Physico-chemistry from initial bacterial adhesion to surface-programmed biofilm growth

Evaluating antimicrobial efficacy in medical devices: The critical role of simulating in use test conditions

Biofilm infections represent the greatest risk associated with medical devices and implants, constituting 65 %-70 % of all device associated infections. Efforts to develop antimicrobial technologies for biomedical applications aim to reduce infection rates, antibiotic use, and the induction of antimicrobial resistance. However, standard laboratory test conditions often overestimate efficacy, highlighting the need for experimental designs that simulate real-world settings. To this end, we evaluated four commercially available antimicrobial materials containing silver (AG1, AG2, AG3) or zinc (ZN1) to assess their ability to mitigate microbial proliferation in for longer duration or multi-use medical devices. The materials' homogeneity and surface topography were characterized through Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) and Atomic Force Microscopy (AFM). Antimicrobial efficacy was tested using a modified ISO 22196 protocol under clinically relevant conditions and a dry contact test developed to mimic in-use conditions for many extracorporeal medical devices. Results revealed homogeneous elemental distributions in AG1, AG2, and ZN1, and heterogeneous clusters for AG3. Surface roughness was highest for AG2 (170.1 nm), followed by TPE control (155.3 nm), ZN1 (83.51 nm) and silicone control (66.74 nm). All test materials demonstrated antimicrobial efficacies against S. aureus and E. coli, but not against C. albicans. In the dry contact assay, only AG2 proved effective against E. coli, and P. aeruginosa, underlining the role of humidity in antimicrobial action. Results were further corroborated by measurement of ion release by the materials at various temperatures, revealing greater release at higher temperatures. These outcomes emphasize the importance of testing antimicrobial materials under in use conditions to minimize discrepancies between laboratory results and clinical outcomes. Our findings provide a valuable framework for testing and integrating these materials into next-generation multi-use medical devices.

Biofilm-mediated infections; novel therapeutic approaches and harnessing artificial intelligence for early detection and treatment of biofilm-associated infections

A biofilm is a group of bacteria that have self-produced a matrix and are grouped together in a dense population. By resisting the host's immune system's phagocytosis process and attacking with anti-microbial chemicals such as reactive oxygen and nitrogen species, a biofilm enables pathogenic bacteria to evade elimination. One of the major problems in managing chronic injuries is treating wounds colonized by biofilms. These days, a major issue is the biofilms, which exacerbate infection pathogenesis and severity. Numerous investigators have already discovered cutting-edge methods for biofilm manipulation. Using phytochemicals is a practical tactic to control and prevent the production of biofilms. Numerous studies conducted in the last few years have demonstrated the antibacterial and antibiofilm qualities of nanoparticles (NPs) against bacteria, fungi, and protozoa. Because hydrogel has antibiofilm properties, it has been employed extensively in wound care recently. It may be removed with ease and without causing trauma. Today, artificial intelligence (AI) is being used to improve these tactics by providing customized treatment alternatives and predictive analytics. Artificial intelligence (AI) algorithms have the capability to examine extensive datasets and detect trends in biofilm formation and resistance mechanisms. This can aid in the creation of more potent antimicrobial drugs. AI models analyze complex datasets, predict biofilm formation, and guide the design of personalized treatment strategies by identifying resistance mechanisms and therapeutic targets with exceptional precision. This review provides an integrative perspective on biofilm formation mechanisms and their role in infections, highlighting the innovative applications of AI in this domain. By integrating data from diverse biological systems, AI accelerates drug discovery, optimizes treatment regimens, and enables real-time monitoring of biofilm dynamics. From predictive analytics to personalized care, we explore how AI enhances biofilm diagnostics and introduces precision medicine in biofilm-associated infections. This approach not only addresses the limitations of traditional methods but also paves the way for revolutionary advancements in infection control, antimicrobial resistance management, and improved patient outcomes.

Biochar mediated differential regulation of oxidative stress and energy supply in Bacillus subtilis and Rhizoctonia solani

Biochar (BC) significantly influences microbial metabolism, but its contrasting effects on different microorganisms remain unclear. This research explores the distinct regulatory mechanisms of BC on B. subtilis and R. solani. BC, consisting of micro-BC and nano-BC, generates reactive oxygen species (ROS), causing oxidative stress. Nano-BC can penetrate cells, leading to damage. In B. subtilis, BC initially inhibits growth, triggering endospore formation to expel nano-BC. B. subtilis secreted extracellular polymeric substances (EPS), which aggregated nano-BC, enhanced cell adhesion, and reduced intracellular ROS (from 2.0 to 1.5-fold), promoting growth later with BC's nutrient support. Conversely, R. solani cannot block nano-BC entry, activating mitophagy and suppressing genes like ATP1,2 involved in oxidative phosphorylation and tricarboxylic acid cycle. This results in ATP deficiency, collapses antioxidant system, raises ROS (from 3.9 to 4.5-fold), decreases cell survival, and leads to cell death. These findings highlight BC's selective microbial regulation and its potential for safe agricultural and environmental use.

Unraveling the anti-biofouling mechanisms of slippery liquid-infused porous surface from molecular interaction perspective

Newly developed slippery liquid-infused porous surfaces (SLIPS) exhibit highly effective anti-fouling performance without harming organisms, making them a promising solution for both environmental and material protection. However, previous studies have primarily understood the anti-fouling effects of SLIPS from a mechanical perspective, neglecting the atomic interactions involved in the anti-fouling process. In this study, we combined microbiological experiments with multi-scale simulations to elucidate the microscopic mechanisms behind the unique anti-biofouling effects of SLIPS. After developing SLIPS with robust liquid-repellency, we characterized its physical and chemical properties and demonstrated its superior effectiveness in preventing Pseudomonas aeruginosa attachment. To probe the initial contact during bacterial attachment, all-atom molecular dynamics (MD) simulations were conducted, revealing that the liquid-liquid interface suppresses the effective pilin adhesion on SLIPS. Further analysis through steered MD, ab initio MD, and density functional theory calculations revealed that the flexible siloxane backbone and the non-polar nature of silicone oil molecules enhance the diffusivity of interfacial water and lead to the continuous nanoscale fluctuation of liquid-liquid interface, thus inhibiting the role of protein dynamics in promoting bio-adhesion. These novel insights into the characteristics of liquid-liquid and nano-bio interface during the anti-biofouling process of SLIPS may promote the future development of bio-inspired functional surfaces.

A comprehensive review of emerging 3D-printing materials against bacterial biofilm growth on the surface of healthcare settings

A significant burden on the healthcare system, microbial contamination of biomedical surfaces can result in hospital-acquired illnesses. Bacteria, viruses, and fungi may live on surfaces for days or months and spread to patients and medical personnel. This article describes the 3D printing technologies, such as fused deposition modeling, bioprinting, binder jetting/inkjet, poly-jet, electron beam manufacturing, stereolithography, selective laser sintering, and laminated object manufacturing used for manufacturing the healthcare setting's surface to reduce bacterial contamination with exploring anti-biofilm activity against different bacterial species responsible for infections, based on the critical evaluation of published reports. This strategy has immense potential to become an upcoming approach for advancing the coating concept on the material's surface in healthcare settings. Our literature evaluation identifies beneficial 3D printing materials and associated technologies against microorganisms' growth, mainly bacteria involved in implant-based infection, emphasizing the development of anti-biofilm 3D-printed surfaces. Additionally, the authors have identified a few key areas where research and development are critically required to advance 3D-printing technology in healthcare settings.

Inhibitory effects of extracts from Prunella vulgaris on biofilm formation of Staphylococcus aureus

Staphylococcus aureus (S. aureus) is a highly prevalent pathogen capable of strongly adhering to food processing equipment and the contact surfaces, where it forms resilient biofilms that are difficult to eliminate. Prunella vulgaris (P. vulgaris), a traditional Chinese herbal medicine, has demonstrated strong potential in inhibiting S. aureus biofilm formation. This study investigated the inhibitory mechanisms of P. vulgaris extracts against S. aureus growth and biofilm formation, evaluating the biofilm inhibitory concentration, bactericidal concentration and their effects on ica operon gene expression. The P. vulgaris extracts exhibited a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 1.25 mg/mL. At the MIC level, the extracts not only suppressed S. aureus growth and metabolic viability but also inhibited polysaccharide intercellular adhesion (PIA), prevented biofilm formation and disrupted mature biofilms. Furthermore, P. vulgaris extracts demonstrated concentration-dependent effects on extracellular polymeric substances (EPS) production: while 1/2 MIC concentrations stimulated EPS synthesis, double-MIC concentrations markedly suppressed it. Notably, the extracts consistently downregulated icaA and icaD expression at both MIC and 2 × MIC concentrations. Therefore, P. vulgaris exhibits significant potential against S. aureus-induced foodborne diseases, demonstrating promise as a novel antibacterial agent for future applications in both pharmaceutical development and food safety enhancement.

Identification and characterization of a novel major facilitator superfamily (MFS) efflux pump conferring multidrug resistance in Staphylococcus aureus and Staphylococcus epidermidis

A novel major facilitator superfamily (MFS) efflux pump in Staphylococcus, designated Nms, was identified via topology prediction. The secondary structure indicated the presence of 12 transmembrane segments (TMSs) and characteristic motif A of MFS efflux pumps. Experimental verification of efflux activity was conducted using ethidium bromide accumulation and efflux assays and biofilm formation assays. Antimicrobial susceptibility testing and efflux pump inhibition confirmed that Nms effectively effluxed various antimicrobial agents to confer multidrug resistance. Comprehensive genomic analyses were used to assess the prevalence and possible origins of the nms gene. The results revealed that the nms gene was present in Staphylococcus aureus ST398/ST541 and Staphylococcus epidermidis ST570/ST1166 strains from global isolates. The transmission of nms was associated with the prevalence of S. aureus ST398-t571 in swine-derived samples from China. Phylogenetic analysis revealed that nms-positive strains formed a distinct clade separate from other S. aureus ST398 strains. Genetic analysis of the nms gene revealed a significant presence of plasmid-related mobile genetic elements, with extended nucleotide sequences containing circular intermediates exhibiting high homology with those found in an S. aureus plasmid. These findings suggested that the nms gene likely initially originated from plasmids and subsequently integrated into chromosomes. In conclusion, Nms is a novel MFS efflux pump that confers multidrug resistance to S. aureus and has been carried predominantly by ST398-t571 isolates in recent years. Ongoing surveillance is essential to elucidate the origin of nms in S. aureus, particularly MRSA ST398-t571, and to understand the transmission among humans, animals, and the environment.

Single-Cell Force Spectroscopy Uncovers Root Zone- and Bacteria-Specific Interactions

Understanding root-bacteria interactions with plant growth-promoting rhizobacteria (PGPR) is key to developing effective biofertilizers for sustainable agriculture. We performed single-cell force spectroscopy using the atomic force microscope (AFM) to study the primary attachment of two PGPR, Bacillus velezensis and Pseudomonas defensor, to different regions of Arabidopsis thaliana roots. Force measurements with individual cells uncovered distinct attachment strategies by each strain, involving binding via micrometer-long polymers from both bacteria and root surfaces. Flagella differentially affected the binding interactions of each PGPR; their removal altered binding characteristics differently for each strain, highlighting the importance of flagella in early root colonization. Using silica beads to mimic the negatively charged bacteria, we demonstrated the influence of electrostatic forces on root-bacteria interactions. We also examined interactions with abiotic surfaces of varying surface energies, revealing the roles of hydrophilic and hydrophobic forces in initial binding. Our measurements show that differences in the physicochemical properties of bacteria and roots are responsible for variations in primary attachment strategies between PGPR strains and root regions. Parallel fluorescence measurements corroborated our AFM single-cell analysis. Overall, our results provide a nanoscale view of bacterial attachment to roots, offering key insights into how beneficial bacteria colonize roots, crucial for enhancing biofertilizer effectiveness.

Synthesis, Microbiology, and Biophysical Characterization of Mutanofactins from the Human Oral Microbiome

Mutanofactins are a family of natural products produced by Streptococcus mutans from the human oral microbiome. We report a unified approach to all mutanofactins by developing a total synthesis amenable to diversification. The key to success for the most complex members, mutanofactins 607 and 697, was an acyl ketene based strategy. Access to the family enabled comprehensive biological profiling, where we demonstrate that all mutanofactins are biofilm promoting in Streptococcus mutans. Experiments were extended to other inhabitants of the oral microbiome for the first time: Streptococcus gordonii and Streptococcus oralis, two early colonizers, were similarly affected with mutanofactins being biofilm promoting. Conversely, Veillonella dispar and Fusobacterium nucleatum showed little to no reaction to mutanofactins. Biophysical investigations based on quartz crystal microbalance with dissipation monitoring and atomic force microscopy reveal a previously unknown mucin-mutanofactin 697 interaction. Incubation of a mucin layer with mutanofactin 697 induces a morphology change within the mucin layer, which promotes bacterial adhesion and biofilm formation. This unique property of mutanofactin 697 might be key to early stages of biofilm formation in the human oral microbiome. Combined, an interdisciplinary approach consisting of total synthesis, microbiology and biophysical characterization provides insight into the roles of mutanofactins in the oral microbiome.

Spatial heterogeneity of EPS-mediated microplastic aggregation in phycosphere shapes polymer-specific Trojan horse effects

The pervasive contamination of aquatic ecosystems by microplastics represented a critical environmental challenge. While algal-bacterial symbiosis systems demonstrated potential for microplastic aggregation via extracellular polymeric substances (EPS), prior studies have focused on temporal dynamics rather than spatial heterogeneity in phycosphere. This study systematically investigated the adsorption mechanisms of Polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyethylene (PE) and polystyrene (PS) across stratified EPS fractions, tightly bound (TB-EPS), loosely bound (LB-EPS), and soluble (S-EPS), in phycosphere. Combining controlled aggregation assays with multimodal characterization, we revealed a hierarchical spatial framework governing EPS-microplastic interactions. Adsorption efficiency governed by polymer-specific interfacial energies and EPS organic composition. EPS at distinct hierarchical levels exhibited material-specific adsorption preferences for microplastics. PVC and PET demonstrated higher affinities for hydrocarbon components, while PE and PS were preferentially captured through interactions with polysaccharides and amide I groups, respectively. The adsorption and aggregation behaviors between EPS and microplastics in the phycosphere promoted eco-corona formation and induced the Trojan horse effect. However, the energy barrier of interaction forces and EPS spatial configurations jointly governed the hierarchical stabilization of polymer-specific microplastics. PVC and PET primarily colonized the outermost S-EPS layer, PS preferentially accumulated in the intermediate LB-EPS layer, and PE penetrated into the innermost TB-EPS layer. These findings addressed a key knowledge gap by delineating the ecological niche-specific distribution of EPS-microplastic binding, offering novel insights for optimizing bioremediation strategies and informing regulatory measures targeting particulate plastic pollution in hydrologic systems.

Bacterial Adhesion on Soft Surfaces: The Dual Role of Substrate Stiffness and Bacterial Growth Stage

The surface adhesion and stiffness of underlying substrates mediate the geometry, mechanics, and self-organization of expanding bacterial colonies. Recent studies have qualitatively indicted that stiffness may impact bacterial attachment and accumulation, yet the variation in the cell-to-surface adhesion with substrate stiffness remains to be quantified. Here, by developing a cell-level force-distance spectroscopy (FDS) technique based on atomic force microscopy (AFM), we simultaneously quantify the cell-surface adhesion and stiffness of the underlying substrates to reveal the stiffness-dependent adhesion of the phototrophic bacterium Chromatium okenii. As the stiffness of the soft substrate, modeled using a low-melting-point (LMP) agarose pad, was varied between 20 kPa and 120 kPa by changing the agarose concentrations, we observed a progressive increase in the mean adhesion force by over an order of magnitude, from 0.21±0.10 nN to 2.42±1.16 nN. In contrast, passive polystyrene (PS) microparticles of comparable dimensions showed no perceptible change in their surface adhesion, confirming that the stiffness-dependent adhesive interaction of C. okenii is of a biological origin. Furthermore, for Escherichia coli, the cell-surface adhesion varied between 0.29±0.17 nN and 0.39±0.20 nN, showing a weak dependence on the substrate stiffness, thus suggesting that stiffness-modulated adhesion is a species-specific trait. Finally, by quantifying the adhesion of the C. okenii population across different timescales, we reported the emergent co-existence of weak and strongly adherent sub-populations, demonstrating diversification of the adherent phenotypes over the growth stages. Taken together, these findings suggest that bacteria, depending on the species and their physiological stage, may actively modulate cell-to-surface adhesion in response to the stiffness of soft surfaces. While the surface properties, for instance, hydrophobicity (or hydrophilicity), play a key role in mediating bacterial attachment, this work introduces substrate stiffness as a biophysical parameter that could reinforce or suppress effective surface interactions. Our results suggest how bacteria could leverage stiffness-dependent adhesion and the diversity therein as functional traits to modulate their initial attachment to, colonization of, and proliferation on soft substrates during the early stages of biofilm development.

Properties and antibacterial effectiveness of metal-ion doped borate-based bioactive glasses

Bioactive glasses (BGs) are physiologically reactive surface biomaterials widely used in biomedical applications and various treatments. Borate bioactive glasses (BBGs) are third-generation BGs, and they exhibit superior biodegradable, bioactive, osteoconductive, antibacterial, and biocompatible properties compared to other types of BGs. Certain concentrations of dopant ions can be incorporated into the chemical structure of BBGs to enhance their biological functionalities and antimicrobial properties. It was demonstrated that those ions play a crucial role in the biological responsiveness in vitro and in vivo once in contact with a physiological environment. The dissolution products of ion-doped BBGs were noted in their ability to stimulate gene expression related to cell differentiation and proliferation, promote angiogenesis, display anti-inflammatory effects, and inhibit bacterial growth within a few hours. Thus, metal-ion-doped BBGs address several limitations encountered by biomedical, tissue engineering, and infection control applications. Considering the research studies on BBGs to date, this review aims to analyze metal-ion-doped BBGs based on their primary antibacterial properties and effectiveness.

The influence of surface materials on microbial biofilm formation in aviation fuel systems

The ability of different microbes to form biofilms on materials found in aviation fuel systems was assessed using both individual isolates and complex microbial communities. Biofilm formation by the Gram-negative bacterium, Pseudomonas putida, the fungus Amorphotheca resinae and the yeast, Candida tropicalis, was influenced by material surface properties although this differed between isolates. Biofilm formation was greatest at the fuel-water interface. The Gram-positive bacterium Rhodococcus erythropolis, in contrast, was able to grow on most surfaces. When a subset of materials was exposed to complex microbial communities, the attached microbial community structure was influenced by surface properties and selected for different genera best able to form biofilms on a specific surface. Distinct sub-populations of Pseudomonads were identified, which favoured growth on aluminium or painted surfaces, with a different subpopulation favouring growth on nitrile.

Investigation of the susceptibility of clinical infection loads to nitric oxide antibacterial treatment

The persistent infection of medical devices by opportunistic pathogens has led to the development of antimicrobial medical device polymers. Nitric oxide (NO) is an endogenous antimicrobial molecule that is released through the degradation of synthetic donor molecules such as S-nitroso-N-acetylpenicillamine (SNAP) embedded into polymer membranes. It is hypothesized that the clinical success of these polymers is enhanced by the physiological release of NO and the consequent prevention of infection. However, such NO-releasing materials have never been evaluated against microbial loads that are commensurate with clinical infection levels. This study aimed to develop a standardized polymer film impregnated with SNAP that consistently releases NO and evaluates its efficacy against bacterial loads that represent clinical infection parameters. Microbial loads of 103, 105, and 108 (colony-forming units) CFU mL-1 were exposed to the NO-releasing polymer, corresponding to bloodstream infections, catheter-associated urinary tract infections, and standard laboratory exposure levels that have been reported in the scientific literature. By 24 h, SNAP films led to >1 log reduction of adhered and viable E. coli at all tested microbial loads compared to control polydimethylsiloxane (PDMS). Further, SNAP films displayed no viable adhered S. aureus at the 103 microbial level for the entire study and showed total planktonic killing by 8 h. NO localization within bacterial cells adhering to the films was evaluated, revealing higher NO uptake and consequent bacterial killing by SNAP samples. This unique study shows that NO-releasing polymers not only kill bacteria adhered to the polymer surface, but localized delivery leads to environmental planktonic bacterial killing that prevents adhesion from occurring. Furthermore, the promising findings of NO-releasing polymers in scientific research indicate their potential for successful application in clinical settings to prevent infections.

Photoimmunologic Therapy of Stubborn Biofilm via Inhibiting Bacteria Revival and Preventing Reinfection

Stubborn biofilm infections pose serious threats to public health. Clinical practices highly rely on mechanical debridement and antibiotics, which often fail and lead to persistent and recurrent infections. The main culprits are 1) persistent bacteria reviving, colonizing, and rejuvenating biofilms, and 2) secondary pathogen exposure, particularly in individuals with chronic diseases. Addressing how to inhibit persistent bacteria revival and prevent reinfection simultaneously is still a major challenge. Herein, an oligo-ethylene glycol-modified lipophilic cationic photosensitizer (PS), TBTCP-PEG7, is developed. It effectively eradicates Methicillin-Resistant Staphylococcus aureus (MRSA) under light irradiation. Furthermore, TBTCP-PEG7-mediated photodynamic therapy (PDT) not only conquers stubborn biofilm infections by downregulating the two-component system (TCS), quorum sensing (QS), and virulence factors, thereby reducing intercellular communication, inhibiting persistent bacterial regrowth and biofilm remodeling but also prevents reinfection by upregulating heat shock protein-related genes to induce immunogenetic cell death (ICD) and establish immune memory. In vivo, TBTCP-PEG7 efficiently eradicates MRSA biofilm adhered to medical catheters, stimulates angiogenesis, reduces inflammatory factor expression, and accelerates wound healing. Furthermore, ICD promotes short-term immune and long-term immunological memory for coping with secondary infections. This two-pronged strategy not only effectively overcomes stubborn, persistent and recurrent biofilm infection, but also provides theoretical guidance for designing the next generation of antibacterial materials.

BTS1-knockout Saccharomyces cerevisiae with broad-spectrum antimicrobial activity through lactic acid accumulation

Bacterial infections pose significant threats to human health, and prudent antibiotic use remains a key strategy for disease treatment and control. However, a global escalation of drug resistance among pathogenic bacteria presents a formidable challenge. Probiotics have emerged as a promising approach to combating pathogenic bacterial infections. In this study, we investigated the antibacterial activity of BTS1-knockout (BTS1-KO) Saccharomyces cerevisiae. Our findings demonstrate its effective inhibition of pathogen growth as evidenced by Minimum inhibitory concentration (MIC) assays, growth curves, bacteriostatic spectrum analyses and co-culture experiments. Additionally, it significantly impedes Escherichia coli and Staphylococcus aureus biofilm formation. Moreover, BTS1-KO S. cerevisiae exhibits low haemolytic activity, acid resistance, resistance to high bile salt concentrations, high auto-aggregation capacity and high co-aggregation capacities with pathogenic bacteria. Moreover, infected larvae treated with BTS1-KO S. cerevisiae in Galleria mellonella-E. coli (in vivo) and G. mellonella-S. aureus (in vivo) infection models showed significantly prolonged survival times. Mechanistic investigations revealed that BTS1-KO S. cerevisiae primarily produced lactic acid via metabolism, thereby lowering the environmental pH and inhibiting pathogenic bacterial growth. In summary, our study underscores the probiotic potential of BTS1-KO S. cerevisiae, offering broad-spectrum antibacterial activity in vitro and in vivo with low toxicity. This highlights BTS1-KO S. cerevisiae as a promising probiotic candidate for clinical prevention and control of bacterial infection.

Unlocking Probiotic Potential: Physicochemical Approaches to Evaluate Probiotic Bacterial Adhesion Potential to the Intestinal Tract

Bacterial adhesion in the gut is critical to evaluate their effectiveness as probiotics. Understanding the bacterial adhesion within the complex gut environment is challenging. This study explores the adhesion mechanisms and the adhesion potential of five selected bacterial strains (Escherichia coli, Lactiplantibacillus plantarum, Faecalibacterium duncaniae, Bifidobacterium longum, and Bifidobacterium longum subsp. infantis) at the initial stages when bacterial cells arriving in the gut, using different physicochemical approaches. Bacterial morphology, rheology, and surface properties were evaluated. Surprisingly, previous methods such as bacterial adhesion to hydrocarbon and the interfacial tension between bacterial suspensions and mineral oil did not fully capture the bacterial adhesion to intestinal mucus. Consequently, this study introduced a novel approach to assess bacterial adhesion to mucus, based on contact angle measurements, calculation of surface tension, and work of adhesion. Interestingly, both small and large intestinal mucus are rather hydrophilic, and thus highly hydrophilic bacteria such as E. coli and B. infantis tend to adhere better. Additionally, a multicriteria evaluation of bacterial adhesion to the gut, from the bulk liquid transport stage until the irreversible adhesion, was proposed. E. coli and B. infantis demonstrated the highest overall adhesion potential in the intestinal tract, followed by Lpb. plantarum, B. longum, and F. duncaniae, respectively. This work contributed original physicochemical approaches to comprehensively examine bacterial adhesion in the gut.

The sorption of algal organic matter by extracellular polymeric substances: Trade-offs in disinfection byproduct formation influenced by divalent ions

Disinfection by-products (DBPs), formed from biofilm extracellular polymeric substances (EPS) and organic matter during regular disinfection practices in drinking water distribution systems, poses a potential threat to drinking water safety. However, the diverse DBP formations induced by the intertwined algal organic matter (AOM) and bacterial EPS remains elusive. In this study, we show substantial variations in EPS and DBP formation patterns driven by AOM biosorption with divalent ions (Ca2+ and Mg2+). Divalent ions in bulk water can significantly inhibit carbonaceous DBPs (C-DBPs) and nitrogenous DBPs (N-DBPs) formation. Mechanistically, divalent ions promote the complexation of negative charged groups and thus inhibit C-DBP formation, while the hindering chlorine substitution of hydrogen atoms on α‑carbon and amine groups reduces N-DBP formation. Conversely, Ca2+ and Mg2+ could facilitate biosorption processes that increased the yields of C-DBPs and N-DBPs. Both EPS and AOM provide halogenated reactive sites for DBP formation, exhibiting diverse aromatic substances and unsaturated (lignin and tannins) compounds. Our results highlight divalent ions acting as a fundamental driving force in DBP formation, suggesting the need for cautious monitoring of divalent ions in karst water.

Surface characteristics, cytotoxicity, and microbial adhesion of 3D-printed hybrid resin-ceramic materials for definitive restoration

OBJECTIVE

This study investigated the surface properties, cytotoxicity, and microbial adhesion of 3D-printed specimens made from hybrid resin-ceramic materials intended for use in definitive crowns.

METHODS

Disc-shaped specimens were 3D-printed using six different hybrid resin-ceramic materials recommended for definitive restorations: Crowntec (CT), VarseoSmile Crown Plus (VS), Tera Harz TC-80DP Graphy (TH), C&B Permanent ODS (CB), Formlabs Permanent Crown (FP), and HeyGears (HG). Surface topography, surface roughness, and water contact angle values were measured for each material (n = 6). Cytotoxicity was assessed using direct contact and extract tests on human gingival fibroblasts (n = 4). Additionally, the adhesion of mixed oral bacteria to the surfaces of the specimens was evaluated by counting colony-forming units (CFUs) after a 2-hour incubation period (n = 6).

RESULTS

The TH group exhibited significantly lower surface roughness (Ra: 0.28 ± 0.13 μm) compared to the other materials (CT: 1.87 ± 0.34 μm; VS: 1.13 ± 0.09 μm; CB: 2.91 ± 0.27 μm; FP: 2.50 ± 0.08 μm; HG: 1.50 ± 0.55 μm). The VS group had the highest water contact angle (129.5 ± 1.1°), indicating greater hydrophobicity, in contrast to the other groups (CT: 72.6 ± 2.1°; TH: 75.0 ± 0.3°; CB: 69.1 ± 0.2°; FP: 93.0 ± 1.6°; HG: 77.7 ± 0.3°). Cytotoxicity testing showed no harmful effects, as relative cell viability exceeded 70 %, and lactate dehydrogenase (LDH) release remained below 30 % for all materials. The TH specimens also demonstrated the lowest bacterial adhesion.

CONCLUSIONS

The surface characteristics of the tested resin-ceramic materials varied significantly, with TH showing the smoothest surface and the least bacterial adhesion. All materials were found to be non-toxic. Therefore, TH material has the potential to provide definitive restorations with less microbial adhesion.

CLINICAL SIGNIFICANCE

The type of resin-ceramic material significantly affects the surface properties of 3D-printed specimens. These findings are crucial for selecting the appropriate resin-ceramic material for definitive restorations.

Understanding the Influence of Rheology on Biofilm Adhesion and Implication for Food Safety

Understanding biofilm rheology is crucial for industrial and domestic food safety practices. This comprehensive review addresses the knowledge gap on the rheology of biofilm. Specifically, the review explores the influence of fluid flow, shear stress, and substrate properties on the initiation, structure, and functionality of biofilms, as essential implications for food safety. The viscosity and shear-thinning characteristics of non-Newtonian fluids may impact the attachment and detachment dynamics of biofilms, influencing their stability and resilience under different flow conditions. The discussion spans multiple facets, including the role of extracellular polymeric substances (EPSs) in biofilm formation, the impact of rheological attributes of biofilm on their adhesion to surfaces, and the influence of shear forces between biofilms and substrate's surface characteristics on biofilm stability. Analytical techniques, encompassing rheometry, microscopy, and molecular biology approaches, are scrutinized for their contributions to understanding these interactions. The paper delves into the implications for the food industry, highlighting potential risks associated with biofilm formation and proposing strategies for effective control and prevention. Future research directions and the integration of rheological considerations into food safety regulations are underscored as pivotal steps in mitigating biofilm-related risks. The synthesis of microbiology, materials science, and engineering perspectives offers a multidimensional exploration of rheology-biofilm interactions, laying the groundwork for informed interventions in diverse industrial settings.

Bacterial Communities and Their Role in Bacterial Infections

Since infections associated with microbial communities threaten human health, research is increasingly focusing on the development of biofilms and strategies to combat them. Bacterial communities may include bacteria of one or several species. Therefore, examining all the microbes and identifying individual community bacteria responsible for the infectious process is important. Rapid and accurate detection of bacterial pathogens is paramount in healthcare, food safety, and environmental monitoring. Here, we analyze biofilm composition and describe the main groups of pathogens whose presence in a microbial community leads to infection (Staphylococcus aureus, Enterococcus spp., Cutibacterium spp., bacteria of the HACEK, etc.). Particular attention is paid to bacterial communities that can lead to the development of device-associated infections, damage, and disruption of the normal functioning of medical devices, such as cardiovascular implants, biliary stents, neurological, orthopedic, urological and penile implants, etc. Special consideration is given to tissue-located bacterial biofilms in the oral cavity, lungs and lower respiratory tract, upper respiratory tract, middle ear, cardiovascular system, skeletal system, wound surface, and urogenital system. We also describe methods used to analyze the bacterial composition in biofilms, such as microbiologically testing, staining, microcolony formation, cellular and extracellular biofilm components, and other methods. Finally, we present ways to reduce the incidence of biofilm-caused infections.

A study on disinfection and adhesion behaviour between bacteria and photocatalytic nanostructures by extended DLVO

Recently, there has been a growing concern regarding the increased contamination of water by bacteria. As a result, more attention has been paid to the potential benefits of utilizing nano adsorbents and photocatalysis for water purification. In order to better manipulate the physicochemical properties, it is crucial to gain a comprehensive understanding of the molecular behaviour between nanoparticles and pathogens. This article investigates the various interactions that can occur between Fe3O4-SiO2-TiO2 (FST) nanoparticles and bacterial cells. Moreover, it explores the impact of the SiO2 mid-layer and the governing interaction in the adhesion and degradation processes. In this regard, FST nanoparticles were prepared, and their adhesion behaviour to E. coli bacterial cells was evaluated using extended DLVO (Derjaguin-Landau-Verwey-Overbeek) theory. The following results revealed that the presence of silica transformed FST into a more hydrophobic material with a positively charged surface, thereby enhancing its affinity for bacterial adsorption. Additionally, SiO2 prevented electron/hole recombination. Amongst the various interactions, Lewis acid-base interactions had the greatest influence on the total energy and lacking energy barriers led to irreversible adhesion. Moreover, the presence of an increased number of ·OH groups on the surface resulted in enhanced bactericidal properties of FST, leading to severe damage of E. coli cells through the formation of a greater number of hydrogen bonds on the bacterial surface, which is the basis of the proposed mechanism for destruction of the bacterial structure.

Effect of shear rate on early Shewanella oneidensis adhesion dynamics monitored by deep learning

Understanding pioneer bacterial adhesion is essential to appreciate bacterial colonization and consider appropriate control strategies. This bacterial entrapment at the wall is known to be controlled by many physical, chemical or biological factors, including hydrodynamic conditions. However, due to the nature of early bacterial adhesion, i.e. a short and dynamic process with low biomass involved, such investigations are challenging. In this context, our study aimed to evaluate the effect of wall shear rate on the early bacterial adhesion dynamics. Firstly, at the population scale by assessing bacterial colonization kinetics and the mechanisms responsible for wall transfer under shear rates using a time-lapse approach. Secondly, at the individual scale, by implementing an automated image processing method based on deep learning to track each individual pioneer bacterium on the wall. Bacterial adhesion experiments are performed on a model bacterium (Shewanella oneidensis MR-1) at different shear rates (0 to1250 s-1) in a microfluidic system mounted under a microscope equipped with a CCD camera. Image processing was performed using a trained neural network (YOLOv8), which allowed information extraction, i.e. bacterial wall residence time and orientation for each adhered bacterium during pioneer colonization (14 min). Collected from over 20,000 bacteria, our results showed that adhered bacteria had a very short residence time at the wall, with over 70 % remaining less than 1 min. Shear rates had a non-proportional effect on pioneer colonization with a bell-shape profile suggesting that intermediate shear rates improved both bacterial wall residence time as well as colonization rate and level. This lack of proportionality highlights the dual effect of wall shear rate on early bacterial colonization; initially increasing it improves bacterial colonization up to a threshold, beyond which it leads to higher bacterial wall detachment. The present study provides quantitative data on the individual dynamics of just adhered bacteria within a population when exposed to different rates of wall shear.

Effects of mscM Gene on Desiccation Resistance in Cronobacter sakazakii

Cronobacter sakazakii, an opportunistic foodborne pathogen, has a strong resistance to osmotic stress and desiccation stress, but the current studies cannot elucidate this resistance mechanism absolutely. A mechanosensitive channel MscM was suspected of involving to desiccation resistance mechanism of C. sakazakii. To investigate the specific molecular mechanism, the mscM mutant strain (ΔmscM) was constructed using the homologous recombination method, and the cpmscM complementary strain was obtained by gene complementation, followed by the analysis of the difference between the wild-type (WT), mutant, and complementary strains. Compared to the wild-type bacteria (WT), the inactivation rate of the ΔmscM strain decreased by 15.83% (p < 0.01) after desiccation stress. The absence of the mscM gene led to an increase in the membrane permeability of mutant strains. Through turbidity assay, it was found that the intracellular content of potassium ion (K+) of the ΔmscM strain increased by 2.2-fold (p < 0.05) compared to the WT strain, while other metal ion contents, including sodium ion (Na+), calcium ion (Ca2+), and magnesium ion (Mg2+), decreased by 48.45% (p < 0.001), 24.29% (p < 0.001), and 26.11% (p < 0.0001), respectively. These findings indicate that the MscM channel primarily regulates cell membrane permeability by controlling K+ efflux to maintain the homeostasis of intracellular osmotic pressure and affect the desiccation tolerance of bacteria. Additionally, the deletion of the mscM gene did not affect bacterial growth and motility but impaired surface hydrophobicity (reduced 20.52% compared to the WT strain, p < 0.001), adhesion/invasion capability (reduced 26.03% compared to the WT strain, p < 0.001), and biofilm formation ability (reduced 30.19% compared to the WT strain, p < 0.05) of the bacteria. This study provides a reference for the role of the mscM gene in the desiccation resistance and biofilm formation of C. sakazakii.

Essential Oil Components Incorporated Emulsion Hydrogels for Eradicating Dermatophytosis Caused by Pathogenic Fungi Trichophyton mentagrophytes and Microsporum canis

Dermatophytosis is a prevalent fungal infection and public health burden, majorly caused by the attack of zoophilic fungi genera of Trichophyton and Microsporum. Among them, T. mentagrophytes and M. canis are the dominating pathogens that cause dermatophytosis in humans. Though anti-fungal treatments are available, the widespread drug resistance and minimal efficacy of conventional therapies cause recurring infections. In addition, prolonged anti-fungal medications induce several systemic side effects, including hepatotoxicity and leucopenia. The anti-dermatophytic formulation of biocompatible essential oil components (EOCs) is attractive due to their highly potent anti-dermatophytic action. Herein, two EOCs, Eugenol (EU) and Isoeugenol (IU), incorporated emulsion hydrogel (EOCs-EHG) synthesized from hydroxypropylmethyl cellulose and poly(ethylene glycol) methyl ether methacrylate. The cytocompatibility of the hydrogels is confirmed by treating them with fibroblast and keratinocyte cell lines. The EOCs-EHG demonstrated pH and temperature-responsive sustained release of entrapped EOCs and inhibited fungal spore germination. T. mentagrophytes and M. canis biofilms are eradicated at a minimal inhibitory concentration of 2 µg mL-1 each of EU and IU. The in vivo anti-dermatophytic activity of EOCs-EHG is confirmed in dermatophyte-infected Wistar albino rat models. The topical application of EOCs-EHG demonstrated complete infection eradication and facilitated skin regeneration, emphasizing the therapeutic potential of EOCs-EHG against dermatophytosis.

Photothermal Iron-Based Riboflavin Microneedles for the Treatment of Bacterial Keratitis via Ion Therapy and Immunomodulation

Bacterial biofilm formation protects bacteria from antibiotics and the immune system, excessive inflammation further complicates treatment. Here, iron-based metal-organic framework (MIL-101)-loaded riboflavin nanoparticles are designed for the therapeutic challenge of biofilm infection and hyperinflammation in bacterial keratitis. Specifically, MIL-101 produces a thermal effect under exogenous near-infrared light irradiation, which synergizes with ferroptosis-like bacterial death induced by iron ions to exert an effective biofilm infection eradication effect. On the other hand, the disintegration of MIL-101 sustains the release of riboflavin, which inhibits the pro-inflammatory response of macrophage over-activation by modulating their phenotypic switch. In addition, to solve the problems of short residence time, poor permeability, and low bioavailability of corneal medication, the MR@MN microneedle patch is further prepared by loading nanoparticles into SilMA hydrogel, which ultimately achieves painless, transepithelial, and highly efficient drug delivery. In vivo and ex vivo experiments demonstrate the effectiveness of this approach in eliminating bacterial infection and promoting corneal healing. Therefore, the MRMN patch, acting as an ocular drug delivery system with the ability of rapid corneal healing, promises a cost-effective solution for the treatment of bacterial keratitis, which may also lead to a new approach for treating bacterial keratitis in clinics.

Surface-programmed microbiome assembly in phycosphere to microplastics contamination

Recalcitrance in microplastics accounts for ubiquitous white pollution. Of special interest are the capabilities of microorganisms to accelerate their degradation sustainably. Compared to the well-studied pure cultures in degrading natural polymers, the algal-bacterial symbiotic system is considered as a promising candidate for microplastics removal, cascading bottom-up impacts on ecosystem-scale processes. This study selected and enriched the algae-associated microbial communities hosted by the indigenous isolation Desmodesmus sp. in wastewater treatment plants with micro-polyvinyl chloride, polyethylene terephthalate, polyethylene, and polystyrene contamination. Results elaborated that multiple settled and specific affiliates were recruited by the uniform algae protagonist from the biosphere under manifold microplastic stress. Alteration of distinct chemical functionalities and deformation of polymers provide direct evidence of degradation in phycosphere under illumination. Microplastic-induced phycosphere-derived DOM created spatial gradients of aromatic protein, fulvic and humic acid-like and tryptophan components to expanded niche-width. Surface thermodynamic analysis was conducted to simulate the reciprocal and reversible interaction on algal-bacterial and phycosphere-microplastic interface, revealing the enhancement of transition to stable and irreversible aggregation for functional microbiota colonization and microplastics capture. Furthermore, pangenomic analysis disclosed the genes related to the chemotaxis and the proposed microplastics biodegradation pathway in enriched algal-bacterial microbiome, orchestrating the evidence for common synthetic polymer particles and ultimately to confirm the effectiveness and potential. The present study emphasizes the necessity for future endeavors aimed at fully leveraging the potential of algal-bacterial mutualistic systems within sustainable bioremediation strategies targeting the eradication of microplastic waste.

Photocatalytic and antibacterial activity properties of Ti surface treated by femtosecond laser-a prospective solution to peri-implant disease

Laser texturing seems to be a promising technique for reducing bacterial adhesion on titanium implant surfaces. This work aims to demonstrate the possibility of obtaining a functionally orientated surface of titanium implant elements with a specific architecture with specific bacteriological and photocatalytic properties. Femtosecond laser-generated surface structures, such as laser-induced periodic surface structures (LIPSS, wrinkles), grooves, and spikes on titanium, have been characterised by XRD, Raman spectroscopy, and scanning electron microscopy (SEM). The photocatalytic activity of the titanium surfaces produced was tested based on the degradation effect of methylene blue (MB). The correlation between the photocatalytic activity of TiO2 coatings and their morphology and structure has been analysed. Features related to the size, shape, and distribution of the roughness patterns were found to influence the adhesion of the bacterial strain on different surfaces. On the laser-structurised surface, the adhesion of Escherichia coli bacteria were reduced by 80% compared to an untreated reference surface.

Quantitative study of early-stage transient bacterial adhesion to bioactive glass and glass ceramics: atomic force microscopic observations

Antimicrobial potential of bioactive glass (BAG) makes it promising for implant applications, specifically overcoming the toxicity concerns associated with traditional antibacterial nanoparticles. The 58S composition of BAG (with high Ca and absence of Na) has been known to exhibit excellent bioactivity and antibacterial behaviour, but the mechanisms behind have not been investigated in detail. In this pioneering study, we are using Atomic Force Microscopy (AFM) to gain insights into 58S BAG's adhesive interactions with planktonic cells of both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria; along with the impact of crystallinity on antibacterial properties. We have recorded greater bacterial inhibition by amorphous BAG compared to semi-crystalline glass-ceramics and stronger effect against gram-negative bacteria via conventional long-term antibacterial tests. AFM force distance curves has illustrated substantial bonding between bacteria and BAG within the initial one second (observed at a gap of 250 ms) of contact, with multiple binding events. Further, stronger adhesion of BAG with E.coli (~ 6 nN) compared to S. aureus (~ 3 nN) has been found which can be attributed to more adhesive nano-domains (size effect) distributed uniformly on E.coli surface. This study has revealed direct evidence of impact of contact time and 58S BAG's crystalline phase on bacterial adhesion and antimicrobial behaviour. Current study has successfully demonstrated the mode and mechanisms of initial bacterial adhesion with 58S BAG. The outcome can pave the way towards improving the designing of implant surfaces for a range of biomedical applications.

The evolution of calcified anaerobic granular sludge bed informs the deep insight into its agglomeration process

Calcium-induced agglomeration of anaerobic granular sludge bed (AGSB) has become a critical factor in performance decline of calcified anaerobic reactors. However, the agglomeration process of AGSB and the underlying mechanisms remain unclear and elusive. This study delved into the evolution of calcified AGSB, and four typical states of normal AGSB (Nor-AGSB), calcified dispersed AGSB (Dis-AGSB), calcified dimeric AGSB (Dim-AGSB), and calcified polymeric AGSB (Pol-AGSB) were characterized. It was found that the minimum transport velocity of Dis-AGSB was 3.14-3.79 times higher than that of Nor-AGSB, and surpassed both the superficial velocity and the bubble-induced wake velocity. This led to the sedimentation of AGS at the bottom of reactor, resulting in stable contacts with each other. Solid fillers between AGS, namely cement, were observed within Dim-AGSB and Pol-AGSB, and could be classified as tightly- and loosely- bonded cement (T- and L-cement). Further analysis revealed that T-cement was rich in extracellular polymeric substances and intertwining pili/flagella, serving as the primary driving force for robust inter-AGS adhesion. While the L-cement was primarily in the form of calcite precipitation, and blocked the convective mass transfer pathways in Pol-AGSB, leading to the decreased convective mass transfer capacity. The critical distance between calcite and AGS was further revealed as 5.33 nm to form stable initial adhesion. Consequently, the agglomeration mechanism involving the evolution of AGSB was proposed as calcium-induced sedimentation, calcium-induced adhesion, and calcium-induced stasis in order. This study is expected to offer deep insight into the calcium-induced agglomeration especially from the overlooked perspective of AGSB, and provides feasible control strategies to manage the pressing calcification issues in engineering applications.

Bacterial Adhesion to Natural and Synthetic Fibre-Forming Polymers: Influence of Material Properties

Polymer-based textiles have a major impact on human well-being, as they provide the desired functional protection and aesthetic comfort when worn. However, natural and synthetic polymer-based textiles can also pose serious health risks, as they are surfaces that allow the adhesion of various bacteria, including pathogenic bacteria. To minimise these problems, antibacterial chemical treatments are generally applicable in the case of polymer-based textiles. However, to avoid the use of potentially toxic chemicals, sustainable approaches require the customised design of non-adhesive polymer-based textiles, considering their chemical, physicochemical, constructional, and textural properties. Before designing, several articles are required to gain sufficient knowledge of the described object. Despite the urgent need to combat bacteria (on polymer-based textiles), which pose a serious global health risk, only a few review articles have been published that address bacterial adhesion in the context of superhydrophobic and antibacterial textile materials, while only one review article holistically addresses the textile factors and their influence on this phenomenon. The aim of this review article is to expand the insufficient knowledge about bacterial adhesion to polymer-based textiles on the basis of theoretical findings and real examples through a high degree of structuring, simplification, holistic consideration, and visualization. Therefore, this review provides an insight into the mechanisms involved in bacterial adhesion and a comprehensive overview of the influence of different textile factors, such as chemical composition, hydrophilicity/hydrophobicity, surface charge, surface free energy, roughness, and porosity, on bacterial adhesion. To emphasise the importance of the synergistic effect of the combined textile factors, examples of the influence of hydrophilicity/hydrophobicity in combination with surface charge, surface roughness, and porosity are discussed. From the review, it can be concluded that the combination of hydrophilicity/hydrophobicity and the surface charge of textile fibres and bacteria is crucial for bacterial adhesion, with roughness and porosity being the most important factors among the constructive and textural properties of polymer-based textiles.

The oral microbiota and periodontal health in orthodontic patients

The oral microbiota develops within the first 2 years of childhood and becomes distinct from the parents by 4 years-of-age. The oral microbiota plays an important role in the overall health/symbiosis of the individual. Deviations from the state of symbiosis leads to dysbiosis and an increased risk of pathogenicity. Deviations can occur not only from daily life activities but also from orthodontic interventions. Orthodontic appliances are formed from a variety of biomaterials. Once inserted, they serve as a breeding ground for microbial attachment, not only from new surface areas and crevices but also from material physicochemical interactions different than in the symbiotic state. Individuals undergoing orthodontic treatment show, compared with untreated people, qualitative and quantitative differences in activity within the oral microbiota, induced by increased retention of supra- and subgingival microbial plaque throughout the treatment period. These changes are at the root of the main undesirable effects, such as gingivitis, white spot lesions (WSL), and more severe caries lesions. Notably, the oral microbiota profile in the first weeks of orthodontic intervention might be a valuable indicator to predict and identify higher-risk individuals with respect to periodontal health and caries risk within an otherwise healthy population. Antimicrobial coatings have been used to dissuade microbes from adhering to the biomaterial; however, they disrupt the host microbiota, and several bacterial strains have become resistant. Smart biomaterials that can reduce the antimicrobial load preventing microbial adhesion to orthodontic appliances have shown promising results, but their complexity has kept many solutions from reaching the clinic. 3D printing technology provides opportunities for complex chemical syntheses to be performed uniformly, reducing the cost of producing smart biomaterials giving hope that they may reach the clinic in the near future. The purpose of this review is to emphasize the importance of the oral microbiota during orthodontic therapy and to use innovative technologies to better maintain its healthy balance during surgical procedures.

Nanocomposite system with photoactive phloxine B eradicates resistant Staphylococcus aureus

Nanomaterials modified with hybrid films functionalized with photoactive compounds can be an effective system to prevent and eradicate biofilms on medical devices. The aim of this research was to extend current knowledge on nanomaterial comprised of polyurethane (PU) modified with a nanocomposite film of organoclay with the functionalized photosensitizer (PS) phloxine B (PhB). Particles of the clay mineral saponite were, at first modified by octadecyltrimethylammonium cations to activate the surface for PhB adsorption. The colloids were filtered to get silicate films on polytetrafluoroethylene membrane filters, which were layered with a liquid mixture of PU precursors. The penetration of PU into the silicate formed a thin nanocomposite film. This nanomaterial demonstrated excellent effectiveness against methicillin-resistant S. aureus (MRSA) resistant to fluoroquinolones (L12 and S61, respectively). It showed more than 1000- and 10 000-fold inhibition of biofilm growth after irradiation with green laser compared to the unmodified PU material. Principal component analysis and multiple linear regression showed that the effectiveness of the nanomaterial was not influenced by virulence factors such as the expression of efflux pumps of the Nor family, the adhesin PIA encoded by the icaADBC operon or the robustness of the biofilms. However, the presence of organoclay, PhB and irradiation had a significant effect on the anti-biofilm properties of the nanocomposite. The anti-microbial properties of the material were strengthened after irradiation, because of high reactive oxygen species release (more than 14-fold compared to non-irradiated sample). Materials based on photoactive molecules can represent a worthwhile pathway towards the development of more complex nanomaterials applicable in various fields of medicine.

Medical Device-Associated Infections Caused by Biofilm-Forming Microbial Pathogens and Controlling Strategies

Hospital-acquired infections, also known as nosocomial infections, include bloodstream infections, surgical site infections, skin and soft tissue infections, respiratory tract infections, and urinary tract infections. According to reports, Gram-positive and Gram-negative pathogenic bacteria account for up to 70% of nosocomial infections in intensive care unit (ICU) patients. Biofilm production is a main virulence mechanism and a distinguishing feature of bacterial pathogens. Most bacterial pathogens develop biofilms at the solid-liquid and air-liquid interfaces. An essential requirement for biofilm production is the presence of a conditioning film. A conditioning film provides the first surface on which bacteria can adhere and fosters the growth of biofilms by creating a favorable environment. The conditioning film improves microbial adherence by delivering chemical signals or generating microenvironments. Microorganisms use this coating as a nutrient source. The film gathers both inorganic and organic substances from its surroundings, or these substances are generated by microbes in the film. These nutrients boost the initial growth of the adhering bacteria and facilitate biofilm formation by acting as a food source. Coatings with combined antibacterial efficacy and antifouling properties provide further benefits by preventing dead cells and debris from adhering to the surfaces. In the present review, we address numerous pathogenic microbes that form biofilms on the surfaces of biomedical devices. In addition, we explore several efficient smart antiadhesive coatings on the surfaces of biomedical device-relevant materials that manage nosocomial infections caused by biofilm-forming microbial pathogens.

Beyond surface modification strategies to control infections associated with implanted biomaterials and devices - Addressing the opportunities offered by nanotechnology

Biomaterial-associated infection (BAI) is considered a unique infection due to the presence of a biomaterial yielding frustrated immune-cells, ineffective in clearing local micro-organisms. The involvement of surface-adherent/surface-adapted micro-organisms in BAI, logically points to biomaterial surface-modifications for BAI-control. Biomaterial surface-modification is most suitable for prevention before adhering bacteria have grown into a mature biofilm, while BAI-treatment is virtually impossible through surface-modification. Hundreds of different surface-modifications have been proposed for BAI-control but few have passed clinical trials due to the statistical near-impossibility of benefit-demonstration. Yet, no biomaterial surface-modification forwarded, is clinically embraced. Collectively, this leads us to conclude that surface-modification is a dead-end road. Accepting that BAI is, like most human infections, due to surface-adherent biofilms (though not always to a foreign material), and regarding BAI as a common infection, opens a more-generally-applicable and therewith easier-to-validate road. Pre-clinical models have shown that stimuli-responsive nano-antimicrobials and antibiotic-loaded nanocarriers exhibit prolonged blood-circulation times and can respond to a biofilm's micro-environment to penetrate and accumulate within biofilms, prompt ROS-generation and synergistic killing with antibiotics of antibiotic-resistant pathogens without inducing further antimicrobial-resistance. Moreover, they can boost frustrated immune-cells around a biomaterial reducing the importance of this unique BAI-feature. Time to start exploring the nano-road for BAI-control.

Nanoscale Spatiotemporal Dynamics of Microbial Adhesion: Unveiling Stepwise Transitions with Plasmonic Imaging

Understanding bacterial adhesion at the nanoscale is crucial for elucidating biofilm formation, enhancing biosensor performance, and designing advanced biomaterials. However, the dynamics of the critical transition from reversible to irreversible adhesion has remained elusive due to analytical constraints. Here, we probed this adhesion transition, unveiling nanoscale, step-like bacterial approaches to substrates using a plasmonic imaging technique. This method reveals the discontinuous nature of adhesion, emphasizing the complex interplay between bacterial extracellular polymeric substances (EPS) and substrates. Our findings not only deepen our understanding of bacterial adhesion but also have significant implications for the development of theoretical models for biofilm management. By elucidating these nanoscale step-like adhesion processes, our work provides avenues for the application of nanotechnology in biosensing, biofilm control, and the creation of biomimetic materials.

Graphene Oxide-Silver-Coated Sulfonated Polyetheretherketone (Ag/GO-SPEEK): A Broad-Spectrum Antibacterial Artificial Bone Implants

Polyetheretherketone (PEEK), particularly its sulfonated form (SPEEK), has emerged as a promising synthetic biomaterial for artificial bone implants, providing an alternative to conventional titanium metal. However, postoperative infections pose a critical challenge, driven by diverse and antibiotic-resistant bacteria. To address this issue, we propose the modification of the SPEEK surface using a thin graphene oxide (GO) film containing silver (Ag) ions. The resulting coating exhibits substantial antibacterial effects against various pathogens, including Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans. Experimental assessments elucidate the coating's impact on bacterial adhesion, biofilm formation, and morphology. The results suggest that hindered bacterial growth stems from reduced biofilm production and the controlled release of Ag ions facilitated by the GO coating. The Ag/GO-SPEEK material holds promise as a bioactive implant, addressing the challenges associated with bacterial targeting in bone tissue engineering applications.

Characterization and morphological methods for oral biofilm visualization: where are we nowadays?

The oral microbiome represents an essential component of the oral ecosystem whose symbiotic relationship contributes to health maintenance. The biofilm represents a state of living of microorganisms surrounding themselves with a complex and tridimensional organized polymeric support and defense matrix. The substrates where the oral biofilm adhere can suffer from damages due to the microbial community metabolisms. Therefore, microbial biofilm represents the main etiological factor of the two pathologies of dental interest with the highest incidence, such as carious pathology and periodontal pathology. The study, analysis, and understanding of the characteristics of the biofilm, starting from the macroscopic structure up to the microscopic architecture, appear essential. This review examined the morphological methods used through the years to identify species, adhesion mechanisms that contribute to biofilm formation and stability, and how the action of microbicidal molecules is effective against pathological biofilm. Microscopy is the primary technique for the morphological characterization of biofilm. Light microscopy, which includes the stereomicroscope and confocal laser microscopy (CLSM), allows the visualization of microbial communities in their natural state, providing valuable information on the spatial arrangement of different microorganisms within the biofilm and revealing microbial diversity in the biofilm matrix. The stereomicroscope provides a three-dimensional view of the sample, allowing detailed observation of the structure, thickness, morphology, and distribution of the various species in the biofilm while CLSM provides information on its three-dimensional architecture, microbial composition, and dynamic development. Electron microscopy, scanning (SEM) or transmission (TEM), allows the high-resolution investigation of the architecture of the biofilm, analyzing the bacterial population, the extracellular polymeric matrix (EPS), and the mechanisms of the physical and chemical forces that contribute to the adhesion of the biofilm to the substrates, on a nanometric scale. More advanced microscopic methodologies, such as scanning transmission electron microscopy (STEM), high-resolution transmission electron microscopy (HR-TEM), and correlative microscopy, have enabled the evaluation of antibacterial treatments, due to the potential to reveal the efficacy of different molecules in breaking down the biofilm. In conclusion, evidence based on scientific literature shows that established microscopic methods represent the most common tools used to characterize biofilm and its morphology in oral microbiology. Further protocols and studies on the application of advanced microscopic techniques are needed to obtain precise details on the microbiological and pathological aspects of oral biofilm.

An updated view of bacterial endophytes as antimicrobial agents against plant and human pathogens

Bacterial endophytes are a crucial component of the phytomicrobiome, playing an essential role in agriculture and industries. Endophytes are a rich source of bioactive compounds, serving as natural antibiotics that can be effective in combating antibiotic resistance in pathogens. These bacteria interact with host plants through various processes such as quorum sensing, chemotaxis, antibiosis, and enzymatic activity. The current paper focuses on how plants benefit extensively from endophytic bacteria and their symbiotic relationship in which the microbes enhance plant growth, nitrogen fixation, increase nutrient uptake, improve defense mechanisms, and act as antimicrobial agents against pathogens. Moreover, it highlights some of the bioactive compounds produced by endophytes.

Poly(methylmethacrylate-co-dimethyl acrylamide)-silver nanocomposite prevents biofilm formation in medical devices

Aim: To investigate whether medical devices coated with a synthesized nanocomposite of poly(methylmethacrylate-co-dimethyl acrylamide) (PMMDMA) and silver nanoparticles (AgNPs) could improve their antibiofilm and antimicrobial activities. We also investigated the nanocomposite's safety. Materials & methods: The nanocomposite was synthesized and characterized using analytical techniques. Medical devices coated with the nanocomposite were evaluated for bacterial adhesion and hemolytic activity in vitro. Results: The nanocomposite formation was demonstrated with the incorporation of AgNPs into the polymer matrix. The nanocomposite proved to be nonhemolytic and significantly inhibited bacterial biofilm formation. Conclusion: The PMMDMA-AgNPs nanocomposite was more effective in preventing biofilm formation than PMMDMA alone and is a promising strategy for coating medical devices and reducing mortality due to hospital-acquired infections.

Plant-derived bioactive compounds for the inhibition of biofilm formation: a comprehensive review

Biofilm formation is a widespread phenomenon that impacts different fields, including the food industry, agriculture, health care and the environment. Accordingly, there is a serious need for new methods of managing the problem of biofilm formation. Natural products have historically been a rich source of varied compounds with a wide variety of biological functions, including antibiofilm agents. In this review, we critically highlight and discuss the recent progress in understanding the antibiofilm effects of several bioactive compounds isolated from different plants, and in elucidating the underlying mechanisms of action and the factors influencing their adhesion. The literature shows that bioactive compounds have promising antibiofilm potential against both Gram-negative and Gram-positive bacterial and fungal strains, via several mechanisms of action, such as suppressing the formation of the polymer matrix, limiting O2 consumption, inhibiting microbial DNA replication, decreasing hydrophobicity of cell surfaces and blocking the quorum sensing network. This antibiofilm activity is influenced by several environmental factors, such as nutritional cues, pH values, O2 availability and temperature. This review demonstrates that several bioactive compounds could mitigate the problem of biofilm production. However, toxicological assessment and pharmacokinetic investigations of these molecules are strongly required to validate their safety.

Biofilm formation and antioxidation were responsible for the increased resistance of N. eutropha to chloramination for drinking water treatment

Chloramination is an effective strategy for eliminating pathogens from drinking water and repressing their regrowth in water distribution systems. However, the inevitable release of NH4+ potentially promotes nitrification and associated ammonia-oxidizing bacteria (AOB) contamination. In this study, AOB (Nitrosomona eutropha) were isolated from environmental water and treated with two disinfection stages (chloramine disinfection and chloramine residues) to investigate the occurrence mechanisms of AOB in chloramination. The results showed that N. eutropha had considerable resistance to monochloramine compared to Escherichia coli, whose inactivation rate constant was 19.4-fold lower. The higher resistance was attributed to high levels of extracellular polymer substances (EPS) in AOB, which contribute to AOB surviving disinfection and entering the distribution system. In AOB response to the chloramine residues stage, the respiratory activity of N. eutropha remained at a high level after three days of continuous exposure to high chloramine residue concentrations (0.5-1.5 mg/L). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) suggested that the mechanism of N. eutropha tolerance involved a significantly high expression of the intracellular oxidative stress-regulating (sodB, txrA) and protein-related (NE1545, NE1546) genes. Additionally, this process enhanced EPS secretion and promoted biofilm formation. Adhesion predictions based on the XDLVO theory corroborated the trend of biofilm formation. Overall, the naturally higher resistance contributed to the survival of AOB in primary disinfection; the enhanced antioxidant response of surviving N. eutropha accompanied by biofilm formation was responsible for their increased resistance to the residual chloramines.

The Role of Metallurgical Features in the Microbially Influenced Corrosion of Carbon Steel: A Critical Review

Microbially influenced corrosion (MIC) is a potentially critical degradation mechanism for a wide range of materials exposed to environments that contain relevant microorganisms. The likelihood and rate of MIC are affected by microbiological, chemical, and metallurgical factors; hence, the understanding of the mechanisms involved, verification of the presence of MIC, and the development of mitigation methods require a multidisciplinary approach. Much of the recent focus in MIC research has been on the microbiological and chemical aspects, with less attention given to metallurgical attributes. Here, we address this knowledge gap by providing a critical synthesis of the literature on the metallurgical aspects of MIC of carbon steel, a material frequently associated with MIC failures and widely used in construction and infrastructure globally. The article begins by introducing the process of MIC, then progresses to explore the complexities of various metallurgical factors relevant to MIC in carbon steel. These factors include chemical composition, grain size, grain boundaries, microstructural phases, inclusions, and welds, highlighting their potential influence on MIC processes. This review systematically presents key discoveries, trends, and the limitations of prior research, offering some novel insights into the impact of metallurgical factors on MIC, particularly for the benefit of those already familiar with other aspects of MIC. The article concludes with recommendations for documenting metallurgical data in MIC research. An appreciation of relevant metallurgical attributes is essential for a critical assessment of a material's vulnerability to MIC to advance research practices and to broaden the collective knowledge in this rapidly evolving area of study.

Bacteria-surface interactions: role of impacting bacteria-laden droplets

Understanding the interactions of pathogenic droplets with surfaces is crucial to biomedical applications. In this study, using E. coli as the model microbe, we investigate the impact of a bacteria-laden droplet on different substrates, both bare and antimicrobial. In doing so, we unveil the significance of kinetic energy and spreading parameters of the impacting droplet in determining the microbes' proliferation capabilities. Our results indicate an inverse relationship between the impact Weber number and the bacterial ability to proliferate. We reveal that the mechanical stress generated during impact impedes the capabilities of microbes present inside the droplet to create their progeny. Following an order analysis of the mechanical stress generated, we argue that the impact does not induce lysis-driven cell death of the bacteria; rather, it promotes a stress-driven transition of viable bacteria to a viable-but-non-culturable (VBNC) state. Furthermore, variations in the concentration of particles on the antimicrobial surfaces revealed the role of the post-impact spreading behaviour in dictating bacterial proliferation capabilities. Contrary to the conventional notion, we demonstrate that during the early stages of interaction, a bare substrate may outperform an antibacterial substrate in the inactivation of the bacterial load. Finally, we present an interaction map illustrating the complex relationship between bacterial colony-forming units, bactericide concentration on the surface, and the impact Weber number. We believe that the inferences of the study, highlighting the effect of mechanical stresses on the soft cell wall of microbes, could be a useful design consideration for the development of antimicrobial surfaces.

Multitasking functions of bacterial extracellular DNA in biofilms

Bacterial biofilms are intricate ecosystems of microbial communities that adhere to various surfaces and are enveloped by an extracellular matrix composed of polymeric substances. Within the context of bacterial biofilms, extracellular DNA (eDNA) originates from cell lysis or is actively secreted, where it exerts a significant influence on the formation, stability, and resistance of biofilms to environmental stressors. The exploration of eDNA within bacterial biofilms holds paramount importance in research, with far-reaching implications for both human health and the environment. An enhanced understanding of the functions of eDNA in biofilm formation and antibiotic resistance could inspire the development of strategies to combat biofilm-related infections and improve the management of antibiotic resistance. This comprehensive review encapsulates the latest discoveries concerning eDNA, encompassing its origins, functions within bacterial biofilms, and significance in bacterial pathogenesis.

Mechanophysical and Anti-Adhesive Properties of a Nanoclay-Containing PMMA Denture Resin

Poly(methyl methacrylate) (PMMA) is commonly used for dental dentures, but it has the drawback of promoting oral health risks due to oral bacterial adhesion. Recently, various nanoparticles have been incorporated into PMMA to tackle these issues. This study aims to investigate the mechanophysical and antimicrobial adhesive properties of a denture resin by incorporating of nanoclay into PMMA. Specimens were prepared by adding 0, 1, 2, and 4 wt % surface-modified nanoclay (Sigma) to self-polymerizing PMMA denture resin. These specimens were then evaluated using FTIR, TGA/DTG, and FE-SEM with EDS. Various mechanical and surface physical properties, including nanoindentation, were measured and compared with those of pure PMMA. Antiadhesion experiments were conducted by applying a Candida albicans (ATCC 11006) suspension to the surface of the specimens. The antiadhesion activity of C. albicans was confirmed through a yeast-wall component (mannan) and mRNA-seq analysis. The bulk mechanical properties of nanoclay-PMMA composites were decreased compared to those of pure PMMA, while the flexural strength and modulus met the ISO 20795-1 requirement. However, there were no significant differences in the nanoindentation hardness and elastic modulus. The surface energy revealed a significant decrease at 4 wt % nanoclay-PMMA. The antiadhesion effect of Candida albicans was evident along with nanoclay content in the nanocomposites and confirmed by the reduced attachment of mannan on nanoclay-PMMA composites. mRNA-seq analysis supported overall transcriptome changes in altering attachment and metabolism behaviors on the surface. The nanoclay-PMMA materials showed a lower surface energy as the content increased, leading to an antiadhesion effect against Candida albicans. These findings indicate that incorporating nanoclay into PMMA surfaces could be a valuable strategy for preventing the fungal biofilm formation of denture base materials.

Anti-Biofilm Strategies: A Focused Review on Innovative Approaches

Biofilm (BF) can give rise to systemic infections, prolonged hospitalization times, and, in the worst case, death. This review aims to provide an overview of recent strategies for the prevention and destruction of pathogenic BFs. First, the main phases of the life cycle of BF and maturation will be described to identify potential targets for anti-BF approaches. Then, an approach acting on bacterial adhesion, quorum sensing (QS), and the extracellular polymeric substance (EPS) matrix will be introduced and discussed. Finally, bacteriophage-mediated strategies will be presented as innovative approaches against BF inhibition/destruction.

Biological characteristics of mechanosensitive channels MscS and MscL in Actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae is an important respiratory pathogen that can cause porcine contagious pleuropneumonia (PCP), resulting in significant economic losses in swine industry. Microorganisms are subjected to drastic changes in environmental osmolarity. In order to alleviate the drastic rise or fall of osmolarity, cells activate mechanosensitive channels MscL and MscS through tension changes. MscL not only regulates osmotic pressure but also has been reported to secrete protein and uptake aminoglycoside antibiotic. However, MscL and MscS, as the most common mechanosensitive channels, have not been characterized in A. pleuropneumoniae. In this study, the osmotic shock assay showed that MscL increased sodium adaptation by regulating cell length. The results of MIC showed that deletion of mscL decreased the sensitivity of A. pleuropneumoniae to multiple antibiotics, while deletion of mscS rendered A. pleuropneumoniae hypersensitive to penicillin. Biofilm assay demonstrated that MscL contributed the biofilm formation but MscS did not. The results of animal assay showed that MscL and MscS did not affect virulence in vivo. In conclusion, MscL is essential for sodium hyperosmotic tolerance, biofilm formation, and resistance to chloramphenicol, erythromycin, penicillin, and oxacillin. On the other hand, MscS is only involved in oxacillin resistance.IMPORTANCEBacterial resistance to the external environment is a critical function that ensures the normal growth of bacteria. MscL and MscS play crucial roles in responding to changes in both external and internal environments. However, the function of MscL and MscS in Actinobacillus pleuropneumoniae has not yet been reported. Our study shows that MscL plays a significant role in osmotic adaptation, antibiotic resistance, and biofilm formation of A. pleuropneumoniae, while MscS only plays a role in antibiotic resistance. Our findings provide new insights into the functional characteristics of MscL and MscS in A. pleuropneumoniae. MscL and MscS play a role in antibiotic resistance and contribute to the development of antibiotics for A. pleuropneumoniae.

Life at the borderlands: microbiomes of interfaces critical to One Health

Microbiomes are foundational components of the environment that provide essential services relating to food security, carbon sequestration, human health, and the overall well-being of ecosystems. Microbiota exert their effects primarily through complex interactions at interfaces with their plant, animal, and human hosts, as well as within the soil environment. This review aims to explore the ecological, evolutionary, and molecular processes governing the establishment and function of microbiome-host relationships, specifically at interfaces critical to One Health-a transdisciplinary framework that recognizes that the health outcomes of people, animals, plants, and the environment are tightly interconnected. Within the context of One Health, the core principles underpinning microbiome assembly will be discussed in detail, including biofilm formation, microbial recruitment strategies, mechanisms of microbial attachment, community succession, and the effect these processes have on host function and health. Finally, this review will catalogue recent advances in microbiology and microbial ecology methods that can be used to profile microbial interfaces, with particular attention to multi-omic, advanced imaging, and modelling approaches. These technologies are essential for delineating the general and specific principles governing microbiome assembly and functions, mapping microbial interconnectivity across varying spatial and temporal scales, and for the establishment of predictive frameworks that will guide the development of targeted microbiome-interventions to deliver One Health outcomes.