Search Results (4,102)

Pectobacterium brasiliense is a highly destructive bacterial plant pathogen with a broad host range, causing soft rot and blackleg diseases. Genomic resources are for understanding the mechanisms of virulence in these necrotrophic bacteria. In this study, we isolated P. brasiliense strain 25ASUB12 from a symptomatic summer squash fruit growing in a field research plot in Mississippi. This is the first documented case of P. brasiliense in Mississippi. We extracted genomic DNA from the bacterial strain and sequenced it using Oxford Nanopore PromethION and Illumina NovaSeq X Plus platforms to produce a chromosome-level genome sequence of strain 25ASUB12. Genome annotation and comparative genomics were conducted to gain further insights into the strain. Results showed that the genome size of this strain was 4.90 megabases (Mb) and comprises several factors related to pathogenicity such as pectate lyases, diverse secretion factors, siderophores, and quorum-sensing genes. The whole genome of P. brasiliense strain 25ASUB12 serves as a genomic tool to conduct further research on diseases caused by this globally important plant pathogen. Full article

Background: Denture stomatitis is strongly associated with Candida biofilms on prosthetic surfaces and remains difficult to manage due to biofilm persistence and antifungal resistance. Selenium-based nanomaterials, particularly biogenic selenium nanoparticles (SeNPs) functionalized with natural polymers or phytochemicals, have emerged as potential material-centered strategies for biofilm control. Objective: To systematically evaluate the antifungal and antibiofilm effects of selenium-based nanomaterials on Candida biofilms in the context of denture materials. Methods: A systematic review was conducted in accordance with the PRISMA guidelines and registered in PROSPERO. Multiple databases were searched from inception without language restrictions. Eligible studies included experimental investigations of biogenic or functionalized SeNPs or organoselenium compounds targeting Candida biofilms on denture materials or in relevant in vitro models. A qualitative synthesis was performed due to anticipated heterogeneity. Results: Eleven studies met the inclusion criteria. Of these, four studies directly evaluated selenium-based interventions on denture materials, while seven provided supporting mechanistic evidence using in vitro models on non-denture substrates. Across denture-related studies, selenium-based modifications reduced fungal adhesion, biofilm biomass, and colony-forming units, without detrimental effects on material properties. Functionalization with polymers or phytochemicals was associated with enhanced antifungal activity and nanoparticle stability. Mechanistic studies suggested multimodal antifungal effects, including membrane disruption, inhibition of virulence factors, and modulation of biofilm-related pathways. Methodological quality was moderate, with common limitations in reporting and experimental standardization. Conclusions: Functionalized biogenic SeNPs show promising antifungal and antibiofilm activity against Candida in preclinical denture-related models. However, all available evidence is in vitro, with no in vivo or clinical studies identified. Substantial heterogeneity and limited long-term safety data preclude clinical recommendations. Further research should focus on standardized methodologies, clinically relevant in vivo models, and controlled clinical trials to assess translational potential. Full article

Brucellosis, acting as a typical chronic zoonotic disease, is caused by the invasion of Brucella into the human body. Outer membrane protein 25 (Omp25), specifically localized on the Brucella membrane, is the main virulence factor of Brucella and participates in multiple links of the damage process. Omp25c, a porin protein of Brucella, is a paralog of Omp25 with high sequence identity. NADH dehydrogenase [ubiquinone] complex I assembly factor 2 (Ndufaf2) has a key function in cell energy metabolism, particularly in the formation and activity of the mitochondrial respiratory chain. Loss of Ndufaf2 results in oxidative stress and mitochondrial DNA (mtDNA) deletion. However, the functional relationship between Omp25c and Ndufaf2, the underlying mechanism of the proteins, remains unclear. In this work, we purified the Omp25c and Ndufaf2proteins. Our data revealed that Omp25c directly interacts with Ndufaf2, as determined using Biacore analysis. In addition, assays revealed that Ompa2c reshapes the host cell’s redox environment by decreasing the oxidized nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide (NAD⁺/NADH) ratioand adenosine triphosphate (ATP) production, whereas Ndufaf2 exerts an opposing regulatory effect; Co-expression results further revealed an antagonistic relationship between the two during metabolic processes. These findings provide a new perspective for elucidating the mechanisms of mitochondrial functional regulation in Brucella–host interactions and lay the theoretical and experimental foundation for drug development targeting metabolic interventions to eliminate intracellular pathogens. Full article

Type II toxin–antitoxin (TA) systems are significantly expanded in the Mycobacterium tuberculosis complex; however, the functional role of the VapBC40 system in Mycobacterium bovis(M. bovis) pathogenesis remains poorly characterized. This study aimed to investigate the role of VapBC40 in mycobacterial virulence and evaluate its potential as a target for rational vaccine attenuation. We performed evolutionary analysis and yeast two-hybrid assays to characterize VapBC40 system specificity, conducted in vitro macrophage infection models and in vivo murine studies to assess virulence contribution, and evaluated the immunoprotective efficacy of a VapC40 knockout strain. Evolutionary analysis revealed progressive sequence conservation and stringent homologous pairing specificity within the VapBC40 system. The VapC40 toxin correlates with enhanced intracellular bacterial survival, increased host cell death, and more severe pulmonary pathology with systemic dissemination. Based on these findings, we evaluated the vaccine potential of a vapC40 knockout strain. Immunization with this attenuated strain elicited a Th1 cellular immune response, characterized by enhanced IFN-γ production and increased frequency of CD4⁺IFN-γ⁺ T cells. Upon challenge with virulent M. bovis, the knockout strain conferred superior protection compared to the conventional BCG vaccine, significantly reducing lung pathology and restricting extrapulmonary bacterial dissemination. Although the molecular mechanisms underlying VapC40-mediated effects remain to be fully elucidated, our findings suggest an important role of the VapBC40 system in mycobacterial-host interactions and support its potential as a target for next-generation tuberculosis vaccine development. Full article

Background/Objectives: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is a major nosocomial pathogen. Although newer agents have reduced colistin use in high-income countries, this polymyxin remains important in many low- and middle-income settings. Colistin resistance in K. pneumoniae is most commonly associated with chromosomal alterations affecting the MgrB–PhoPQ pathway, or with plasmid-mediated mcr genes. This study aimed to investigate chromosomally mediated colistin resistance in CRKP clinical isolates from a Tunisian tertiary hospital. Methods: Between 2010 and 2015, 317 non-duplicate CRKP isolates were collected at Charles Nicolle Hospital, Tunis. Colistin MICs were determined by broth microdilution. Phenotypic tests and PCR characterized carbapenemases, extended-spectrum β-lactamases, AmpC, plasmid-mediated quinolone resistance, mcr and virulence genes. Porins (OmpK35/OmpK36) and the mgrB, phoP and phoQ loci were analyzed by SDS-PAGE and sequencing. Clonal relatedness was assessed by ERIC-PCR and multilocus sequence typing. We additionally compared colistin-resistant isolates with a panel of colistin-susceptible CRKP controls and assessed phenotypic stability after serial passages without colistin. Results: Five isolates (1.6%) were colistin-resistant. All were multidrug-resistant, produced OXA-48, and two also carried NDM-1. The isolates belonged to five distinct sequence types, including high-risk clones (ST11, ST101, ST147). No mcr genes were detected. Four isolates carried disruptive mutations in mgrB, and the remaining strain harbored inactivating mutations in both phoP and phoQ with an intact mgrB. Truncating alterations in PhoP/PhoQ and frequent loss or truncation of OmpK35/OmpK36 were observed. No mgrB/phoP/phoQ alterations were detected among colistin-susceptible controls, and colistin MICs remained stable after 7 days of drug-free passaging. Conclusions: In Tunisian CRKP, colistin resistance was associated with chromosomal alterations, predominantly involving disruption of the MgrB–PhoPQ pathway, in the absence of mcr genes. These mechanisms in both high-risk and emerging sequence types underscore the adaptability of CRKP and the need for surveillance where colistin remains an important therapeutic option. Full article

Listeria monocytogenes (Lm) is an important zoonotic foodborne pathogen that causes severe rhombencephalitis in ruminants. The trigeminal ganglion is a critical node for Lm invasion of the central nervous system via neural pathways. However, the roles of key virulence factors InlA, InlB, and LLO from ovine-derived Lm in trigeminal ganglion neuron infection remain unclear. In this study, LM90SB2, an ovine-derived Lm strain isolated from a sheep with encephalitis in Xinjiang, China, was used as the wild type, and its ΔInlAB double-gene deletion and ΔInlABO triple-gene deletion mutants were constructed. Primary mouse trigeminal ganglion cells (TGCs) were infected with these strains, and cell-association and invasion assays, bacterial colonization analysis, cell scratch tests, Western blotting, and qRT-PCR were performed to explore the effects of InlA, InlB, and LLO on Lm infection of TGCs and their regulatory roles in host adhesion molecules N-cadherin and NCAM1. The results showed that the wild-type LM90SB2 had significantly stronger cell-association, invasion, and colonization abilities in TGCs than the ΔInlAB and ΔInlABO mutants (p < 0.01 or p < 0.0001). LM90SB2 infection significantly upregulated the mRNA and protein expression levels of N-cadherin and NCAM1 in TGCs and enhanced TGC migration, while these effects were gradually attenuated with the sequential deletion of InlA, InlB and LLO. This study clarifies the synergistic roles of InlA, InlB, and LLO in mediating the infection of trigeminal ganglion neurons by ovine-derived Lm and reveals the molecular mechanism by which Lm promotes neural invasion by regulating the expression of host cell adhesion molecules. Our findings provide important experimental data for elucidating the neural invasion pathway of Lm in ruminants and lay a theoretical foundation for the development of targeted prevention and control strategies for ruminant listeriosis in veterinary clinical practices. Full article

Background/Objectives: Necrotic enteritis (NE), induced by Clostridium perfringens, is responsible for significant economic losses in the poultry industry worldwide. The growing restrictions on antibiotic use have driven the search for alternative strategies for disease control. The purpose of this study is to isolate and characterize lytic phages targeting multidrug-resistant C. perfringens type G recovered from chickens with NE. Methods: C. perfringens was isolated from chickens with NE using a culture method with selective TSC agar. Bacterial identification was carried out using biochemical tests and PCR. C. perfringens isolates were toxinotyped by PCR. Antibiotic susceptibility test was performed using the agar dilution method. Bacteriophages were isolated from chicken intestine samples collected from wet markets using the double-layer agar technique. Phage isolates were characterized by host range, one-step growth, stability, and whole genome sequencing. The efficacy of phage CPP8 in controlling multidrug-resistant C. perfringens type G was evaluated in GAM broth. Results: In this study, 16 C. perfringens strains were isolated from 100 chickens suspected of NE. Among these isolates, 10 (62.5%) belonged to type G, while the remaining 6 (37.5%) were type A. A total of 11 phages capable of lysing C. perfringens type G were isolated from the chicken intestine. Among them, phage CPP8 has the widest host range, short latent period, large burst size, and high stability. Moreover, the genome of CPP8 lacked genes related to antibiotic resistance, toxins, virulence factors, or lysogeny. Treatment with CPP8 resulted in a significant reduction in viable counts of C. perfringens at 37 °C. Conclusions: Our findings highlight phage CPP8 as a promising candidate for bio-control of multidrug-resistant C. perfringens type G. Full article

A pathogenic bacterium strain, LBK2, was isolated from giant spiny frog (Quasipaa spinosa) tadpoles infected with perforation disease in this study. Pathogenic strain LBK2, a Gram-negative bacterium with a certain degree of infectivity, was demonstrated to cause anorexia, lethargy, epidermal necrosis, and abdominal perforation in tadpoles in artificial infection experiments. The identification results of 16S rDNA gene sequencing showed that pathogenic strain LBK2 was identified as Pseudomonas sp. Virulence gene identification displayed that strain LBK2 carried three virulence genes: aer, epr, and fla. Finally, the antibiotic susceptibility testing of 11 antibiotics suggested that strain LBK2 was highly sensitive to nine antibiotics, including chloramphenicol, enrofloxacin, and rifampicin, but was resistant to erythromycin, sulfamethoxazole/trimethoprim, and low-concentration trichloroisocyanuric acid. This study determined the pathogenicity of Pseudomonas sp. to giant spiny frog tadpoles based on histopathological analysis and virulence factor carriage, and the drug susceptibility testing further provided a scientific basis for the selection of drugs in the prevention and treatment of abdominal perforation disease in giant spiny frog tadpoles. Full article

A bacterial strain M4 exhibiting high nattokinase (NK) activity and favorable antibacterial properties was isolated from fermented soybean paste in Northeast China. Based on morphological observation, physiological and biochemical characterization, 16S rDNA sequence analysis, and whole-genome sequencing, the strain was identified as Bacillus velezensis. Its probiotic potential and safety were systematically evaluated using a combination of in vitro assays and genome mining. Genomic analysis revealed that M4 possessed a complete genome consisting of a single circular chromosome of 4,473,838 bp with a GC content of 46.94%, encoding 4516 predicted proteins. Functional domain annotation identified four proteins (XLQ58132.1, XLQ58158.1, XLQ59409.1, and XLQ59873.1) containing both the Peptidase inhibitor I9 and Peptidase S8 domains, confirming the presence of the typical molecular signature of NK. Furthermore, the genome harbored 132 genes encoding carbohydrate-active enzymes, 37 biosynthetic gene clusters, and 142 genes encoding proteolytic enzymes. Comparative genomic analysis revealed a close phylogenetic relationship with other B. velezensis strains and identified 98 strain-specific genes. Safety assessment demonstrated that M4 exhibited no hemolytic activity, was susceptible to eight commonly tested antibiotics, and lacked genes encoding high-risk virulence factors. Probiotic characterization indicated that M4 exhibited certain levels of gastrointestinal tolerance, acid resistance, bile salt resistance, antioxidant activity, and antibacterial properties. In conclusion, B. velezensis M4 shows potential for development as a functional strain. Full article

The life-threatening disease pertussis, also known as whooping cough, is caused by a complex interplay of several virulence factors produced by the bacterium Bordetella (B.) pertussis. These include the AB-type protein toxin pertussis toxin (PT), the main causative agent of pertussis. After infection with B. pertussis, PT is released and binds to its human target cells, which internalize PT. The enzyme subunit of PT is then taken up into the cytosol, where it catalyzes the ADP-ribosylation of the α-subunit of inhibitory GTP-binding proteins from the Gαi type. This ultimately leads to the development of the characteristic clinical symptoms associated with pertussis. Pertussis is a vaccine-preventable but highly infectious respiratory disease, and especially younger children are prone to develop severe pertussis. Despite the vaccination, over the past few years, increasing case numbers have been reported globally. Moreover, treatment options are strongly limited to antibiotics and symptomatic treatment. Therefore, novel therapies against toxin-mediated diseases are urgently required, while AB-type toxins such as PT are promising pharmacological targets to combat these associated diseases. To identify novel pharmacological inhibitors for AB-type toxins, huge potential lies within the human proteome/peptidome. Endogenous protein or peptide inhibitors for bacterial toxins might have evolved as part of the innate immunity and are awaited to be discovered. The scientific community is committed to identify potential candidates through targeted screening or explorative hypothesis-driven approaches. This review summarizes the recent efforts in the identification and characterization of the human body’s own proteins and peptides that inhibit PT. PT-inhibiting peptides were found by unbiased screening of peptide libraries from human hemofiltrate or hypothesis-driven evaluation, and PT-neutralizing mechanisms were discovered in cell-based approaches. The identification of endogenous peptides and proteins, e.g., defensins and α₁-antitrypsin, as potent inhibitors of PT paves the way towards the development of novel therapeutic options against pertussis. Full article

Tocosh, an ancestral fermented potato product, relies on spontaneous processes near freshwater springs under extreme high-altitude conditions and represents an underexplored reservoir of microbial diversity with significant potential for the discovery of probiotics. This study provides, for the first time, a comprehensive probiogenomic characterization of 19 lactic acid bacteria (LAB) isolated from tocosh, in the Peruvian Andes, at three distinct altitudes—2992, 3882, and 4451 m above sea level (m.a.s.l.)—using whole genome sequencing (WGS) and bioinformatic profiling. A total of six species were identified: Lactiplantibacillus plantarum and Levilactobacillus brevis at all three study sites, Lacticaseibacillus paracasei and Lentilactobacillus buchneri at the lowest altitude (2992 m.a.s.l.), and Latilactobacillus curvatus and Latilactobacillus sakei at the highest altitudes (3882 and 4451 m.a.s.l.). Our results reveal that the extreme Andean environment is associated with stability in L. plantarum (genome sizes from 3.36 to 3.38 Mb) across all altitudinal levels. Functional analysis using CAZymes determined that L. brevis and L. buchneri act as primary degraders (high percentage of glycosyl hydrolases/carbohydrate binding) while L. curvatus and L. sakei function as primary builders through exopolysaccharide biosynthesis, likely a cryoprotective adaptation preventing cell damage during cold temperatures at high altitudes. Additionally, L. sakei and L. plantarum exhibited unique auxiliary activity (AA) enzymes, suggesting an oxidative mechanism to breach recalcitrant starch surfaces. All isolates were confirmed as genomically safe, lacking transferable antibiotic resistance genes and virulence factors. Pathogenic risk potential scores (PPRS) were consistently ≤ 2.0, fulfilling qualified presumption of safety (QPS) criteria. These findings provide the first genomic characterization of tocosh-associated LAB, establishing a basis for tocosh standardization, enabling the rational design of starter cultures that preserve ancestral traits and ensure microbiological safety in modern food applications. Full article

Candida albicans is a yeast found in the oral cavity, gastrointestinal tract, and vaginal mucosa. This species is the most prevalent and virulent in conditions such as oral candidiasis. Myrtenol is a bicyclic monoterpene alcohol recognized for its antioxidant and anti-inflammatory attributes. Its primary source is the essential oil extracted from plants of the Myrtaceae family. This study evaluated the effect of (−)-myrtenol on the virulence factors of Candida albicans. Ten clinical isolates of Candida albicans and one reference strain (ATCC 90028) were used in this study. The virulence factors examined included adhesion, morphogenesis, and lipase production. Assays were conducted in the presence and absence of (−)-myrtenol, using a concentration corresponding to the minimum inhibitory concentration (MIC; 256 µg/mL). Results: The compound reduced the adherence of C. albicans to human oral epithelial cells (92.24 vs. 28.69), and reduced filamentation in liquid (3.17 vs. 2.57) and solid media. Furthermore, (−)-myrtenol inhibited lipase activity (0.68 vs. 1.00). Virulence factors expressed by C. albicans contribute to increased infection rates and, consequently, increased morbidity and mortality. The present findings demonstrate that (−)-myrtenol affects virulence-associated phenotypes of C. albicans in vitro. This compound represents a promising candidate for further investigation, particularly in studies addressing its mechanisms of action, safety, and potential applicability. Full article

Quorum Quenching (QQ) is a mechanism that disrupts Quorum Sensing (QS) signaling systems, which regulate gene expression based on bacterial population density. Many fish pathogens, such as Aeromonas, utilize QS systems to regulate the expression of their virulence factors. Disrupting these systems using QQ is a promising approach for infection control in aquaculture and may provide a safe alternative to antibiotics. Therefore, identifying microorganisms with QQ activity is a relevant task in agricultural microbiology and veterinary medicine. This study examines the identification of isolates with QQ activity in the microbial community of perch and assesses their probiotic potential for the prevention of aeromonosis. In this study, we isolated 32 strains of microorganisms capable of degrading N-acylhomoserine lactone (AHL), six of which exhibited stable QQ activity. Five strains were found to belong to the genus Rhodococcus, and one strain to the genus Exiguobacterium. The selected strains were tested for the enzymatic/non-enzymatic and intra-/extracellular QQ activity, pathogen growth inhibition, biofilm formation, and hemolytic activity, as well as growth ability under various environmental conditions (salinity, pH, bile acids, and temperature). Based on the results of these tests, the R. erythropolis PFS1.20 strain was selected as the most promising probiotic. The genomic analysis revealed that the studied strain contains genes encoding QQ enzymes, siderophore biosynthesis clusters, osmoprotectors, and compounds with antimicrobial properties. These results indicate the high probiotic potential of the R. erythropolis PFS1.20. Full article

The retromer is a highly conserved complex that mediates the trafficking of cargo proteins to the plasma membrane or the trans-Golgi network. In pathogenic microorganisms, retromer-dependent transport contributes to the delivery of virulence factors and promotes infection. The retromer consists of a sorting nexin dimer (SNX) and a cargo-selection complex (CSC), formed by Vps26, Vps35, and Vps29. In Entamoeba histolytica, the parasite that causes human amoebiasis, the retromer functions as a Rab7A GTPase effector and participates in phagocytosis and cytotoxicity. Although we previously characterized the roles of EhVps26 and EhVps35, the function of EhVps29 remained unclear. In this study, we analyzed the subcellular localization and functional role of EhVps29 in adhesion, phagocytosis, and cytopathic effect. EhVps29 localized to the plasma membrane, cytosol, vesicles, tubules, Golgi-like structures, MVBs and, for the first time, the nucleus. Immunofluorescence and Western blot assays demonstrated that EhVps29 modulates the localization of EhVps26, EhADH adhesin, and EhCP112 cysteine protease. Ehvps29 gene silencing and overexpression confirmed its involvement in virulence-associated processes. Immunoprecipitation and confocal microscopy results showed the interaction among EhVps29 and the ESCRT machinery members EhVps36 and EhADH. Our results indicate that EhVps29 is involved in parasite virulence and protein trafficking through recycling or degradation pathways. Full article

Baicalin is a natural compound sourced from Scutellaria baicalensis which possesses various biological activities. To date, a large amount of research has been conducted on the antibacterial activity and related mechanisms of baicalin, making it a promising candidate for new broad-spectrum antibacterial drugs. However, the solubility of baicalin is limited. To improve its solubility and overcome the clinical application bottleneck, researchers have developed various solubilization techniques. Therefore, this article introduces the biological characteristics of baicalin; explores its effects as an antibacterial agent on bacterial biofilms, quorum sensing, virulence factors, inflammatory responses, and the immune system; and discusses the applications of nano-carrier loading technology, cyclodextrin inclusion technology, metal ion coordination and organometallic complexation technology, and dynamic covalent hydrogel assembly technology in improving the solubility of baicalin, thereby enhancing its antibacterial activity. Full article