Reduction In Bacterial Viability Research Articles

Wearable nitric oxide-releasing antibacterial insert for preventing device-associated infections

Medical device-associated infections are a pervasive global healthcare concern, often leading to severe complications. Bacterial biofilms that form on indwelling medical devices, such as catheters, are significant contributors to infections like bloodstream and urinary tract infections. This study addresses the challenge of biofilms on medical devices by introducing a portable antimicrobial catheter insert (PACI) designed to be efficient, biocompatible, and anti-infective. The PACI utilizes nitric oxide (NO), known for its potent antimicrobial properties, to deter bacterial adhesion and biofilm formation. To achieve this, a photoinitiated NO donor, S-nitroso-N-acetylpenicillamine (SNAP), is covalently linked to a polydimethylsiloxane (PDMS) polymer. This design allows for higher NO loading for long-term impact and prevents premature donor leaching, a common challenge with SNAP-blended polymers. The SNAP-PDMS material was applied to a side-glowing fiber optic and connected to a wearable light module emitting 450 nm light, creating a functional antimicrobial insert. Activation of the fiber optic, accomplished with a one-click mechanism, enables real-time NO release, maintaining controlled NO levels for a minimum of 24 h. The therapeutic levels of NO released via photocatalysis from the PACI demonstrated remarkable efficacy, with >90 % reduction in bacterial viability against S. aureus, S. epidermidis, and P. mirabilis without any cytotoxic impact on mammalian cells. This study underscores the potential of the NO-releasing insert in clinical settings, providing a portable and adaptable solution for preventing catheter-associated infections.

Bacteriophage-like Nanobiocatalysts with Spiky Topography and Dual-Atom Sites for Treating Drug-Resistant Bacteria.

Overuse of antibiotics leads to the proliferation of drug-resistant bacterial strains, worsening global morbidity, and mortality rates. Bioinspired nanomaterials present a promising avenue for developing nonantibiotic strategies against drug-resistant bacteria. Here, we engineer a bacteriophage-inspired artificial nanobiocatalyst via nonstoichiometric W18O49 that features a spiky topography and synergistic dual-atom sites for combating drug-resistant bacterial infection. Benefiting from the strong interaction within the synergistic Fe-O-Mo sites, the synthesized spiky artificial nanobiocatalyst exhibits superior reactive oxygen species (ROS)-catalytic activity, attributed to the regulated adsorption affinity between the reaction intermediates and catalytic sites. The experimental and theoretical investigations demonstrate that the bioinspired biocatalyst can effectively capture and kill bacteria through its spiky morphology and potent ROS-catalytic activity, which can enable a significant reduction in bacterial viability through downregulating genes associated with biosynthesis, cellular maintenance, and respiration. In vivo experiments demonstrate that the spiky artificial biocatalyst accelerates the reconstruction of drug-resistant bacteria-infected skin wounds in rabbits, exhibiting efficacy comparable to that of vancomycin. It is expected that this bioinspired study on spiky artificial nanobiocatalysts offers a straightforward path to facilitate the development of both bionic and nonantibiotic disinfection strategies.

Enhancing the efficacy of antimicrobial photodynamic therapy through curcumin modifications.

Curcumin serves as a photosensitizer (PS) in the context of microbial inactivation when subjected to light exposure, to produce reactive oxygen species, which exhibit efficacy in eradicating microorganisms. This remarkable property underscores the growing potential of antimicrobial photodynamic therapy (aPDT) in the ongoing fight against bacterial infections. Considering this, we investigate the efficacy of various invitro curcumin formulations within a PDT protocol designed to target Staphylococcus aureus. Specifically, we conduct a comparative analysis involving synthetic curcumin (Cur-Syn) and curcumin derivatives modified with chlorine (Cl), selenium (Se), and iodine (I) (Cur-Cl, Cur-Se, Cur-I). To assess the impact of aPDT, we subject S. aureus to incubation with curcumin, followed by irradiation at 450 nm with energy doses of 3.75, 7.5, and 15 J/cm2. Our investigation encompasses an evaluation of PS uptake and photobleaching across the various curcumin variants. Notably, all three modifications (Cur-Cl, Cur-Se, Cur-I) induce a significant reduction in bacterial viability, approximately achieving a 3-log reduction. Interestingly, the uptake kinetics of Cur-Syn and Cur-Se exhibit similarities, reaching saturation after 20 min. Our findings suggest that modifications to curcumin have a discernible impact on the photodynamic properties of the PS molecule.

Development of latex/zinc oxide compounds with antibacterial properties for applications in biomedical engineering

Natural rubber latex (NRL)—a polymer extracted from the rubber tree (Hevea brasiliensis)—has been used in multiple biomedical applications but does not have antibacterial properties. In this work, ZnO nanoparticles with two different morphologies were synthesized and added to NRL at different concentrations in order to evaluate the antibacterial properties of the resulting compounds. The characterization results obtained by electron microscopy and x-ray diffraction showed nanoparticles with spherical (mean size 69 ± 17 nm) and sheet morphology (mean size 154 ± 46 nm) with Wurtzite crystalline phase for both nanomaterials, respectively. The results of antibacterial tests showed that both compounds are effective against E. coli, and the reduction in bacterial viability was 90.3% and 96.4% for sheets and spherical nanomaterials, respectively. In the case of S. aureus, bacterial viability was reduced in both cases. The greatest antibacterial activity was evidenced in the nanoparticles with spherical morphology.

Susceptibility of Salmonella enterica Typhimurium dry surface biofilms to disinfection

AbstractIn food preparation and manufacturing environments, surfaces contaminated with Salmonella can lead to outbreaks of Salmonellosis. We hypothesise that Salmonella resides on dry surfaces in a biofilm form leading to potential environmental persistence and transfer following contact. This is the first study reporting that Salmonella Typhimurium can form dry surface biofilm (DSB). Six disinfectants commonly used in the food industry were evaluated for their efficacy against the DSB. The two most efficacious formulations reduced bacterial viability in DSB by >99.99% when combined with mechanical removal (5 sec wiping; 300 g weight). Five out of six formulations significantly reduced bacterial transfer when combined with wiping. Complete eradication of Salmonella Typhimurium DSB was challenging, and mechanical removal was essential to produce a >99.99% reduction in bacterial viability within DSB. This study highlights a potential mode of survival of Salmonella Typhimurium on food‐contact surfaces and DSB challenges for disinfection.

Cellular uptake and in vitro antibacterial activity of lipid-based nanoantibiotics are influenced by protein corona.

Bacteria have evolved survival mechanisms that enable them to live within host cells, triggering persistent intracellular infections that present significant clinical challenges due to the inability for conventional antibiotics to permeate cell membranes. In recent years, antibiotic nanocarriers or 'nanoantibiotics' have presented a promising strategy for overcoming intracellular infections by facilitating cellular uptake of antibiotics, thus improving targeting to the bacteria. However, prior to reaching host cells, nanocarriers experience interactions with proteins that form a corona and alter their physiological response. The influence of this protein corona on the cellular uptake, drug release and efficacy of nanoantibiotics for intracellular infections is poorly understood and commonly overlooked in preclinical studies. In this study, protein corona influence on cellular uptake was investigated for two nanoparticles; liposomes and cubosomes in macrophage and epithelial cells that are commonly infected with pathogens. Studies were conducted in presence of fetal bovine serum (FBS) to form a biologically relevant protein corona in an in vitro setting. Protein corona impact on cellular uptake was shown to be nanoparticle-dependent, where reduced internalization was observed for liposomes, the opposite was observed for cubosomes. Subsequently, vancomycin-loaded cubosomes were explored for their drug delivery performance against intracellular small colony variants of Staphylococcus aureus. We demonstrated improved bacterial killing in macrophages, with greater reduction in bacterial viability upon internalization of cubosomes mediated by the protein corona. However, no differences in efficacy were observed in epithelial cells. Thus, this study provides insights and evidence to the role of protein corona in modulating the performance of nanoparticles in a dynamic manner; these findings will facilitate improved understanding and translation of future investigations from in vitro to in vivo.

Gold nanoparticle conjugation enhances berberine's antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Nanoparticle (NP) conjugation with various biomolecules is one of the most promising approaches for targeting Methicillin-resistant Staphylococcus aureus (MRSA). In this study, berberine (BER) was conjugated with gold nanoparticles (AuNPs) to enhance its antibacterial activity against MRSA. Chemically synthesized AuNPs were characterized by UV–vis spectroscopy, size distribution and Field Emission-Scanning Electron Microscope (FE-SEM) analysis. Berberine was conjugated with AuNPs and the conjugants were characterized using UV–vis spectroscopy and Fourier Transform Infrared (FTIR). The cytotoxicity of free and conjugated BER was also investigated. Comparative studies were conducted based on the Minimum Inhibitory Concentration (MIC) and anti-biofilm activities of conjugants and free BER against MRSA isolates. To verify cell membrane disruption and intracellular imbalance following treatment exposure, reactive oxygen species (ROS) and live-dead staining experiments were performed. In vivo antibacterial efficacy of treated groups was also assessed in a BALB/c mouse-infected skin model. DLS measurement, FE-SEM, and UV–vis spectroscopy confirmed the synthesis of AuNPs with a narrow size distribution of 49.38 nm and a zeta potential of −31.9 mV. The results from UV–vis spectroscopy and FTIR provided support for the functionalization of AuNPs by BER functional groups. The In vitro antibacterial results demonstrated that the conjugated BER exhibited a lower MIC value against MRSA (109.5 μg/ml) compared to free BER (165 μg/ml). Free and conjugated BER, at their MIC concentrations, demonstrated anti-biofilm activity, resulting in biofilm eradication of 13.9 and 22.33 %, respectively. The highest level of ROS production (93 %) was associated with the conjugated BER at a concentration of 27.37 μg/ml. This finding indicates a disruption in cell membrane integrity and a reduction in bacterial viability, as demonstrated by ROS and live/dead staining assays. The cytotoxicity study on the mouse L929 fibroblast cell line revealed approximately 100 % cell viability when exposed to free or conjugated BER at their MIC concentration. This result indicates the biosafety of both of the compounds. The in vivo study in the infected skin model groups treated with conjugated and free BER revealed MRSA survival rate of 2.7 % and 26 %, respectively. These findings suggest that conjugated BER could be an effective nanoformulation candidate with a potential role in managing MRSA associated infections.

Efficacy of Plasma-Treated Water against Salmonella Typhimurium: Antibacterial Activity, Inhibition of Invasion, and Biofilm Disruption.

Plasma-treated water (PTW) has emerged as a potential sanitizing agent. This study evaluated antibacterial activity, inhibition of invasion, and biofilm disruption effects of PTW against Salmonella Typhimurium. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined for different PTW types. Time-kill assays were conducted to assess bactericidal effects, while polarized Caco-2 cells were used to evaluate invasion inhibition. Biofilm formation and cell viability were examined following PTW treatment using Salmonella Typhimurium isolates, while biofilm disruption and regrowth prevention were investigated using the Bioflux system. PTW exhibited antibacterial activity against all Salmonella Typhimurium isolates, with MICs of 25% for PTW1 and PTW2, and 50% for PTW3, PTW4, and PTW5. MBCs of 50% in media were observed for all PTW types. Undiluted PTW1 and PTW2 showed the highest bactericidal capacity, significantly reduced Salmonella viability, and completely inhibited bacterial invasion, while PTW3 and PTW5 also showed significant invasion reduction. Bioflux experiments confirmed the eradication of biofilms by PTW1 and PTW2, with no regrowth observed 72 h after PTW was removed. PTW demonstrated significant antibacterial activity, inhibition of invasion, biofilm disruption, and reduction of bacterial viability against Salmonella Typhimurium. This highlights PTW's potential as an effective sanitizer for reducing Salmonella contaminations.

Preparation and characterization of novel poly (lactic acid)/calcium oxide nanocomposites by electrospinning as a potential bone tissue scaffold

Calcium oxide nanoparticles (n-CaO) ca. 22 nm were obtained from eggshell waste. The n-CaO was incorporated into the PLA matrix in 10 and 20 wt% of filler content by electrospinning process to get PLA/n-CaO fibers with homogenous morphology and diameter as a potential use in scaffold for bone tissue regeneration. The incorporation of n-CaO into PLA modifies the mechanical properties, having a reinforcement effect on the matrix. The Young modulus for PLA/n-CaO nanocomposites increased between 122 and 138 % concerning neat PLA fibers, showing a more rigid behavior. The PLA/n-CaO nanocomposite fibers showed in vitro bioactivity, capable of inducing the precipitation of hydroxyapatite (HA) layer in the fiber surface after seven days in SBF solution. The biocidal and biological properties of PLA/n-Cao with 20 wt% showed a 30 % reduction in bacterial viability against S. aureus and 11 % against E. coli after 6 h of bacterial exposure. Furthermore, the fibers did not show a cytotoxic effect on the bone marrow ST-2 cell line, allowing cell adhesion and proliferation in the RPMI medium. The PLA/n-CaO with 20 wt% of nanoparticles showed a higher capacity to promote osteogenic differentiation, significantly increasing the alkaline phosphatase (ALP) expression after seven days compared to PLA and cell control. The in vivo analysis corroborated the biocompatibility of the prepared scaffolds; the presence of n-CaO in PLA reduced the formation of fibrous encapsulation of the material, improving the healing process. These results validated using n-CaO to enhance the functionality of polymer matrices as a PLA, bringing bioactive, biocide, and biocompatible properties, opening a new and interesting route to develop new biomaterials as a scaffold for bone tissue engineering.

Antibacterial, antibiofilm, and anti-quorum sensing activities of pyocyanin against methicillin-resistant Staphylococcus aureus: in vitro and in vivo study

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) infections are considered a major public health problem, as the treatment options are restricted. Biofilm formation and the quorum sensing (QS) system play a pivotal role in S. aureus pathogenicity. Hence, this study was performed to explore the antibacterial effect of pyocyanin (PCN) on MRSA as well as its effect on MRSA biofilm and QS.ResultsData revealed that PCN exhibited strong antibacterial activity against all test MRSA isolates (n = 30) with a MIC value equal to 8 µg/ml. About 88% of MRSA biofilms were eradicated by PCN treatment using the crystal violet assay. The disruption of MRSA biofilm was confirmed using confocal laser scanning microscopy, which showed a reduction in bacterial viability (approximately equal to 82%) and biofilm thickness (approximately equal to 60%). Additionally, the disruption of the formation of microcolonies and the disturbance of the connection between bacterial cells in the MRSA biofilm after PCN treatment were examined by scanning electron microscopy. The 1/2 and 1/4 MICs of PCN exerted promising anti-QS activity without affecting bacterial viability; Agr QS-dependent virulence factors (hemolysin, protease, and motility), and the expression of agrA gene, decreased after PCN treatment. The in silico analysis confirmed the binding of PCN to the AgrA protein active site, which blocked its action. The in vivo study using the rat wound infection model confirmed the ability of PCN to modulate the biofilm and QS of MRSA isolates.ConclusionThe extracted PCN seems to be a good candidate for treating MRSA infection through biofilm eradication and Agr QS inhibition.

Bioprotective potential of lactic acid bacteria for Salmonella biocontrol in vitro.

Lactic acid bacteria (LAB) are an important option for Salmonella control in animal production, resulting in lower antibiotic use. The objective of this research was to isolate LAB from meat products and from commercial probiotics sold as nutritional supplements for in vitro verification of their bioprotective potential. Eleven bacteria were identified as Pediococcus acidilactici, two as Lacticaseibacillus rhamnosus, one as Lacticaseibacillus paracasei paracasei, one as Limosilactobacillus fermentum, and one as a consortium of Lactobacillus delbrueckii bulgaricus and L. fermentum. All bacteria showed inhibitory activity against Salmonella, with emphasis on the inhibition of P. acidilactici PUCPR 011 against Salmonella Enteritidis 33SUSUP, S. Enteritidis 9SUSP, S. Enteritidis 56301, S. Enteritidis CRIFS 1016, Salmonella Typhimurium ATCC™ 14,028®, and Salmonella Gallinarum AL 1138, with inhibition halos of 7.3 ± 0.5mm, 7.7 ± 1.0mm, 9.0 ± 1.8mm, 7.3 ± 0.5mm, 7.7 ± 1.0mm, and 7.3 ± 0.5, respectively. The isolates P. acidilactici PUCPR 011, P. acidilactici PUCPR 012, P. acidilactici PUCPR 014, L. fermentum PUCPR 005, L. paracasei paracasei PUCPR 013, and L. rhamnosus PUCPR 010 showed inhibition greater than 2mm against at least 3 Salmonella and were used for encapsulation and in vitro digestion. The encapsulation efficiency ranged from 76.89 ± 1.54 to 116.48 ± 2.23%, and the population after 12months of storage was from 5.31 ± 0.17 to 9.46 ± 0.09 log CFU/g. When simulating swine and chicken digestion, there was a large reduction in bacterial viability, stabilizing at concentrations close to 2.5 log CFU/mL after the analyses. The analyzed bacteria showed strong in vitro bioprotective potential; further analyses are required to determine in vivo effectiveness.

A dentifrice containing salivary enzymes and xylitol exhibits superior antimicrobial activity in vitro against adherent Streptococcus mutans compared to a chlorhexidine dentifrice.

Human saliva contains natural antimicrobial enzymes. In this in vitro study, we evaluate the antimicrobial activity of a dentifrice containing a salivary enzyme complex (SEC) with xylitol versus a standard 0.12% chlorhexidine (CHX) dentifrice. Adherent cells of Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, Fusobacterium nucleatum subsp polymorphum and Corynebacterium matruchotii were exposed to SEC-xylitol and CHX dentifrices for 2 mins and viable CFUs were enumerated. Exposure to the SEC-xylitol dentifrice resulted in a significant reduction in bacterial viability, which was greater than that shown by the CHX dentifrice, against all organisms tested. The SEC-xylitol dentifrice also exhibited greater antimicrobial activity against all organsims in well diffusion assays compared to CHX. Dentifrice activity was also evaluated against a three species community of Streptococcus gordonii, Streptococcus mutans and Corynebacterium matruchotii using bacterial live/dead stain. The SEC-xylitol dentifrice was at least as effective as CHX in removal of the multispecies community. The combination of SEC and xylitol generates a highly effective antimicrobial dentifrice with greater anti-bacterial activity than a standard 0.12% CHX formulations. SEC and xylitol combinations are worthy of further investigation for routine use and in the management of gingivitis and periodontal disease.

Facile post modification synthesis of copper-doped mesoporous bioactive glass with high antibacterial performance to fight bone infection

Successful treatment of infected bone defects caused by multi-drug resistant bacteria (MDR) has become a major clinical challenge, stressing the urgent need for effective antibacterial bone graft substitutes. Mesoporous bioactive glass nanoparticles (MBGNs), a rapidly emerging class of nanoscale biomaterials, offer specific advantages for the development of biomaterials to treat bone infection due to endowed antibacterial features. Herein, we propose a facile post-modification sol-gel strategy to synthesize effective antibacterial MBGNs doped with copper ions (Cu-PMMBGNs). In this strategy, amine functional groups as chelating agents were introduced to premade mesoporous silica nanoparticles (MSNs) which further facilitate the incorporation of high content of calcium (∼17 mol%) and copper ions (∼8 mol%) without compromising nanoparticle shape, mesoporosity, and homogeneity. The resulting nanoparticles were degradable and showed rapidly induce abundant deposition of apatite crystals on their surface upon soaking in simulated body fluids (SBF) after 3 days. Cu-PMMBGNs exhibited a dose-dependent inhibitory effect on Methicillin-resistant Staphylococcus aureus (MRSA) bacteria, which are common pathogens causing severe bone infections. Most importantly, the nanoparticles containing 5 mol% copper ions at concentrations of 500 and 1000 μg.mL−1 showed highly effective antibacterial performance as reflected by a 99.9 % reduction of bacterial viability. Nanoparticles at a concentration of 500 μg.mL−1 showed no significant cytotoxicity toward preosteoblast cells (∼85–89 % cell viability) compared to the control group. In addition, the nanoscale properties of synthesized Cu-PMMBGNs (∼100 nm in size) facilitated their internalization into preosteoblast cells, which highlights their potential as intracellular carriers in combating intracellular bacteria. Therefore, these copper-doped nanoparticles hold strong promise for use as an antibacterial component in antibacterial bone substitutes such as hydrogels, nanocomposites, and coatings.

Synergy of R-(–)carvone and cyclohexenone-based carbasugar precursors with antibiotics to enhance antibiotic potency and inhibit biofilm formation

The widespread use of antibiotics in recent decades has been a major factor in the emergence of antibiotic resistances. Antibiotic-resistant pathogens pose increasing challenges to healthcare systems in both developing and developed countries. To counteract this, the development of new antibiotics or adjuvants to combat existing resistance to antibiotics is crucial. Glycomimetics, for example carbasugars, offer high potential as adjuvants, as they can inhibit metabolic pathways or biofilm formation due to their similarity to natural substrates. Here, we demonstrate the synthesis of carbasugar precursors (CSPs) and their application as biofilm inhibitors for E. coli and MRSA, as well as their synergistic effect in combination with antibiotics to circumvent biofilm-induced antibiotic resistances. This results in a biofilm reduction of up to 70% for the CSP rac-7 and a reduction in bacterial viability of MRSA by approximately 45% when combined with the otherwise ineffective antibiotic mixture of penicillin and streptomycin.

Micro response mechanism of mini MFC sensor performance to temperature and its applicability to actual wastewater

Miniaturized MFC-based BOD biosensors have attracted attention due to their fast response and low cost. However, the influence of ambient temperature and poor response to actual wastewater restrict their practical application. To clarify the influence mechanism of temperature on the biosensor performance, the anodic biofilm was analyzed in-depth. The biosensor performances increased between 5 and 35 °C, while decreased at higher temperature (45 °C) due to a significant reduction in bacterial viability. Further, the variation of dominant exoelectrogen with different electrical production capacity with temperature is the main mechanism of temperature influence. In addition, the factors affecting the accuracy of actual wastewater detection were discussed. Although the microorganisms in the actual wastewater interfered with the metabolism of exoelectrogen, the deviation between the sensing results and the real BOD value was mainly due to the fact that the exoelectrogen only metabolize the acid and alcohol components in the wastewater. In general, our research will provide some suggestions for the practical application of MFC sensors.

Probiotics viability in frozen food products

Improving gastrointestinal flora with probiotics is a promising method of treating and preventing many diseases. However, in food industry, introduction of probiotics is limited by the shelf life of products, as well as by the reduction of bacterial viability during storage. Thus, introduction of probiotics into foods to be frozen is a promising method to extend the shelf life of probiotic products. However, the storage of living cells in frozen products involves their damage during freezing and subsequent storage at temperatures below 0 °C. Therefore, some technological solutions are required to protect probiotics during storage at sub-zero. Today, encapsulation, addition of cryoprotectants and prebiotics, as well as adaptation of microorganisms are widely used techniques of protecting probiotics. The combination of various protection methods is a promising way to improve the viability of probiotics during storage. Studies aimed at investigating various combinations of hurdle methods and their effect on bacterial survival are of great interest.This review compiles the most common methods of preserving probiotics in frozen foods, describing their effects, variety of approaches, and effectiveness. The main mechanisms of bacterial cell damage by freezing are described. Further trends in probiotic protection in frozen foods are also discussed.

Antibiofilm Efficacy of Silver Nanoparticles Alone or Mixed with Calcium Hydroxide as Intracanal Medicaments: An Ex-Vivo Analysis

IntroductionThis study aimed to determine the most effective antibiofilm concentration of silver nanoparticles (AgNPs) alone or in combination with calcium hydroxide (Ca[OH]2) against Fusobacterium nucleatum biofilm. MethodsThe minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNPs alone or with Ca(OH)2 were determined. Dentin slices were sterilized and inoculated with F. nucleatum for 3 weeks to establish a biofilm. Samples were randomly assigned to determine the MIC and MBC for AgNPs alone or mixed with Ca(OH)2. A higher concentration of AgNPs for both preparations was also used. Triple antibiotic paste, Ca(OH)2, and saline were used as controls. Specimens in each group were subdivided over 2 observation periods: 7 and 14 days. At the end of each period, specimens were analyzed with 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to determine the metabolic activity. Also, samples from each group were assessed by scanning electron microscopy. ResultsThe MIC and MBC of AgNPs alone against F. nucleatum coincided at 0.04%. The combination of AgNPs + Ca(OH)2 exhibited a lower MIC and MBC of 0.03%. MTT analysis showed a significant reduction in bacterial viability in all groups compared with negative controls (P < .05). A more substantial reduction in bacterial cells was observed with increasing concentrations of AgNPs at both periods. The combination (AgNPs [0.06%] + Ca[OH]2) was the most potent against F. nucleatum. ConclusionsThe findings demonstrated that combining AgNPs with Ca(OH)2 was more effective on the F. nucleatum biofilm than either material alone, suggesting a combined effect.

Photodynamic antimicrobial chemotherapy coupled with the use of the photosensitizers methylene blue and temoporfin as a potential novel treatment for Staphylococcus aureus in burn infections.

Photodynamic antimicrobial chemotherapy (PACT) is a novel alternative antimicrobial therapy that elicits a broad mechanism of action and therefore has a low probability of generating resistance. Such properties make PACT ideally suited for utilization in localized applications such as burn wounds. The aim of this study was to determine the antimicrobial activity of MB and temoporfin against both a S. aureus isolate and a P. aeruginosa isolate in light (640 nm) and dark conditions at a range of time points (0–20 min). A Staphylococcus aureus isolate and a Pseudomonas aeruginosa isolate were treated in vitro with methylene blue (MB) and temoporfin under different conditions following exposure to light at 640 nm and in no-light (dark) conditions. Bacterial cell viability [colony-forming units (c.f.u.) ml−1] was then calculated. Against P. aeruginosa , when MB was used as the photosensitizer, no phototoxic effect was observed in either light or dark conditions. After treatment with temoporfin, a reduction of less than one log (7.00×107 c.f.u. ml−1) was observed in the light after 20 min of exposure. However, temoporfin completely eradicated S. aureus in both light and dark conditions after 1 min (where a seven log reduction in c.f.u. ml−1 was observed). Methylene blue resulted in a loss of S. aureus viability, with a two log reduction in bacterial viability (c.f.u. ml−1) reported in both light and dark conditions after 20 min exposure time. Temoporfin demonstrated greater antimicrobial efficacy than MB against both the S. aureus and P. aeruginosa isolates tested. At 12.5 µM temoporfin resulted in complete eradication of S. aureus . In light of this study, further research into the validity of PACT, coupled with the photosensitizers (such as temoporfin), should be conducted in order to potentially develop alternative antimicrobial treatment regimes for burn wounds.

A traditional Ugandan Ficus natalensis bark cloth exhibits antimicrobial activity against methicillin-resistant Staphylococcus aureus.

Surgical site, soft tissue and wound infections are some of the most prominent causes of healthcare-associated infections (HCAIs). Developing novel antimicrobial textiles and wound dressings may help alleviate the risk of developing HCAIs. We aimed to determine the antimicrobial efficacy of natural Ugandan bark cloth derived exclusively from the Ficus natalensis tree. Antimicrobial contact and disc diffusion assays, coupled with time-kill kinetic assays, demonstrated that bark cloth inhibited the growth of a clinically relevant methicillin-resistant Staphylococcus aureus (MRSA) strain and acted as a bactericidal agent causing a seven-log reduction in bacterial viability. Scanning electron microscopy was used to reveal morphological changes in the bacterial cell ultrastructure when exposed to bark cloth, which supported a proposed mechanism of antimicrobial activity. The observed antimicrobial properties, combined with the physical characteristics elicited by bark cloth, suggest this product is ideally suited for wound and other skin care applications. This is the first report where a whole bark cloth product made by traditional methods has been employed as an antimicrobial fabric against MRSA. Bark cloth is a highly sustainable and renewable product and this study presents a major advance in the search for natural fabrics which could be deployed for healthcare applications.

Is a reduction in viability enough to determine biofilm susceptibility to a biocide?

The abundance and prevalence of dry-surface biofilms (DSBs) in hospitals constitute an emerging problem, yet studies rarely report the cleaning and disinfection efficacy against DSBs. Here, the combined impact of treatments on viability, transferability, and recovery of bacteria from DSBs has been investigated for the first time. Staphylococcus aureus DSBs were produced in alternating 48-hour wet-dry cycles for 12 days on AISI 430 stainless steel discs. The efficacy of 11 commercially available disinfectants, 4 detergents, and 2 contactless interventions were tested using a modified standardized product test. Reduction in viability, direct transferability, cross transmission (via glove intermediate), and DSB recovery after treatment were measured. Of 11 disinfectants, 9 were effective in killing and removing bacteria from S. aureus DSBs with >4 log10 reduction. Only 2 disinfectants, sodium dichloroisocyanurate 1,000 ppm and peracetic acid 3,500 ppm, were able to lower both direct and cross transmission of bacteria (<2 compression contacts positive for bacterial growth). Of 11 disinfectants, 8 could not prevent DSB recovery for >2 days. Treatments not involving mechanical action (vaporized hydrogen peroxide and cold atmospheric plasma) were ineffective, producing <1 log10 reduction in viability, DSB regrowth within 1 day, and 100% transferability of DSB after treatment. Reduction in bacterial viability alone does not determine product performance against biofilm and might give a false sense of security to consumers, manufacturers and regulators. The ability to prevent bacterial transfer and biofilm recovery after treatment requires a better understanding of the effectiveness of biocidal products.