Reduction In Bacterial Numbers Research Articles

The Impact of Hydrogen Peroxide (H2O2) Fumigation on Bacterial Levels in Dental Office Environments: A Randomized Clinical Trial Investigation.

Fumigation with hydrogen peroxide has proven to be a highly effective approach to maintaining biological safety within dental offices. The main purpose of this research was to investigate the efficacy of hydrogen peroxide (H2O2) fumigation in reducing bacterial levels in dental office environments. The study involved 30 participants diagnosed with moderate caries decay (ICDAS 3 and 4) in their mandibular molars. Sixty Petri dishes (two per patient) with Columbia Agar and 5% Sheep Blood were opened at the beginning of the caries treatment. After the completion of caries treatment and tooth restoration, 30 plates (G1 group) were closed. Following this, a 20 min fumigation procedure with 6% hydrogen peroxide biosanitizer using a compressed air device was conducted. After the fumigation, the remaining plates were closed (G2 group). The total number of bacteria CFUs (colony-forming units) in the dental office air was determined using the Koch sedimentation method. The total bacterial colony (TBC) level, measured in cfu/m3, demonstrated a significant decrease in the number of bacteria following room environment fumigation (163.1 ± 145.7; G2 group) compared to non-fumigated samples (817.2 ± 208.2; G1 group) (p < 0.001). The predominant bacteria observed in the microbiological plates before fumigation were Micrococcus and Bacillus species, found in 80% (24/30) and 60% (18/30) of the plates, respectively. Application of H2O2 room fumigation resulted in a significant reduction in bacterial numbers: 79.2% (5/30) for Micrococcus species (p < 0.001), 83.3% (3/30) for Bacillus species (p < 0.001), and 100% (0/30) for Staphylococcus arlettae (p < 0.05). Fumigation with 6% H2O2 is an effective method for reducing bacterial counts in a dental office environment.

Phage-antibiotic synergy: Cell filamentation is a key driver of successful phage predation.

Phages are promising tools to fight antibiotic-resistant bacteria, and as for now, phage therapy is essentially performed in combination with antibiotics. Interestingly, combined treatments including phages and a wide range of antibiotics lead to an increased bacterial killing, a phenomenon called phage-antibiotic synergy (PAS), suggesting that antibiotic-induced changes in bacterial physiology alter the dynamics of phage propagation. Using single-phage and single-cell techniques, each step of the lytic cycle of phage HK620 was studied in E. coli cultures treated with either ceftazidime, cephalexin or ciprofloxacin, three filamentation-inducing antibiotics. In the presence of sublethal doses of antibiotics, multiple stress tolerance and DNA repair pathways are triggered following activation of the SOS response. One of the most notable effects is the inhibition of bacterial division. As a result, a significant fraction of cells forms filaments that stop dividing but have higher rates of mutagenesis. Antibiotic-induced filaments become easy targets for phages due to their enlarged surface areas, as demonstrated by fluorescence microscopy and flow cytometry techniques. Adsorption, infection and lysis occur more often in filamentous cells compared to regular-sized bacteria. In addition, the reduction in bacterial numbers caused by impaired cell division may account for the faster elimination of bacteria during PAS. We developed a mathematical model to capture the interaction between sublethal doses of antibiotics and exposition to phages. This model shows that the induction of filamentation by sublethal doses of antibiotics can amplify the replication of phages and therefore yield PAS. We also use this model to study the consequences of PAS on the emergence of antibiotic resistance. A significant percentage of hyper-mutagenic filamentous bacteria are effectively killed by phages due to their increased susceptibility to infection. As a result, the addition of even a very low number of bacteriophages produced a strong reduction of the mutagenesis rate of the entire bacterial population. We confirm this prediction experimentally using reporters for bacterial DNA repair. Our work highlights the multiple benefits associated with the combination of sublethal doses of antibiotics with bacteriophages.

Synergistic antibacterial and anti-biofilm mechanisms of ultrasound combined with citral nanoemulsion against Staphylococcus aureus 29213

This study investigated the antibacterial and antibiofilm mechanism of ultrasound (US) combined with citral nanoemulsion (CLNE) against Staphylococcus aureus and mature biofilm. Combined treatments resulted in greater reductions in bacterial numbers compared to ultrasound or CLNE treatments alone. Confocal laser scanning microscopy (CLSM), flow cytometry (FCM), protein nucleic acid leakage, and N-phenyl-l-naphthylamine (NPN) uptake analysis showed that the combined treatment disrupted cell membrane integrity and permeability. Reactive oxygen species (ROS) and malondialdehyde (MDA) assays indicated that US+CLNE exacerbated cellular oxidative stress and membrane lipid peroxidation. Field emission scanning electron microscopy (FESEM) revealed that the synergistic processing of ultrasound and CLNE resulted in cell rupture and collapse. In addition, US+CLNE showed a more pronounced removal effect than both alone in the biofilm on the stainless steel sheet. US+CLNE reduced biomass, the number of viable cells in the biofilm, cell viability and EPS polysaccharide contents. The results of CLSM also showed that US+CLNE disrupted the structure of the biofilm. This research elucidates the synergistic antibacterial and anti-biofilm mechanism of ultrasound combined citral nanoemulsion, which provides a safe and efficient sterilization method for the food industry.

TA-AgNPs/Alginate Hydrogel and Its Potential Application as a Promising Antibiofilm Material against Polymicrobial Wound Biofilms Using a Unique Biofilm Flow Model.

The presence of biofilm within a chronic wound may delay the healing process. Thus, control of biofilm formation and providing bactericidal effect are crucial factors for wound healing management. Alginate-based nanocomposite hydrogels have been suggested as dressing materials for wound treatment, which are employed as a biocompatible matrix. Therefore, in this study, we aimed to develop a biocompatible antimicrobial wound dressing containing AgNPs and demonstrate its efficacy against polymicrobial wound biofilms by using a biofilm flow device to simulate a chronic infected, exuding wound and specific wound environment. The results from agar well diffusion, the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays showed that TA-AgNPs exhibited antibacterial activity against wound pathogens. Additionally, the Minimum Biofilm Eradication Concentration assay (MBEC) demonstrated it could impair biofilm formation. Importantly, our TA-AgNPs/Alginate hydrogel clearly showed antibacterial activities against Streptococcus pyogenes, Staphylococcus aureus and Pseudomonas aeruginosa. Furthermore, we used the biofilm flow device to test the topical antimicrobial hydrogel against a three-species biofilm. We found that TA-AgNPs/Alginate hydrogel significantly showed a 3-4 log reduction in bacterial numbers when applied with multiple doses at 24 h intervals, and was especially effective against the chronic wound pathogen P. aeruginosa. This work highlighted that the TA-AgNPs/Alginate hydrogel is a promising material for treating complex wound biofilms.

The antibacterial and antibiofilm activity of Granudacyn in vitro in a 3D collagen wound infection model.

It is widely agreed that infection and the formation of biofilms play a major role in increasing inflammation and delaying wound healing. The aim of this study was to evaluate, in vitro, the antimicrobial activity of the wound irrigation solution, Granudacyn (Mölnlycke Health Care AB, Sweden) against planktonic bacteria and mature biofilms of clinically relevant bacterial species. Quantitative evaluation of bacterial numbers and confocal and/or scanning electron microscopy were used to evaluate the wound irrigation solution's antimicrobial/antibiofilm activity in standard laboratory conditions as well as in a three-dimensional (3D) collagen wound infection model. The wound irrigation solution exhibited a rapid and strong antibacterial activity against both Gram-positive and Gram-negative strains isolated from infected wounds in planktonic form, with a reduction in bacterial number of >4 Logs after as little as one minute of treatment. The wound irrigation solution also exerted an evident activity against preformed biofilms of Pseudomonas aeruginosa and Staphylococcus aureus (>3 Log and >1 Log reduction in colony forming unit number, respectively, after 15 minutes of incubation). Although the wound irrigation solution was partially inhibited in the presence of simulated wound fluid, it maintained a marked antibiofilm activity in in vivo-like conditions (ie. in a 3D collagen wound infection model) with a strong killing and a mild debridement effect, which was superior to standard saline. The results obtained in this study suggest that although the wound irrigation solution used might be partially inhibited by wound exudate, it has the potential to effectively kill wound infecting planktonic as well as biofilm bacteria.

The combined bactericidal effect of nisin and thymoquinone against Listeria monocytogenes in Tryptone Soy Broth and sterilized milk

In this study, the combined bactericidal effect of nisin and thymoquinone (TQ) on Listeria monocytogenes was investigated in Tryptone Soy Broth (TSB) and sterilized milk. The combined treatment resulted in a greater reduction in bacterial number than either nisin or TQ treatment alone. Nisin and TQ respectively caused depolarization and hyperpolarization of the cell membrane of L. monocytogenes , which indicated early injury to the bacteria. Confocal laser scanning microscopy and N -phenyl-l-naphthylamine uptake assay showed disruption of the cell membrane on treatment. Field emission scanning electron microscopy revealed depression and collapse of the cell surface following treatment with nisin and TQ. Growth curves showed that nisin and TQ acted on the bacteria in different growth phases. Fourier-transform infrared spectroscopy demonstrated a reversible hydrogen-bonding interaction between nisin and TQ. Our results suggest that nisin combined with TQ is a more effective antibacterial effect against L. monocytogenes in both TSB and in sterilized milk than either agent alone. Our study sheds light on the inhibitory mechanisms of nisin, TQ, and their combination, and provides a theoretical basis for the synergistic antibacterial application of nisin and TQ in the food industry. • The anti bacterial effect of combined nisin and thymoquinone (TQ) treatment exceeded that of either treatment alone. • Nisin and TQ damaged the bacterial membrane and morphology by different mechanisms. • The inhibitory effects of nisin and TQ on the growth phases of L. monocytogenes were different. • Nisin and TQ interact via intermolecular hydrogen bonding.

Antimicrobial Photodynamic Therapy Involving a Novel Photosensitizer Combined With an Antibiotic in the Treatment of Rabbit Tibial Osteomyelitis Caused by Drug-Resistant Bacteria.

Osteomyelitis is deep tissue inflammation caused by bacterial infection. If such an infection persists, it can lead to dissolution and necrosis of the bone tissue. As a result of the extensive use of antibiotics, drug-resistant bacteria are an increasingly common cause of osteomyelitis, limiting the treatment options available to surgeons. Photodynamic antibacterial chemotherapy has attracted increasing attention as a potential alternative treatment. Its advantages are a broad antibacterial spectrum, lack of drug resistance, and lack of toxic side effects. In this study, we explored the impact of the new photosensitizer LD4 in photodynamic antimicrobial chemotherapy (PACT), both alone and in combination with an antibiotic, on osteomyelitis. A rabbit tibial osteomyelitis model was employed and microbiological, histological, and radiological studies were performed. New Zealand white rabbits (n = 36) were randomly divided into a control group, antibiotic group, PACT group and PACT + antibiotic group for treatment. In microbiological analysis, a reduction in bacterial numbers of more than 99.9% was recorded in the PACT group and the PACT + antibiotic group 5 weeks after treatment (p < 0.01). In histological analysis, repair of the damaged bone tissue was observed in the PACT group, and bone repair in the PACT + antibiotic group was even more significant. In radiological analysis, the X-ray Norden score showed that the severity of bone tissue defects or destruction followed the pattern: PACT + antibiotic group < PACT group < antibiotic group < control group.

Longevity of hand sanitisers on fingers

ABSTRACT Clinical relevance Hand hygiene is important to reduce the spread of microbes in clinical settings. Hand sanitisers that last longer may be beneficial. Background Longevity of hand sanitisation products on fingers and hands may be important to help reduce microbial transmission. The current study evaluated the persistence of disinfection of three hand sanitisers. Methods Initially the minimum inhibitory concentrations of the hand sanitisers were determined using strains of Staphylococcus epidermidis and S. aureus. Then a cross-over study with participants randomly assigned to use three different hand sanitisers for 30 seconds was undertaken. The number of bacteria and fungi on fingers was assessed 10 and 20 minutes and 4 hours after use. The type of microbial inhibition of the capric acid sanitiser was studied by examining the effects of adding Tween 80 and lecithin to microbial agar. Results The minimum inhibitory concentration of an alcohol-based sanitiser (AS) was 10%, for the capric acid-based (CS) sanitiser was 70%, and for the quaternary ammonium-based (QS) sanitiser was < 10%. AS significantly reduced the number of microbes on fingers 10 minutes after hand washing (18.2 cfu/mL) compared to CS (59.7 cfu/mL; p < 0.0001) or QS (64.5 cfu/mL; p < 0.0001). Twenty minutes after use, microbes on fingers after AS (23 cfu/mL) or CS (16.7 cfu/mL) were significantly reduced compared to QS (72.2 cfu/mL; p < 0.0001) and the numbers on fingers after CS was significantly less than after AS (p = 0.002). Four hours after use of any hand sanitiser, the number of microbes increased to near baseline levels. The reduction in bacterial numbers was not affected by the use of neutralisers in agar (48 ± 28% reduction with, 47 ± 49% reduction without; p = 0.876). Conclusions Hand sanitisers containing capric acid or alcohol out-performed one containing quaternary ammonium in the clinical trial and may help reduce the spread of microbes.

Removal Performance of Faecal Indicators by Natural and Silver-Modified Zeolites of Various Particle Sizes under Dynamic Batch Experiments: Preliminary Results

One of the oldest and most promising applications of natural zeolites (NZs) is in water and wastewater treatment processes. Modified zeolites (MZs), with improved ion exchange and adsorption capacities, have been extensively applied to the removal of pollutants from aqueous solutions. However, the application of MZs in pathogens or indicator organisms has not been extensively explored. This study examines the effect of both natural Greek zeolite (NZ), with a clinoptilolite content of up to 85% (OLYMPUS SA-INDUSTRIAL MINERALS), and modified Greek zeolite through incorporation with silver ions (Ag-MNZ), on the survival of two selected faecal indicator bacteria (Escherichia coli and Enterococcus faecalis). A series of dynamic batch experiments with a slow agitation of 12 rpm were conducted at a constant ambient temperature (22°C) in order to examine the inactivation of the above bacteria by NZ and Ag-MNZ. It was found that the Ag-MNZ resulted in a much higher reduction in the bacterial numbers when compared to the NZ and the control (absence of zeolites). Moreover, the reduction in bacterial numbers was affected by NZ particle size, with higher removal rates observed for coarse (1–3 mm) than for fine (0–1 mm) NZ. Finally, the E. faecalis was found to be more resistant than E. coli to Ag-MNZ.

Disparate regulation of IMD signaling drives sex differences in infection pathology in Drosophila melanogaster

Male and female animals exhibit differences in infection outcomes. One possible source of sexually dimorphic immunity is the sex-specific costs of immune activity or pathology, but little is known about the independent effects of immune- versus microbe-induced pathology and whether these may differ for the sexes. Here, by measuring metabolic and physiological outputs in Drosophila melanogaster with wild-type and mutant immune responses, we test whether the sexes are differentially impacted by these various sources of pathology and identify a critical regulator of this difference. We find that the sexes exhibit differential immune activity but similar bacteria-derived metabolic pathology. We show that female-specific immune-inducible expression of PGRP-LB, a negative regulator of the immune deficiency (IMD) pathway, enables females to reduce immune activity in response to reductions in bacterial numbers. In the absence of PGRP-LB, females are more resistant to infection, confirming the functional importance of this regulation and suggesting that female-biased immune restriction comes at a cost.

Cytokine-Mediated Regulation of ARG1 in Macrophages and Its Impact on the Control of Salmonella enterica Serovar Typhimurium Infection.

Arginase 1 (ARG1) is a cytosolic enzyme that cleaves L-arginine, the substrate of inducible nitric oxide synthase (iNOS), and thereby impairs the control of various intracellular pathogens. Herein, we investigated the role of ARG1 during infection with Salmonella enterica serovar Typhimurium (S.tm). To study the impact of ARG1 on Salmonella infections in vitro, bone marrow-derived macrophages (BMDM) from C57BL/6N wild-type, ARG1-deficient Tie2Cre+/−ARG1fl/fl and NRAMPG169 C57BL/6N mice were infected with S.tm. In wild-type BMDM, ARG1 was induced by S.tm and further upregulated by the addition of interleukin (IL)-4, whereas interferon-γ had an inhibitory effect. Deletion of ARG1 did not result in a reduction in bacterial numbers. In vivo, Arg1 mRNA was upregulated in the spleen, but not in the liver of C57BL/6N mice following intraperitoneal S.tm infection. The genetic deletion of ARG1 (Tie2Cre+/−ARG1fl/fl) or its pharmacological inhibition with CB-1158 neither affected the numbers of S.tm in spleen, liver and blood nor the expression of host response genes such as iNOS, IL-6 or tumour necrosis factor (TNF). Furthermore, ARG1 was dispensable for pathogen control irrespective of the presence or absence of the phagolysosomal natural resistance-associated macrophage protein 1 (NRAMP1). Thus, unlike the detrimental function of ARG1 seen during infections with other intraphagosomal microorganisms, ARG1 did not support bacterial survival in systemic salmonellosis, indicating differential roles of arginine metabolism for host immune response and microbe persistence depending on the type of pathogen.

Ultrasmall FeS2 Nanoparticles-Decorated Carbon Spheres with Laser-Mediated Ferrous Ion Release for Antibacterial Therapy.

Recent progress in nanotechnology and the ancient use of sulfur in treating dermatological disorders have promoted the development of nano-sulfides for antimicrobial applications. However, the variable valences and abundant forms of nano-sulfides have complicated investigations on their antibacterial activity. Here, carbon nanospheres (CNSs) with decoration of ultrasmall FeS2 nanoparticles (CNSs@FeS2 ) is synthesized, and their antibacterial ability and mechanism are explored. The CNSs@FeS2 released Fe2+ and sulfur ions simultaneously through dissolution and disproportionation. In vitro study indicated that the released Fe2+ killed bacteria by increasing the oxidative state of bacterial surfaces and intracellular molecules. Importantly, the released sulfur exhibited a protective effect on Fe2+ , ensuring the stable existence of Fe2+ to continuously combat bacteria. Moreover, the carbon shells of CNSs@FeS2 not only prevented the aggregation of FeS2 but also accelerated the release of Fe2+ through photothermal effects to achieve synergistic hyperthermia/Fe2+ therapy. In vivo experiments indicated that treatment with CNSs@FeS2 resulted in a marked reduction in bacterial number and improvement in survival in an acute peritonitis mouse model, and antibacterial wound experiments demonstrated high efficacy of CNSs@FeS2 -enabled synergistic hyperthermia/Fe2+ therapy. Thus, this study clarifies the antibacterial mechanism of FeS2 and offers a synergetic therapeutic platform with laser-mediated Fe2+ release for antibacterial applications.

Irrigation Of Wounds with Red betel 20% And 40% to Bacterial Numbers In Diabetic Foot Infection (DFI) Patients

Background: The most frequent complications of diabetes mellitus are Diabetic Foot Ulcers (DFU), which has a risk of death 2.5 times compared to those without DFU. More than half of them have problems with infection (Diabetic Foot Infections). Research on wound washing to control diabetic wound infections originating from phytopharmaca using tropical natural resources such as red betel has not developed. They are a tropical plant that has many benefits containing flavonoids, tannins, alkaloids, saponins. Washing the wound with irrigation and swab techniques using red betel 20% effectively reduces the total number of bacteria with diabetic ulcer isolates in white mice alloxan-induced. It reduces staphylococcus growth aureus at concentrations of 10%, 20%, 40%, 80%, 100%. Purpose: This study aimed to determine the effectiveness of wound irrigation red betel 20% and 40% of the bacterial rate in DFI patients.Methods: This study used a quasi-experiment with pre-post test control group design two treatment groups where bacterial samples were taken before and after irrigation using 20% and 40% red betel extracts while the control group used 0.9% NaCl. Sampling using consecutive sampling with a large sample of 10 respondents, the total sample swab is 20 samples. The Levine technique swab does perform in the area of the diabetic wound. Wilcoxon test was used as a different test in each group showing a group.Results: The results showed that the Wilcoxon test was used as a different test in each group showing a group. of 20% p-value 0,109, group 40% p-value 0,109 and a dick group p-value 0,180. Conclusion: There was a decrease in the number of bacteria after irrigation betel leaf extract in all groups. The 40% betel extract irrigation group showed an average reduction in bacterial numbers. The DFI wound had an average difference in all groups but was not significant. The suggestion for research follows: Taking more samples, the use of red betel extract as an alternative for infection control in wounds. Further research can be done by isolating the red betel content need for more sampling

Effect of Sub-MICs of Macrolides on the Sensitivity of Pseudomonas aeruginosa to Nitrosative Stress: Effectiveness against P. aeruginosa with and without Multidrug Resistance.

Sub-MICs of the 14-membered macrolides erythromycin (EM) and clarithromycin (CAM) decreased the growth of Pseudomonas aeruginosa PAO1 and increased its sensitivity to endogenous and exogenous nitrosative stress. However, a 16-membered macrolide, josamycin (JM), was not or less effective. In 9 of 13 non-multidrug-resistant P. aeruginosa (non-MDRP) and 9 of 27 MDRP ST235 strains, the sub-MIC of EM induced significant reductions in bacterial numbers following treatment with a nitric oxide donor.

Probiotic Effects on Multispecies Biofilm Composition, Architecture, and Caries Activity In Vitro.

While probiotics have been tested for their anti-caries effect in vitro and also clinically, there is a lack of understanding of their effects on complex dental biofilms. We assessed two probiotics, Lactobacillus reuteri and Streptococcus oligofermentans, on a continuous-cultured model containing Streptococcus mutans, Lactobacillus rhamnosus and Actinomyces naeslundii. Cariogenic biofilms were grown on bovine enamel specimens and daily challenged with L. reuteri or S. oligofermentans whole culture (LC/SC) or cell-free supernatant (LS/SS) or medium only (negative control, NC) (n = 21/group) for 10 days. Biofilm was assessed via counting colony-forming units, quantitative polymerase chain reaction, and fluorescence in situ hybridization. Caries activity was determined by pH measurements and by assessing mineral loss (ΔZ) using transverse microradiography. Both LC and SC significantly reduced total and strain-specific cariogenic bacterial numbers (p < 0.05). ΔZ was reduced in LC (mean ± SD: 1846.67 ± 317.89) and SC (3315.87 ± 617.30) compared to NC (4681.48 ± 495.18, p < 0.05). No significant reductions in bacterial numbers and ΔZ was induced by supernatants. Biofilm architecture was not considerably affected by probiotic applications. Viable probiotics L. reuteri and S. oligofermentans, but not their culture supernatants, could reduce the caries activity of multi-species biofilms in vitro.

Ash depth filter sanitation eliminates all bacteria and makes source-separated urine waste sterile

Abstract Remote houses cannot use sewerage systems and so they must make their own arrangements for waste disposal. A solution is the use of ash depth filters which simultaneously trap nitrogen and phosphorus from human waste streams and all bacteria during long periods (750 ml per day for more than 6 weeks) of operation by filtration under gravity. Bacteria entering the filtration system, those trapped by the filter and the living material which eventually emerges if the system is operated till it eventually fails, are characterized. Reduction of bacterial numbers is achieved by two mechanisms: physical filtration and chemical sanitation.

Effect of Face Surgical Mask Application Face Skin Flora, Staphylococcus epidermedis As A Symbol

Skin flora is a group of microbiota residing normally skin, it has an important function through the preservation of skin from infection by their natural probiotics or other defending tools. This study aimed to show the effect of surgical masks wearing on skin flora, depending on Staphylococcus epidermedis as a bacterial symbol. The study was done on 20 normal individuals who are wearing surgical mask daily during their performing their normal life activities during COVID-19 global outbreak. Skin swabs before and after mask-wearing were taken from each individual from both genders equally (10 male and 10 female individuals). Bacteriological investigations were done for each swab as soon as at the private lab at Drmatology Private Clinic. These investigations were focused on staphylococcus epidermedis as bacteriological skin flora before and after mask application. Results revealed a significant reduction in bacterial numbers after wearing face masks by two genders. the bacterial count was reduced from 1x10 3 to 102 bacterial in males and the count was 1x102 to 10 cells in females. In conclusion, wearing masks was affecting skin flora on the face through the reduction of some types of bacterial skin flora,Staphylococcus epidermedis her as a sample.

Dental Materials Incorporated with Nanometals and Their Effect on the Bacterial Growth of Staphylococcus aureus.

PurposeThe purpose of this study was to investigate the effect of different commercially used dental materials (RelyX Luting Plus and Dyract Extra) mixed with either a metallic ionic solution or a colloidal suspension of metallic nanoparticles. Both the solution and the suspension contained a mixture of silver, copper, and lithium ions.MethodsThe metal/ion-incorporated dental materials were prepared into disk-shaped samples and tested against the growth of Staphylococcus aureus. The susceptibility of bacteria against the antibacterial dental disks was tested using two methods: counting the colony-forming units per milliliter and disk diffusion (Kirby–Bauer). The incorporated materials (Dyract and Rely cement) were tested for ion release using flame atomic absorption spectroscopy.ResultsAssessment showed efficient antibacterial activity of metal ion–incorporated Rely luting cement, exhibited by the formation of inhibition zones larger than those formed by the standard antibiotic, as well as a reduction in bacterial number of sevenfold after incubation for 24 hours. Dyract material incorporated with nanoparticles showed no significant clear zones and had no inhibiting effect on bacterial colony numbers after incubation for 24 hours. The release of silver, copper, and lithium metal ions depended on the type of both dental material and the incorporated nanoagents. The metal ion–incorporated Rely Plus cement released the highest levels of metal ions, which was attributed to its antibacterial efficiency.ConclusionRely Plus cement incorporated with the nanoparticle suspension demonstrated high antibacterial potency, due to the release of the highest concentrations of silver, copper, and lithium metal ions. This work is the first direct comparative study of dental materials with different forms of nanomixtures (metallic nanoparticles and soluble metallic ions) and their antibacterial effects after incubation with bacterial culture for 24 hours.

Characterization of Mixed-Species Biofilm Formed by Vibrio parahaemolyticus and Listeria monocytogenes.

Mixed-species biofilms are the predominant form of biofilms found in nature. Research on biofilms have typically concentrated on single species biofilms and this study expands the horizon of biofilm research, where the characterization and dynamic changes of mono and mixed-species biofilms formed by the pathogens, Vibrio parahaemolyticus and Listeria monocytogenes were investigated. Compared to mono-species biofilm, the biomass, bio-volume, and thickness of mixed-species biofilms were significantly lower, which were confirmed using crystal violet staining, confocal laser scanning microscopy and scanning electron microscopy. Further experimental analysis showed these variations might result from the reduction of bacterial numbers, the down-regulation of biofilm-regulated genes and loss of metabolic activity in mixed-species biofilm. In addition, V. parahaemolyticus was located primarily on the surface layers of the mixed-species biofilms thus accruing competitive advantage. This competitive advantage was evidenced in a higher V. parahaemolyticus population density in the mixed-species biofilms. The adhesion to surfaces of the mixed-species biofilms were also reduced due to lower concentrations of extracellular polysaccharide and protein when the structure of the mixed-species was examined using Raman spectral analysis, phenol-sulfuric acid method and Lowry method. Furthermore, the minimum biofilm inhibitory concentration to antibiotics obviously decreased when V. parahaemolyticus co-exited with L. monocytogenes. This study firstly elucidated the interactive behavior in biofilm development of two foodborne pathogens, and future studies for biofilm control and antibiotic therapy should take into account interactions in mixed-species biofilms.

Strong antibacterial dental resin composites containing cellulose nanocrystal/zinc oxide nanohybrids

ObjectiveThe aim is to explore the reinforcing and antibacterial effect of cellulose nanocrystal/zinc oxide (CNC/ZnO) nanohybrids on dental resin composites (DRCs). MethodsCNC/ZnO nanohybrids were prepared through precipitating Zn2+ on the surface of CNC and then introduced into the DRCs. The mechanical properties of DRCs including compressive strength, flexural modulus, flexural strength, and Vickers microhardness were characterized. The antibacterial activity of DRCs to Streptococcus mutans was determined and the morphology of Streptococcus mutans on the surface of DRCs after incubation was observed. The morphology of fractured surface after flexural test and Zn content in DRCs were analyzed. ResultsCompared with DRCs without CNC/ZnO nanohybrids, DRCs containing 2 wt.% CNC/ZnO nanohybrids possess higher compressive strength and flexural modulus and there is no significantly statistical difference (P＞0.05) on the flexural strength and Vickers microhardness. The excess use of CNC/ZnO nanohybrids decreases the mechanical properties of DRCs except flexural modulus. DRCs containing CNC/ZnO nanohybrids show excellent antibacterial properties and a 78% reduction in bacterial number is obtained when 2% CNC/ZnO nanohybrids are added. ConclusionThe small amounts of CNC/ZnO nanohybrids have a positive influence on the mechanical and antibacterial properties of DRCs. SignificanceThe prepared DRCs are promising to address bulk fracture and secondary caries.