Narrow Results

Electrochemical measurement and surface analysis methods were employed to investigate the Microbiologically Influenced Corrosion (MIC) influenced by Thiobacillus ferrooxidans biofilm. Electrochemical impedance spectroscopy (EIS) results indicated that the impedance value of steel A3 after 21 days of immersion in sterile solution was much higher than that of T.f solution. Atomic Force Microscopy (AFM) results showed the adsorption state of the microorganism on the metal surface for 7 days of exposure in T.f solution. The morphologies of the surface film were analyzed with the Scanning Electron Microscope (SEM), which showed the changes with exposure time of the film on the metal surface. The special morphology and the heterogeneity of Thiobacillus ferrooxidans biofilm induced the localized corrosion of steel A3. After 21 days of exposure, general corrosion occurred in the sterile solution, while localized corrosion was detected under the effect of Thiobacillus ferrooxidans.

The nitriding process is a surface treatment that improves the surface properties of titanium alloys and increases wear/corrosion resistance. This study investigates the structural and mechanical property changes in titanium alloy after nitriding. Micro-hardness differences between the nitrided and non-nitrided surface and morphological changes on the surface were determined. In addition to evaluating the effect of vanadium and aluminum ions on the nonnitrided surface, the impact of nitrided and non-nitrided surfaces on biofilm layer formation was investigated. It was determined that the TiN layer formed on the nitrided surface showed superior properties to its non-nitrided surface in the biofilm tests performed for 6 h. As a result of the tensile tests, it can be said that the nitriding process increases the elasticity module of the Ti–6Al–4V alloy and provides the material to have a more rigid structure. It was also analyzed using finite element analysis (FEA) of mechanical behaviors of the test sample under the tension loads.

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/$\mu$m${}^2)$ and SS304 (Disk-12: 1654 peaks/$\mu$m${}^2)$ 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 600mV 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 2h contact time. Our observations exhibit that the nanotextured surface topographies and surface negative potential effectively inhibit bacterial adhesion and biofilm formation.

The following topics are under this section:

• ASIA-PACIFIC — Discovery of Protease Inhibitors hold Promise against COVID-19
• ASIA-PACIFIC — Nano-sensors for Real-Time Plant Health Monitoring
• ASIA-PACIFIC — Study Finds Underweight Patients with Diabetes have Increased Risk of Tuberculosis
• ASIA-PACIFIC — Guide Developed for Remote Consultation for Suspected COVID-19 Patients
• ASIA-PACIFIC — Scientific Challenges of Kimchi Fermentation
• ASIA-PACIFIC — Increasing Charge Capacity of Lithium Batteries
• ASIA-PACIFIC — Newly-discovered Small Mitochondrial Protein Essential for Energy Production
• ASIA-PACIFIC — Overcoming Chemotherapy Resistance in Ovarian Cancer
• REST OF THE WORLD — Safety of Antibiotics for C-Section Mothers
• REST OF THE WORLD — Early Screening of Colorectal Cancer based on Family History
• REST OF THE WORLD — Maternal Hypertensive Disorders may cause Mental Health Disorders in Children
• REST OF THE WORLD — Biofilm Formation and Hyper-infectivity of Cholera

Zinc oxide (ZnO) thin films have been deposited onto thoroughly cleaned stainless steel (AISI SS 304) substrates by reactive direct current (dc) magnetron sputtering and the films were doped with silver (Ag). The prepared thin films were analyzed using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) to investigate the structural and morphological properties. The thickness values of the films were in the range of 194 to 256nm. XRD results revealed that the films were crystalline with preferred (002) orientation. Grain size values of pure ZnO films were found to be 19.82–23.72nm. On introducing Ag into ZnO film, the micro-structural properties varied. Adhesion test was carried out with Staphylococcus aureus (S. aureus) in order to know the adherence property of the deposited films. Colony formation units (CFU) were counted manually and bacterial adhesion inhibition (BAI) was calculated. We observed a decrease in the CFU on doping Ag in the ZnO films. BAI of the film deposited at – 100 V substrate bias was found to be increased on Ag doping from 69 to 88%.

The present study focuses on the development of an in vitro model system for biofilm growth by Pseudomonas aerouginosa onto small discs of foley catheter. Catheter disc used for the study was coated with graphene oxide–titanium oxide composite (GO–TiO${}_2)$ and titanium oxide (TiO${}_2)$ and characterized through XRD, UV–visible spectroscopy. Morphological analysis was done by scanning electron microscopy (SEM). The biofilm formed on the catheter surface was quantified by crystal violet (CV) staining method and a colorimetric assay (MTT assay) which involves the reduction of tetrazolium salt. The catheter coated with GO–TiO₂ showed reduced biofilm growth in comparison to the TiO₂-coated and uncoated catheter, thus indicating that it could be successfully used in coating biomedical devices to prevent biofilm formation which is a major cause of nosocomial infection.

The hot aqueous extract of E. camaldensis leaves as a degradable agent and copper nitrate as a copper source with cold plasma was used in this work to present an easy and green technique for copper oxide nanoparticles (CuO NPs) synthesis. UV-Vis absorption spectroscopy, X-ray diffraction (XRD), Atomic Force Microscopes (AFM), and Scanning Electron Microscopes (SEM) were all used to determine the production of copper oxide nanoparticles (SEM). The energy gap was 4.9eV, and the average crystalline size of CuO NPs evaluated using the Scherrer equation was 15.06nm, according to the X-ray diffraction pattern (XRD). CuO NPs had a grain size of 70.63 nanometers, according to AFM morphology study. Finally, the effect of copper oxide nanoparticles on Gram-positive and Gram-negative bacteria, as well as fungi, was studied.

This work synthesizes iron oxide nanoparticles using plant extracts of Camellia sinensis, Matricaria chamomilla L., and Artemisia herba-alba Asso. and Punica granatum L. peel. with an evaluation of its antimicrobial activity. Fe₂O₃ nanoparticles (NPs) are highly stable and significantly affect gram-positive and gram-negative bacteria. The synthesized Fe₂O₃ nanoparticles were examined using X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray (EDX), Fourier transform infrared spectroscopy (FTIR), zeta potential (ZP), and UV–Vis spectrophotometer analysis (UV–Vis). The band gap ranged between 3.1eV and 3.8eV, which corresponds to the grain size, as its value ranged between 10.77nm and 32.31nm, that is, the smaller the grain size, the higher the band gap. On bacteria, iron oxide nanoparticles have remarkable efficacy in the formation of biofilms for gram-positive, gram-negative bacteria, and fungal.

Experiments showed that bacterial biofilms are heterogeneous, for example, the density, the diffusion coefficient, and mechanical properties of the biofilm are different along the biofilm thickness. In this paper, we establish a multi-layer composite model to describe the biofilm mechanical inhomogeneity based on unified multiple-component cellular automaton (UMCCA) model. By using our model, we develop finite element simulation procedure for biofilm tension experiment. The failure limit and biofilm extension displacement obtained from our model agree well with experimental measurements. This method provides an alternative theory to study the mechanical inhomogeneity in biological materials.

Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) ST9 has emerged as a potential zoonotic pathogen for humans and animals. Bacterial adhesion factors and biofilms mediate host colonization and infection of MRSA. This study investigated the dynamics of microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), biofilm formation gene (intercellular adhesion [ica]), and biofilm expression in MRSA from the nasal samples of asymptomatic pigs (the nasal group, n = 147) and swine slaughterhouse wastewater samples (the environmental group, n = 86). Biofilm formation was quantified by microtiter plate assay. The most prevalent MSCRAMM profile was clfA-clfB-spa-eno-ebps-fib and more than 70% of the LA-MRSA ST9 isolates harbored the biofilm formation gene. Environmental MRSA harbored lower levels of the ica locus and MSCRAMMs (clfA and fib) than did the nasal group, suggesting possible gene loss. Biofilm production in the nasal group was higher than in the environmental group, indicating the difference in biofilm formation in MRSA isolates from different ecological niches. The higher prevalence of MSCRAMMs, biofilm formation gene, and biofilm production in LA-MRSA ST9 may enhance the persistence and infectivity of MRSA in the swine population and present a threat to the health of livestock as well as farm workers.

This study sought to determine the minimum bactericidal concentrations (MBCs) of didecyldimethylammonium chloride (DDAC), povidone iodine (PI), and chlorhexidine and the differences in these values among coagulase-negative staphylococci (CNSs) that harbor or do not harbor biofilm-related genes (eno, bap, and ica). Using the limiting dilution technique, the MBCs against three different disinfectants were estimated and compared using statistical methods. The results showed that the biofilm-gene-positive CNS isolates exhibited higher tolerance ($p=0.02$, upper-tailed test) to 2mgL${}^{-1}$ DDAC and 10mgL${}^{-1}$ povidone iodine ($p=0.03$, upper-tailed test). Different resistance capacities were found among these three biofilm formation-related genes. The isolates that contained the bap gene exhibited a higher tolerance level. This observation was confirmed by logistic regression models, which revealed that the bap (odds ratio $=5.17$) and eno (odds ratio $=3.56$) genes significantly affected the survival capacity. This study demonstrated that biofilm-gene-positive CNS isolates exhibited increased survival in the presence of higher concentrations of all three disinfectants and that both the bap and eno genes could affect the survival capacity. Among the three genes, the bap gene had the strongest effect on the survival capacity of CNSs in the presence of all three disinfectants. The appropriate use of disinfectants can control these biofilm-gene embedded CNSs more efficiently.

Silver nanoparticles have attracted much interest from scientists to develop nanosilver-based disinfectant products due to their unique properties of high antimicrobial activity. This study focused on biosynthesis, characterization, antimicrobial and antibiofilm effects of silver nanoparticles against vegetative and starved Shigella strains. The silver nanoparticles were synthesized using the yeast Yarrowia lipolytica and characterized by ultraviolet–visible spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The antimicrobial and antibiofilm activities of silver nanoparticles were tested against the growth of vegetative and starved Shigella strains. After the addition of silver nitrate solution to the supernatant of Y. lipolytica, we noticed the appearance of a brown-black coloration that suggested the formation of silver nanoparticles. The presence of silver nanoparticles was manifested by a maximum absorption in the ultraviolet–visible range, precisely at the wavelength 420nm. The crystalline nature and the stability of silver nanoparticles were confirmed, respectively, by XRD and FTIR analysis. The antibacterial activity of silver nanoparticles showed significant toxicity on Shigella strains indicating that the starved cells were more sensitive to treatment with silver nanoparticles than vegetative cells. Surprisingly, the biofilm formation had not been inhibited by silver nanoparticles for both vegetative and starved cells. In conclusion, a new class of nanosilver containing disinfectant nanoproducts will be promising for advanced environmental treatments including air disinfection, water disinfection, surface disinfection and personal hygiene that will help to prevent the further outbreak of diseases.

As changes in hard or soft oral tissues normally have a microbiological component, it is important to develop diagnostic techniques that support clinical evaluation, without destroying microbiological formation. The optical coherence tomography (OCT) represents an alternative to analyze tissues and microorganisms without the need for processing. This imaging technique could be defined as a fast, real-time, in situ, and non-destructive method. Thus, this study proposed the use of the OCT to visualize biofilm by Candida albicans in reline resins for removable prostheses. Three reline resins (Silagum-Comfort, Coe-Comfort, and Soft-Confort), with distinct characteristics related to water sorption and fungal inhibition were used. A total of 30 samples (10 for each resin group) were subjected to OCT scanning before and 96 h after inoculation with Candida albicans (URM 6547). The biofilm analysis was carried out through a 2D optical Callisto SD-OCT (930 nm) operated in the spectral domain. Then, the images were preprocessed using a $3\times 3$ Gaussian filter to remove the noise, and then Otsu binarization, allowing segmentation and pixel counting. The layer’s biofilm formed was clearly defined and, indeed, its visualization is modified by water sorption of each material. Silagum-Comfort and Soft-Confort showed some similarities in the scattering of light between the clean and inoculated samples, in which, the latter samples presented higher values of light signal intensity. Coe-Comfort samples were the only ones that showed no differences between the clean or inoculated images. Therefore, the results of this study suggest that OCT is a viable technique to visualize the biofilm in reline materials. Because findings in the literature are still scarcely using the OCT technique to visualize biofilm in reline resins, further studies are encouraged. It should not contain any references or displayed equations.

Bacterial pathogens, such as Pseudomonas aeruginosa, readily form biofilms on surfaces, limiting the efficacy of antimicrobial and antibiotic treatments. To mitigate biofilm formation, surfaces are often treated with antimicrobial agents, which have limited lifetime and efficacy. Recent studies have shown that well-ordered topographic patterns can limit bacterial attachment to surfaces and limit biofilm formation. In this study, nano and microscale patterned poly(dimethylsiloxane) surfaces were evaluated for their ability to affect adhesion and biofilm formation by Pseudomonas aeruginosa. Feature size and spacing were varied from 500 nm to 2 μm and included repeating arrays of square pillars, holes, lines and biomimetc Sharklet™ patterns. Bacterial surface adhesion and biofilm formation was assessed in microfluidic flow devices and under static conditions. Attachment profiles under static and fluid flow varied within topography types, sizes and spacing. Pillar structures of all sizes yielded lower surface attachment than line-based patterns and arrays of holes. This trend was also observed for biomimetic Sharklet™ patterns, with reduced bacterial attachment to "raised" features as compared to "recessed" features. Notably, none of the topographically patterned surfaces outperformed smooth surfaces (without topography) for resisting cell adhesion. Initial surface attachment patterns were indicative of subsequent biofilm formation and coverage, suggesting a direct role of surface topography in biofilm-based biofouling.

In this nano era, biomaterials associated infection is a serious problem in the biomedical arena. The race between microbial adhesion and tissue integration becomes a major cause of concern, during the implantation process. Microbial adhesion further gives rise to biofilm formation which finally leads to implant failure. We have therefore designed a strategy to fight effectively against the encroachment of Staphylococcus aureus biofilm, which is chiefly responsible for majority of biomaterials associated infections. Silver nanoparticles have been synthesized for the purpose using foliage needles of the plant Pseudotsuga menziesii, our Christmas tree. Thereafter the nanoparticles were dispersed in chitosan, a biopolymer matrix and a bionanocomposite, self-sterilizing coating biomaterial was developed. The silver nanoparticles produced, the bionanocomposite developed, and the coating over medical implant, have been characterized through various techniques. The efficacy of the silver/chitosan bionanocomposite, against S. aureus biofilm has been studied here, after being coated over medical implant. It was found that coating of medical implants with this material can definitely restrict bacterial adhesion and their subsequent biofilm formation. This biomaterial was found to be blood and biocompatible at specific levels through testing.

This study was based on the hypothesis that spatial–temporal characterization of contaminant-affected redox gradients in a quiescent system could be measured by microbial potentiometric sensor (MPS) arrays incorporated in large, natural biofilm networks. Two experimental chambers, each containing at least 48 equidistantly located MPS electrodes, were fabricated to examine reproducibility of the patterns. The MPS electrodes were exposed to biofilm growth conditions by introducing high dissolved organic carbon (DOC) and dechlorinated tap water at the bottom of the experimental chamber; and the spatial–temporal changes in the MPS array signals were recorded, which showed that signal trends were correlated to the induced changes in DOC. The results indicated that MPS arrays measured the spatial–temporal changes in the aqueous solution caused by an influx of carbon rich water, which could not be detected by conventional oxidation-reduction potential (ORP) electrodes. Interestingly, the experiments conducted over long time periods revealed unusual behaviors like electrical signaling and possible potentiometrically driven communication within the biofilm. These observed behaviors suggest that biofilms may create a large network through which communication signals can be generated and propagated by inducing changes in electric potentials similar to a sophisticated electronic device.

Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that is found ubiquitously in the environment. It is also the cause of nosocomial infections, which affects patients with cystic fibrosis (CF) and cathether-related infections. Treatment and eradication of P. aeruginosa is an uphill task as it has already developed resistance to many commonly used antibiotics. Some of the resistance mechanisms that P. aeruginosa employ are having low cell wall permeability, developing efflux system to pump antibiotics out, producing enzymes to inactivate antibiotics, modifying antibiotic targets, forming biofilm as a protection layer against antibiotics, and turning into more pathogenic small colony variant form. In addition, P. aeruginosa uses a host of signaling mechanisms, such as secretion system and quorum sensing, to aid its virulence. With numerous resistance mechanisms developed against conventional antibiotics, new strategies to treat P. aeruginosa infection are required. Bacteriophages such as natural bacteria viruses and studies have suggested that they can be used as an alternative to antibiotics for treatment against P. aeruginosa infections. However, phage therapy also shares the same problem with that of antibiotics, i.e., the development and emergence of bacteria resistance by masking or altering surface recognition features, inhibiting phage DNA injection and employing abortive infection (Abi) system. Another alternative treatment strategy is to use antimicrobial peptides, which are small cationic peptides that are naturally found in most organisms’ immune system. These peptides disrupt cell membrane and key cellular processes, which requires major gene alteration if evasion is needed. Hence, lowering likelihood of resistance development. This paper aims to review our current understanding of the clinical implications of P. aeruginosa infections, the mechanisms of antibiotic resistance, phage-inspired and antimicrobial peptide approaches for treatment of P. aeruginosa infections.

Various genetic mechanisms including point mutations, genetic rearrangements and lateral gene transfer processes contribute to the evolution of microbes. Long-term processes leading to the development of new species or subspecies are termed macroevolution, and short-term developments, which occur during days or weeks, are considered as microevolution. Both processes, macro- and microevolution need horizontal gene transfer, which is particularly important for the development of pathogenic microorganisms. Plasmids, bacteriophages and so-called pathogenicity islands (PAIs) play a crucial role in the evolution of pathogens. During microevolution, genome variability of pathogenic microbes leads to new phenotypes, which play an important role in the acute development of an infectious disease. Infections due to Staphylococcus epidermidis, Candida albicans and Escherichia coli will be described with special emphasis on processes of microevolution. In contrast, the development of PAIs is a process involved in macro-evolution. PAIs are especially important in processes leading to new pathotypes or even species. In this review, particular attention will be given to the fact that the evolution of pathogenic microbes can be considered as a specific example for microbial evolution in general.

Polyoxovanadates (POVs) emerge from polyoxometalates (POMs), which are a class of oxoanions of transition metals ions (e.g., Mo, W, V) and have led to a range of catalytical investigations and biological studies in recent years. A series of POVs have endorsed their efficiency as catalysts due to their versatile redox activity (V^V, V^IV, V^III) in oxidation reactions of organic compounds. The pharmacological action of vanadium compounds has sparked interest as potential candidates for therapeutic applications. Here, we summarized the antibacterial and anticancer activities of POVs. Decavanadate and its derivatives, probably the most studied POV in biology, are highlighted as possible antibacterial and anticancer agents in the near future.

Streptococcus agalactiae (GBS) is a human pathogen, that forms biofilms in vitro with variable efficiency. Aim of this study was to investigate the relationships between hydrophobicity and the ability of GBS to form biofilm. Twenty strains of GBS were investigated for the purpose. Biofilm experiments were performed, in unmodified atmosphere, in 96-well polystyrene microtiter plates containing Todd-Hewitt Broth. Increasing concentrations of glucose were also investigated for their influence on both hydrophobicity and biofilm production. The quantitative measurement was achieved by means of colorimetric methods using crystal violet. The hydrophobicity was investigated by using the hexadecane test, and expressed as percent of hydrophobicity. The hydrophobicity varied a little in most cases and independently of glucose concentrations, while BI increased with increasing concentration of glucose. Although most of the strains had a hydrophobicity index of > 80%, any correlation between hydrophobicity and biofilm formation has not been found.