Search Results (33)

In response to the intermittent discharge and frequent flow interruptions characteristic of rural domestic wastewater, this study evaluated the treatment performance and microbial mechanisms of basalt fiber (BF) felt as a novel biofilm carrier, with comparative analyses against traditional polyurethane (PU) carrier. Under continuous-flow conditions, both carriers showed no significant difference in the removal efficiencies of COD and NH₄⁺-N. However, when switching to intermittent feeding mode with flow interruption, the BF reactor maintained high removal efficiencies for pollutants (COD, NH₄⁺-N and TN removals averaged 90.5%, 89.4% and 64.5%, respectively), significantly outperforming the PU reactor (COD, NH₄⁺-N and TN removals averaged 82.3%, 32.7% and 20.7%, respectively). High-throughput sequencing results revealed that the BF carrier significantly enriched nitrifiers (e.g., Nitrospira) and aerobic denitrifiers (e.g., Terrimonas and Bacillus) during the intermittent operation phase. Functional prediction further indicated increased abundances of functional genes associated with nitrification (amoA, hao), complete denitrification (narG, nosZ), as well as glycolysis (GAPDH) and the TCA cycle (IDH1, korA) related to NADH generation, suggesting an enhanced coupling mechanism of carbon and nitrogen metabolism in the BF system. Conversely, a significant reduction in microbial diversity and the abundance of relevant functional genes was observed on the traditional carriers. This study confirms that BF felt, serving as a biocarrier for rural domestic wastewater treatment, exhibits superior shock load resistance and nitrogen removal performance, which provides an efficient and reliable carrier option for decentralized wastewater treatment in rural areas. Full article

Background/Objectives: In this study, we aimed to investigate the antimicrobial and antibiofilm activity of seven hydroxyphenyl-thiazolyl-coumarin hybrid compounds with antioxidant properties (1a–g), previously reported by our group. Methods: The compounds were evaluated in vitro through MIC, MBC, and MFC determinations, and percentage of biofilm (BF) inhibition and in silico, respectively, through molecular docking, molecular dynamics simulations, and ADMETox prediction. Results: All compounds showed antibacterial and antifungal activities. In terms of antibacterial activity, all the compounds were active on Pseudomonas aeruginosa (MICs = 15.62–31.25 μg/mL), Enterococcus faecalis (MICs = 15.62–31.25 μg/mL), and Staphylococcus aureus (MICs = 62.5–125 μg/mL). Regarding the antifungal activity, the effect against Candida albicans was similar to fluconazole (MIC = 15.62 μg/mL), compounds 1b and 1g being the most active against Aspergillus brasiliensis (MIC = 15.62 μg/mL). Furthermore, all compounds were both bactericidal and fungicidal. Regarding the antibiofilm activity, compounds 1d–g showed superior P. aeruginosa BF inhibition compared to gentamicin. The in vitro results for the antibacterial activity were well correlated with the observations drawn in the molecular docking studies, where the best binding affinities (BAs) were observed against P. aeruginosa PAO1 GyrB subunit, and the molecular dynamics simulations confirmed the antibacterial mechanism of compounds 1a, 1b, 1d, 1f, and 1g through GyrB subunit inhibition. Regarding the antifungal activity, all compounds showed better BAs than fluconazole against CYP51 in all instances. ADMETox predictions concluded that all the compounds could have low gastrointestinal absorption and reduced risk of pharmacokinetic interactions. Conclusions: The investigated compounds bring novelty into the actual research due to their dual antibacterial and antibiofilm activity against biofilm-associated P. aeruginosa infections. Full article

Helicobacter pylori (H. pylori), a prevalent human pathogen affecting nearly half the global population, is a major contributor to chronic gastritis, peptic ulcer, and gastric cancer. H. pylori develops biofilms (BFs) allowing bacteria to evade the immune response. Differences in composition between planktonic and biofilm cells influence the host’s immune response, yet the specific biofilm components modulating this response remain uncharacterized. Considering the above, this study evaluated the effect of in vitro-generated H. pylori BF on the antibacterial activity of neutrophils. This work utilized sonication to obtain disaggregated H. pylori BF (d-BF-Hp) to challenge human neutrophils, assessing their bactericidal and phagocytic activity against Staphylococcus aureus. S. aureus survival in the presence of neutrophils was enhanced by 10 μg/mL of d-BF-Hp’s protein. Conversely, S. aureus survival was significantly lower at 30 µg/mL compared to 10 µg/mL d-BF-Hp. Furthermore, 10 and 30 µg/mL of d-BF-Hp significantly reduced the neutrophil phagocytosis rate. Our findings suggest that d-BF-Hp components diminish neutrophil bactericidal activity, although this effect was not observed at higher d-BF-Hp concentrations. Increased d-BF-Hp concentrations proportionally reduced neutrophil phagocytic capacity. Future work should explore the mechanisms underlying the alteration of neutrophil microbicidal properties. Full article

Commonly available essential oils (EOs) are pure aromatic substances derived from natural plant sources (fresh or dried raw materials), with broad biological activity, including antimicrobial activity. The activity of EOs is of great interest due to the serious problem of diseases caused by microorganisms. Pathogenic microorganisms (PAMs) show increased resistance to physical and chemical factors due to their association with a form of specific biological membrane called biofilm (BF), which is resistant to extreme conditions and significantly hinders effective therapy. The decreasing effectiveness of antibiotics, combined with the increasing resistance of microorganisms, has prompted the search for alternative antimicrobial (AM) therapies. EOs and some of their components are currently considered as potential agents useful in the prevention, treatment, and control of infections transmitted by microbial BF. In combination with antibiotics, EOs can prevent the transfer of resistance to AM agents due to the synergistic antibiofilm (ABF) effect. BF inhibition by EO is not based on killing bacterial cells but on the inhibition of the quorum sensing (QS) pathway. EOs also affect growth regulation, nutritional balance, and energy conversion in bacteria. It can be assumed that this group of substances will be of significant importance in the treatment of infectious diseases in the near future. This article reviews the results of the latest research on essential oils and their main components as potential factors limiting/inhibiting the development of PAMs. Full article

Biofilms formed by Candida albicans pose therapeutic challenges due to their resistance to conventional antimicrobials, highlighting the need for more effective treatments. Rhamnolipids (RLs) are biosurfactants with diverse antimicrobial properties. Bacteriophages are viruses that target specific bacterial strains. Recent studies have shown that they may affect biofilm formation by fungi and yeasts. This study investigated the combined antimicrobial effects of RLs and bacteriophages against C. albicans biofilms, focusing on their anti-adhesive and inhibitory effects on biofilm development. RT-PCR assays were used to analyze gene modulation in C. albicans biofilm formation in response to RLs and bacteriophage treatments, while hyphae formation was examined using microscopy. The results showed that RLs-bacteriophage combinations significantly reduced biofilm formation compared to individual treatments. A combination of 200 mg/L RLs with bacteriophage BF9 led to a 94.8% reduction in biofilm formation. In a subsequent model, the same RL concentration with bacteriophage LO5/1f nearly eliminated biofilm formation (~96%). Gene expression analysis revealed downregulation of key biofilm-associated genes when Candida cells were treated with 200 mg/L RLs and four bacteriophages (BF17, LO5/1f, JG004, FD). These results show the potential of RL and bacteriophage combinations in combating C. albicans biofilms, presenting a promising therapeutic approach against resilient infections. Full article

Acinetobacter (A.) baumannii is a major nosocomial pathogen in human and veterinary medicine. The emergence of certain international clones (ICs), often with multidrug-resistant (MDR) phenotypes and biofilm formation (BF), facilitates its spread in clinical environments. The global rise in antimicrobial resistance demands alternative treatment strategies, such as antimicrobial peptides (AMPs). In this study, 45 human and companion animal MDR-A. baumannii isolates, belonging to the globally spread IC1, IC2 and IC7, were tested for antimicrobial resistance and biofilm-associated genes (BAGs) and their capacity for BF. Of these, 13 were used to test the inhibitory effect of AMPs on bacterial growth (BG) and BF through the application of a crystal violet assay. The two novel AMP variants Bac7(17) (target cell inactivation) and Pasmr5-17 (efflux pump inhibition) and the well-known AMP phenylalanine-arginine-β-naphthylamide (PAβN) were tested at concentrations of 1.95 to 1000 µg/mL. Based on whole-genome sequence data, identical patterns of BAGs were detected within the same IC. AMPs inhibited BG and BF in a dose-dependent manner. Bac7(17) and PAsmr5-17 were highly effective against BG, with growth inhibition (GI) of >99% (62.5 and 125 µg/mL, respectively). PAβN achieved only 95.7% GI at 1000 µg/mL. Similar results were obtained for BF. Differences between the ICs were found for both GI and BF when influenced by AMPs. PAsmr5-17 had hardly any inhibitory effect on the BF of IC1 isolates, but for IC2 and IC7 isolates, 31.25 µg/mL was sufficient. Our data show that the susceptibility of animal MDR-A. baumannii to AMPs most likely resembles that of human isolates, depending on their assignment to a particular IC. Even low concentrations of AMPs had a significant effect on BG. Therefore, AMPs represent a promising alternative in the treatment of MDR-A. baumannii, either as the sole therapy or in combination with antibiotics. Full article

Background/Objectives: The aim of this in vitro study was to analyze and compare the Streptococcus mutans ability to adhere and form biofilm on the surface of light-cured VS heat-cured dental composite resins; Methods: Three composite resins with different chemical formulations were selected: GrandioSO (GR), Venus Diamond (VD) and Enamel Plus Hri Biofunction (BF). Disk-shaped specimens were manufactured by light-curing the composite resins (light-cured subgroups) and subjecting them to a further heat-curing cycle at 80° for 10 min (heat-cured subgroups). Specimens were analyzed for planktonic CFU count (CFU/mL), sessile CFU count (CFU/mL) and for biomass quantification (OD_570nm); Results: The planktonic CFU count was higher in all the light-cured subgroups than in the heat-cured subgroups (light-cured: GR = 7.23 × 10⁶, VD = 2.14 × 10⁷, BF = 4.40 × 10⁷; heat-cured: GR = 4.89 × 10⁶, VD = 4.95 × 10⁶, BF = 2.80 × 10⁷), with a statistically significant increase for BF and VD. Focusing on the sessile CFUs, both GR (light-cured = 7.49 × 10⁶; heat-cured = 3.97 × 10⁶) and VD (light-cured = 2.93 × 10⁷; heat-cured = 6.07 × 10⁶) showed a significantly increased number of colonies in the light-cured subgroups. The OD_570nm values recorded for the light-cured BF subgroup (0.4280) were significantly increased compared to the heat-cured BF subgroup (0.1931); Conclusions: A more complete polymerization protocol seems to lead to a potential reduction in the risk of secondary caries. Full article

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

Since they are difficult and sometimes impossible to treat, infections sustained by multidrug-resistant (MDR) pathogens, emerging especially in nosocomial environments, are an increasing global public health concern, translating into high mortality and healthcare costs. In addition to having acquired intrinsic abilities to resist available antibiotic treatments, MDR bacteria can transmit genetic material encoding for resistance to non-mutated bacteria, thus strongly decreasing the number of available effective antibiotics. Moreover, several pathogens develop resistance by forming biofilms (BFs), a safe and antibiotic-resistant home for microorganisms. BFs are made of well-organized bacterial communities, encased and protected in a self-produced extracellular polymeric matrix, which impedes antibiotics’ ability to reach bacteria, thus causing them to lose efficacy. By adhering to living or abiotic surfaces in healthcare settings, especially in intensive care units where immunocompromised older patients with several comorbidities are hospitalized BFs cause the onset of difficult-to-eradicate infections. In this context, recent studies have demonstrated that quaternary ammonium compounds (QACs), acting as membrane disruptors and initially with a low tendency to develop resistance, have demonstrated anti-BF potentialities. However, a paucity of innovation in this space has driven the emergence of QAC resistance. More recently, quaternary phosphonium salts (QPSs), including tri-phenyl alkyl phosphonium derivatives, achievable by easy one-step reactions and well known as intermediates of the Wittig reaction, have shown promising anti-BF effects in vitro. Here, after an overview of pathogen resistance, BFs, and QACs, we have reviewed the QPSs developed and assayed to this end, so far. Finally, the synthetic strategies used to prepare QPSs have also been provided and discussed to spur the synthesis of novel compounds of this class. We think that the extension of the knowledge about these materials by this review could be a successful approach to finding effective weapons for treating chronic infections and device-associated diseases sustained by BF-producing MDR bacteria. Full article

Microbial adhesion on dental restorative materials may jeopardize the restorative treatment long-term outcome. The goal of this in vitro study was to assess Candida albicans capability to adhere and form a biofilm on the surface of heat-cured dental composites having different formulations but subjected to identical surface treatments and polymerization protocols. Three commercially available composites were evaluated: GrandioSO (GR), Venus Diamond (VD) and Enamel Plus HRi Biofunction (BF). Cylindrical specimens were prepared for quantitative determination of C. albicans S5 planktonic CFU count, sessile cells CFU count and biomass optical density (OD_{570 nm}). Qualitative Concanavalin-A assays (for extracellular polymeric substances of a biofilm matrix) and Scanning Electron Microscope (SEM) analyses (for the morphology of sessile colonies) were also performed. Focusing on planktonic CFU count, a slight but not significant reduction was observed with VD as compared to GR. Regarding sessile cells CFU count and biomass OD_{570 nm}, a significant increase was observed for VD compared to GR and BF. Concanavalin-A assays and SEM analyses confirmed the quantitative results. Different formulations of commercially available resin composites may differently interact with C. albicans. The present results showed a relatively more pronounced antiadhesive effect for BF and GR, with a reduction in sessile cells CFU count and biomass quantification. Full article

Streptococcus mutans form oral biofilms (BFs) and cause dental caries. Roasted green tea (RGT) is prepared by roasting the tea plant, and RGT-specific polyphenols are produced during the roasting process. Catechins, polyphenols in green tea, have BF inhibitory activity against S. mutans; therefore, RGT-specific polyphenols are also expected to have this activity. However, there are few reports on the structural and functional properties of RGT. This study aimed to investigate the inhibitory activity of RGT against S. mutans BF formation and to investigate the active compounds. RGT extract fractionation and BF inhibitory assay were performed. Strong activity was confirmed in the RGT fractions that had medium-high hydrophobicity, were rich in phenolic hydroxyl groups, and lacked catechins. A peak comprising compounds with molecular weights of 918 (mw918) and 1050 (mw1050) was purified from the fraction. Since BF inhibitory activity was confirmed for this peak, these compounds were considered to be part of the active ingredients. The mw918 polyphenol was detected only in RGT and it was thought to be produced during the roasting process. The results of this research will serve as a basis for the future application of RGT as a safe and effective anti-caries agent. Full article

Biofilm formation can lead to the persistence of Salmonella Typhimurium (ST) and E. coli O157:H7 (O157). This study investigated the impact of meat processing surface bacteria (MPB) on biofilm formation by O157 (non-biofilm former; NF) and ST (strong biofilm former; BF). MPB were recovered from the contacting surfaces (CS), non-contacting surfaces (NCS), and roller surfaces (RS) of a beef plant conveyor belt after sanitation. O157 and ST were co-inoculated with MPB (CO), or after a delay of 48 h (IS), into biofilm reactors containing stainless steel coupons and incubated at 15 °C for up to 144 h. Coupons were withdrawn at various intervals and analyzed by conventional plating and 16S rRNA gene amplicon sequencing. The total bacterial counts in biofilms reached approximately 6.5 log CFU/cm², regardless of MPB type or development mode. The mean counts for O157 and ST under equivalent conditions mostly did not differ (p > 0.05), except for the IS set at 50 h, where no O157 was recovered. O157 and ST were 1.6 ± 2.1% and 4.7 ± 5.0% (CO) and 1.1 ± 2.2% and 2.0 ± 2.8% (IS) of the final population. Pseudomonas dominated the MPB inocula and biofilms, regardless of MPB type or development mode. Whether or not a pathogen is deemed BF or NF in monoculture, its successful integration into complex multi-species biofilms ultimately depends on the presence of certain other residents within the biofilm. Full article

Although synthetic colorants are widely used in many industries due to their high stability at different conditions in industrial processes, evidence of its negative impact on health and the environment is undeniable. Filamentous fungi are well known for their use as alternative sources to produce natural pigments. However, an adequate comparison of the productivity parameters between the fermentation systems could be limited to their heterogeneous conditions. Even though Solid-State Fermentations (SSF) on natural substrates are widely used for pigments production, complex media, and non-controlled variables (T, pH, medium composition), these systems could not only hamper the finding of accurate productivity parameters, but also mathematical modeling and genomics-based optimization. In this context, the present study screened five pigment-producing fungi by comparing Submerged (SmF) and Surface Adhesion Fermentation [biofilm (BF) and Solid-State (SSF)] with defined media and controlled variables. For this purpose, we used the same defined media with sucrose as the carbon source for pigment production on SmF, BF, and SSF, and BF and SSF were carried out on inert supports. Five molecularly identified Penicillium and Talaromyces strains isolated from the Peruvian rainforest were selected for their ability to produce yellowish-orange colorants. Highest productivities were obtained from T. brunneus LMB-HP43 in SmF (0.18 AU/L/h) and SSF (0.17 AU/L/h), and P. mallochii LMB-HP37 in SSF (0.18 AU/L/h). Both strains also exhibited the highest yields (AU/g biomass) in the three fermentation systems, reaching values greater than 18-folds in SSF compared to the other strains. Conversely, T. wortmannii LMB-HP14 and P. maximae LMB-HP33 showed no ability to produce pigments in the SSF system. The performed experiments accurately compared the effect of the fermentation system on yield and productivity. From this, further genomics approaches can be considered for an extensive analysis of pigment synthesis pathways and a genomics-driven optimization in the best fermentation system. Full article

Experimental adhesives with functional nitrogen-doped titanium dioxide nanoparticles (N_TiO₂) have been shown to display improved properties. However, these materials have not been characterized regarding their degree of conversion (DC), biaxial flexure strength (BFS), surface roughness (SR), elastic modulus (EM), and long-term antibacterial functionalities. Experimental adhesives were synthesized by dispersing N_TiO₂ (10%, 20%, or 30%, v/v%) into OptiBond Solo Plus (OPTB, Kerr Corp., USA). Unpolymerized adhesives (volume = 50 μL/drop, n = 3/group) were individually placed onto a heated (37 °C) attenuated total reflectance (ATR) monolithic diamond crystal (Golden Gate, Specac). The spectra of composites were obtained with a Fourier-transform infrared (FTIR) spectrometer (Nicolet IS50; 500–4500 cm⁻¹; resolution = 4 cm⁻¹, 10 internal scans/spectrum) before and after polymerization. Disk-shaped specimens (diameter = 6.0 mm, thickness = 0.5 mm) for BFS (n = 12/group), SR and EM (n = 3/group), and for antibacterial testing (n = 18/group/time-point) were fabricated and photopolymerized (1 min each; 385–515 nm, 1000 mW/cm²; VALO). DC values (%) were calculated from pre- and post-polymerization spectra using the two-frequency method and tangent-baseline technique. BFS was assessed using a universal testing machine (Instron 68TM-5, crosshead speed = 1.27 mm/min, 25 °C). SR and EM were investigated using an atomic force microscope (Multimode 8) with aluminum-coated silicon probes (8 nm pyramidal tip, spring constant 40 N/m, Bruker). Antibacterial testing was performed by growing Streptococcus mutans biofilms (UA159-ldh, 37 °C, microaerophilic) on the surfaces of specimens for 24 h and then measuring the relative luminescence units (RLU) with a Biotek Synergy HT multi-well plate reader. Results demonstrate that experimental materials containing 10%, 20%, and 30% of N_TiO₂ displayed higher levels of DC, had better mechanical properties, and were able to exert strong and durable antibacterial properties without visible light irradiation and after extended periods of simulated shelf-life and aging in PBS. The reported experimental materials are expected to increase the service lives of polymer-based bonded restorations by decreasing the incidence of secondary caries. Full article

Multidrug resistance (MDR) among pathogens and the associated infections represent an escalating global public health problem that translates into raised mortality and healthcare costs. MDR bacteria, with both intrinsic abilities to resist antibiotics treatments and capabilities to transmit genetic material coding for further resistance to other bacteria, dramatically decrease the number of available effective antibiotics, especially in nosocomial environments. Moreover, the capability of several bacterial species to form biofilms (BFs) is an added alarming mechanism through which resistance develops. BF, made of bacterial communities organized and incorporated into an extracellular polymeric matrix, self-produced by bacteria, provides protection from the antibiotics’ action, resulting in the antibiotic being ineffective. By adhering to living or abiotic surfaces present both in the environment and in the healthcare setting, BF causes the onset of difficult-to-eradicate infections, since it is difficult to prevent its formation and even more difficult to promote its disintegration. Inspired by natural antimicrobial peptides (NAMPs) acting as membrane disruptors, with a low tendency to develop resistance and demonstrated antibiofilm potentialities, cationic polymers and dendrimers, with similar or even higher potency than NAMPs and with low toxicity, have been developed, some of which have shown in vitro antibiofilm activity. Here, aiming to incite further development of new antibacterial agents capable of inhibiting BF formation and dispersing mature BF, we review all dendrimers developed to this end in the last fifteen years. The extension of the knowledge about these still little-explored materials could be a successful approach to find effective weapons for treating chronic infections and biomaterial-associated infections (BAIs) sustained by BF-producing MDR bacteria. Full article