Search Results (277)

Municipal wastewater with a low carbon-to-nitrogen (C/N) ratio presents challenges for conventional nitrogen removal processes, often requiring costly external carbon sources. This study investigated the enhancement of nitrogen removal in a simultaneous nitrification and denitrification (SND) system by incorporating heterotrophic nitrification and aerobic denitrification (HN-AD) bacterial agents (Klebsiella variicola L3, Acinetobacter beijerinckii W4, and Acinetobacter sp. Z1) with modified basalt fiber carriers. Three reactors were compared: mixed HN-AD strains (M), mixed strains with activated sludge (A+M), and activated sludge alone (A). Results demonstrated that the A+M reactor achieved superior performance, with median removal efficiencies of 82.2% for NH₄⁺-N, 52.9% for total nitrogen (TN), and 51.6% for COD, outperforming the M reactor (75.2%, 43.6%, and 51.6%) and the A reactor (63.2%, 29.3%, and 44.8%). The A+M reactor also exhibited a 40% reduction in COD consumption per unit TN removed (2.55 ± 1.75) compared to the control reactor A (4.25 ± 3.99). Microbial analysis revealed Acinetobacter sp. Z1 (6.1%) and K. variicola L3 (1.1%) as dominant species, with the A+M reactor showing higher microbial diversity (56.4% Proteobacteria, 10.2% Bacteroidota) and biological viability (VSS/SS ratio of 0.70 ± 0.01). Extracellular polymeric substance (EPS) content in A+M reached 242.26 ± 15.52 mg/g-VSS, with a protein-to-polysaccharide ratio of 2.77 ± 0.00, indicating robust biofilm activity. These findings highlight the potential of HN-AD bacterial agents to enhance nitrogen removal in low C/N wastewater treatment, offering a cost-effective and sustainable alternative to traditional methods by reducing reliance on external carbon sources and improving system efficiency. Full article

Candida albicans and Staphylococcus aureus are opportunistic pathogens that cause life-threatening infections. This study focused on using photodynamic inactivation (PDI) to eliminate mixed biofilms of C. albicans–S. aureus formed on poly (urethane) (PU) discs functionalized with a nanocomposite layer containing phloxine B (PhB). Additionally, the effect of PDI on the ALS3 and HWP1 genes of C. albicans was examined in mixed biofilms. Spectral analysis showed a continuous release of PhB from the nanocomposite in Mueller–Hinton broth within 48 h, with a released amount of PhB < 5% of the total amount. The anti-biofilm effectiveness of the light-activated nanocomposite with PhB showed a reduction in the survival rate of biofilm cells to 0.35% and 31.79% for S. aureus and C. albicans, respectively, compared to the control biofilm on PU alone. Scanning electron microscopy images showed that the nanocomposite effectively reduced the colonization and growth of the mixed biofilm. While PDI reduced the regulation of the ALS3 gene, the HWP1 gene was upregulated. Nevertheless, the cell survival of the C. albicans–S. aureus biofilm was significantly reduced, showing great potential for the elimination of mixed biofilms. Full article

Polymicrobial biofilms involving fungal and bacterial species are increasingly recognized as contributors to persistent infections, particularly in the oral cavity. Candida albicans and Aggregatibacter actinomycetemcomitans are two commensals that can turn into opportunistic pathogens and are able to form robust biofilms. Objectives: This study aimed to assess the interaction dynamics between these two microorganisms and to evaluate their susceptibility to fluconazole and azithromycin in single- and mixed-species forms. Methods: Biofilm biomass was quantified using crystal violet assays, while biofilm cell viability was assessed through CFU enumeration (biofilm viability assay). To assess the resistance properties of single versus mixed-species coincubations, we applied the antimicrobial susceptibility test (AST) to each drug, and analysed spatial organization with confocal laser scanning microscopy, using PNA-FISH. Results: The results indicated that both species can coexist without significant mutual inhibition. However, a non-reciprocal synergism was also observed, whereby mixed-species biofilm conditions promoted the growth of A. actinomycetemcomitans, while C. albicans growth remained stable. As expected, antimicrobial tolerance was elevated in mixed cultures, likely due to enhanced extracellular matrix production and potential quorum-sensing interactions, contributing to increased resistance against azithromycin and fluconazole. Conclusions: This study provides novel insights into previously rarely explored interactions between C. albicans and A. actinomycetemcomitans. These findings underscore the importance of investigating interspecies interactions within polymicrobial biofilms, as understanding their mechanisms, such as quorum-sensing molecules and metabolic cooperation, can contribute to improved diagnostics and more effective targeted therapeutic strategies against polymicrobial infections. Full article

The prevention of biofilm formation and algal biodeterioration on building materials, particularly on cultural heritage sites, is a growing concern. Due to regulatory restrictions on conventional algicidal biocides in Europe, natural alternatives such as essential oils are gaining interest for their potential use in heritage conservation. This study evaluates the anti-algal activity of Salvia officinalis and Equisetum arvense (essential oils, hydrolates, and extracts) against a mixed culture of five green algae species (Bracteacoccus minor, Stichococcus bacillaris, Klebsormidium nitens, Chloroidium saccharophilum, and Diplosphaera chodatii). The plant materials were processed using hydrodistillation and solvent extraction, followed by chemical characterization through gas chromatography–mass spectrometry (GC-MS). Biological efficacy was assessed by measuring algal growth inhibition, changes in biomass colour, chlorophyll a concentration, and fluorescence. S. officinalis yielded higher extract quantities (extraction yield: 23%) than E. arvense and contained bioactive compounds such as thujone, camphor, and cineole, which correlated with its strong anti-algal effects. The essential oil of S. officinalis demonstrated the highest efficacy, significantly inhibiting biofilm formation (zones of inhibition: 15–94 mm) and photosynthetic activity at 0.5% concentration (reduction in chlorophyll a concentration 90–100%), without causing visible discolouration of treated surfaces (∆E < 2). These findings highlight the potential of S. officinalis essential oil as a natural, effective, and material-safe algicidal biocide for the sustainable protection of cultural heritage sites. Full article

Fungal prosthetic joint infection (fPJI) is one of the orthopaedic pathologies where there is no clear evidence, guidelines or algorithm to guide the surgeon in its management. This is in addition to the difficulty with which these infections are diagnosed, isolated and treated. Fungi form notorious biofilms that are difficult to eradicate once formed and that display resistance to antimicrobial agents. These biofilms have been shown to act synergistically with biofilms of bacteria, further adding to medical treatment resistance. We have reviewed the literature for reports that describe the results of different methods in surgically treating fPJI. We found that surgical management with two stages remains the gold standard for treatment of fPJI, as is the case for bacterial PJI (bPJI). We have investigated medical treatment, debridement with implant retention (DAIR) and staged revisions and whether a reasonable recommendation can be made based on the best knowledge and practice available. From the data on bPJI, there exists a role for conservative management of acute PJI with debridement, antibiotics and implant retention (DAIR). While fPJI and bPJI both represent infections, the differences in our ability to detect these infections clinically, culture the pathogens and treat them with proper antimicrobial agents, along with the difference in the reported results of the surgical treatment, make us believe that these two types of infections should not be treated in the same manner. With all this in mind, we reviewed several reports in the literature on fPJI to determine the efficacy of current treatment modalities, including DAIR, which followed current guidelines for PJI. Data show an overall treatment success rate of 64.4% [range 17.4–100%]. Subgroup analysis revealed a success rate of 11.6% [range 0–28.7%] in patients treated with DAIR. There is no doubt that DAIR should not be encouraged as it consistently has a bad record. Although there are not enough studies or numbers of patients to show an evidence-based preference over one- or two-staged revisions, the two-stage revision of fPJI consistently shows better results and should be considered as the gold standard of management in cases of revision fPJI. This should also be coupled with proper expertise, follow-ups and recommended lengths of medical treatment, which should not be less than six months. From the review of these data, we have developed reasonable recommendations for the management of fPJI. These recommendations center on staged surgical debridement along with medical management. Medical treatment should be for at least 6 months under the guidance of an infectious disease team and based on intraoperative cultures. In the case of local antimicrobial treatment reported in the literature, many patients with fPJI were found to have a polymicrobial infection. As a result, it is our recommendation that antifungals as well as antibacterials should be incorporated into the cement spacer mix of these cases. Fungal PJI remains an exceedingly difficult pathology to treat and should be managed by experienced surgeons in a well-equipped institution. Full article

Endodontic infections are characterized by complex polymicrobial communities residing within the intricate root canal system. Traditional chemomechanical methods frequently fail to achieve complete microbial eradication, especially in cases involving biofilm-forming and resistant species. This systematic review synthesizes current evidence on the molecular basis and antimicrobial efficacy of the neodymium-doped yttrium aluminum garnet (Nd:YAG) laser in root canal disinfection, particularly against polymicrobial infections. A comprehensive literature search was conducted in the PubMed, Embase, Scopus, and Cochrane databases in accordance with PRISMA 2020 guidelines. Experimental and preclinical studies evaluating the bactericidal properties of Nd:YAG laser therapy were included. The Nd:YAG laser demonstrated significant reductions in total microbial load through photothermal effects, including denaturation of proteins, disruption of cell membranes, and degradation of mixed-species biofilms. Although complete sterilization was not consistently achieved, its ability to penetrate dentinal tubules and target microbial consortia offers substantial adjunctive value. Standardization of laser parameters and further clinical studies are needed to validate these findings and establish Nd:YAG laser use in routine endodontic disinfection protocols. Full article

Mycobacterium abscessus complex (MABc) poses a major therapeutic challenge due to its intrinsic multidrug resistance and ability to form biofilms. This study evaluated the in vitro activity of three antimycobacterial agents—bedaquiline, delamanid, and clofazimine—on 20 clinical MABc isolates, including M. abscessus subsp. abscessus, massiliense, and bolletii, with a focus on biofilm-forming phenotypes. Biofilm analysis showed that the rough colony morphotypes were mostly weak biofilm formers, while the smooth and mixed morphotypes were predominantly moderate or strong biofilm formers. A statistically significant association was observed between the mixed colony morphology and strong biofilm formation (p = 0.032). Importantly, bedaquiline exhibited potent and consistent activity across all isolates, regardless of the biofilm-forming ability, with MIC values ranging from 0.125 to 1 µg/mL. In contrast, delamanid and clofazimine showed limited efficacy, with MIC values exceeding 16 µg/mL and 8 µg/mL, respectively. These findings strongly support the role of bedaquiline as a promising core agent for future combination therapies targeting drug-resistant MABc infections, including biofilm-associated infections. Our results, among the first from Poland, highlight the critical need for incorporating novel agents such as bedaquiline into therapeutic strategies against this difficult-to-treat pathogen. Full article

This study explores the feasibility of producing biohydrogen from winery wastewater using a dual-chamber microbial electrolysis cell (MEC). A mixed microbial consortium pre-adapted to heavy-metal environments and enriched with Geobacter sulfurreducens was anaerobically cultivated from diverse waste streams. Over 5000 h of development, the MEC system was progressively adapted to winery wastewater, enabling long-term electrochemical stability and high organic matter degradation. Upon winery wastewater addition (5% v/v), the system achieved a sustained hydrogen production rate of (0.7 ± 0.3) L H₂ L⁻¹ d⁻¹, with an average current density of (60 ± 4) A m⁻³, and COD removal efficiency exceeding 55%, highlighting the system’s resilience despite the presence of inhibitory compounds. Coulombic efficiency and cathodic hydrogen recovery reached (75 ± 4)% and (87 ± 5)%, respectively. Electrochemical impedance spectroscopy provided mechanistic insight into charge transfer and biofilm development, correlating resistive parameters with biological adaptation. These findings demonstrate the potential of MECs to simultaneously treat agro-industrial wastewaters and recover energy in the form of hydrogen, supporting circular resource management strategies. Full article

Climate change will have a significant impact on saltwater intrusion in coastal aquifers between now and 2150. Global sea levels are predicted to rise somewhere between 0.5 and 1.8 m. To mitigate sea level rise, coastal aquifers will require intensive management to avoid inland migration of seawater that could impact water supplies. In addition to reducing pumping of freshwater, the construction and operation of salinity barriers will be required in many locations. Eleven types of salinity barriers were investigated, including physical barriers (curtain wall and grout curtains), infiltration canals filled with freshwater paralleling the coastline, injection of freshwater (treated surface water or wastewater), pumping or abstraction barriers, mixed injection and abstraction barriers, combined abstraction, desalination, and recharge (ADR), ADR hybrid barriers using various water sources including desalinated water and treated wastewater, compressed air barriers, aquifer storage and recovery dual use systems, biofilm barriers, and clay swelling or dispersion barriers. Feasibility of the use of each salinity barrier type was evaluated within the context of the most recent projections of sea level changes. Key factors used in the evaluation included local hydrogeology, land surface slope, water use, the rate of sea level rise, technical feasibility (operational track record), and economics. Full article

A biofilm is a group of bacterial cells in the polysaccharide matrix bonded to the surface (biotic or abiotic). Clinicians now realize that most infections are biofilm-related. Biofilm infections are often induced by more than one bacterial species. The aim of this study is to characterize a mixed biofilm composed of Pseudomonas aeruginosa and Proteus mirabilis strains. Forty-six isolates derived from chronic wound infections were cultivated to establish mature biofilms. The biofilm biomass and cell viability were measured by colorimetric assays. P. aeruginosa strains were tested for the presence of virulence and biofilm-related genes. The quorum sensing assay using the biosensor strain was also performed. A mixed biofilm of P. aeruginosa and P. mirabilis was visualized using fluorescence microscopy. Four groups of P. aeruginosa and P. mirabilis pairs, also visualized with fluorescence microscopy, were distinguished based on the biofilm biomass growth and metabolic activity loss. The exoY gene observed among P. aeruginosa isolates was connected to the metabolic activity loss of the biofilm. Generally, the interactions between P. aeruginosa and P. mirabilis species are not uniform. It is crucial to further research the interactions between microorganisms in biofilms. This may provide information on the mechanisms of biofilm formation in the complicated chronic wound environment. Full article

Staphylococcus aureus and Pseudomonas aeruginosa are classified as ESKAPE pathogens that present a significant challenge to treatment due to their increased resistance to a considerable number of antimicrobial agents. Background/Objective: Biofilms exacerbate treatment challenges by providing enhanced antimicrobial and environmental protection. Mixed-species biofilms further complicate treatment options through numerous complex interspecies interactions, leading to potentially severe adverse clinical outcomes. Methods: This study assessed the interaction between clinical S. aureus and P. aeruginosa isolates during biofilm formation using microplate biofilm formation assays, scanning electron microscopy, and confocal microscopy. Results: We identified a competitive relationship between P. aeruginosa and S. aureus, where both pathogens exhibited a reduction in biofilm formation during mixed-species biofilms compared with monocultures, although P. aeruginosa outcompeted S. aureus. Furthermore, we found that the cell-free conditioned media (CFCM) of P. aeruginosa significantly reduced the S. aureus biofilms. Using fractioned CFCM, we identified that the anti-staphylococcal activity of the >10 kDa fraction was almost identical to the non-fractioned CFCM. Our confocal microscopy results suggest that P. aeruginosa CFCM depolarize S. aureus membranes and reduces the biofilm burden. Conclusions: These findings contribute to our understanding of the mechanisms underlying the interactions between these pathogens, suggesting that there is an antagonistic relationship between S. aureus and P. aeruginosa in a biofilm setting. Full article

Zirconia crowns are employed in pediatric dentistry for the complete restoration of anterior and posterior deciduous teeth. They are considered the best option due to their esthetic appeal, high strength, biocompatibility, and resistance to wear and corrosion. This study aims to evaluate the physico-chemical, cytological, and microbial properties of zirconia crowns to determine their biocompatibility, safety for surrounding tissues, and effectiveness in preventing microbial influence on tooth tissue based on their biofilm deposition potential. XRD measurements were conducted to confirm the crown composition. For the microbiological examination, a quantitative assessment of the adhesion capacity of the analyzed strains and the formation of a mixed biofilm was performed using a Zeiss Cell Observer SD confocal microscope. This study used a mixed biofilm containing Streptococcus mutans (ATCC 25175), Lactobacillus rhamnosus (ATCC 9595), Candida albicans (ATCC 90028), and Candida albicans (ATCC 10231) to simulate the oral environment and the possible dynamics created between different types of microorganisms. A direct contact method was used to assess cytotoxic properties. The zirconia crown biomaterial shows a low ability to adhere to specific microorganisms, with L. rhamnosus predominating, indicating low clinical potential for causing inflammation of the tissues surrounding the crown. The cytotoxic properties of the biomaterial were found to be at level 2, indicating moderate cytotoxicity. Their biggest flaws are price and the need for passive fitting, which involves aggressive grinding; this is a potential limitation when it occurs in children, as their cooperation with the treatment can be difficult to guarantee. Full article

Staphylococcus aureus, an opportunistic bacterium found in the oral cavity, has been reported as a causative agent of infective endocarditis and pneumonia. Salt is an essential mineral for cell maintenance in the human body. This study was conducted to clarify how salt affects the formation of biofilms by S. aureus and Streptococcus mutans, pathogens implicated in dental caries. Bacteria were cultivated with various concentrations of NaCl on a 96-well microtiter plate in tryptic soy broth with 0.25% sucrose or 0.25% glucose (TSBs and TSBg, respectively) for 16 h. The effects of glucosyltransferase in S. mutans membrane vesicles (MVs) and extracellular DNA during biofilm formation were also analyzed. S. aureus biofilms were induced by 0.004–0.25 M NaCl but not by NaCl at concentrations greater than 0.25 M in TSBs. The mixed S. aureus and S. mutans biofilms gradually grew and were constructed by dead cells in a NaCl concentration-dependent manner in both TSBs and TSBg. Moreover, biofilms were slightly induced by glucan generation mediated by the glucosyltransferases in MVs under high-salinity conditions. The formation of mixed-species S. aureus and S. mutans biofilms increased in the presence of both extracellular DNA and MVs. Therefore, extracellular DNA, MVs, and dead cells are factors that promote S. aureus biofilm formation under harsh conditions containing NaCl. The sugar (sucrose and glucose) ingestion-induced S. mutans biofilm may be a risk factor for infection by opportunistic pathogens such as S. aureus in individuals who consume food and drinks containing high concentrations of salt. Full article

Background: Compared to soybean oil intravenous fat emulsion (SO-IFE), use of mixed-oil IFE (MO-IFE) is associated with reduced rates of catheter-related bloodstream infections caused by coagulase-negative Staphylococcus species (CoNS) in pediatric patients receiving parenteral nutrition. Methods: Using an in vitro biofilm model, this study aimed to assess the impact of IFEs on biofilm formation among Staphylococcus species. S. aureus, S. capitis, S. epidermidis, S. haemolyticus, S. hominis, and S. lugdunensis were cultivated as biofilms in media supplemented with SO-IFE, MO-IFE, or fish oil IFE (IFE). Biomass was quantified by the crystal violet method, and follow-up planktonic growth assays assessed antimicrobial effects of IFEs. Results: Compared to SO-IFE, MO-IFE and FO-IFE significantly inhibited biofilm formation of S. aureus but did not impact planktonic growth. Contrary to clinical data, CoNS biofilm formation was not impacted by any of the IFEs tested. S. aureus biofilm inhibition in IFEs was further investigated by comparing differences following growth in SO-IFE supplemented with capric acid, docosahexaenoic acid (DHA), or eicosapenaenoic acid (EPA) to concentrations matching those of MO-IFE. Capric acid supplementation was associated with significant reduction in biofilm formation compared to SO-IFE alone. However, this was attributed to a bactericidal effect based on follow-up planktonic growth assays. Conclusions: These results suggest that biofilm formation in S. aureus is variably impacted by fatty acid composition in clinically relevant IFEs, with capric acid exhibiting bactericidal activity against tested isolates. Full article

Furfural is a relevant industrial product, but its presence in water and soil generates contamination and health risks. Moving bed biofilm reactors (MBBRs) are an increasingly used alternative to eliminate contaminants with the advantage of occupying small spaces, despite their high dependence on support and the microorganisms involved in the process. This work proposes furfural elimination through a laboratory-scale MBBR using Bacillus licheniformis GTQ1, Microbacterium sp. GISTAQ2, and Brevundimonas sp. GISTAQ1 isolated from an industrial effluent and agroforestry waste (rice husks, pine sawdust, and quebracho chips) as supports. The biofilm development was tested with both axenic and mixed cultures, confirming high coverage by Scanning Electron Microscope (SEM) images, especially in triple-mixed cultures. Biodegradation tests were carried out in the MBBR with 15 g rice husks or quebracho chips as supports and a 4000 mg L⁻¹ initial furfural concentration for 72 h. The mixed culture achieved almost a 100% furfural removal in three days with a rate of 3.97% per hour with rice husks and 2.61% per hour with quebracho chips. This laboratory-scale MBBR development is a promising first step ready for a scale-up for its implementation in industries to significantly reduce the environmental impact of the discharge of this type of effluent. Full article