans ΔgsT in the mixed biofilm (8.50%) was significantly lower than that of the wild type (16.89%) (P<0.05). CONCLUSIONS GST enhances the acid resistance, oxidative stress tolerance, and nutrient adaptation of S. mutans by regulating metabolism-related and stress response-related genes.
Streptococcus mutans/enzymology* ; Biofilms ; Glutathione Transferase/physiology* ; Adaptation, Physiological ; Hydrogen Peroxide/pharmacology* ; Gene Expression Regulation, Bacterial ; Oxidative Stress ; Metabolic Reprogramming

Shewanella oneidensis MR-1, a Gram-negative bacterium with a significant role in the adsorption and reduction of uranium in wastewater and a quorum-sensing effect, can be used to remove uranium from wastewater. Exogenous signaling molecules (acyl-homoserine lactones, AHLs) can be added to induce the quorum sensing behavior for rapid biofilm formation, thereby improving the removal efficiency of this bacterium for uranium. Extracellular polymeric substances (EPS), as the significant components of biofilm, play a key role in biofilm formation. To investigate the quorum sensing behavior induced by AHLs, we systematically investigated the effects of AHLs on the EPS secretion and biofilm properties of S. oneidensis MR-1 by regulating parameters such as AHL species, concentration, addition time point, and contact time. The results showed that the addition of 10 μmol/L N-butyryl-l-homoserine lactone (C4-HSL) after 6 h of culture and continued incubation to reach the time point of 72 h significantly promoted the secretion of EPSs, in which the content of extracellular proteins and extracellular polysaccharides was increased by 15.2% and 28.2%, respectively, compared with that of the control group. The biofilm electrodes induced by signaling molecules showed superior properties, which were evidenced by an increase of exceeding 20 μm in biofilm thickness, an increase of 33.9% in the proportion of living cells, enhanced electroactivity, and an increase of 10.7% in the uranium removal rate. The biofilm electrode was confirmed to immobilize uranium in wastewater mainly by electrosorption, physicochemical adsorption, and electro-reduction through characterization means such as X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). This study provides a new technical idea for the efficient recovery of uranium in wastewater and enriches the theoretical system of quorum sensing regulation of electroactive biofilms.
Biofilms/drug effects* ; Acyl-Butyrolactones/pharmacology* ; Quorum Sensing/drug effects* ; Uranium/metabolism* ; Shewanella/metabolism* ; Adsorption ; Uranium Compounds/metabolism* ; Wastewater/chemistry* ; Biodegradation, Environmental ; Extracellular Polymeric Substance Matrix/metabolism*

OBJECTIVE: To map the potent antifungal properties of the medicinal plant Vitex negundo, in vitro and in silico studies were performed to decipher the pharmacokinetics and ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) properties of their phytoconstituents. METHODS: With the PASS (Prediction of Activity Spectra for Substances) prediction tool, many parameters of V. negundo phenolics were examined, including drug-likeness, bioavailability, antifungal activity, and anti-biofilm activity. Moreover, ADMET parameters were also determined. RESULTS: Eighteen phenolic compounds from V. negundo with significant antifungal activity against Candida species (human fungal pathogens) were detected. The antioxidant activity, inhibition percentage, and minimum inhibitory concentration value of V. negundo phenolic extracts indicate it as an effective antifungal agent for the treatment of candidiasis caused by the fungal pathogen Candida albicans. Many phenolic compounds showed a significantly high efficiency against Candida's planktonic cells and biofilm condition. CONCLUSIONS The phenolics fraction of V. negundo has potent antifungal activities, however, some more pre-clinical studies are a matter of future research to further investigate V. negundo phenolic compound as a potential new antifungal arsenal.
Candida albicans/physiology* ; Vitex/chemistry* ; Antifungal Agents/chemistry* ; Microbial Sensitivity Tests ; Biofilms/drug effects* ; Phenols/pharmacokinetics* ; Plant Extracts/chemistry* ; Antioxidants/pharmacology* ; Phytochemicals/pharmacology* ; Humans

OBJECTIVE: To investigate the regulatory effects of two traditional mineral medicines (TMMs), Gypsum Fibrosum (Shigao, GF) and Terra Flava Usta (Zaoxintu, TFU), on gut-beneficial bacteria in mice, and preliminarily explore their mechanisms of action. METHODS: Mice were randomly divided into 3 groups (n=10 per group): the control group (standard diet), the GF group (diet supplemented with 2% GF), and the TFU group (diet supplemented with 2% TFU). After 4-week intervention, 16S rRNA gene sequencing was used to analyze the changes in the gut microbiota (GM). Scanning electron microscopy, in combination with coumarin A tetramethyl rhodamine conjugate and Hoechst stainings, was used to observe the bacteria and biofilm formation. RESULTS: Principal coordinate analysis revealed that GF and TFU significantly altered the GM composition in mice. Further analysis revealed that GF and TFU affected different types of gut bacteria, suggesting that different TMMs may selectively modulate specific bacterial populations. For certain bacteria, such as Faecalibaculum and Ileibacterium, both GF and TFU exhibited growth-promoting effects, implying that they may be sensitive to TMMs and that different TMMs can increase their abundance through their respective mechanisms. Notably, Lactobacillus reuteri, a widely recognized and used probiotic, was significantly enriched in the GF group. Random forest analysis identified Ileibacterium valens as a potential indicator bacterium for TMMs' impact on GM. Further mechanistic studies showed that gut bacteria formed biofilm structures on the TFU surface. CONCLUSIONS This study provides new insights into the interaction between TMMs and GM. As safe and effective natural clays, GF and TFU hold promise as potential candidates for prebiotic development.
Animals ; Gastrointestinal Microbiome/drug effects* ; Bacteria/growth & development* ; Mice ; Biofilms/drug effects* ; Male ; RNA, Ribosomal, 16S/genetics*

Chronic rhinosinusitis with nasal polyps（CRSwNP） represents a prevalent inflammatory disorder, which is often accompanied by nasal congestion, mucopurulent discharge, olfactory dysfunction, dizziness, and headache. Staphylococcus aureus（SA）, a predominant opportunistic pathogen within the sinonasal microenvironment, has been implicated in modulating the pathogenesis and progression of CRSwNP through multifaceted mechanisms. The physiological activities of SA-dependent quorum-sensing system and biofilm in the nasal microenvironment, including interactions with host, fungi, viruses, and other bacteria, as well as the effects of important superantigens secreted by SA on the microenvironment and immune barrier, are briefly reviewed in this article. These insights provide theoretical foundations for elucidating CRSwNP mechanisms and advancing clinical therapeutic strategies.
Humans ; Sinusitis/microbiology* ; Nasal Polyps/microbiology* ; Staphylococcus aureus ; Chronic Disease ; Rhinitis/microbiology* ; Staphylococcal Infections/microbiology* ; Quorum Sensing ; Biofilms ; Rhinosinusitis

OBJECTIVES: To explore the efficacy of low-intensity pulsed ultrasound (LIPUS) combined with nystatin for treatment of vaginal Candida albicans biofilm infection. METHODS: In vitro cultured Candida albicans biofilm were treated with LIPUS, nystatin, or both, and the minimum inhibitory concentration (MIC) of nystatin was determined. Crystal violet staining, confocal laser microscopy (CLSM) and scanning electron microscopy were used to quantify the biofilm and observe the activity and morphological changes of the biofilms; DCFH-DA was used to detect the changes in reactive oxygen species (ROS). Twenty female New Zealand White rabbits with vaginal inoculation of Candida albicans biofilm were randomized into 4 groups for treatment with normal saline, LIPUS, nystatin, or both LIPUS and nystatin. The changes in vulvar symptoms of the rabbits were observed, and the histopathological and ultrastructural changes of the vagina before and after treatment were observed using HE staining and transmission electron microscopy. RESULTS: In the combined treatment group, the MIC₅₀ and MIC₈₀ of nystatin in Candida albicans biofilms were both reduced by 50% compared with those in nystatin group, and the biofilm clearance rate increased by 26% and 68% compared with nystatin and LIPUS groups, respectively. Compared with nystatin and LIPUS treatment alone, the combined treatment produced stronger effects for inhibiting biofilm activity, causing structural disruption and promoting ROS production. In the rabbit models, the combined treatment more effectively improved vulvar symptoms and inflammatory infiltration, reduced residual vaginal hyphae/strains, and improved ultrastructure of the vaginal epithelium than LIPUS and nystatin treatment alone. CONCLUSIONS LIPUS combined with nystatin produces a significant synergistic antifungal effect against Candida albicans biofilm both in vitro and in vivo.
Animals ; Rabbits ; Female ; Biofilms/drug effects* ; Candida albicans/physiology* ; Nystatin/therapeutic use* ; Candidiasis, Vulvovaginal/microbiology* ; Ultrasonic Waves ; Antifungal Agents/therapeutic use* ; Vagina/microbiology* ; Ultrasonic Therapy ; Microbial Sensitivity Tests ; Combined Modality Therapy

Dental implants have restored masticatory function to over 100 000 000 individuals, yet almost 1 000 000 implants fail each year due to peri-implantitis, a disease triggered by peri-implant microbial dysbiosis. Our ability to prevent and treat peri-implantitis is hampered by a paucity of knowledge of how these biomes are acquired and the factors that engender normobiosis. Therefore, we combined a 3-month interventional study of 15 systemically and periodontally healthy adults with whole genome sequencing, fine-scale enumeration and graph theoretics to interrogate colonization dynamics in the pristine peri-implant sulcus. We discovered that colonization trajectories of implants differ substantially from adjoining teeth in acquisition of new members and development of functional synergies. Source-tracking algorithms revealed that this niche is initially seeded by bacteria trapped within the coverscrew chamber during implant placement. These pioneer species stably colonize the microbiome and exert a sustained influence on the ecosystem by serving as anchors of influential hubs and by providing functions that enable cell replication and biofilm maturation. Unlike the periodontal microbiome, recruitment of new members to the peri-implant community occurs on nepotistic principles. Maturation is accompanied by a progressive increase in anaerobiosis, however, the predominant functionalities are oxygen-dependent over the 12-weeks. The peri-implant community is easily perturbed following crown placement, but demonstrates remarkable resilience; returning to pre-perturbation states within three weeks. This study highlights important differences in the development of the periodontal and peri-implant ecosystems, and signposts the importance of placing implants in periodontally healthy individuals or following the successful resolution of periodontal disease.
Humans ; Dental Implants/microbiology* ; Microbiota ; Male ; Adult ; Female ; Biofilms ; Middle Aged ; Peri-Implantitis/microbiology*

The caries-preventive effects of arginine have been attributed to its impact on biofilm composition and pH. Recent in vitro studies suggest that arginine also affects the production of biofilm matrix components that contribute to virulence, but this mechanism has not been investigated clinically. This randomized, placebo-controlled, triple-blind, split-mouth in situ trial assessed arginine's impact on the microbial composition, matrix architecture, and microscale pH of biofilms from caries-active patients (N = 10). We also examined whether individual differences in the pH response to arginine were related to biofilm composition and matrix structure. Biofilms were grown for four days on carriers attached to intraoral splints. Three times daily, the biofilms were treated extraorally with sucrose (5 min), followed by arginine or placebo (30 min), in a split-mouth design. After growth, the microscale biofilm pH response to sucrose was monitored by pH ratiometry. Microbial biofilm composition and carbohydrate matrix architecture were analyzed by 16S rRNA gene sequencing and fluorescence lectin-binding analysis, respectively. Arginine treatment significantly mitigated sucrose-induced pH drops, reduced total carbohydrate matrix production, and altered the spatial distribution of fucose- and galactose-containing carbohydrates. Both arginine- and placebo-treated biofilms were dominated by streptococci and Veillonella spp. Paired analyses showed a significant reduction in mitis/oralis group streptococci and a non-significant increase in several arginine metabolizers in arginine-treated biofilms. Individual pH responses were not significantly associated with the abundance of specific bacterial taxa or carbohydrate matrix components. In conclusion, arginine reduced the virulence of biofilms from caries-active patients through multiple mechanisms, including suppressing matrix carbohydrate production.
Biofilms/drug effects* ; Humans ; Arginine/pharmacology* ; Hydrogen-Ion Concentration ; Dental Caries/prevention & control* ; Male ; Female ; Adult ; Double-Blind Method ; Sucrose/pharmacology*