Influence of Surface Properties on the Adhesion of Staphylococcus epidermidis to Acrylic and Silicone

Amorphous TiO2nano-coating on stainless steel to improve its biological response

This study delves into the potential of amorphous titanium oxide (aTiO2) nano-coating to enhance various critical aspects of non-Ti-based metallic orthopedic implants. These implants, such as medical-grade stainless steel (SS), are widely used for orthopedic devices that demand high strength and durability. The aTiO2nano-coating, deposited via magnetron sputtering, is a unique attempt to improve the osteogenesis, the inflammatory response, and to reduce bacterial colonization on SS substrates. The study characterized the nanocoated surfaces (SS-a TiO2) in topography, roughness, wettability, and chemical composition. Comparative samples included uncoated SS and sandblasted/acid-etched Ti substrates (Ti). The biological effects were assessed using human mesenchymal stem cells (MSCs) and primary murine macrophages. Bacterial tests were carried out with two aerobic pathogens (S. aureusandS. epidermidis) and an anaerobic bacterial consortium representing an oral dental biofilm. Results from this study provide strong evidence of the positive effects of the aTiO2nano-coating on SS surfaces. The coating enhanced MSC osteoblastic differentiation and exhibited a response similar to that observed on Ti surfaces. Macrophages cultured on aTiO2nano-coating and Ti surfaces showed comparable anti-inflammatory phenotypes. Most significantly, a reduction in bacterial colonization across tested species was observed compared to uncoated SS substrates, further supporting the potential of aTiO2nano-coating in biomedical applications. The findings underscore the potential of magnetron-sputtering deposition of aTiO2nano-coating on non-Ti metallic surfaces such as medical-grade SS as a viable strategy to enhance osteoinductive factors and decrease pathogenic bacterial adhesion. This could significantly improve the performance of metallic-based biomedical devices beyond titanium.

Microbiological evaluation of conjunctival anopthalmic flora after using digital 3D-printed ocular prosthesis compared to conventional one: a randomized clinical trial

BACKGROUND

This study aims to assess the influence of using 3D-printed acrylic resin versus conventional Poly-methyl methacrylate (PMMA) for fabricating ocular prostheses on the biofilm and microbial flora of anophthalmic socket.

METHODS

A randomized controlled trial was designed as a parallel group study. Participants were allocated randomly into two groups: the control group, which received conventionally fabricated ocular prostheses (CG, n = 11), and the test group, which received digitally 3D-printed ocular prostheses (DG, n = 11). Microbiological analysis was conducted before prosthesis insertion and three months after using the ocular prosthesis. Swab samples were inoculated on blood agar, MacConkey's agar, and Sabouraud's dextrose agar (SDA) for isolating Gram-positive, Gram-negative, and fungal organisms, respectively. Subsequently, the plates were incubated at 37 degrees Celsius for 48 h. Additionally, a validated questionnaire was used for subjective clinical evaluation, including parameters such as comfort level, socket discharge, lacrimation, and frequency of lubrication for each ocular prosthesis patient in both groups.

RESULTS

Test group (DG, n = 11) exhibited a positive, though statistically insignificant, difference (p > 0.001) in microbial growth when compared to the control group (CG, n = 11). A statistically significant difference was observed in comfort levels between the two groups, with more comfort level within group II (test group) patients. While parameters such as discharge amount, discharge location, lacrimation and lubrication frequency displayed statistically insignificant differences between the two groups, all parameters showed improved results after three months of prosthesis use.

CONCLUSIONS

The choice of ocular prosthesis fabrication technique did not yield a statistically significant difference in anophthalmic flora. However, the 3D-printed acrylic resin, as an artificial eye material, displayed potential advantages in reducing the colonization of opportunistic pathogens. All subjective clinical evaluation parameters exhibited enhanced outcomes after three months of prosthesis use, emphasizing the need for an adaptation period during which patients complains are alleviated. In comparison with PMMA, 3D-printed acrylic resin showcased a certain degree of anti-colonization ability against pathogenic bacteria, along with a significant level of patient comfort, suggesting its potential as a promising material for ocular prostheses.

TRIAL REGISTRATION

This parallel double-blinded RCT has been registered at ClinicalTrials.gov with identification number: NCT05584865, 18/10/2022.

phoP maintains the environmental persistence and virulence of pathogenic bacteria in mechanically stressed desiccated droplets

Despite extensive studies on kinematic features of impacting drops, the effect of mechanical stress on desiccated bacteria-laden droplets remains unexplored. In the present study, we unveiled the consequences of the impaction of bacteria-laden droplets on solid surfaces and their subsequent desiccation on the virulence of an enteropathogen Salmonella typhimurium (STM). The methodology elucidated the deformation, cell-cell interactions, adhesion energy, and roughness in bacteria induced by impact velocity and low moisture because of evaporation. Salmonella retrieved from the dried droplets were used to understand fomite-mediated pathogenesis. The impact velocity-induced mechanical stress deteriorated the in vitro viability of Salmonella. Of interest, an uninterrupted bacterial proliferation was observed in macrophages at higher mechanical stress. Wild-type Salmonella under mechanical stress induced the expression of phoP whereas infecting macrophages. The inability of STM ΔphoP to grow in nutrient-rich dried droplets signifies the role of phoP in sensing the mechanical stress and maintaining the virulence of Salmonella.

Improving biomass and carbohydrate production of microalgae in the rotating cultivation system on natural carriers

Biofilm-based algal technologies have gained popularity due to higher biomass productivity, efficient harvesting, and water-saving over suspended growth systems. A rotating attached system was designed to assess the biofilm-forming capacity of different isolated microalgal strains from the Persian Gulf. Four microalgal strains, including two Chlorella sp., one Picochlorum sp. and one filamentous cyanobacterium Desmonostoc sp. were cultivated on four carriers: jute, cotton, yarn and nylon. The carriers' physicochemical surface characteristics and attachment effects, like contact angle, were investigated. The incorporated biomass and exopolysaccharides (EPS) content in the suspended and biofilm system was calculated and compared. The results showed that the cyanobacterium strain had the biofilm formation capability on both jute and cotton in the attached cultivation system. Under the same culture conditions, the biomass productivity on jute and cotton carriers was significantly higher (4.76 and 3.61 g m^- 2 respectively) than the growth in aqueous suspension (1.19 g m^- 2 d^- 1). The greatest incorporated exopolysaccharides amount was observed on jute (43.62 ± 4.47%) and the lowest amount was obtained from the growth on positive charge yarn (18.62 ± 1.88%). This study showed that in comparison with planktonic growth, the colonization of cyanobacterial cells and subsequent production of extracellular matrix and biofilm formation can lead to increased biomass production.

Role of surface physicochemical properties of pipe materials on bio-clogging in leachate collection systems from a thermodynamic perspective

Bio-clogging in pipes poses a significant threat to the operation of leachate collection systems. Bio-clogging formation is influenced by the pipe materials. However, the relationship between bio-clogging and the physicochemical properties of different pipe materials has not been clarified yet, especially from a thermodynamic aspect. In this study, the dynamic bio-clogging processes in pipes of different materials (high-density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE)) were compared, and their correlation with the physicochemical properties was investigated. Results showed that the bio-clogging in HDPE and PVC pipes was more severe than that in PP and PE pipes. In bio-clogging development, the predominant factor changed from the surface roughness to the electron donator parameter (γ^-). In the initial phase, the most severe bio-clogging was observed in the HDPE pipe, which exhibited the highest roughness (432 ± 76 nm). In the later phase, the highest γ^- (2.2 mJ/m²) and protein content (2623.1 ± 33.2 μg/cm²) were observed in the PVC simultaneously. Moreover, the interaction energy indicated that the bacteria could irreversibly and reversibly adhere to the HDPE, whereas irreversible adhesion was observed in the PVC, PP, and PE cases. The findings clarify the thermodynamic mechanism underlying bio-clogging behaviors and provide novel insights into the bio-clogging behaviors in pipes of different materials, which can facilitate the development of effective bio-clogging control strategies.

The Inflammation Level and a Microbiological Analysis of the Anophthalmic Cavities of Unilateral Ocular Prosthesis Users: A Blind, Randomized Observational Study

Irritation and biofilm adhesion are complaints associated with ocular prosthesis use. This study aimed to evaluate the effects of prosthesis repolishing on several conditions of anophthalmic volunteers. Participants were divided into two groups: intervention (IG, n = 10) and nonintervention (NIG, n = 6) groups. The anophthalmic cavity, contralateral eye, and prosthesis surface were evaluated at initial, day 15, and day 30 after repolishing. Microbiological analysis (colony-forming units), exfoliative cytology (conjunctiva inflammatory cells), sensory analysis (quantitative mechanical sensory test), tear production (Schirmer’s test), and conjunctival inflammation (clinical evaluation) were performed. Nonparametric tests were used to compare groups in the initial period and to analyze periods for the IG (p < 0.05). More microorganisms were formed in the anophthalmic socket and prosthesis than in the contralateral eye in the initial period. For IG, the anophthalmic cavity exhibited more microorganisms and inflammatory clinical signs in the initial period than at 15 and 30 after repolishing. The prosthesis showed greater accumulations of total bacteria and Candida albicans in the initial period than at 15 and 30 days after repolishing. The anophthalmic cavity had more palpebral inflammation than the contralateral eye. In conclusion, repolishing reduced the number of microorganisms and inflammatory signs over time.

Surface Free Energy Dominates the Biological Interactions of Postprocessed Additively Manufactured Ti-6Al-4V

Additive manufacturing (AM) has emerged as a disruptive technique within healthcare because of its ability to provide personalized devices; however, printed metal parts still present surface and microstructural defects, which may compromise mechanical and biological interactions. This has made physical and/or chemical postprocessing techniques essential for metal AM devices, although limited fundamental knowledge is available on how alterations in physicochemical properties influence AM biological outcomes. For this purpose, herein, powder bed fusion Ti-6Al-4V samples were postprocessed with three industrially relevant techniques: polishing, passivation, and vibratory finishing. These surfaces were thoroughly characterized in terms of roughness, chemistry, wettability, surface free energy, and surface ζ-potential. A significant increase in Staphylococcus epidermidis colonization was observed on both polished and passivated samples, which was linked to high surface free energy donor γ^– values in the acid–base, γ^AB component. Early osteoblast attachment and proliferation (24 h) were not influenced by these properties, although increased mineralization was observed for both these samples. In contrast, osteoblast differentiation on stainless steel was driven by a combination of roughness and chemistry. Collectively, this study highlights that surface free energy is a key driver between AM surfaces and cell interactions. In particular, while low acid–base components resulted in a desired reduction in S. epidermidis colonization, this was followed by reduced mineralization. Thus, while surface free energy can be used as a guide to AM device development, optimization of bacterial and mammalian cell interactions should be attained through a combination of different postprocessing techniques.

Modeling Bacterial Attachment Mechanisms on Superhydrophobic and Superhydrophilic Substrates

Superhydrophilic and superhydrophobic substrates are widely known to inhibit the attachment of a variety of motile and/or nonmotile bacteria. However, the thermodynamics of attachment are complex. Surface energy measurements alone do not address the complexities of colloidal (i.e., bacterial) dispersions but do affirm that polar (acid-base) interactions (ΔGAB) are often more significant than nonpolar (Lifshitz-van der Waals) interactions (ΔGLW). Classical DLVO theory alone also fails to address all colloidal interactions present in bacterial dispersions such as ΔGAB and Born repulsion (ΔGBorn) yet accounts for the significant electrostatic double layer repulsion (ΔGEL). We purpose to model both motile (e.g., P. aeruginosa and E. coli) and nonmotile (e.g., S. aureus and S. epidermidis) bacterial attachment to both superhydrophilic and superhydrophobic substrates via surface energies and extended DLVO theory corrected for bacterial geometries. We used extended DLVO theory and surface energy analyses to characterize the following Gibbs interaction energies for the bacteria with superhydrophobic and superhydrophilic substrates: ΔGLW, ΔGAB, ΔGEL, and ΔGBorn. The combination of the aforementioned interactions yields the total Gibbs interaction energy (ΔGtot) of each bacterium with each substrate. Analysis of the interaction energies with respect to the distance of approach yielded an equilibrium distance (deq) that seems to be independent of both bacterial species and substrate. Utilizing both deq and Gibbs interaction energies, substrates could be designed to inhibit bacterial attachment.

Growth of Staphylococcus epidermidis on the Surface of Teatcups from Milking Parlours

The growth of two Staphylococcus epidermidis isolates (one biofilm-forming and one not) on teatcups for cattle (made of rubber) or sheep (made of silicone) were assessed in nine multiplicates for 24 h post-smearing on the teatcup surface. Staphylococci were smeared on an area of 0.0003142 m² on the material and their growth and expansion further on were monitored for 24 h. There were no differences in the frequency of recoveries between the two isolates (p > 0.82 for all comparisons). There were more recoveries from sheep teatcups than from cattle teatcups: 1280/1728 (74.1%) versus 942/1728 (54.5%), for both isolates (p < 0.0001). Significance was observed only 6 h to 15 h after smearing (p < 0.0001 for all comparisons). The median speed of linear dissemination of the isolates was 0.00000021 m s⁻¹ on cattle teatcups and 0.00000033 m s⁻¹ on sheep teatcups (p < 0.0001). The increased growth and faster expansion of staphylococci on silicone teatcups raise important points from a clinical viewpoint. The model could be used in the testing of staphylococcal growth in the material of milking parlours in various conditions.

Bioactivity Performance of Pure Mg after Plasma Electrolytic Oxidation in Silicate-Based Solutions

The biodegradable metals, including magnesium (Mg), are a convenient alternative to permanent metals but fast uncontrolled corrosion limited wide clinical application. Formation of a barrier coating on Mg alloys could be a successful strategy for the production of a stable external layer that prevents fast corrosion. Our research was aimed to develop an Mg stable oxide coating using plasma electrolytic oxidation (PEO) in silicate-based solutions. 99.9% pure Mg alloy was anodized in electrolytes contained mixtures of sodium silicate and sodium fluoride, calcium hydroxide and sodium hydroxide. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), contact angle (CA), Photoluminescence analysis and immersion tests were performed to assess structural and long-term corrosion properties of the new coating. Biocompatibility and antibacterial potential of the new coating were evaluated using U2OS cell culture and the gram-positive Staphylococcus aureus (S. aureus, strain B 918). PEO provided the formation of a porous oxide layer with relatively high roughness. It was shown that Ca(OH)₂ was a crucial compound for oxidation and surface modification of Mg implants, treated with the PEO method. The addition of Ca²⁺ ions resulted in more intense oxidation of the Mg surface and growth of the oxide layer with a higher active surface area. Cell culture experiments demonstrated appropriate cell adhesion to all investigated coatings with a significantly better proliferation rate for the samples treated in Ca(OH)₂-containing electrolyte. In contrast, NaOH-based electrolyte provided more relevant antibacterial effects but did not support cell proliferation. In conclusion, it should be noted that PEO of Mg alloy in silicate baths containing Ca(OH)₂ provided the formation of stable biocompatible oxide coatings that could be used in the development of commercial degradable implants.

Osteointegration, antimicrobial and antibiofilm activity of orthopaedic titanium surfaces coated with silver and strontium-doped hydroxyapatite using a novel blasting process

Poor integration of orthopaedic devices with the host tissue owing to aseptic loosening and device-associated infections are two of the leading causes of implant failure, which represents a significant problem for both patients and the healthcare system. Novel strategies have focused on silver to combat antimicrobial infections as an alternative to drug therapeutics. In this study, we investigated the impact of increasing the % substitution (12% wt) of silver and strontium in hydroxyapatite (HA) coatings to enhance antimicrobial properties and stimulate osteoblasts, respectively. Additionally, we prepared a binary substituted coating containing both silver and strontium (AgSrA) at 12% wt as a comparison. All coatings were deposited using a novel blasting process, CoBlast, onto biomedical grade titanium (V). Surface physicochemical properties, cytocompatibility and antimicrobial functionality were determined. The anticolonising properties of the coatings were screened using Staphylococcus aureus ATCC 1448, and thereafter, the AgA coating was evaluated using clinically relevant strains. Strontium-doped surfaces demonstrated enhanced osteoblast viability; however, a lower inhibition of biofilm formation was observed compared with the other surfaces. A co-substituted AgSrA surface did not show enhanced osteoblast or anticolonising properties compared with the SrA and AgA surfaces, respectively. Due to its superior anticolonising performance in preliminary studies, AgA was chosen for further studies. The AgA coated surfaces demonstrated good antibacterial activity (eluted and immobilised ion) against methicillin-resistant S. aureus followed by methicillin-sensitive Staphylococcus aureus clinical isolates; however, the AgA surface displayed poor impact against Staphylococcus epidermidis. In conclusion, herein, we demonstrate that HA can be substituted with a range of ions to augment the properties of HA coatings on orthopaedic devices, which offer promising potential to combat orthopaedic device-associated infections and enhance device performance.

Development of Polythiourethane/ZnO-Based Anti-Fouling Materials and Evaluation of the Adhesion of Staphylococcus aureus and Candida glabrata Using Single-Cell Force Spectroscopy

The attachment of bacteria and other microbes to natural and artificial surfaces leads to the development of biofilms, which can further cause nosocomial infections. Thus, an important field of research is the development of new materials capable of preventing the initial adhesion of pathogenic microorganisms. In this work, novel polymer/particle composite materials, based on a polythiourethane (PTU) matrix and either spherical (s-ZnO) or tetrapodal (t-ZnO) shaped ZnO fillers, were developed and characterized with respect to their mechanical, chemical and surface properties. To then evaluate their potential as anti-fouling surfaces, the adhesion of two different pathogenic microorganism species, Staphylococcus aureus and Candida glabrata, was studied using atomic force microscopy (AFM). Our results show that the adhesion of both S. aureus and C. glabrata to PTU and PTU/ZnO is decreased compared to a model surface polydimethylsiloxane (PDMS). It was furthermore found that the amount of both s-ZnO and t-ZnO filler had a direct influence on the adhesion of S. aureus, as increasing amounts of ZnO particles resulted in reduced adhesion of the cells. For both microorganisms, material composites with 5 wt.% of t-ZnO particles showed the greatest potential for anti-fouling with significantly decreased adhesion of cells. Altogether, both pathogens exhibit a reduced capacity to adhere to the newly developed nanomaterials used in this study, thus showing their potential for bio-medical applications.

A scope at antifouling strategies to prevent catheter-associated infections

The use of invasive medical devices is becoming more common nowadays, with catheters representing one of the most used medical devices. However, there is a risk of infection associated with the use of these devices, since they are made of materials that are prone to bacterial adhesion with biofilm formation, often requiring catheter removal as the only therapeutic option. Catheter-related urinary tract infections (CAUTIs) and central line-associated bloodstream infections (CLABSIs) are among the most common causes of healthcare-associated infections (HAIs) worldwide while endotracheal intubation is responsible for ventilator-associated pneumonia (VAP). Therefore, to avoid the use of biocides due to the potential risk of bacterial resistance development, antifouling strategies aiming at the prevention of bacterial adherence and colonization of catheter surfaces represent important alternative measures. This review is focused on the main strategies that are able to modify the physical or chemical properties of biomaterials, leading to the creation of antiadhesive surfaces. The most promising approaches include coating the surfaces with hydrophilic polymers, such as poly(ethylene glycol) (PEG), poly(acrylamide) and poly(acrylates), betaine-based zwitterionic polymers and amphiphilic polymers or the use of bulk-modified poly(urethanes). Natural polysaccharides and its modifications with heparin, have also been used to improve hemocompatibility. Recently developed bioinspired techniques yielding very promising results in the prevention of bacterial adhesion and colonization of surfaces include slippery liquid-infused porous surfaces (SLIPS) based on the superhydrophilic rim of the pitcher plant and the Sharklet topography inspired by the shark skin, which are potential candidates as surface-modifying approaches for biomedical devices. Concerning the potential application of most of these strategies in catheters, more in vivo studies and clinical trials are needed to assure their efficacy and safety for possible future use.

Nasolacrimal stent with shape memory as an advanced alternative to silicone products

Epiphora is the overflow of tears typically caused by obstruction or occlusion of the nasolacrimal duct. More attention is required to address this global health issue owing to the increase in air pollution. Implantation of a silicone stent is the preferred treatment for epiphora; however, introducing a silicone stent into a narrow duct with complex geometry is challenging as it requires guidance by a sharp metal needle. Additionally, silicone can cause adverse reactions such as biofilm formation and tear flow resistance due to its extreme hydrophobicity. To overcome these problems, in this study we developed a new type of biocompatible shape memory polymer (SMP) stent with elasticity capacity for self-expansion. First, SMPs in the form of x%poly(ε-caprolactone)-co-y%poly(glycidyl methacrylate) (x%PCL-y%PGMA) were synthesized via ring opening polymerization by varying the molar ratio of PCL (x%) and PGMA (y%). Second, the shape memory and mechanical properties were tuned by controlling the crosslinking degree and concentration of x%PCL-y%PGMA solution to produce a test type of SMP stent. Lastly, this 94%PCL-06%PGMA stent exhibited more standout critical functions in a series of in vitro and in vivo experiments such as a cell growth-supporting level of biocompatibility with nasal epithelial cells without significant inflammatory responses, better resistance to biofilm formation, and more efficient capacity to drain tear than the silicone control. Overall, 94%PCL-06%PGMA can be suggested as a superior alternative to the currently used materials for nasolacrimal stents. STATEMENT OF SIGNIFICANCE: Silicone intubation (stenting) has been widely used to treat nasolacrimal duct obstruction, however, it can cause adverse clinical effects such as bacterial infection; presents procedural challenges because of the curved nasolacrimal duct structure; and shows poor drainage efficiency stemming from the highly hydrophobic nature of silicone. In this work, we describe an innovative shape memory polymer (SMP) as a superior alternative to conventional silicone-based materials for nasolacrimal duct intubation. We demonstrate the clear advantages of the SMP over conventional silicone, including a much higher drainage capacity and superior resistance to bacterial infection.

Functionalization of hydrophobic surfaces with antimicrobial peptides immobilized on a bio-interfactant layer

The design of functionalized polymer surfaces using bioactive compounds has grown rapidly over the past decade within many industries including biomedical, textile, microelectronics, bioprocessing and food packaging sectors. Polymer surfaces such as polystyrene (PS) must be treated using surface activation processes prior to the attachment of bioactive compounds. In this study, a new peptide immobilization strategy onto hydrocarbonaceus polymer surfaces is presented. A bio-interfactant layer made up of a tailored combination of laccase from trametes versicolor enzyme and maltodextrin is applied to immobilize peptides. Using this strategy, immobilization of the bio-inspired peptide KLWWMIRRWG-bromophenylalanine-3,4-dihydroxyphenylalanine-G and KLWWMIRRWG-bromophenylalanine-G on polystyrene (PS) was achieved. The interacting laccase layers allows to immobilize antimicrobial peptides avoiding the chemical modification of the peptide with a spacer and providing some freedom that facilitates different orientations. These are not strongly dominated by the substrate as it is the case on hydrophobic surfaces; maintaining the antimicrobial activity. Films exhibited depletion efficiency with respect to the growth of Escherichia coli bacteria and did not show cytotoxicity for fibroblast L929. This environmentally friendly antimicrobial surface treatment is both simple and fast, and employs aqueous solutions. Furthermore, the method can be extended to three-dimensional scaffolds as well as rough and patterned substrates.

A bio-interfactant layer is applied on hydrophobic surfaces to immobilize antimicrobial peptides.

Disinfectant Activity of A Portable Ultraviolet C Equipment

Healthcare-associated infections (HAIs) can be caused by microorganisms present in common practice instruments generating major health problems in the hospital environment. The aim of this work was to evaluate the disinfection capacity of a portable ultraviolet C equipment (UV Sanitizer Corvent^® -UVSC-) developed to disinfect different objects. For this purpose, six pathogens causing HAIs: Acinetobacter baumannii, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans, were inoculated on slides and discs of different biomaterials (borosilicate, polycarbonate, polyurethane, silicone, Teflon and titanium) and exposed to ultraviolet C radiation. UVSC disinfection was compared with ethanol and chlorhexidine antimicrobial activities following the standards EN14561 and EN14562. Disinfection, established as a reduction of five logarithms from the initial inoculum, was achieved with the UVSC at 120 s of exposure time, with and without the presence of organic matter. The disinfectant effect was observed against S. aureus, P. aeruginosa, E. coli, B. subtilis and C. albicans (reduction >99.999%). Disinfection was also achieved with 70% ethanol and 2% chlorhexidine. As conclusion, UVSC was effective disinfecting the most contaminated surfaces assayed, being a promising alternative for disinfecting hospital materials and inanimate objects that cannot be immersed in liquid biocides, reducing the risk of pathogen transmission.

Fused Deposition Modelling as a Potential Tool for Antimicrobial Dialysis Catheters Manufacturing: New Trends vs. Conventional Approaches

The rising rate of individuals with chronic kidney disease (CKD) and ineffective treatment methods for catheter-associated infections in dialysis patients has led to the need for a novel approach to the manufacturing of catheters. The current process requires moulding, which is time consuming, and coated catheters used currently increase the risk of bacterial resistance, toxicity, and added expense. Three-dimensional (3D) printing has gained a lot of attention in recent years and offers the opportunity to rapidly manufacture catheters, matched to patients through imaging and at a lower cost. Fused deposition modelling (FDM) in particular allows thermoplastic polymers to be printed into the desired devices from a model made using computer aided design (CAD). Limitations to FDM include the small range of thermoplastic polymers that are compatible with this form of printing and the high degradation temperature required for drugs to be extruded with the polymer. Hot-melt extrusion (HME) allows the potential for antimicrobial drugs to be added to the polymer to create catheters with antimicrobial activity, therefore being able to overcome the issue of increased rates of infection. This review will cover the area of dialysis and catheter-related infections, current manufacturing processes of catheters and methods to prevent infection, limitations of current processes of catheter manufacture, future directions into the manufacture of catheters, and how drugs can be incorporated into the polymers to help prevent infection.

Shear Stress as a Major Driver of Marine Biofilm Communities in the NW Mediterranean Sea

While marine biofilms depend on environmental conditions and substrate, little is known about the influence of hydrodynamic forces. We tested different immersion modes (dynamic, cyclic and static) in Toulon Bay (north-western Mediterranean Sea; NWMS). The static mode was also compared between Toulon and Banyuls Bays. In addition, different artificial surfaces designed to hamper cell attachment (self-polishing coating: SPC; and fouling-release coating: FRC) were compared to inert plastic. Prokaryotic community composition was affected by immersion mode, surface characteristics and site. Rhodobacteriaceae and Flavobacteriaceae dominated the biofilm community structure, with distinct genera according to surface type or immersion mode. Cell density increased with time, greatly limited by hydrodynamic forces, and supposed to delay biofilm maturation. After 1 year, a significant impact of shear stress on the taxonomic structure of the prokaryotic community developed on each surface type was observed. When surfaces contained no biocides, roughness and wettability shaped prokaryotic community structure, which was not enhanced by shear stress. Conversely, the biocidal effect of SPC surfaces, already major in static immersion mode, was amplified by the 15 knots speed. The biofilm community on SPC was 60% dissimilar to the biofilm on the other surfaces and was distinctly colonized by Sphingomonadaceae ((Alter)Erythrobacter). At Banyuls, prokaryotic community structures were more similar between the four surfaces tested than at Toulon, due possibly to a masking effect of environmental constraints, especially hydrodynamic, which was greater than in Toulon. Finally, predicted functions such as cell adhesion confirmed some of the hypotheses drawn regarding biofilm formation over the artificial surfaces tested here.

Effect of Substrate and Bacterial Zeta Potential on Adhesion of Mycobacterium smegmatis

Bacterial adhesion is described as a multistep process of interactions between microbes and the substrate, beginning with reversible contact, followed by irreversible adhesion. We explore the influence of substrate zeta potential on adhesion of Mycobacterium smegmatis, a nonpathogenic bacterial model for tuberculosis-causing Mycobacterium tuberculosis and a common foulant of reverse osmosis filtration systems. Substrates having a range of zeta potentials were prepared by coating silica with the polycation, poly(diallyldimethyl ammonium chloride) (pDADMAC), by adjusting the pH of alumina, a pH-responsive material, and by coating silica with a hydrophobic self-assembled monolayer coating of octadecyltrichlorosilane. Our observations using these surfaces demonstrated that adhesion of M. smegmatis increased significantly by more than 200% on the silica-pDADMAC system and more than 300% on alumina substrates, as zeta potential became less negative, and that the variation of pH did not affect adhesion on alumina surfaces. Live and heat-killed bacteria were studied to investigate the contribution of biological response to adhesion with respect to zeta potential. While approximately 60% fewer heat-killed M. smegmatis adhered to pDADMAC-coated silica substrates, the trend of significantly increasing adhesion with less negative zeta potential was still observed. These results show the influence of zeta potential on adhesion of M. smegmatis, which is a separate process from that of the biological response. Across the range of substrate surface chemistries, hydrophobicities, and zeta potentials tested, adhesion of M. smegmatis can primarily be controlled by zeta potential. The bacterial zeta potential was not changed by the various experimental conditions and was -28.3 ± 2.4 mV.

Recent insights on nanomedicine for augmented infection control

Antimicrobial agents have been widely investigated for protecting against microbial infections in modern health. Drug-related limitations, poor bioavailability, toxicity to mammalian cells, and frequent bacteria drug resistance are major challenges faced when exploited in nanomedicine forms. Specific attention has been paid to control nanomaterial-based infection against numerous challenging pathogens in addition to improved drug delivery, targeting, and pharmacokinetic (PK) profiles, and thus, efficient antimicrobials have been fabricated using diverse components (metals, metal oxides, synthetic and semisynthetic polymers, natural or biodegradable polymers, etc). The present review covers several nanocarriers delivered through various routes of administration, highlighting major findings to control microbial infection as compared to using the free drug. Results over the past decade support the consistent development of various nanomedicines capable of improving biological significance and therapeutic benefits against an array of microbial strains. Depending on the intended application of nanomedicine, infection control will be challenged by various factors such as weighing the risk-benefits in healthcare settings, nanomaterial-induced (eco)toxicological hazards, frequent development of antibiotic resistance, scarcity of in vivo toxicity data, and a poor understanding of microbial interactions with nanomedicine at the molecular level. This review summarizes well-established informative data for nanomaterials used for infection control and safety concerns of nanomedicines to healthcare sectors followed by the significance of a unique "safe-by-design" approach.

In vitro evaluation of microbial adhesion on the different surface roughness of acrylic resin specific for ocular prosthesis

OBJECTIVE

The purpose of this study was to evaluate the influence of surface roughness in biofilm formation of four microorganisms (Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis, and Candida albicans) on acrylic resin surface of ocular prostheses.

MATERIALS AND METHODS

Acrylic resin samples were divided into six groups according to polishing: Group 1200S (1200 grit + silica solution); Group 1200; Group 800; Group 400; Group 120 and Group unpolished. Surface roughness was measured using a profilometer and surface images obtained with atomic force microscopy. Microbial growth was evaluated after 4, 24, and 48 hours of incubation by counting colony-forming units.

STATISTICAL ANALYSIS USED

For roughness, it was performed 1-way ANOVA and parametric Tukey test α5% (P ≤ 0.05). For CFU data found, it was applied Kruskal-Wallis and Mann-Whitney tests.

RESULTS

Group 120 and 400 presented the highest roughness values. For S. epidermidis and S. aureus, Group 1200S presented the lowest values of microbial growth. For E. faecalis at 4 hour, microbial growth was not observed. C. albicans did not adhere to the acrylic resin. Except for Group 1200S, different surface roughnesses did not statistically interfere with microbial adhesion and growth on acrylic surfaces of ocular prostheses.

CONCLUSIONS

The roughness did not interfere with the microbial adhesion of the microorganisms evaluated. The use of silica decreases significantly microbial growth.

Biomodification Strategies for the Development of Antimicrobial Urinary Catheters: Overview and Advances

Microbial burden associated with medical devices poses serious health challenges and is accountable for an increased number of deaths leading to enormous medical costs. Catheter-associated urinary tract infections are the most common hospital-acquired infections with enhanced patient morbidity. Quite often, catheter-associated bacteriuria produces apparent adverse outcomes such as urosepsis and even death. Taking this into account, the methods to modify urinary catheters to control microbial infections with relevance to clinical drug resistance are systematically evaluated in this review. Technologies to restrict biofilm formation at initial stages by using functional nanomaterials are elucidated. The conventional methodology of using single therapeutic intervention for developing an antimicrobial catheter lacks clinically meaningful benefit. Therefore, catheter modification using naturally derived antimicrobials such as essential oils, curcumin, enzymes, and antimicrobial peptides in combination with synthetic antibiotics/nanoantibiotics is likely to exert sufficient inhibitory effect on uropathogens and is extensively discussed. Futuristic efforts in this area are projected here that demand clinical studies to address areas of uncertainty to avoid development of bacterial resistance to the new generation therapy with minimum discomfort to the patients.

Ica-status of clinical Staphylococcus epidermidis strains affects adhesion and aggregation: a thermodynamic analysis

Staphylococcus epidermidis is a major nosocomial pathogen associated with infections of indwelling medical devices. One important virulence factor of these organisms is their ability to adhere to devices and form biofilms. In this study, we evaluated the effect of the ica operon on cell surface hydrophobicity, thermodynamics of adhesion, and biofilm formation for seven S. epidermidis strains. The surface free energy parameters of the bacterial cell surface and the substratum were determined by contact angle measurement. Biofilm formation was assayed using crystal violet staining. Results showed that ica-positive strains demonstrated a higher hydrophobic characteristic than ica-negative strains, suggesting that the ica-operon seems to determine the cell surface hydrophobicity of S. epidermidis. Interaction of ica-positive strains with a tissue-culture treated polystyrene surface was energetically favourable (ΔG^Tot < 0), in contrast to ica-negative strains (ΔG^Tot > 0). The interfacial free energy of aggregation of S. epidermidis was lower for ica-positive than for ica-negative strains. Our study suggests that, in addition to biofilm formation, adhesion and aggregation of clinical S. epidermidis is stimulated in ica-positive strains by influencing the thermodynamics of interaction.

Proactive Approach for Safe Use of Antimicrobial Coatings in Healthcare Settings: Opinion of the COST Action Network AMiCI

Infections and infectious diseases are considered a major challenge to human health in healthcare units worldwide. This opinion paper was initiated by EU COST Action network AMiCI (AntiMicrobial Coating Innovations) and focuses on scientific information essential for weighing the risks and benefits of antimicrobial surfaces in healthcare settings. Particular attention is drawn on nanomaterial-based antimicrobial surfaces in frequently-touched areas in healthcare settings and the potential of these nano-enabled coatings to induce (eco)toxicological hazard and antimicrobial resistance. Possibilities to minimize those risks e.g., at the level of safe-by-design are demonstrated.

SEM Analysis of Surface Impact on Biofilm Antibiotic Treatment

The aim of this work was to use scanning electron microscopy (SEM) to investigate the effect of ampicillin treatment on Escherichia coli biofilms formed on two surface materials with different properties, silicone (SIL) and glass (GLA). Epifluorescence microscopy (EM) was initially used to assess biofilm formation and killing efficiency on both surfaces. This technique showed that higher bacterial colonization was obtained in the hydrophobic SIL than in the hydrophilic GLA. It has also shown that higher biofilm inactivation was attained for GLA after the antibiotic treatment (7-log reduction versus 1-log reduction for SIL). Due to its high resolution and magnification, SEM enabled a more detailed analysis of the antibiotic effect on biofilm cells, complementing the killing efficiency information obtained by EM. SEM micrographs revealed that ampicillin-treated cells have an elongated form when compared to untreated cells. Additionally, it has shown that different materials induced different levels of elongation on cells exposed to antibiotic. Biofilms formed on GLA showed a 37% higher elongation than those formed on SIL. Importantly, cell elongation was related to viability since ampicillin had a higher bactericidal effect on GLA-formed biofilms. These findings raise the possibility of using SEM for understanding the efficacy of antimicrobial treatments by observation of biofilm morphology.

Design of an anti-adhesive surface by a pilicide strategy

Biofilm formation on surfaces is one of major problems in medical, cosmetic and food industries. Nowadays any efficient treatment is known, as consequence, research of new strategies to inhibit biofilm formation is urgent. Recently, virstatin, which interferes with bacterial type IV pili formation, has demonstrated a capacity to inhibit biofilm formation developed by Acinetobacter baumannii after 24h. In this study, we aim to elaborate anti-adhesive surfaces preventing biofilm development by the covalent immobilization of virstatin on silicon surface. Surfaces were functionalized by self-assembled monolayers of two aminosilanes (11-aminoundecyltrimethoxysilane (AUTMS) and 3-aminopropyltrimethoxysilane (APTMS)). Then, virstatin (2mM) was immobilized on those modified surfaces. We observed an increase in surface hydrophobicity of AUTMS modified substratum leading to an increase of A. baumannii ATCC 17978 adhesion (after 4h). Immobilization of virstatin molecule on APTMS modified surface was efficient to decrease cell attachment by 32.1±5.7% compared to unmodified surface. As virstatin is known to inhibit type IV pili formation in solution, the observed decrease of bacterial adhesion might be due to this pilicide action. We also demonstrated that hydrophobicity of strains plays a role in adhesion according to surface properties. In conclusion, immobilized virstatin succeeded to inhibit bacterial attachment of various Acinetobacter baumannii strains comparing to APTMS modified support.

Efficacy of commercially available wipes for disinfection of pulse oximeter sensors

BACKGROUND

This study examined the effectiveness of commercially available disinfecting wipes and cosmetic wipes in disinfecting pulse oximeter sensors contaminated with pathogenic bacterial surrogates.

METHODS

Surrogates of potential biological warfare agents and bacterial pathogens associated with hospital-acquired infections (HAIs) were spotted on test surfaces, with and without an artificial test soil (sebum), allowed to dry, and then cleaned with different commercially available cleaning and disinfecting wipes or sterile gauze soaked in water, bleach (diluted 1:10), or 70% isopropanol. The percentage of microbial survival and an analytical estimation of remaining test soil on devices were determined.

RESULTS

Wipes containing sodium hypochlorite as the active ingredient and gauze soaked in bleach (1:10) were the most effective in removing both vegetative bacteria and spores. In the presence of selective disinfectants, sebum had a protective effect on vegetative bacteria, but not on spores.

CONCLUSIONS

The presence of sebum reduces the cleaning efficiency of some commercially available wipes for some select microbes. Various commercial wipes performed significantly better than the designated cleaning agent (70% isopropanol) in disinfecting the oximetry sensor. Cosmetic wipes were not more effective than the disinfecting wipes in removing sebum.

Biofilm formation of Brazilian meticillin-resistant Staphylococcus aureus strains: prevalence of biofilm determinants and clonal profiles

Biofilms plays an important role in medical-device-related infections. This study aimed to determine the factors that influence adherence and biofilm production, as well as the relationship between strong biofilm production and genetic determinants in clinical isolates of meticillin-resistant Staphylococcus aureus (MRSA). Fifteen strains carrying different chromosomal cassettes recovered from hospitalized patients were selected; five SCCmecII, five SCCmecIII and five SCCmecIV. The SCCmec type, agr group and the presence of the virulence genes (bbp, clfA, icaA, icaD, fnbB, bap, sasC and IS256) were assessed by PCR. PFGE and multilocus sequence typing (MLST) techniques were also performed. The initial adhesion and biofilm formation were examined by quantitative assays. The surface tension and hydrophobicity of the strains were measured by the contact angle technique to evaluate the association between these parameters and adhesion ability. SCCmecIII and IV strains were less hydrophilic, with a high value for the electron acceptor parameter and higher adhesion in comparison with SCCmecII strains. Only SCCmecIII strains could be characterized as strong biofilm producers. The PFGE showed five major pulsotypes (A-E); however, biofilm production was related to the dissemination of one specific PFGE clone (C) belonging to MLST ST239 (Brazilian epidemic clonal complex). The genes agrI, fnbB and IS256 in SCCmecIII strains were considered as genetic determinants associated with strong biofilm-formation by an ica-independent biofilm pathway. This study contributes to the understanding of biofilm production as an aggravating factor potentially involved in the persistence and severity of infections caused by multidrug-resistant MRSA belonging to this genotype.

The role of plasma, albumin, and fibronectin in Staphylococcus epidermidis adhesion to polystyrene surface

The influence of soluble and immobilized plasma, albumin, and fibronectin (Fn) on the adhesion of three Staphylococcus epidermidis strains to polystyrene was investigated. Both soluble and immobilized plasma and albumin cause to 7-fold reduction of the amounts of adhered cells, regardless of the strain used. The soluble Fn exhibited the adhesion for one strain and did not affect the bacterial sorption for remaining strains, whereas on Fn-coated polystyrene two of the three strains showed about 1.5-fold increase in the number of adsorbed bacteria. The plasma- and albumin-coated surfaces became much more hydrophilic as the contact angle changed from 78 ± 2° for control to 18 ± 2° for plasma and 21 ± 3° for albumin. The ligand-receptor specific interactions strains S. epidermidis with Fn-coated surfaces were proved by measuring the adhesion forces between cell surface and Fn-coated AFM tip. The surface roughness measured using AFM after the plasma and proteins immobilization was changed within 10 nm and not correlate with changes in bacterial adhesion.

Chemical functionalization of graphene to augment stem cell osteogenesis and inhibit biofilm formation on polymer composites for orthopedic applications

Toward designing the next generation of resorbable biomaterials for orthopedic applications, we studied poly(ε-caprolactone) (PCL) composites containing graphene. The role, if any, of the functionalization of graphene on mechanical properties, stem cell response, and biofilm formation was systematically evaluated. PCL composites of graphene oxide (GO), reduced GO (RGO), and amine-functionalized GO (AGO) were prepared at different filler contents (1%, 3%, and 5%). Although the addition of the nanoparticles to PCL markedly increased the storage modulus, this increase was largest for GO followed by AGO and RGO. In vitro cell studies revealed that the AGO and GO particles significantly increased human mesenchymal stem cell proliferation. AGO was most effective in augmenting stem cell osteogenesis leading to mineralization. Bacterial studies revealed that interaction with functionalized GO induced bacterial cell death because of membrane damage, which was further accentuated by amine groups in AGO. As a result, AGO composites were best at inhibiting biofilm formation. The synergistic effect of oxygen containing functional groups and amine groups on AGO imparts the optimal combination of improved modulus, favorable stem cell response, and biofilm inhibition in AGO-reinforced composites desired for orthopedic applications. This work elucidates the importance of chemical functionalization of graphene in polymer composites for biomedical applications.

Escherichia coli adhesion, biofilm development and antibiotic susceptibility on biomedical materials

The aim of this work was to test materials typically used in the construction of medical devices regarding their influence in the initial adhesion, biofilm development and antibiotic susceptibility of Escherichia coli biofilms. Adhesion and biofilm development was monitored in 12-well microtiter plates containing coupons of different biomedical materials--silicone (SIL), stainless steel (SS) and polyvinyl chloride (PVC)--and glass (GLA) as control. The susceptibility of biofilms to ciprofloxacin and ampicillin was assessed, and the antibiotic effect in cell morphology was observed by scanning electron microscopy. The surface hydrophobicity of the bacterial strain and materials was also evaluated from contact angle measurements. Surface hydrophobicity was related with initial E. coli adhesion and subsequent biofilm development. Hydrophobic materials, such as SIL, SS, and PVC, showed higher bacterial colonization than the hydrophilic GLA. Silicone was the surface with the greatest number of adhered cells and the biofilms formed on this material were also less susceptible to both antibiotics. It was found that different antibiotics induced different levels of elongation on E. coli sessile cells. Results revealed that, by affecting the initial adhesion, the surface properties of a given material can modulate biofilm buildup and interfere with the outcome of antimicrobial therapy. These findings raise the possibility of fine-tuning surface properties as a strategy to reach higher therapeutic efficacy.

Comparative isocline analysis upon microbial decolorization in immobilized cell bioreactor using biocarriers

This study used various biocarriers (e.g., porites corals, Biolite™, porous ceramic filter media (PCFM)) to immobilize cells in fixed bed bioreactor (FBB) for wastewater decolorization. As prior studies proposed, an innovative graphical method of constant-slope isoclines to determine maximal allowable treatment capacity (MATC) was used as screening criteria for feasibility of packing matrices of immobilized cell systems (ICSs). Moreover, detailed inspection upon physical and chemical characteristics of packing matrices was also carried out to confirm the consistency of MTAC. The result of isocline analysis was in parallel with physical characteristics of biocarriers (i.e., porites coral>Biolite™>PCFM). This first-attempt study successfully provided perspective in general terms to assess how the selected supporting materials were suitable to be packing matrices of ICSs for industrial applications (e.g., wastewater treatment).

Calculation of intraocular lens surface free energy and its components from contact angle measurements

One of the most important biomaterial characteristics involved in bacterial adhesion on intraocular lenses (IOLs) is hydrophobicity. We calculated the hydrophobicity parameters of IOLs made of 6 different materials (polymethylmethacrylate, PMMA, heparin surface-modified PMMA, HSM-PMMA, silicone, hydrophilic and hydrophobic acrylics and collamer). Values of IOL surface free energy components were determined from contact angle measurements, using the Fowkes, Owens-Wendt and Good-van Oss calculations. Contact angles were higher for silicone and hydrophobic acrylic materials and lower for collamer and hydrophilic acrylic materials. The values of IOL surface free energy components obtained with the 3 different calculations were homogenous. According to the Owens-Wendt calculation, the IOLs could be separated into dispersive implants (hydrophobic acrylic, silicone and PMMA) and polar implants (collamer, hydrophilic acrylic and HSM-PMMA).

Staphylococcus epidermidis biofilm formation and structural organization on different types of intraocular lenses under in vitro flow conditions

AIM

To compare the adherence and structural organization of Staphylococcus epidermidis biofilm on intraocular lenses (IOLs).

METHODS

IOLs made of 3 different biomaterials [polymethyl methacrylate (PMMA), hydrophilic acrylic or hydrophobic acrylic] were incubated into an S. epidermidis bacterial solution. Scanning electron microscopy was used to count the bound bacteria and to analyze the structural biofilm architecture.

RESULTS

After 4-6 h of incubation, adherence was statistically weakest on the hydrophilic acrylic polymer. On the hydrophobic acrylic material, the bacterial cells tended to cover the substratum in a horizontal spread in a continuous monolayer. On the hydrophilic acrylic material or on the PMMA material bacterial cells tended to form only few, small scattered cell clusters.

CONCLUSIONS

The data suggest that the pattern of S. epidermidis adhesion varies with the IOL biomaterial. Hydrophobic IOLs seem to be more permissive to S. epidermidis adhesion.

Influence of surface features on the adhesion of Staphylococcus epidermidis to Ag-TiCN thin films

Staphylococcus epidermidis has emerged as one of the major nosocomial pathogens associated with infections of implanted medical devices. The initial adhesion of these organisms to the surface of biomaterials is assumed to be an important stage in their colonization. The main objective of this work is to assess the influence of surface features on the adhesion of S. epidermidis to Ag-TiCN coatings deposited by dc reactive magnetron sputtering. The structural results obtained by x-ray diffraction show that the coatings crystallize in a B1-NaCl crystal structure typical of TiC0.3N0.7. The increase of Ag content promoted the formation of Ag crystalline phases. According to the results obtained with atomic force microscopy, a decrease on the surface roughness of the films from 39 to 7 nm is observed as the Ag content increases from 0 to 15 at.%. Surface energy results show that the increase of Ag promotes an increase in hydrophobicity. Bacterial adhesion and biofilm formation on coatings were assessed by the enumeration of the number of viable cells. The results showed that the surface with lower roughness and higher hydrophobicity leads to greater bacterial adhesion and biofilm formation, highlighting that surface morphology and hydrophobicity rule the colonization of materials.

Nanotechnology tools for antibacterial materials

The understanding of the interactions between biological systems and nanoengineered devices is crucial in several research fields, including tissue engineering, biomechanics, synthetic biology and biomedical devices. This review discusses the current knowledge of the interactions between bacteria and abiotic nanostructured substrates. First, the effects of randomly organized nanoscale topography on bacterial adhesion and persistence are described. Second, the interactions between microorganisms and highly organized/ordered micro- and nano-patterns are discussed. Finally, we survey the most promising approaches for the fabrication of silver polymeric nanocomposites, which have important applications as antimicrobial materials. The advantages, drawbacks and limitations of such nanotechnologies are critically discussed in view of potential future applications.

Biofilm formation with mixed cultures of Pseudomonas aeruginosa/Escherichia coli on silicone using artificial urine to mimic urinary catheters

In this study, single and dual species biofilms of Pseudomonas aeruginosa and Escherichia coli, two common bacteria associated with urinary tract infections, were formed in silicon coupons immersed in artificial urine medium. In single species experiments, E. coli appeared to form biofilms more easily than P. aeruginosa. In mixed biofilms, both species apparently benefited from the presence of the other, as the average Log total cells cm(-2) of mixed biofilms (7.29 cells cm(-2)) was higher than obtained for single cultures (6.99 cells cm(-2)). However, the use of selective media seemed to indicate that P. aeruginosa was the only microorganism to benefit in mixed biofilms (Log 7 CFU of P. aeruginosa cm(-2), compared to Log 6 CFU cm(-2) obtained in pure cultures). Peptide nucleic acid-fluorescence in situ hybridization combined with confocal laser scanning microscopy confirmed that E. coli was indeed being outnumbered by P. aeruginosa at 48 h. Whereas E. coli is the main causative agent of catheter-associated urinary tract infections, the results from this study indicate that the reason for the higher prevalence of this microorganism is not related to an enhanced ability to form biofilm and outcompete other species that may also be present, but rather to a better ability to form single-species biofilms possibly due to a more frequent access to the catheter surface.

Inhibition of Staphylococcus epidermidis biofilm by trimethylsilane plasma coating

Biofilm formation on implantable medical devices is a major impediment to the treatment of nosocomial infections and promotes local progressive tissue destruction. Staphylococcus epidermidis infections are the leading cause of biofilm formation on indwelling devices. Bacteria in biofilms are highly resistant to antibiotic treatment, which in combination with the increasing prevalence of antibiotic resistance among human pathogens further complicates treatment of biofilm-related device infections. We have developed a novel plasma coating technology. Trimethylsilane (TMS) was used as a monomer to coat the surfaces of 316L stainless steel and grade 5 titanium alloy, which are widely used in implantable medical devices. The results of biofilm assays demonstrated that this TMS coating markedly decreased S. epidermidis biofilm formation by inhibiting the attachment of bacterial cells to the TMS-coated surfaces during the early phase of biofilm development. We also discovered that bacterial cells on the TMS-coated surfaces were more susceptible to antibiotic treatment than their counterparts in biofilms on uncoated surfaces. These findings suggested that TMS coating could result in a surface that is resistant to biofilm development and also in a bacterial community that is more sensitive to antibiotic therapy than typical biofilms.