Search Results (875)

Klebsiella pneumoniae is a prominent pathogen implicated in a wide range of infections, including pneumonia, urinary tract infections, and septicemia. Its ability to acquire and disseminate antibiotic resistance, coupled with the rising prevalence of hypervirulent strains, represents a significant public health threat. Understanding the molecular basis of drug resistance can guide the design and development of effective treatment strategies. Antimicrobial resistance (AMR) in these bacteria is a complicated process and cannot be attributed to a single resistance mechanism. K. pneumoniae develops resistance to antibiotics through a variety of mechanisms, ranging from single molecular mechanisms to complex interactions, where molecular synergy exacerbates resistance. This review summarizes the current understanding of the molecular mechanisms that contribute to the drug resistance and virulence of this pathogen. Key antibiotic resistance mechanisms include drug inactivation via B-lactamases and carbapenemases, membrane remodeling, efflux pump systems, such as AcrAB-TolC and OqxAB, and biofilm formation facilitated by quorum sensing. Additionally, the role of ribosomal changes in resistance is highlighted. This review also examines the mechanisms of virulence, emphasizing fimbriae, iron acquisition systems, and immune evasion strategies. Understanding these mechanisms of drug resistance and virulence is crucial for remodeling existing antibiotics and developing new therapeutic strategies. Full article

Postbiotics represent a promising strategy for reconciling increasing consumer demand for clean-label foods with the need to maintain high microbiological safety standards. The present review analyzed the applications of postbiotics in meat products, other food matrices and bioactive packaging, with particular emphasis on their production methods, compositional analysis and antimicrobial properties. Available evidence indicates that postbiotics offer important technological advantages over live probiotics, including enhanced stability during processing and storage and the absence of viable cells, which facilitates their integration into established food quality and safety control systems. The reviewed studies show that postbiotics produced mainly via fermentation with selected lactic acid bacteria and subsequently stabilized, most often by freeze-drying, exhibit pronounced antimicrobial activity in diverse food matrices, particularly meat and dairy products. Their ability to inhibit the growth of major foodborne pathogens, such as Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella spp., highlights their potential as effective biopreservatives contributing to shelf-life extension and improved microbiological safety. From an industrial perspective, postbiotics can be implemented within the framework of hurdle technology and incorporated into active packaging systems and edible coatings. The wider use of postbiotics in industry remains limited by regulatory uncertainty and methodological diversity. Key challenges include inconsistent taxonomic/strain reporting, divergent methods of inactivation and final processing (which alter bioactive profiles), lack of standardized composition and potency testing, and limited food matrix validation and toxicological data. To eliminate these gaps, regulatory definitions and labelling should be harmonized, and guidelines for production and reporting (strain identity, inactivation parameters, preservation method), and targeted safety and shelf-life testing are recommended. These steps are necessary to translate the documented antibacterial and antioxidant properties of postbiotics into industrial applications. Full article

Background/Objectives: Acne vulgaris is a chronic inflammatory skin disorder characterized by sebaceous gland hyperactivity, follicular hyperkeratinization, proliferation of Cutibacterium acnes (C. acnes), and subsequent inflammation. The development of effective therapeutics necessitates reliable preclinical models that accurately replicate key pathological aspects of the human disease. Methods: In this study, we established an inflammatory acne model in Wistar rats via the intradermal injection of live C. acnes into the ear pinnae and thoroughly characterized its temporal dynamics of the induced inflammation. Utilizing this model, we evaluated the protective efficacy of a whole-cell inactivated C. acnes vaccine (HI-C. acnes) formulated with adjuvants WS03 or MA107b. Results: Inflammation peaked between days 1 and 3 post-infection, manifesting as pronounced erythema, ear swelling, increased ear thickness, elevated bacterial load, and significant upregulation of pro-inflammatory cytokines (IL-6, IL-1β, and MCP-1). Histopathological examination revealed extensive neutrophil infiltration and microabscess formation, while immunohistochemistry confirmed localized overexpression of TNF-α, IL-1β, and CXCL1 within the lesional tissue. Inflammatory manifestations gradually subsided by day 5 and were fully resolved by day 7, which coincided with complete bacteria clearance and normalization of pro-inflammatory cytokine levels. Vaccinated rats developed significantly higher C. acnes-specific IgG titers and, upon challenge, exhibited markedly reduced ear swelling, diminished bacterial burden, and suppressed expression of key inflammatory mediators compared to control groups, indicating that vaccine-induced protection is associated with humoral immunity. Conclusions: Collectively, our standardized and quantifiable rat ear inflammation model provides a robust platform for mechanistic investigations and preclinical assessment of novel anti-acne vaccines and therapeutic agents. Full article

Microbial components are part of the composition of all waste, including lignocellulosic biomass (e.g., agricultural, domestic, industrial, and municipal wastes) generated via human activities. If little attention is given to these wastes or if they are not adequately managed, they tend to end up in the environment (soil, water, and farmland), decomposing naturally through microbial activities, producing greenhouse gases, causing eutrophication, preventing sunlight penetration, and depleting oxygen in the water. Several treatment methods are applicable to these wastes. However, anaerobic digestion is presented as the best option to properly treat the waste. It is regarded as the best technique to achieve sustainable energy development in both developing and developed countries. During anaerobic digestion, the organic matter in the waste is converted via the concerted activities of microbes belonging to different trophic levels, in the absence of oxygen, to yield biogas (renewable energy), bio-fertiliser, and sanitisation of the waste, rendering it better and safer for human handling. Varying levels of loss of bacterial viability and their antibiotic-resistance genes are observed with this process, as bacteria differ in susceptibility to temperature, pH, nutrient scarcity, and the presence of antimicrobials. Anaerobic digestion of agricultural residues and the immediate processing (post-treatment) of the digestate help to stabilise the digestate, making it safe for land applications, tackling waste management, and protecting food chains from contamination, in addition to the environment. This review focuses on the anaerobic digestion of lignocellulosic biomass, yielding biogas as energy, alongside sanitising the wastes by inactivating microbial components found therein, therefore reducing the contamination potential of the effluent or digestate discharged from the biodigester following the process. Several findings registered by different researchers through different studies performed in different countries under different scenarios while employing varying methods have been assembled in a chronological fashion to emphasise similarities and divergences or variations that deepen knowledge pertaining to the significance of the anaerobic digestion process in terms of the microbial interactions responsible for producing energy, addressing sanitisation and hygiene crisis, and the post-treatment of the digestate to ensure its use as biofertiliser. In other words, it is a comprehensive review that synthesises knowledge from multiple fields covering comparative aspects of anaerobic digestion in terms of sanitation, hygiene, and energy production and consolidates it in a single document to present and address the problem of waste management through anaerobic digestion technology. Full article

Periodontal pathogens, including Porphyromonas gingivalis (P. gingivalis), are implicated in respiratory inflammatory conditions, and aspirated oral bacterial components may contribute to airway inflammation. This association has prompted the exploration of innovative therapeutic strategies in addition to conventional oral hygiene practices. We evaluated the anti-inflammatory efficacy of an alkaline extract of Sasa senanensis leaves (SE) against heat-inactivated P. gingivalis-induced inflammation in respiratory tissues. In human bronchial epithelial cells (BEAS-2B), SE reduced interleukin (IL)-6 and IL-8 mRNA expression and cytokine secretion in a dose-dependent manner. Moreover, SE attenuated nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPKs), including p38 and c-Jun N-terminal kinase (JNK), indicating broad anti-inflammatory actions. In mice, SE administration decreased early lung cytokine levels and reduced NF-κB activity following intratracheal challenge with heat-inactivated P. gingivalis. Together, these in vitro and in vivo findings indicate that SE suppresses proinflammatory signaling triggered by P. gingivalis components and may serve as a natural adjunct to mitigate bacteria-associated airway inflammatory responses. Full article

The growing threat of antibiotic-resistant bacteria necessitates the development of alternative antimicrobial strategies. This study investigated the design and evaluation of novel photodynamic agents based on Rose Bengal (RB) conjugated to two plant lectins, Pisum sativum agglutinin (PSA) and Laburnum anagyroides agglutinin (LABA), for targeted photodynamic inactivation of Gram-positive and Gram-negative bacteria. Both conjugates demonstrated high singlet oxygen quantum yields compared with free RB. Antibacterial efficacy was assessed against methicillin-sensitive and methicillin-resistant Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella paratyphi B under white LED illumination. PSA-RB exhibited superior bactericidal activity against all strains, whereas LABA-RB showed strain-specific efficacy, particularly against Gram-negative species. A binary mixture of PSA-RB and LABA-RB synergistically inactivated both MSSA and MRSA at RB concentrations of 6–10 nM and light doses of 3.1–7.8 J/cm². Complete killing of E. coli and S. paratyphi B was achieved at approximately half the RB concentrations needed for individual conjugates. PSA-RB activity primarily drove the inactivation of P. aeruginosa. Uptake studies revealed significantly enhanced accumulation of lectin-conjugated RB compared to free RB, with synergistic uptake observed for the conjugate mixture. These results suggest that lectin-based RB conjugates are effective antibacterial agents for photodynamic treatment, especially via the dual-targeting method. Full article

Multidrug resistance (MDR) in Gram-negative bacteria is a global issue and needs to be addressed urgently. MDR can emerge through genetic mutations and horizontal gene transfer and deteriorate under antibiotic selective pressure. The emergence of resistance to last-resort antibiotics, which are used to treat MDR bacteria, is of particular concern. Colistin has been recognized as a last-line antibiotic for the treatment of MDR Gram-negative bacterial infections caused by Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Recently, the increasing reports of colistin resistance pose a significant threat to public health, caused by both acquired and intrinsic mechanisms. The review aimed to elucidate the trends in colistin resistance, the use of colistin in human and veterinary medicine, underlying resistance mechanisms and transmission pathways, and potential mitigation of this emerging threat through novel intervention strategies. Colistin resistance is mediated by plasmid-encoded phosphoethanolamine transferases (mcr-1 to mcr-10) and chromosomal lipid A remodeling pathways. In Escherichia coli, resistance involves mcr-1–10, acrB efflux mutations, pmrA/pmrB, arnBCADTEF, and mgrB inactivation. Klebsiella pneumoniae exhibits mcr-1, mcr-8, mcr-9, mgrB disruption and phoP/phoQ–pmrAB activation. Acinetobacter baumannii harbors mcr-1–4, while Salmonella enterica and Enterobacter spp. carry mcr variants with arnBCADTEF induction. Therapeutic options include adjunct strategies such as antimicrobial peptides, nanomaterials, therapeutic adjuvants, CRISPR-Cas9-based gene editing, probiotics, vaccines, and immune modulators to restore susceptibility. This review identified that specific and wide actions are required to handle the growing colistin resistance, including genomic surveillance, tracing novel resistance mechanisms, and the application of alternative management strategies. The One Health approach is considered a key strategy to address this growing issue. Full article

Background: Phototherapy utilizes targeted irradiation to inactivate bacteria or treat various medical conditions. Depending on the therapeutic goal, wavelengths from violet to infrared (IR) are applied. Within the visible and near-IR spectrum, photodynamic therapy (PDT) combines light with photosensitizers that generate reactive oxygen species (ROS), leading to bacterial inactivation. Optimizing photodynamic efficacy can involve either enhancing ROS formation through specific topical agents that modulate ROS generation or employing dual-wavelength light irradiation (DWLR) to achieve synergistic excitation. Established DWLR protocols typically combine blue and red light or IR to activate distinct photosensitizers. Materials and Methods: This study investigates whether a similar synergistic effect can be achieved within the green spectral range by simultaneously exciting a single photosensitizer—coproporphyrin III (CP III)—at 496 nm and 547 nm. Results: Convolution analysis and in vitro bacterial reduction experiments with Cutibacterium acnes subsp. elongatum revealed that cyan irradiation (496 nm) achieved the strongest photoreduction (2.31 log steps at 1620 J/cm²), whereas PC-lime irradiation (547 nm) produced a smaller effect (0.74 log steps). DWLR protocols (simultaneous and sequential irradiation) resulted in intermediate reductions (1.64 and 1.73 log steps, respectively), exceeding PC-lime but not surpassing cyan irradiation alone. Conclusions: These findings demonstrate that excitation efficiency at the local absorption maximum of CP III is the primary determinant of ROS generation, while spectral broadening through DWLR does not enhance bacterial inactivation within this wavelength range and in vitro setup. Full article

Photocatalytic water sterilization has emerged as a promising sustainable technology for addressing microbial contamination across diverse sectors including healthcare, food production, and environmental management. This review examines the fundamental mechanisms and recent advances in photocatalytic water sterilization, with a particular emphasis on the differential bactericidal pathways against Gram-negative and Gram-positive bacteria. Gram-negative bacteria undergo a two-step inactivation process involving initial outer membrane lipopolysaccharide (LPS) degradation followed by inner membrane disruption, whereas Gram-positive bacteria exhibit simpler kinetics due to direct oxidative attacks on their thick peptidoglycan layer. Escherichia coli has long been used as the gold standard in photocatalytic sterilization studies owing to its aerobic nature and suitability for the colony-counting method. In contrast, Lactobacillus casei, a facultative anaerobe, can be cultured statically and evaluated rapidly using turbidity-based optical density measurements. Therefore, both organisms serve complementary roles depending on the experimental objectives—E. coli for precise quantification and L. casei for rapid, practical assessments of Gram-positive bacterial inactivation under laboratory conditions. We also describe sterilization using light alone while comparing it to photocatalytic sterilization and then discuss two innovative suspension-based photocatalyst systems: polystyrene bead-supported TiO₂/SiO₂ composites offering balanced reactivity and separability and magnetic TiO₂-SiO₂/Fe₃O₄ nanoparticles enabling rapid magnetic recovery. Future research directions should prioritize enhancing visible-light efficiency using metal-doped TiO₂ such as Cu-doped systems; improving catalyst durability; developing new applications of photocatalysts, such as protecting RO membranes; and validating scalability across diverse industrial and medical water treatment applications. Full article

Concentrated wastewater streams, like vacuum blackwater (VBW), pose significant management challenges due to their high organic strength and pathogen loads. This review evaluates an integrated biorefinery model employing sequential black soldier fly larvae (BSFL) bioconversion and thermophilic anaerobic digestion (TAD) as a circular solution for effective VBW management. The BSFL pretreatment facilitates bio-stabilization, mitigates ammonia inhibition via nitrogen assimilation, and initiates contaminant degradation. However, this stage alone does not achieve complete hygienization, as it fails to inactivate resilient pathogens, including helminth eggs and spore-forming bacteria, thus precluding the safe direct use of frass as fertilizer. By directing the frass into TAD, the system addresses this limitation while enhancing bioenergy recovery: the frass serves as an optimized, nutrient-balanced substrate that increases biomethane yields, while the sustained thermophilic conditions ensure comprehensive pathogen destruction, resulting in the generation of a sterile digestate. Additionally, the harvested larval biomass offers significant valorization flexibility, making it suitable for use as high-protein animal feed or for conversion into biodiesel through lipid transesterification or co-digestion in TAD to yield high biomethane. Consequently, the BSFL-TAD synergy enables net-positive bioenergy production, achieves significant greenhouse gas mitigation, and co-generates digestate as sanitized organic biofertilizer. This cascading approach transforms hazardous waste into multiple renewable resources, advancing both process sustainability and economic viability within a circular bioeconomy framework. Full article

Background/Objectives: Three distinct strains of lactic acid bacteria (LAB), isolated from naturally fermented bread sourdough and representing the local autochthonous microflora, were selected to evaluate their potential probiotic properties. In addition, we evaluated whether these strains could be used in topical formulations. Methods: We evaluated probiotic properties such as the ability to co-aggregate with pathogens, antimicrobial activity, inhibition of pathogenic biofilms, and ability to adhere to human keratinocyte cells. Further, bacteria were encapsulated in calcium alginate microspheres using the emulsification/external gelation method, and their viability in topical formulations was assessed. Results: LAB significantly inhibited biofilm formation by the tested pathogens with complete inhibition observed in certain cases. The strength and specificity of these probiotic effects varied depending on the LAB strain and the target pathogen. Furthermore, among the tested strains, L. reuteri 182 exhibited the highest adhesion rates, reaching 77.94 ± 1.84%. In the context of potential topical applications, the preservative present in the formulation completely inactivated the planktonic cells of L. reuteri 182. In contrast, encapsulation within a biopolymeric system conferred protection against the preservative’s bactericidal effect. After 35 days of storage at room temperature, viable cell counts reached 5.94 ± 0.06 lg CFU/g. Conclusions: Our findings confirm that local LAB strains, specifically L. reuteri 182 and L. plantarum F1, possess essential probiotic characteristics and can be effectively incorporated into preservative-containing topical formulations via efficient encapsulation strategies. This underscores the potential of these topical probiotics for skin health and highlights the need for clear regulatory guidance to ensure their safe and effective application. Full article

Background/Objectives: New vaccine platforms that rapidly yield low-cost, easily manufactured vaccines are highly desired, yet current approaches lack key features. We developed the Killed Whole-Cell/Genome-Reduced Bacteria (KWC/GRB) platform, which uses a genome-reduced Gram-negative chassis to enhance antigen exposure and modularity via an autotransporter (AT) system. Integrated within a Design–Build–Test–Learn (DBTL) framework, KWC/GRB enables rapid iteration of engineered antigens and immunomodulatory elements. Here, we applied this platform to the HIV-1 fusion peptide (FP) and tested multiple antigen engineering strategies to enhance its immunogenicity. Methods: For a new vaccine, we synthesized DNA encoding the antigen together with selected immunomodulators and cloned the constructs into a plasmid. The plasmids were transformed into genome-reduced bacteria (GRB), which were grown, induced for antigen expression, and then inactivated to produce the vaccines. We tested multiple strategies to enhance antigen immunogenicity, including multimeric HIV-1 fusion peptide (FP) designs separated by different linkers and constructs incorporating immunomodulators such as TLR agonists, mucosal-immunity-promoting peptides, and a non-cognate T-cell agonist. Vaccines were selected based on structure prediction and confirmed surface expression by flow cytometry. Mice were vaccinated, and anti-FP antibody responses were measured by ELISA. Results: ELISA responses increased nearly one order of magnitude across design rounds, with the top-performing construct showing an ~8-fold improvement over the initial 1mer vaccine. Multimeric antigens separated by an α-helical linker were the most immunogenic. The non-cognate T-cell agonist increased responses context-dependently. Flow cytometry showed that increased anti-FP-mAb binding to GRB was associated with greater induction of antibody responses. Although anti-FP immune responses were greatly increased, the sera did not neutralize HIV. Conclusions: Although none of the constructs elicited detectable neutralizing activity, the combination of uniformly low AlphaFold pLDDT scores and the functional data suggests that the FP region may not adopt a stable native-like structure in this display context. Importantly, the results demonstrate that the KWC/GRB platform can generate highly immunogenic vaccines, and when applied to antigens with well-defined native tertiary structures, the approach should enable rapidly produced, high-response, very low-cost vaccines. Full article

Background/Objectives: Recurrent urinary tract infections (rUTIs) remain a major clinical challenge, but sublingual immunoprophylaxis with inactivated whole bacteria is a promising alternative to antibiotic prophylaxis. The objective of this systematic review was to assess the efficacy and safety of sublingual bacterial vaccines. Methods: We searched MEDLINE, Cochrane CENTRAL, and Embase (January 1979–August 2025) for English-language studies evaluating bacterial vaccines for rUTI prevention. Eligible studies included adults receiving sublingual immunoprophylaxis with heat-inactivated whole bacteria. Outcomes were UTI recurrence, infection-free interval, and adverse events. Both MV140 and autovaccines were assessed. Results: Of the 262 records identified, 14 studies met the inclusion criteria (4 comparatives, including 1 randomized trial, and 10 observational studies). UTI incidence decreased from 3.2–6.8 to 0–1.5 episodes/year at 12 months. The proportion of UTI-free patients ranged from 9.8 to 90% with immunoprophylaxis versus 0 to 25% with antibiotics or placebo. At 12 months, UTI-free rates were 10–49% with autovaccines and 9.7–60% with MV140. Patients with ≥3 UTIs ranged from 14.3 to 60.2% and 20 to 56.1% with autovaccines and MV140, respectively. The RCT reported adverse events in 0–40.8% of treated patients and 50% of placebo patients, predominantly mild. Conclusions: Although the available evidence is heterogeneous and largely derived from observational studies, sublingual immunoprophylaxis with heat-inactivated whole-bacteria—either standardized (MV140) or tailored to urine culture results—appears to be an effective and safe strategy for reducing the frequency of rUTI and prolonging infection-free intervals. However, larger randomized trials are required to confirm these findings. Full article

The article describes the interaction between 4-amino-1,8-naphthalic anhydride and the terminal amine groups of the first-generation poly(amidoamine) (PAMAM) dendrimer. Cotton fabric was treated with the newly obtained photoactive dendrimer (DA) to achieve its antimicrobial photodynamic inactivation. The photodynamic inactivation method is an innovative approach in which, upon irradiation with visible light, photosensitizers generate highly reactive oxygen species, specifically singlet oxygen (¹O₂), which destroys microbial cells. In the dark, the DA dendrimer strongly inhibits the development of the model bacteria Bacillus cereus (a Gram-positive bacterium) and Pseudomonas aeruginosa (a Gram-negative bacterium) in solution. Upon irradiation with visible light, the inhibition is significantly enhanced, achieving almost complete inactivation of B. cereus and 94% of P. aeruginosa. Cotton fabric was treated with the DA dendrimer at two concentrations (0.15% and 0.30% weight of fabric). It was found that the dendrimer molecules are adherent to the cellulose fiber surfaces and do not leach in washing. Treatment of the fabric with DA partially increases its hydrophobicity, which prevents the adhesion of some bacteria. In the dark, the treated fabric shows weak antibacterial activity because the dendrimer DA molecules are attached to the textile surface, and inactivation depends solely on the microorganism’s surface contact. However, upon irradiation, a significant increase in the fabric’s antimicrobial activity is observed, as the fixed dendrimer participates in the release of singlet oxygen, which effectively attacks microorganism cell membranes and components. For the fabric with the higher concentration (DA30), 94% inactivation of B. cereus and 89% inactivation of P. aeruginosa were achieved. Thus, a synergistic effect between photodynamic activity and increased hydrophobicity was achieved, making the modified cotton fabric an example of a high-tech textile with permanent, renewable disinfection. Full article

The high temperatures of the spray-drying process can cause thermal inactivation of probiotic bacteria. This study evaluated the effect of chia seed mucilage (CM) on the survival and viability of Lactobacillus rhamnosus GG (LGG) encapsulated by spray-drying in cross-linked alginate matrices (CLAM). Two types of microcapsules were used: CLAM without CM (M0-LGG) and with CM (M1-LGG). Viability was assessed under storage conditions (4 °C and 25 °C), heat treatments, and gastrointestinal simulations. The results show that LGG survival improved after spray drying in CLAM (M0-LGG), reaching levels above 92%. Microcapsules containing CM (M1-LGG) maintained high viability, exceeding 8 log CFU/g, under storage at 4 °C for 60 days. CM demonstrated the ability to preserve LGG viability during gastrointestinal digestion (above 6 log CFU/g) and to confer thermal stability under heat stress conditions at 80 °C for 5 min. This study can be a valuable reference for the food industry, as the incorporation of CM as an encapsulating agent for probiotics can improve their viability under adverse processing and storage conditions. Full article