Search Results (1,990)

Background/Objectives: This study aimed to characterize the epidemiology, resistance, virulence determinants, and genomic relatedness of OXA-48-producing Klebsiella pneumoniae in a secondary-care hospital in north-eastern Italy, and to assess the in vitro activity of cefepime-based β-lactam/β-lactamase inhibitor combinations. Methods: We performed a retrospective observational study of consecutive, non-duplicate isolates (September 2024–January 2025). Susceptibility testing was performed using VITEK^® 2 and MIC TestStrip. All isolates underwent single-read Nanopore whole-genome sequencing, with assembly and in silico detection of resistance genes, porin alterations, plasmid replicons and virulence loci. Core-genome single-nucleotide polymorphism analysis with recombination filtering assessed genetic relatedness. Results: Thirteen isolates were recovered from elderly, highly comorbid inpatients, mainly from urine (46.2%) and rectal/fecal screening (38.5%). Twelve patients were classified as colonized, whereas one patient had an infection due to OXA-48-producing K. pneumoniae, with the organism recovered from both blood and urine cultures. All belonged to sequence type 395 and carried blaOXA-48 and blaCTX-M-15, together with a truncated OmpK35 and an OmpK36 loop-3 GD insertion. The yersiniabactin locus ybt16 within integrative conjugative element ICEKp12 was detected in 92.3% of isolates. Core-genome analysis showed high genomic similarity among isolates, consistent with local circulation of an ST395 lineage. Although yersiniabactin may contribute to iron acquisition and bacterial fitness, its presence alone does not establish a hypervirulent phenotype or predict clinical virulence. In the absence of aerobactin, salmochelin, rmpADC, and rmpA2, and without phenotypic virulence testing, these isolates should be regarded as yersiniabactin-positive but non-hypervirulent based on their genomic profile. Core-genome analysis indicated close genetic relatedness among the isolates, consistent with possible local clonal circulation. In a subset, cefepime/enmetazobactam and especially cefepime/zidebactam substantially reduced cefepime minimum inhibitory concentrations. Conclusions: We identified a multidrug-resistant OXA-48-producing K. pneumoniae ST395 lineage circulating locally, predominantly in colonization contexts. Active screening and genomic surveillance may support infection control and inform the potential role of emerging cefepime-based inhibitor combinations. Full article

Salmonella remains a leading global foodborne pathogen, whereas low-water-activity foods are often underestimated as transmission vehicles. Here, whole-genome sequencing and bioinformatic analyses were performed on 59 Salmonella strains isolated from low-water-activity foods (2017–2025) to investigate their genomic traits, antimicrobial resistance profiles, virulence genes, and mobile genetic elements. The isolates were mainly recovered from dried meat (44.07%) and dried soybean products (33.90%), covering 33 serovars and 36 sequence types. Salmonella Agona (ST13), S. Senftenberg (ST14), and S. Idikan (ST1561) predominated. Forty antimicrobial resistance genes across ten categories were detected. Notably, one S. Schwarzengrund isolate harbored the IncHI2 plasmid pWW013_mcr-9.2 carrying the mcr-9.2 gene, as well as various antibiotic resistance genes and heavy metal resistance operons. Comparative genomics revealed a conserved plasmid backbone and a distinctive resistance island. This study documents the first detection of an mcr-9.2-carrying Salmonella in low-water-activity foods in Beijing. Our findings demonstrate high genomic diversity, widespread resistance determinants, and the emergence of an mcr-9.2-carrying plasmid, supplying key genomic evidence for risk assessment and targeted control of Salmonella in low-water-activity foods. Full article

The transport mechanisms for substrates and nutrients within the heme pathway of the Toxoplasma gondii apicoplast remain poorly understood. However, studies on heme metabolic enzymes have employed disparate genetic manipulation approaches, limiting direct phenotypic comparisons among different enzymes. This research involved screening potential apicoplast proteins in Toxoplasma gondii by cross-referencing and analyzing protein–protein interaction networks. Within the heme enzyme pathway of the apicoplast, eight enzymes were found to be predominantly conserved in the Sarcocystide family. Utilizing the CRISPR-Cas9 system alongside a U1 snRNP-mediated gene-silencing approach, we developed inducible knockdown strains—iKD-PBGD, iKD-UROS, and iKD-UROD—targeting three key metabolic enzymes crucial for the parasite lytic cycle, as demonstrated through replication experiments. To investigate the transport mechanisms for heme-related nutrients or substrates, we knocked down these three enzymes, using TgGRA12 as an initial marker. Continuous fluorescence signals highlighted the parasitophorous vacuole (PV) membrane surrounding tachyzoites during both early and late replication stages, particularly at 48 h post-rapamycin treatment, indicating a transformation of the cyst-like PV resembling that in Toxoplasma gondii. Phenotypically, knockdown of these heme enzymes led to the formation of slowly replicating, cyst-like parasitophorous vacuoles. However, this morphological change did not significantly affect the acute virulence of the parasites in vivo, as determined by mouse survival assays. This study explored the functional roles of the three intermediate metabolic enzymes, offering a novel viewpoint on the gradual demise of Toxoplasma gondii as a potential target for drug development. Full article

Candida tropicalis has emerged as one of the most clinically relevant non-albicans Candida species, owing to its increasing global prevalence, high mortality associated with invasive infections, and rising rates of antifungal resistance. Although traditionally considered an opportunistic pathogen, growing evidence indicates that its remarkable adaptive capacity is driven by the coordinated regulation of multiple biological processes that promote host colonization, persistence, and immune evasion. In this review, we summarize current knowledge on the epidemiology, biology, genomic organization, virulence factors, and host–pathogen interactions of C. tropicalis. Particular emphasis is placed on recent advances in comparative genomics and functional studies that have expanded our understanding of the molecular determinants underlying adhesion, biofilm formation, morphogenesis, extracellular hydrolytic enzyme production, thermotolerance, cell wall remodeling, and immune evasion. We also integrate orthology analyses identifying putative C. tropicalis homologs of well-characterized Candida albicans virulence genes, highlighting the evolutionary conservation of key pathogenic mechanisms while emphasizing species-specific adaptations that remain functionally unexplored. Finally, we discuss current knowledge of antifungal resistance and the emerging relationship between genomic plasticity, stress adaptation, and pathogenicity. Together, this review provides an updated and comprehensive overview of the biological mechanisms that contribute to the success of C. tropicalis as an emerging opportunistic pathogen and identifies key areas requiring further investigation to improve diagnosis, treatment, and the development of novel antifungal strategies. Full article

Background/Objectives: Streptococcus parasuis is an under-recognized member of the Streptococcus suis complex that can be misidentified by routine diagnostic methods. Human clinical isolates remain sparsely characterized. This study investigated the antimicrobial phenotype, genomic features, population position, and larval pathogenicity of a human pleural-fluid isolate. Methods: Strain HUGSPH was recovered during the care of a patient with pneumonia. Hybrid whole-genome sequencing (WGS), average nucleotide identity analysis, multilocus sequence typing (MLST), core-genome phylogenetics, comparative pan-genomics, and an exploratory host-origin association analysis were performed. Minimum inhibitory concentrations (MICs) were determined using the VITEK 2 Compact system with an AST-ST03 card, and virulence was evaluated in Galleria mellonella larvae. Results: Genome-based analysis confirmed HUGSPH as S. parasuis and assigned it to the novel sequence type (ST) 181. The isolate clustered within a predominantly human-origin phylogenetic clade. Because species-specific clinical breakpoints are unavailable, the MICs were interpreted provisionally using explicitly stated surrogate Clinical and Laboratory Standards Institute (CLSI) criteria; erythromycin, clindamycin, and levofloxacin were categorized as resistant under those criteria. Several predicted antimicrobial-resistance-associated genes were detected. In a restricted comparison of seven human-origin and nine swine-origin genomes, eight genes were present in all included human-origin isolates and absent from all included swine-origin isolates, whereas metQ, metP, and metN showed the reciprocal pattern. HUGSPH caused dose-dependent larval mortality, reaching 100% at 10⁷ colony-forming units (CFU) by 96 h. Conclusions: HUGSPH expands the genomic record of human clinical S. parasuis and highlights the diagnostic and surveillance relevance of antimicrobial resistance in this species. The susceptibility categories, source-associated genes, and larval phenotype require validation by reference susceptibility testing, broader phylogenetically balanced collections, comparative strains, and mammalian models. Full article

Mucormycosis is a highly lethal invasive fungal infection caused by fungi of the order Mucorales, with mortality rates exceeding 50% despite current antifungal therapies with polyenes or azoles. Because iron acquisition is essential for Mucorales growth and virulence, we investigated whether transferrin, the primary physiological iron-sequestering protein in plasma, could serve as a host-directed therapeutic strategy against mucormycosis. Transferrin inhibited the growth of clinically relevant Mucorales species, including Rhizopus delemar (R. delemar), Rhizomucor, and Lichtheimia corymbifera (L. corymbifera) in a concentration-dependent manner. Checkerboard assays demonstrated synergistic interactions between transferrin and liposomal amphotericin B (LAMB), with fractional inhibitory concentration index values below 0.5 for all tested species. In endothelial cell infection model, transferrin significantly reduced expression of the fungal invasion ligand spore coat protein homolog 3 (CotH3) and the host receptor glucose-regulated protein 78 (GRP78), key mediators of angioinvasion during mucormycosis. In a neutropenic murine model of pulmonary mucormycosis, transferrin enhanced the therapeutic efficacy of both LAMB and isavuconazole (ISAV), resulting in improved survival compared with antifungal monotherapy. Collectively, these findings provide preclinical evidence that transferrin modulates pathogenic determinants associated with mucormycosis and enhances the efficacy of current antifungal therapies, supporting further investigation of transferrin as a potential host-directed adjunctive treatment. Full article

Background/Objectives: Shiga toxin-producing Escherichia coli (STEC) are important zoonotic pathogens associated with gastrointestinal infections and hemolytic–uremic syndrome (HUS). Increasing serotype diversity, emergence of hybrid strains, and growing antimicrobial resistance complicate surveillance and treatment. This review summarizes recent data on STEC isolated from major animal reservoirs between 2020 and 2026. Methods: We comparatively analyzed peer-reviewed, open-access studies investigating STEC from cattle, sheep, goats, poultry, wildlife, and related animal products. We extracted and evaluated data on serotypes, virulence genes, hybrid pathotypes, and antimicrobial resistance determinants. Results: High serotype diversity was observed across all reservoirs, with non-O157 STEC frequently predominating over O157:H7. Ruminant isolates commonly carried stx2 and additional virulence determinants associated with severe human disease, confirming cattle and small ruminants as major reservoirs of highly pathogenic STEC. Poultry-associated isolates showed greater variability in virulence profiles but frequently exhibited high rates of multidrug resistance. Hybrid strains combining virulence traits characteristic of multiple E. coli pathotypes were increasingly reported. Livestock-associated STEC commonly carried resistance determinants against β-lactams, tetracyclines, sulfonamides, quinolones, and polymyxins, whereas wildlife isolates generally showed lower rates of resistance. Conclusions: Animal-associated STEC populations demonstrate increasing genomic diversity, pathogenic potential, and antimicrobial resistance. The growing prevalence of non-O157 and hybrid strains highlights the limitations of traditional serotype-focused surveillance and emphasizes the need for integrated One Health monitoring strategies. Full article

The increasing detection of Riemerella anatipestifer in chickens poses severe challenges to the poultry industry. However, the genomic differences among R. anatipestifer isolates from different poultry hosts remain poorly understood. Here, we investigated host-associated genomic differences among 158 R. anatipestifer strains isolated from different hosts in China, using pan-genome, phylogenetic, virulence factor, and antimicrobial resistance analyses. The core-genome phylogeny showed no apparent separation according to host, sampling period, or geographic origin. Conserved genes including groEL, tufA, and katB were detected in all strains, whereas tviB and ureG displayed host-associated distribution patterns. More than 40 putative antimicrobial resistance (AMR) genes were detected across 158 R. anatipestifer strains, indicating the presence of multiple putative AMR determinants. Among these, bla_RAD-1, bla_RASA-1, and dfrA36 exhibited host-associated distribution patterns. Pan-genome analysis further identified host-associated genomic differences in R. anatipestifer. These included genes contributing to cell-surface modification pathways mediated by pglH, and genes involved in toxin–antitoxin system-dependent stress regulation via parD1/parE1 and yefM-yoeB. Overall, our comparative genomic characterization of R. anatipestifer characterizes host-associated genomic differences and provides a basis for further investigation of their biological significance. Full article

Aeromonas hydrophila is a globally distributed aquatic pathogen. Antibiotic overuse in traditional management practices has intensified problems such as antimicrobial resistance and environmental pollution, creating an urgent need for safe alternatives. This study characterized a BLIS produced by Leuconostoc falkenbergense SBL-85-2, which shows potential as an antibiotic alternative in aquaculture. L. falkenbergense SBL-85-2 exhibited no hemolytic activity, lacked typical high-risk virulence factors, and only low-identity vancomycin-related intrinsic genes (vanT and vanY) were identified by the CARD database, which may preliminarily indicate its potential biosafety for aquatic applications. The BLIS exhibited marked activity against A. hydrophila, with an inhibition zone of 39.14 ± 0.65 mm, as well as other critical pathogens including Aeromonas rivipollensis, Aeromonas salmonicida, Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus, and Vagococcus fluvialis. Furthermore, the BLIS exhibited remarkable thermal stability (retained 87.18 ± 0.14% activity after treatment at 100 °C for 10 min) and UV stability (92.67 ± 0.75% residual activity after 3 h exposure) coupled with sensitivity to proteases, confirming its proteinaceous nature. Molecular weight determination indicated that the BLIS is a low-molecular-weight peptide (<2.7 kDa). Mechanistically, the BLIS disrupted bacterial cell membrane integrity, ultimately resulting in the leakage of cellular contents and a time-dependent reduction in intracellular ATP levels (reduced by 69.16 ± 4.10% at 2 h), exerting its antimicrobial effect. Collectively, our results indicate that this BLIS combines potent antibacterial efficacy with a favorable biosafety profile, suggesting its significant potential for the biological control of A. hydrophila in aquaculture. Full article

Non-O1/non-O139 Vibrio cholerae (NOVC) isolates are non-toxigenic and regarded as etiological agents of infrequent but mild-to-severe human gastroenteritis. In response to the 2022–2023 cholera outbreak in Tshwane, this study investigated the occurrence of NOVC isolates in wastewater within the Tshwane district, South Africa. A total of 341 wastewater samples were screened using Thiosulfate citrate bile salts sucrose (TCBS) media, with subsequent confirmation of Vibrio cholerae (V. cholerae) isolates by multiplex-PCR assays. Rep-PCR was performed to determine the genetic relatedness of the isolates. Selected isolates were subjected to whole genome sequencing (WGS). Of the 341 samples, PCR confirmed 143 isolates as NOVC. Genetic fingerprinting grouped these isolates into 12 distinct clusters, from which 12 representative isolates were selected for WGS and 10 isolates were confirmed as NOVC. The isolates harboured pathogenicity-related genes, such as hlyA and rtxA, as well as other genes contributing to bacterial adaptation such as trkH and tnaA. Drug resistance was mostly observed to first-line antibiotics, ciprofloxacin, chloramphenicol, and trimethoprim–sulfamethoxazole. Plasmid analysis showed six isolates harboured plasmids (pA, p21L, and PVN84) bearing multiple resistance determinants. Phylogenetic analysis showed evidence of genetic diversity amongst isolates. Although the isolates lacked classical toxigenic genes, they carried other virulence determinants associated with pathogenicity, posing a potential risk for clinical infection, highlighting the need for sustained surveillance. Full article

Background: Aircraft wastewater (AWW) provides a composite environmental matrix reflecting passengers from diverse geographic origins and may serve as a surveillance tool for AMR monitoring. Objectives: To characterize microbial community composition, antimicrobial resistance genes (ARGs), virulence factor genes (VFGs), and genome-resolved features of AWW. Methods: Samples (N = 10) were collected from long-haul flights arriving in the UAE between October 2024 and February 2025. Shotgun metagenomic sequencing and high-throughput quantitative PCR (HT-qPCR) were performed. Metagenome-assembled genomes (MAGs) were reconstructed. Results: Shotgun metagenomics identified 752 bacterial species dominated by gut-associated families, including Lachnospiraceae and Ruminococcaceae. A total of 345 ARGs were detected, with tetracycline resistance genes being most abundant. Regional variation in resistome composition was supported by permutational multivariate analysis of variance (PERMANOVA, p = 0.010), and principal coordinate analysis indicated separation by flight-origin region. MAG reconstruction recovered 1012 genomes, with 85.4% resolved to species level. MAG-based annotation identified 280 VFGs corresponding to 116 non-redundant virulence genes. HT-qPCR confirmed the widespread presence of key ARG classes and mobile genetic elements across samples, in keeping with metagenomic findings. Conclusions: AWW contains diverse microbial communities and AMR determinants. Genome-resolved analysis provided organism-level context for resistome and virulome characterization, confirming AWW as an environmental matrix for monitoring transboundary AMR dynamics. Full article

Porphyromonas gingivalis is a keystone periodontal pathogen strongly associated with periodontitis progression. Although testosterone levels have been associated with periodontal health, its direct effects on P. gingivalis virulence remain poorly understood. The aim of this study was to investigate the impact of testosterone exposure on the key virulence characteristics of P. gingivalis strain W50. We found that testosterone significantly increased the growth and biofilm biomass of P. gingivalis W50 after 48 h. Furthermore, testosterone enhanced the extracellular gingipain activity of both lysine and arginine gingipains from P. gingivalis. We also found that IL-1β release from gingival epithelial cells was significantly lowered following infection with testosterone-primed P. gingivalis compared with unprimed W50. At the mRNA level, no differences in pro-IL-1β, IL-8, or CXCL10 gene expression were detected in gingival epithelial cells infected with testosterone-primed P. gingivalis compared with unprimed W50. Finally, testosterone priming significantly enhanced the ability of P. gingivalis to colonize and invade gingival epithelial cells. Overall, these findings indicate that testosterone exposure modulates several virulence-associated phenotypes of P. gingivalis W50 in vitro. The mechanisms underlying these effects and their relevance to periodontal disease in vivo remain to be determined. Full article

Rabies virus causes fatal neurological disease, but the mechanisms by which its glycoprotein G influences neuronal dysfunction remain incompletely understood. In this study, we rescued two recombinant RABV LBNSE strains carrying G proteins from either the attenuated SAD-B19 strain or the virulent CVS11 strain, designated as rLBNSE-SfG and rLBNSE-CfG, respectively. Infection of primary mouse neurons and challenge experiments in mice showed that rLBNSE-CfG was associated with increased early neuronal infectivity and greater neurovirulence after intracerebral (i.c.) injection. Western blot analysis revealed that the SAD-B19-derived G protein exhibited a higher apparent molecular weight than the CVS11-derived G protein. Bioinformatic analysis identified strain-specific differences in putative post-translational modification sites, which may contribute to the observed migration difference. Quantitative proteomic analysis of mouse brain tissue showed that proteins downregulated in the rLBNSE-CfG group were enriched in synaptic vesicle cycle-related pathways and synapse-associated Gene Ontology (GO) terms. Integrated analysis identified a SNARE-associated module containing Snap25, Stx1a, and Vamp2, among which Vamp2 was significantly reduced in the rLBNSE-CfG group. In primary neurons, reduced Vamp2 abundance was associated with the extracellular domain of CVS11 G protein. These findings associate CVS11-derived G protein variation with reduced Vamp2 abundance and a presynaptic vesicle-related proteomic signature, although whether these molecular alterations directly impair synaptic vesicle release remains to be determined. Full article

Chronic infection with Helicobacter pylori (H. pylori) is a major environmental risk factor for gastric carcinogenesis. Malignancy is largely driven by variations within the virulence factor CagA, with East Asian lineages exhibiting higher oncogenic potential than Western ones. However, how these variants modulate cellular crosstalk remains poorly understood. We integrated molecular dynamics (MD) simulations with single-cell transcriptomics across progressive disease stages, including chronic atrophic gastritis, intestinal metaplasia, and gastric cancer. Local niche remodeling was evaluated via cell–cell communication profiling among epithelial, stromal, and immune circuits, while simulations of MARK2 kinase bound to distinct CagA lineages determined binding affinities. Single-cell analysis revealed that H. pylori toxicity progressively dampens epithelial–stromal crosstalk, marked by severe epithelial polarity aberrations that disrupt neuroendocrine-like secretory and synaptic pathways during malignant transformation. Mechanistically, MD simulations and MM/GBSA calculations demonstrated that East Asian CagA lineages exhibit higher binding affinity toward host MARK2 than Western lineages. Specific East Asian amino acid substitutions dramatically tighten the protein interface, driving stronger signaling perturbations. This study bridges atomistic structural virulence with microenvironmental shifting, establishing geographic CagA toxicity divergence as a critical determinant for pathogen-driven gastric cancer risk. Full article

Pseudomonas aeruginosa is a nosocomial pathogenic bacterium that causes a wide range of human infectious diseases. The type III secretion system (T3SS) serves as a key virulence determinant underlying the pathogenesis of this bacterium in acute infections. As the master transcriptional activator of T3SS, ExsA binds to target promoter regions and modulates the expression of all currently identified T3SS genes. In this study, we identified tyrosine phosphoprotein A (TypA) as a repressor that restricts expression of the T3SS in P. aeruginosa. TypA interacts with ExsA to block its binding to target promoters, thereby inhibiting T3SS expression. We show that the typA expression is induced in response to low calcium, low temperature, a biofilm lifestyle, and direct contact with host cells. Additionally, the absence of TypA caused a growth defect in P. aeruginosa at low temperatures. Collectively, these data confirm the significant role of TypA and reveal a novel molecular mechanism by which P. aeruginosa regulates T3SS. Full article