Bacterial Adhesion Research Articles

The nucleoid protein HU positively regulates the expression of type VI secretion systems in Enterobacter cloacae.

T6SS is a nanomachine that functions as a weapon of bacterial destruction crucial for successful colonization in a specific niche. Enterobacter cloacae expresses two T6SSs required for bacterial competition, adherence, biofilm formation, and intestinal colonization. Expression of T6SS genes in pathogenic bacteria is controlled by multiple regulatory systems, including two-component systems, global regulators, and nucleoid proteins. Here, we reported that the HU nucleoid protein directly activates both T6SSs in E. cloacae, affecting the T6SS-related phenotypes. Our data describe HU as a new regulator involved in the transcriptional regulation of T6SS and its impact on E. cloacae pathogenesis.

Acquired enamel pellicle and biofilm engineering with a combination of acid-resistant proteins (CaneCPI-5, StN15, and Hemoglobin) for enhanced protection against dental caries - in vivo and in vitro investigations.

This study was designed in two-legs. In the in vivo, we explored the potential of a rinse solution containing a combination (Comb) of 0.1mg/mL CaneCPI-5 (sugarcane-derive cystatin), 1.88 × 10- 5M StN15 (statherin-derived peptide) and 1.0mg/mL hemoglobin (Hb) to change the protein profile of the acquired enamel pellicle(AEP) and the microbiome of the enamel biofilm. The in vitro, was designed to reveal the effects of Comb on the viability and bacterial composition of the microcosm biofilm, as well as on enamel demineralization. In vivo study, 10 participants rinsed (10mL,1min) with either deionized water (H2O-control) or Comb. AEP and biofilm were collected after 2 and 3h, respectively, after rinsing. AEP samples underwent proteomics analysis, while biofilm microbiome was assessed via 16S-rRNA Next Generation Sequencing(NGS). In vitro study, a microcosm biofilm protocol was employed. Ninety-six enamel specimens were treated with: 1)Phosphate-Buffered Solution-PBS(negative-control), 2)0.12%Chlorhexidine, 3)500ppmNaF and 4)Comb. Resazurin, colony-forming-units(CFU) and Transversal Microradiography(TMR) were performed. The proteomic results revealed higher quantity of proteins in the Comb compared to control associated with immune system response and oral microbial adhesion. Microbiome showed a significant increase in bacteria linked to a healthy microbiota, in the Comb group. In the in vitro study, Comb group was only efficient in reducing mineral-loss and lesion-depth compared to the PBS. The AEP modification altered the subsequent layers, affecting the initial process of bacterial adhesion of pathogenic and commensal bacteria, as well as enamel demineralization. Comb group shows promise in shaping oral health by potentially introducing innovative approaches to prevent enamel demineralization and deter tooth decay.

Generalized Multifunctional Coating Strategies Based on Polyphenol-Amine-Inspired Chemistry and Layer-by-Layer Deposition for Blood Contact Catheters.

Blood-contacting catheters play a pivotal role in contemporary medical treatments, particularly in the management of cardiovascular diseases. However, these catheters exhibit inappropriate wettability and lack antimicrobial characteristics, which often lead to catheter-related infections and thrombosis. Therefore, there is an urgent need for blood contact catheters with antimicrobial and anticoagulant properties. In this study, we employed tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) to create a stable hydrophilic coating under mild conditions. Heparin (Hep) and poly(lysine) (PL) were then modified on the TA-APTES coating surface using the layer-by-layer (LBL) technique to create a superhydrophilic TA/APTES/(LBL)4 coating on silicone rubber (SR) catheters. Leveraging the superhydrophilic nature of this coating, it can be effectively applied to blood-contacting catheters to impart antibacterial, antiprotein adsorption, and anticoagulant properties. Due to Hep's anticoagulant attributes, the activated partial thromboplastin time and thrombin time tests conducted on SR/TA-APTES/(LBL)4 catheters revealed remarkable extensions of 276 and 103%, respectively, when compared to uncoated commercial SR catheters. Furthermore, the synergistic interaction between PL and TA serves to enhance the resistance of SR/TA-APTES/(LBL)4 catheters against bacterial adherence, reducing it by up to 99.9% compared to uncoated commercial SR catheters. Remarkably, the SR/TA-APTES/(LBL)4 catheter exhibits good biocompatibility with human umbilical vein endothelial cells in culture, positioning it as a promising solution to address the current challenges associated with blood-contact catheters.

Film Formation of Iodinated Latex Dispersions and Its Role in Their Antimicrobial Activity.

Waterborne coatings with intrinsic antibacterial attributes have attracted significant attention due to their potential in mitigating microbial contamination while simultaneously addressing the environmental drawbacks of their solvent-based counterparts. Typically, antimicrobial coatings are designed to resist and eliminate microbial threats, encompassing challenges such as biofilm formation, fungal contamination, and proliferation of black mold. Iodine, when solubilized using ethylene glycol and incorporated as a complex into waterborne latex dispersions, has shown remarkable antimicrobial activity. Here, we demonstrate the effect of the film formation process of these iodinated latex dispersions on their antimicrobial properties. The effect of iodine on the surface morphology and mechanical, adhesion, and antimicrobial properties of the generated films was investigated. Complete integration and uniform distribution of iodine in the films were confirmed through UV-vis spectrophotometry and a laser Raman imaging system (LRIS). In terms of properties, iodinated films showed improved mechanical strength and adhesion compared with blank films. Further, the presence of iodine rendered the films rougher, making them susceptible to bacterial adhesion, but interestingly provided enhanced antibiofilm activity. Moreover, thicker films had a lower surface roughness and reduced biofilm growth. These observations are elucidated through the complex interplay among film thickness, surface morphology, and iodine properties. The insights into the interlink between the film formation process and antimicrobial properties of iodinated latex dispersions will facilitate their enhanced application as sustainable alternatives to solvent-based coatings.

Biofilm Growth on Orthopaedic Cerclage Materials: Nonmetallic Polymers Are Less Resistant to Methicillin-Resistant Staphylococcus Aureus Bacterial Adhesion

BackgroundData on bacterial adhesion to cerclage cables are sparse. We aimed to compare 5 cerclage products for methicillin-resistant Staphylococcus aureus (MRSA) adhesion to determine the claim: Are nonmetallic polymer cables more resistant to bacterial adhesion than common metallic wires and cables? MethodsThe following 5 cerclage products were compared: (1) monofilament stainless steel (SS) wires; (2) multifilament SS cables; (3) multifilament cobalt chrome cables; (4) multifilament Vitallium alloy (cobalt-chrome-molybdenum [Co-Cr-Mo]) cables; and (5) multifilament nonmetallic polymer cables. Each was cut into 2 cm lengths and placed into 12-well plates. Of the wells, 5 were wire or cables in trypticase soy broth with MRSA, with the remaining wells being appropriate controls incubated for 24 hours at 37° C and 5% CO2 with shaking. Wires and cables were prepared and randomly imaged via scanning electron microscopy, with bacterial counts performed on 3 images of 3 different wires or cables per study group. The scanning electron microscopy technician and counting investigator were blinded. Additionally, SS wire and polymer cables were analyzed by microcalorimetry for metabolic activity and bacterial load. ResultsBacterial attachment differed significantly between study groups in the middle section (P = .0003). Post hoc comparison showed no difference between groups individually (all P > .05) apart from polymer cables (median 551 bacteria) having significantly increased attached bacteria compared to the Vitallium alloy cable (157, P = .0004), SS cable (101, P = .0004), and SS wire (211, P = .0004). There was no difference between polymer and cobalt chrome cables (133, P = .056). Microcalorimetry supported these results, as polymer cables had a shorter time to max heat flow (6.2 versus 7.5 hours, P = .006), increased max heat flow (117 versus 64 uW, P = .045), and increased colony-forming units, indicating an increased bacterial load compared to SS wires. ConclusionsThis in vitro study demonstrated that polymer cables have increased MRSA adhesion compared to common metallic wires and cables. Future studies are necessary to confirm the translation of increased bacterial adherence on polymer cables to increased rates of orthopaedic infections.

Enhancing antibacterial properties of titanium implants through a novel Ag-TiO2-OTS nanocomposite coating: a comprehensive study on resist-killing-disintegrate approach

Titanium (Ti) implants are widely used in orthopedic and dental applications due to their excellent biocompatibility and mechanical properties. However, bacterial adhesion and subsequent biofilm formation on implant surfaces pose a significant risk of postoperative infections and complications. Conventional surface modifications often lack long-lasting antibacterial efficacy, necessitating the development of novel coatings with enhanced antimicrobial properties. This study aims to develop a novel Ag-TiO2-OTS (Silver-Titanium dioxide-Octadecyltrichlorosilane, ATO) nanocomposite coating, through a chemical plating method. By employing a ‘resist-killing-disintegrate’ approach, the coating is designed to inhibit bacterial adhesion effectively, and facilitate pollutant removal with lasting effects. Characterization of the coatings was performed using spectroscopy, electron microscopy, and contact angle analysis. Antibacterial efficacy, quantitatively evaluated against E. coli and S. aureus over 168 h, showed a significant reduction in bacterial adhesion by 76.6% and 66.5% respectively, and bacterial removal rates were up to 83.8% and 73.3% in comparison to uncoated Ti-base material. Additionally, antibacterial assays indicated that the ratio of the Lifshitz-van der Waals apolar component to electron donor surface energy components significantly influences bacterial adhesion and removal, underscoring a tunable parameter for optimizing antibacterial surfaces. Biocompatibility assessments with the L929 cell line revealed that the ATO coatings exhibited excellent biocompatibility, with minimal cytotoxicity and no significant impact on cell proliferation or apoptosis. The ATO coatings provided a multi-functionality surface that not only resists bacterial colonization but also possesses self-cleaning capabilities, thereby marking a substantial advancement in the development of antibacterial coatings for medical implants.

Ag@Co/Zn N‐Doped Carbon as Antibacterial Oxygen Reduction Catalysts for Microbial Fuel Cells

Biofouling of air cathode surface decreases the electricity generation performance of membrane‐free microbial fuel cells (MFCs). Ag@Co/Zn N‐doped carbon (Ag@Co/Zn‐NC) is designed as an antibacterial oxygen reduction reaction (ORR) catalyst to inhibit biofouling on the cathode surface. The Co/Zn‐NC active component promotes ORR catalytic activity through the advantages of well‐distributed Co nanoparticles and numerous active sites. Superficial Ag nanoparticles act as antibacterial active species to inhibit bacterial proliferation and suppress biofilm growth. Ag@Co/Zn‐NC catalyst prevents bacterial adhesion and biofilm formation, effectively preventing excessive biofouling on the cathode surface. The antibacterial catalyst maintains a high catalytic activity and good ion diffusion properties without the adverse effects of biofouling, resulting in enhanced ORR durability of the air cathode. The assembled MFCs achieve high electricity generation during long‐term cyclic operation. The maximum power density retention percentage (82.6%) is higher than that of Co/Zn‐NC MFC (65.3%) and Pt/C MFC (52.4%) after continuous operation for 1200 h. Excellent operational durability is revealed for the air‐cathode MFCs assembled with the antibacterial ORR catalyst during the cyclic process. The novelty of this study is that the design of antibacterial catalysts inhibits the excessive growth of the cathode biofilm to improve the cyclic electricity generation performance of MFCs.

Electrospun superhydrophobic polyvinyl chloride /polydimethylsiloxane-nanodiamond nanocomposite with enhanced antifouling and mechanical properties for fresh produce packaging

Food package films serve the important functions of preserving food quality, extending shelf life, and protecting against external contaminants while also providing a barrier to moisture and oxygen. In consideration of the increasing frequency of foodborne outbreaks, there is a growing demand for food packaging films with additional functionality to prevent cross-contamination and the attachment of pathogens, thereby enhancing bacterial safety. Herein, we report a one-step fabrication approach relying on electrospinning of a blend of polyvinyl chloride (PVC) and polydimethylsiloxane (PDMS) together with nanodiamond (ND) on a rotating drum collector for the formation of bacterially antifouling food package films. In this approach, by adjusting the concentrations of PVC, PDMS, and ND and the drum angular velocity, the nanofiber diameter could be tuned in the range of 0.4 μm to 2.0 μm. Furthermore, these process parameters could also be used to modulate the water contact angle on the resultant films, with a minimum contact angle of 136.2 ± 5.6° and a maximum of 159.5 ± 3.8°. The lowest water contact angles were observed for films with bare PVC fibers while the highest contact angles were seen for films with nanocomposite fibers containing ND and PVC/PDMS. Compared with the films with bare PVC, nanocomposite films with ND-PVC/PDMS achieved up to 99.8 % and 99.6 % reduction in bacterial adhesion against S. typhimurium LT2 and Listeria innocua, respectively. The tensile strength of nanofibrous PVC film can be increased from 1.2 ± 0.4 MPa to 4.4 ± 0.3 MPa by the inclusion of PDMS (1:1 wt.%) and further increased to 8.9 ± 0.3 MPa with the additional inclusion of ND (PVC/PDMS/ND 1:1:0.1 wt.%). Considering the notable antifouling properties against bacteria and the improved mechanical characteristics, these nanocomposite films represent a noteworthy step in the development of sustainable and active food packaging solutions for a safer and healthier food supply chain.

Optogenetic Control of Bacterial Cell-Cell Adhesion Dynamics: Unraveling the Influence on Biofilm Architecture and Functionality.

The transition of bacteria from an individualistic to a biofilm lifestyle profoundly alters their biology. During biofilm development, the bacterial cell-cell adhesions are a major determinant of initial microcolonies, which serve as kernels for the subsequent microscopic and mesoscopic structure of the biofilm, and determine the resulting functionality. In this study, the significance of bacterial cell-cell adhesion dynamics on bacterial aggregation and biofilm maturation is elucidated. Using photoswitchable adhesins between bacteria, modifying the dynamics of bacterial cell-cell adhesions with periodic dark-light cycles is systematic. Dynamic cell-cell adhesions with liquid-like behavior improve bacterial aggregation and produce more compact microcolonies than static adhesions with solid-like behavior in both experiments and individual-based simulations. Consequently, dynamic cell-cell adhesions give rise to earlier quorum sensing activation, better intermixing of different bacterial populations, improved biofilm maturation, changes in the growth of cocultures, and higher yields in fermentation. The here presented approach of tuning bacterial cell-cell adhesion dynamics opens the door for regulating the structure and function of biofilms and cocultures with potential biotechnological applications.

Development of a visual Adhesion/Invasion Inhibition Assay to assess the functionality of Shigella-specific antibodies.

Shigella is the etiologic agent of a bacillary dysentery known as shigellosis, which causes millions of infections and thousands of deaths worldwide each year due to Shigella's unique lifestyle within intestinal epithelial cells. Cell adhesion/invasion assays have been extensively used not only to identify targets mediating host-pathogen interaction, but also to evaluate the ability of Shigella-specific antibodies to reduce virulence. However, these assays are time-consuming and labor-intensive and fail to assess differences at the single-cell level. Here, we developed a simple, fast and high-content method named visual Adhesion/Invasion Inhibition Assay (vAIA) to measure the ability of anti-Shigellaantibodies to inhibit bacterial adhesion to and invasion of epithelial cells by using the confocal microscope Opera Phenix. We showed that vAIA performed well with a pooled human serum from subjects challenged with S. sonnei and that a specific anti-IpaD monoclonal antibody effectively reduced bacterial virulence in a dose-dependent manner. vAIA can therefore inform on the functionality of polyclonal and monoclonal responses thereby supporting the discovery of pathogenicity mechanisms and the development of candidate vaccines and immunotherapies. Lastly, this assay is very versatile and may be easily applied to other Shigella species or serotypes and to different pathogens.

Novel Lactic Acid Bacteria Strains from Regional Peppers with Health-Promoting Potential

This study provides a comprehensive investigation of lactic acid bacteria (LAB) isolated from Argentinean Capsicum annum L. This research covers important aspects, including genotypic characterization, bacterial stress tolerance, adhesion ability, safety evaluation, and functional and technological properties. The predominant isolates were identified as Lactilactobacillus curvatus and Lactiplantibacillus plantarum. A Rep-PCR analysis grouped the isolates into 11 clonal groups. Lp. plantarum LVP 40 and LV 46, Levilactobacillus brevis LVP 41, Pediococcus pentosaceus LV P43, and Lt. curvatus LVP44 displayed both safety and resilience against adverse conditions such as a slow pH, bile, and simulated gastric and intestinal juices. Moreover, the LAB strains exhibited high hydrophobicity and auto-aggregation percentages, NaCl tolerance, and a substantial acidifying capacity. LAB supernatants demonstrated promising surfactant and emulsifying properties. Likewise, they differentially inhibited Staphylococcus aureus and Pseudomonas aeruginosa biofilms, showcasing their potential as antipathogenic agents. Noteworthily, some strains displayed considerable co-aggregation with these pathogens, and several isolates showed an effective antimutagenic and detoxifying power, further emphasizing their multifaceted capabilities. Five pepper bacterial strains showcased beneficial properties, suggesting their potential for gut health enhancement. In summary, these LAB strains hold promise as vegetable fermentation starters, contributing to food safety and versatile applications in food science.

In vitro anti-Helicobacter pylori activity and antivirulence activity of cetylpyridinium chloride.

The primary treatment method for eradicating Helicobacter pylori (H. pylori) infection involves the use of antibiotic-based therapies. Due to the growing antibiotic resistance of H. pylori, there has been a surge of interest in exploring alternative therapies. Cetylpyridinium chloride (CPC) is a water-soluble and nonvolatile quaternary ammonium compound with exceptional broad-spectrum antibacterial properties. To date, there is no documented or described specific antibacterial action of CPC against H. pylori. Therefore, this study aimed to explore the in vitro activity of CPC against H. pylori and its potential antibacterial mechanism. CPC exhibited significant in vitro activity against H. pylori, with MICs ranging from 0.16 to 0.62 μg/mL and MBCs ranging from 0.31 to 1.24 μg/mL. CPC could result in morphological and physiological modifications in H. pylori, leading to the suppression of virulence and adherence genes expression, including flaA, flaB, babB, alpA, alpB, ureE, and ureF, and inhibition of urease activity. CPC has demonstrated in vitro activity against H. pylori by inhibiting its growth, inducing damage to the bacterial structure, reducing virulence and adherence factors expression, and inhibiting urease activity.

New strontium-based coatings show activity against pathogenic bacteria in spine infection.

Infections of implants and prostheses represent relevant complications associated with the implantation of biomedical devices in spine surgery. Indeed, due to the length of the surgical procedures and the need to implant invasive devices, infections have high incidence, interfere with osseointegration, and are becoming increasingly difficult to threat with common therapies due to the acquisition of antibiotic resistance genes by pathogenic bacteria. The application of metal-substituted tricalcium phosphate coatings onto the biomedical devices is a promising strategy to simultaneously prevent bacterial infections and promote osseointegration/osseoinduction. Strontium-substituted tricalcium phosphate (Sr-TCP) is known to be an encouraging formulation with osseoinductive properties, but its antimicrobial potential is still unexplored. To this end, novel Sr-TCP coatings were manufactured by Ionized Jet Deposition technology and characterized for their physiochemical and morphological properties, cytotoxicity, and bioactivity against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P human pathogenic strains. The coatings are nanostructured, as they are composed by aggregates with diameters from 90nm up to 1μm, and their morphology depends significantly on the deposition time. The Sr-TCP coatings did not exhibit any cytotoxic effects on human cell lines and provided an inhibitory effect on the planktonic growth of E. coli and S. aureus strains after 8h of incubation. Furthermore, bacterial adhesion (after 4h of exposure) and biofilm formation (after 24h of cell growth) were significantly reduced when the strains were cultured on Sr-TCP compared to tricalcium phosphate only coatings. On Sr-TCP coatings, E. coli and S. aureus cells lost their organization in a biofilm-like structure and showed morphological alterations due to the toxic effect of the metal. These results demonstrate the stability and anti-adhesion/antibiofilm properties of IJD-manufactured Sr-TCP coatings, which represent potential candidates for future applications to prevent prostheses infections and to promote osteointegration/osteoinduction.

Creating Anti‐Biofouling Surfaces by Degradable Main‐chain Polyphosphoester Polymer Brushes

AbstractThe implementation of polymer brush coatings has proven crucial in biomedical and biotechnological applications for controlling biological interactions. Despite the extensive research and use of synthetic polymer coatings, concerns regarding their long‐term non‐biodegradability have arisen. This issue is significant as non‐degradable polymers can lead to complications such as inflammatory responses and bioaccumulation, highlighting the need for polymers that degrade in a controlled manner. To address this, polyphosphonate brushes are synthesized as anti‐biofouling coatings on silicon surfaces via controlled surface‐initiated organocatalytic ring‐opening polymerization (SI‐ROP) of cyclic phospholanes. 2‐Ethyl‐2‐oxo‐1,3,2‐dioxaphospholane and 2‐hexyl‐2‐oxo‐1,3,2‐dioxaphospholane are chosen as the monomers to prepare hydrophilic and hydrophobic brushes with thicknesses up to 55 nm, with a proven degradability in aqueous media. In addition, protein adsorption, bacterial adhesion, and biofilm formation are investigated as a function of the polyphosphonate side chain. Compared to non‐coated surfaces and polyester brushes, hydrophilic poly(2‐ethyl‐2‐oxo‐1,3,2‐dioxaphospholane) brushes have an enhanced resistance toward fouling of albumin, fibrinogen, and diluted human serum proteins, as well as toward Escherichia coli and Staphylococcus aureus bacteria. The stability and anti‐biofouling performance of hydrophilic polyphosphonate brushes position them as an attractive option as degradable materials for anti‐biofouling matrices on medical devices and/or lubricious coatings for artificial implant technologies.

Role of Staphylococcus aureus's Buoyant Density in the Development of Biofilm Associated Antibiotic Susceptibility.

Biofilms are clusters of microorganisms that form at various interfaces, including those between air and liquid or liquid and solid. Due to their roles in enhancing wastewater treatment processes, and their unfortunate propensity to cause persistent human infections through lowering antibiotic susceptibility, understanding and managing bacterial biofilms is of paramount importance. A pivotal stage in biofilm development is the initial bacterial attachment to these interfaces. However, the determinants of bacterial cell choice in colonizing an interface first and heterogeneity in bacterial adhesion remain elusive. Our research has unveiled variations in the buoyant density of free-swimming Staphylococcus aureus cells, irrespective of their growth phase. Cells with a low cell buoyant density, characterized by fewer cell contents, exhibited lower susceptibility to antibiotic treatments (100 μg/mL vancomycin) and favored biofilm formation at air-liquid interfaces. In contrast, cells with higher cell buoyant density, which have richer cell contents, were more vulnerable to antibiotics and predominantly formed biofilms on liquid-solid interfaces when contained upright. Cells with low cell buoyant density were not able to revert to a more antibiotic sensitive and high cell buoyant density phenotype. In essence, S. aureus cells with higher cell buoyant density may be more inclined to adhere to upright substrates.

Mussel-Inspired Antimicrobial and Antifouling Coating Constructed by the Combination of Zwitterionic Copolymers and Silver Nanoparticles.

Biofouling and bacterial infections are significant challenges in biomedical devices. In this study, a biocompatible dual-functional coating with antimicrobial and antifouling properties is developed by co-depositing the zwitterionic copolymer and silver nanoparticles via a dopamine-assisted strategy. Inspired by mussel adhesion, the coating exhibits substrate-independent adhesion as a result of the formation of irreversible covalent bonds. The zwitterionic copolymer in the dual coating plays a crucial role in improving surface wettability and reducing protein adsorption and platelet and bacterial adhesion, thereby improving its antifouling property significantly. The silver nanoparticles reduced by self-polymerized polydopamine without the addition of any chemical reductants can effectively improve the antimicrobial activity. Furthermore, as the zwitterion content in the zwitterion polymer increases, the antibacterial and antifouling properties of the coating can be further advanced. The simple and effective approach presented here provides a promising pathway for constructing potent antibacterial and antifouling surfaces, demonstrating great potential for clinical applications in implanted materials.

Phytosphingosine, a new ingredient for oral care products?

Despite the availability of a wide range of (fluoridated) oral care products, there is a constant search under way for new substances that contribute to a healthy mouth. Laboratory research shows that the lipid phytosphingosine forms a molecular layer on hydroxyapatite and protects it against acid-induced demineralization and bacterial adhesion. In the future, phytosphingosine may be used in the future as a new ingredient in oral care products for the prevention of tooth erosion and biofilm-related disorders, such as caries, gingivitis and periodontitis.

FORMATION OF NANOCONES AND GENERATION OF NEGATIVE POTENTIAL ON STAINLESS STEEL SURFACES BY ELECTROCHEMICAL ETCHING SYNERGISTICALLY REDUCE PSEUDOMONAS AERUGINOSA'S BIOFILM

Hospital-acquired infections cause severe patient problems because of the augmented appearance of antibiotic-resistant bacteria, including Pseudomonas aeruginosa. Material surfaces modified with several biophysical parameters can decrease bacterial biofilm formation, which could be an advantageous alternative to treatment with antibiotics. Since stainless steel is an extensively used material for manufacturing medical implants and in healthcare settings, in this study, we used stainless steel (SS 316L and SS 304) to examine the result of the material surface topographies on bacterial biofilm establishment. This work used the electrochemical etching method to modify the stainless steel surface topography as an anode. The electrochemical etching method influenced the nanocones’ formation on stainless steel surfaces of both SS316L (Disk-6: 2682 peaks/[Formula: see text]m[Formula: see text] and SS304 (Disk-12: 1654 peaks/[Formula: see text]m[Formula: see text] estimated by atomic force microscopy and 3D Profilometer reduced the biofilm by 78% and 85%, respectively. Additionally, the higher negative potential on an average of 600[Formula: see text]mV measured by Kelvin probe atomic force microscopy reduced the biofilm formation on both SS316L and SS304 surface synergistically compared to the non-electrochemically etched surface. Biofilm growth and nanopotrusions on the stainless-steel surface examined by atomic force microscopy and scanning electron microscopy demonstrated significantly dead bacterial cells (20%) on the electrochemically etched surface than on the non-electrochemically etched surface after 2[Formula: see text]h contact time. Our observations exhibit that the nanotextured surface topographies and surface negative potential effectively inhibit bacterial adhesion and biofilm formation.

Significance of a minor pilin PilV in biofilm cohesion of Geobacter sulfurreducens

Bacterial adhesion plays a vital role in forming and shaping the structure of electroactive biofilms that are essential for the performance of bioelectrochemical systems (BESs). Type IV pili are known to mediate cell adhesion in many Gram-negative bacteria, but the mechanism of pili-mediated cell adhesion of Geobacter species on anode surface remains unclear. Herein, a minor pilin PilV2 was found to be essential for cell adhesion ability of Geobacter sulfurreducens since the lack of pilV2 gene depressed the cell adhesion capability by 81.2% in microplate and the anodic biofilm density by 23.1 % at −0.1 V and 37.7 % at −0.3 V in BESs. The less cohesiveness of mutant biofilms increased the charge transfer resistance and biofilm resistance, which correspondingly lowered current generation of the pilV2-deficient strain by up to 63.2 % compared with that of the wild-type strain in BESs. The deletion of pilV2 posed an insignificant effect on the production of extracellular polysaccharides, pili, extracellular cytochromes and electron shuttles that are involved in biofilm formation or extracellular electron transfer (EET) process. This study demonstrated the significance of pilV2 gene in cell adhesion and biofilm formation of G. sulfurreducens, as well as the importance of pili-mediated adhesion for EET of electroactive biofilm.

Visible light-induced photocatalytic and antibacterial adhesion properties of superhydrophilic TiO2 nanoparticles

Bacterial infections triggered by patient or healthcare worker contact with surfaces are a major cause of medically acquired infections. By controlling the kinetics of tetrabutyl titanate hydrolysis and condensation during the sol–gel process, it is possible to regulate the content of Ti3+ and oxygen vacancies (OVs) in TiO2, and adjust the associated visible light-induced photocatalytic performance and anti-bacterial adhesion properties. The results have shown that the Ti3+ content in TiO2 was 9.87% at the calcination temperature of the reaction system was 300 °C and pH was 1.0, corresponding to optimal photocatalytic and hydrophilic properties. The formation of a hydrated layer on the superhydrophilic surface provided resistance to bacterial adhesion, preventing cross-contamination on high-touch surfaces. The excellent photocatalytic self-cleaning performance and anti-bacterial adhesion properties can be attributed to synergistic effects associated with the high specific surface area of TiO2 nanoparticles, the mesoporous structure, and the presence of Ti3+ and OVs. The formation of superhydrophilic self-cleaning surfaces under visible light can serve as the basis for the development of a new class of anti-bacterial adhesion materials.