2D TiO2 nanosheets decorated via sphere-like BiVO4: a promising non-toxic material for liquid phase photocatalysis and bacterial eradication.

An in-depth investigation was conducted on a promising composite material (BiVO4/TiO2), focusing on its potential toxicity, photoinduced catalytic properties, as well as its antibiofilm and antimicrobial functionalities. The preparation process involved the synthesis of 2D-TiO2 using the lyophilization method, which was subsequently functionalized with sphere-like BiVO4. Finally, we developed BiVO4/TiO2 S-scheme heterojunctions which can greatly promote the separation of electron-hole pairs to achieve high photocatalytic performance. The evaluation of concentration- and time-dependent viability inhibition was performed on human lung carcinoma epithelial A549 cells. This assessment included the estimation of glutathione levels and mitochondrial dehydrogenase activity. Significantly, the BiVO4/TiO2 composite demonstrated minimal toxicity towards A549 cells. Impressively, the BiVO4/TiO2 composite exhibited notable photocatalytic performance in the degradation of rhodamine B (k =0.135 min-1) and phenol (k = 0.016 min-1). In terms of photoinduced antimicrobial performance, the composite effectively inactivated both gram-negative E. coli and gram-positive E. faecalis bacteria upon 60-min of UV-A light exposure, resulting in a significant log6(log10CFU/mL) reduction in bacterial count. These promising results can be attributed to the unique 2D morphology of TiO2 modified by sphere-like BiVO4, leading to an increased generation of (intracellular)hydroxyl radicals, which plays a crucial role in treatments of both organic pollutants and bacteria.

Mechanism of Action and Efficiency of Ag3PO4-Based Photocatalysts for the Control of Hazardous Gram-Positive Pathogens.

Silver phosphate and its composites have been attracting extensive interest as photocatalysts potentially effective against pathogenic microorganisms. The purpose of the present study was to investigate the mechanism of bactericidal action on cells of opportunistic pathogens. The Ag3PO4/P25 (AGP/P25) and Ag3PO4/HA (HA/AGP) powders were prepared via a co-precipitation method. Thereafter, their antimicrobial properties against Enterococcus faecalis, Staphylococcus epidermidis, and Staphylococcus aureus (clinical and reference strains) were analyzed in the dark and after exposure to visible light (VIS). The mechanism leading to cell death was investigated by the leakage of metabolites and potassium ions, oxidative stress, and ROS production. Morphological changes of the bacterial cells were visualized by transmission electron microscopy (TEM) and scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy (SEM EDS) analysis. It has been shown that Ag3PO4-based composites are highly effective agents that can eradicate 100% of bacterial populations during the 60 min photocatalytic inactivation. Their action is mainly due to the production of hydroxyl radicals and photogenerated holes which lead to oxidative stress in cells. The strong affinity to the bacterial cell wall, as well as the well-known biocidal properties of silver itself, increase undoubtedly the antimicrobial potential of the Ag3PO4-based composites.

Biocidal activity of multifunctional cuprite-doped anion exchanger - Influence of bacteria type and medium composition.

The study presents unconventional, bifunctional, heterogeneous antimicrobial agents - Cu2O-loaded anion exchangers. The synergetic effect of a cuprous oxide deposit and polymeric support with trimethyl ammonium groups was studied against the reference strains of Enterococcus faecalis ATCC 29212 and Pseudomonas aeruginosa ATCC 27853. Biological testing (minimum bactericidal concentration, MBC), time- and dose-dependent bactericidal effect (under different conditions - medium composition and static/dynamic culture) demonstrated promising antimicrobial activity and confirmed its multimode character. The standard values of MBC, for all studied hybrid polymers and bacteria, were similar (64-128 mg/mL). However, depending on the medium conditions, due to the copper release into the bulk solution, bacteria were actively killed even at much lower doses of the hybrid polymer (25 mg/mL) and low Cu(II) concentrations in solution (0.01 mg/L). Simultaneously, confocal microscopic studies confirmed the effective inhibition of bacterial adhesion and biofilm formation on their surface. The studies conducted under different conditions showed also the influence of the structure and physical properties of studied materials on the biocidal efficacy and an antimicrobial action mechanism was proposed that could be significantly affected by electrostatic interactions and copper release to the solution. Although the antibacterial activity was also dependent on various strategies of bacterial cell resistance to heavy metals present in the aqueous medium, the studied hybrid polymers are versatile and efficient biocidal agents against bacteria of both types, Gram-positive and Gram-negative. Therefore, they can be a convenient alternative for point-of-use water disinfection systems providing water quality in medical devices such as dental units, spa equipment, and aesthetic devices used in the cosmetic sector.

Testing Antimicrobial Properties of Selected Short Amyloids.

Amyloids and antimicrobial peptides (AMPs) have many similarities, e.g., both kill microorganisms by destroying their membranes, form aggregates, and modulate the innate immune system. Given these similarities and the fact that the antimicrobial properties of short amyloids have not yet been investigated, we chose a group of potentially antimicrobial short amyloids to verify their impact on bacterial and eukaryotic cells. We used AmpGram, a best-performing AMP classification model, and selected ten amyloids with the highest AMP probability for our experimental research. Our results indicate that four tested amyloids: VQIVCK, VCIVYK, KCWCFT, and GGYLLG, formed aggregates under the conditions routinely used to evaluate peptide antimicrobial properties, but none of the tested amyloids exhibited antimicrobial or cytotoxic properties. Accordingly, they should be included in the negative datasets to train the next-generation AMP prediction models, based on experimentally confirmed AMP and non-AMP sequences. In the article, we also emphasize the importance of reporting non-AMPs, given that only a handful of such sequences have been officially confirmed.

Antimicrobial O-Alkyl Derivatives of Naringenin and Their Oximes Against Multidrug-Resistant Bacteria.

New antimicrobial agents are needed to address infections caused by multidrug-resistant bacteria. Here, we are reporting novel O-alkyl derivatives of naringenin and their oximes, including novel compounds with a naringenin core and O-hexyl chains, showing activity against clinical strains of clarithromycin-resistant Helicobacter pylori, vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, and beta-lactam-resistant Acinetobacter baumannii and Klebsiella pneumoniae. The minimum inhibitory concentrations (MICs), which provide a quantitative measure of antimicrobial activity, were in the low microgram range for the selected compounds. Checkerboard assays for the most active compounds in combination with antibiotics revealed interactions that varied from synergistic to neutral.

Photo-catalytic inactivation of an Enterococcus biofilm: the anti-microbial effect of sulphated and europium-doped titanium dioxide nanopowders.

The control and prevention of biofilm-related infections is an important public healthcare issue. Given the increasing antibiotic resistance among bacteria and fungi that cause serious infections in humans, promotion of new strategies combating microorganisms has been essential. One attractive approach to inactivate microorganisms is the use of semiconductor photo-catalysis, which has become the subject of extensive research. In this study, the bactericidal properties of four photo-catalysts, TiO2, TiO2-S, TiO2-Eu and TiO2-Eu-S, were investigated against established 24, 48, 72 and 96 h biofilms of Enterococcus The exposure of biofilms to the catalysts induced the production of superoxide radical anions. The best photo-catalytic inactivation was achieved with the TiO2-Eu-S and TiO2-S nanopowders and 24 h biofilms. Transmission electron microscopy images showed significant changes in the structure of the biofilm cells following photo-inactivation. The results suggest that doping with europium and modifying the surface with sulphate groups enhanced the bactericidal activity of the TiO2 nanoparticles against enterococcal biofilms.

Enterococcus--virulence and susceptibility to photodynamic therapy of clinical isolates from Lower Silesia, Poland.

BACKGROUND: A collection of 400 enterococcal isolates from clinical samples of hospitalized patients were studied for their virulence traits according to the isolation site. Formation of biofilm and production of DNase, hemolysin, lipase, and gelatinase were characterized. Biofilms of selected strains were examined for their susceptibility to antimicrobial photodynamic therapy (aPDT). METHODS: All strains were tested for biofilm production by microtiter method and the activity of hemolysin, gelatinase, lipase, and DNase by plate method with an adequate substrate. Photodynamic therapy with Photolon and red laser light was performed towards 48 h biofilms of eight representative strains. The viability of biofilms was tested by the BactLight assay and visualized under a fluorescent microscope. RESULTS: Among the 400 isolates, 69.8% strains of Enterococcus faecalis, 30% of Enterococcus faecium, and 0.2% of Enterococcus casseliflavus were identified. In vitro, production of biofilm was found in 65.7% of enterococci. Biofilm-positive strains were isolated from urinary tract infections (81%), wound infections (71%), respiratory tract infections (62%), and gastrointestinal tract (47%) (colonization). Hemolysin activity was observed in 28.5%, gelatinase in 24.5%, lipase in 23%, and DNase in 3.5% of all, mostly biofilm-positive, isolates. Photodynamic therapy with Photolon efficiently reduced the enterococcal biofilms. CONCLUSIONS: The study demonstrated the high prevalence of biofilm-producing clinical enterococci, their virulence potential being higher than for biofilm-negative strains, and the susceptibility to aPDT of mature biofilms produced by strains, regardless of their species and site of isolation.

Enterococcus in wound infections: virulence and antimicrobial resistance.

Enterococci, a complex group of facultative pathogens have become increasingly isolated in various hospital settings. They are considerable frequently cultured from traumatic and surgical wounds. We investigated 57 strains of the species E. faecalis, E. faecium and E. casseliflavus isolated from infected wounds. Their ability to produce virulence factors and their sensitivity to antibiotics were evaluated using phenotypic and genotyping methods. In the phenotype studies, significant portion of the isolates produced biofilm (66.7%) and gelatinase (36.8%). Nearly 30% of the strains expressed hemolytic properties. Only a few produced DNAse (15.8%) and lipase (7.0%). The genes esp, gelE, cylA, cylB, cylM and agg were detected in most of the isolates (38.6-87.7%). All the isolated enterococci were susceptible to vancomycin and were characterized by their low resistance to antibiotics, except aminoglycosides (HLR).

Virulence of Enterococcus isolates collected in Lower Silesia (Poland).

148 enterococcal strains: E.faecalis (108), E.faecium (35), E.gallinarum (3), E.casseliflavus (1) and E.durans (1) from various clinical specimens were investigated for their ability to adhere to Caco-2 and HEp-2 cell lines, and also for the presence of the esp gene, biofilm formation, production of haemolysins, DNAse and lipase. Several types of enterococcal adhesion to both cell lines were noted. An aggregative adherence was the most frequent among E.faecalis and E.faecium isolates. Other species presented various adhesive types. The occurrence of virulence factors in the whole group of strains was as follows: esp gene in 53.4%, biofilm in 45.3%, haemolysins in 15.5%, DNAse in 12.2% and lipase in 33.1% of enterococcal isolates. It appears that the adherence of the enterococci studied was not significantly associated with the presence of virulence factors.