Pathogenicity of cultivated murine leprosy bacilli in mice. 2. The pathogenicity of bacilli from smooth colonies.
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Animals↗
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Results for “pathogenicity”
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[Studies on pathogenic Escherichia coli. (II) The pathogenicity of capsular polysaccharide-synthesizing Escherichia coli].
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Animals↗
[Anaerobic bacteria as pathogens and co-pathogens in multiple clinical cases. Study of the in vitro sensitivity to 8 antibiotics in samples isolated from patients at the Hospital das Clínicas].
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Anti-Bacterial Agents↗
[Sodium nucleinate increase of nonspecific macroorganism resistance to conditionally pathogenic and pathogenic microorganisms].
Sodium nucleinate significantly increased the non-specific resistance of mice to E. coli O26, Ps. vulgaris, Ser. marcesens, Ps. aeruginosa, Kl. ozaenae and their associations and total resistance also accompanied by a significant decrease in the number of the bacteria in the spleen and blood, the total number of the cells in the peritoneal exudate and the number of the cells adhering to the glass (macrophages). The preparation is a low molecular RNA consisting mainly of fraction 3S and a small amount of fraction 4S. It contains 1.5 per cent of protein and 2 per cent of DNA and does not contain any polysaccharides. Repeated purification of sodium nucleinate lowering the levels of the admixtures 5 times did not change its efficacy. The low molecular RNA of the rat liver (4S) had a pronounced stimulating activity. On infection of the host stimulated with sodium nucleinate, formation of the post-infection immunity was not decreased.
Animals↗
Effect of growth temperature on the thermal destruction pattern of pathogenic & non-pathogenic strains of E. coli.
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Animals↗
[Pathogens, host and milieu, the concept of pathogenicity as applied to the respiratory tract (author's transl)].
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Airway Obstruction↗
Pathogen local adaptation shapes Pierce's disease of grapevines outcomes under field conditions.
Climate change is broadly expected to increase the range of many plant diseases, yet the current status of local thermal adaptation in many pathogens is poorly understood. Xylella fastidiosa (Xf) is a global bacterial plant pathogen that causes Pierce's disease (PD) of grapevines and infects over 700 other host plant species, impacting both agricultural and natural ecosystems. In a common garden experiment with 477 vines in the field, we compared PD outcomes from a local (colder climate in CA) vs non-local (warmer climate in CA) bacterial strain in 13 Mediterranean grapevine varieties over 3 years. Relative to the local strain, there was 77% lower overwinter survival in the non-local strain from a warmer climate, strongly indicating local adaptation in these CA Xf populations. Host genotype also had a significant effect on pathogen winter survival, and grapevine varieties differed in PD susceptibility. Additionally, we assessed in planta evolution of the two pathogen strains over 3 years by whole-genome sequencing 58 field-derived isolates. There were convergent loss-of-function mutations in genes encoding minor Type IV pilin (T4P) proteins, which control twitching motility and other virulence phenotypes, suggesting rapid adaptive evolution. Our results suggest local adaptation to cold temperatures in a bacterial plant pathogen and a possible role for minor Type IV pilins in thermal adaptation. These findings demonstrate the urgent need to incorporate X. fastidiosa evolution and local thermal adaptation into global models of PD spread. Differentiating pathotypes with distinct thermal adaptations will improve disease forecasting and inform quarantine decisions.IMPORTANCEForecasting the movement of plant pathogens is a critical issue under global warming to effectively manage future plant disease outbreaks. Yet, current plant pathogen local thermal adaptation is often unaccounted for, especially in bacterial pathogens. Our study examines local adaptation to temperature in a bacterial plant pathogen, Xylella fastidiosa, that causes disease in grapevines in addition to infecting 700 other plant species. In a large-scale field experiment across 13 grapevine varieties, we demonstrate local adaptation in pathogen winter survival in distinct Xylella fastidiosa strains. Additionally, we found evidence of adaptive evolution in just 3 years, as we observed convergent mutations after resequencing strains that evolved in the field. Our results suggest that X. fastidiosa populations-even within a small geographic area-have distinct adaptations to winter temperatures and may exhibit differential responses to warming winters.
Type IV pili↗
Double heterozygous germline pathogenic variants in patients referred to a tertiary cancer genetics clinic in Singapore.
BACKGROUND: The increasing use of multigene panel testing has led to a rise in the identification of double heterozygous (DH) pathogenic variants in cancer patients, although their frequency and clinical relevance remain poorly characterised, particularly in Asian populations. METHODS: We conducted a retrospective review of 5,178 patients referred to a tertiary cancer genetics clinic in Singapore. DH pathogenic variants were defined as the presence of two or more distinct pathogenic or likely pathogenic germline variants identified by multigene panel testing. Clinical, pathological, and family history data were reviewed and analysed using appropriate non-parametric and exact statistical methods. RESULTS: Among 2,802 index patients with available genetic test results, 593 (21.2%) carried at least one pathogenic/likely pathogenic variant. DH pathogenic variants were identified in 21 individuals (0.75%), of which 9 were patients with breast cancer, 10 with non-breast malignancies, and 2 were cancer-free. The frequency of multiple primary cancers was 26.3% in DH variant carriers, 23.3% in single variant carriers, and 16.5% in those with no pathogenic variants. The median ages of first cancer diagnosis were 47, 44, and 48 years. Several DH combinations involved moderate- or low-penetrance genes, and some clinically unsuspected variants were detected only through broad multigene testing. CONCLUSION: DH pathogenic variants represent a rare subgroup that is increasingly detected through multigene panel testing. Their phenotypic expression is variable, and the influence of additional pathogenic variants remains uncertain. Our findings emphasise the need for tailored genetic evaluation and further research to guide evidence-based management for this complex patient population.
Asia↗
Beyond water and soil: Air emerges as a major reservoir of human pathogens.
Assessing the risk of human pathogens in the environment is crucial for controlling the spread of diseases and safeguarding human health. However, conducting a thorough assessment of low-abundance pathogens in highly complex environmental microbial communities remains challenging. This study compiled a comprehensive catalog of 247 human-pathogenic bacterial taxa from global biosafety agencies and identified more than 78 million genome-specific markers (GSMs) from their 17,470 sequenced genomes. Subsequently, we analyzed these pathogens' types, abundance, and diversity within 474 shotgun metagenomic sequences obtained from diverse environmental sources. The results revealed that among the four habitats studied (air, water, soil, and sediment), the detection rate, diversity, and abundance of detectable pathogens in the air all exceeded those in the other three habitats. Air, sediment, and water environments exhibited identical dominant taxa, indicating that these human pathogens may have unique environmental vectors for their transmission or survival. Furthermore, we observed the impact of human activities on the environmental risk posed by these pathogens, where greater amounts of human activities significantly increased the abundance of human pathogenic bacteria, especially in water and air. These findings have remarkable implications for the environmental risk assessment of human pathogens, providing valuable insights into their presence and distribution across different habitats.
Humans↗
Diversification, loss, and virulence gains of the major effector AvrStb6 during continental spread of the wheat pathogen Zymoseptoria tritici.
Interactions between plant pathogens and their hosts are highly dynamic and mainly driven by pathogen effectors and plant receptors. Host-pathogen co-evolution can cause rapid diversification or loss of pathogen genes encoding host-exposed proteins. The molecular mechanisms that underpin such sequence dynamics remains poorly investigated at the scale of entire pathogen species. Here, we focus on AvrStb6, a major effector of the global wheat pathogen Zymoseptoria tritici, evolving in response to the cognate receptor Stb6, a resistance widely deployed in wheat. We comprehensively captured effector gene evolution by analyzing a global thousand-genome panel using reference-free sequence analyses. We found that AvrStb6 has diversified into 59 protein isoforms with a strong association to the pathogen spreading to new continents. Across Europe, we found the strongest differentiation of the effector consistent with high rates of Stb6 deployment. The AvrStb6 locus showed also a remarkable diversification in transposable element content with specific expansion patterns across the globe. We detected AvrStb6 gene losses and evidence for transposable element-mediated disruptions. We used virulence datasets of genome-wide association mapping studies to predict virulence changes across the global panel. Genomic predictions suggested marked increases in virulence on Stb6 cultivars concomitant with the spread of the pathogen to Europe and the subsequent spread to further continents. Finally, we genotyped French bread wheat cultivars for Stb6 and monitored resistant cultivar deployment concomitant with AvrStb6 evolution. Taken together, our data provides a comprehensive view of how a rapidly diversifying effector locus can undergo large-scale sequence changes concomitant with gains in virulence on resistant cultivars. The analyses highlight also the need for large-scale pathogen sequencing panels to assess the durability of resistance genes and improve the sustainability of deployment strategies.
Ascomycota↗
Molecular Diagnostics for WHO Priority Bacterial Pathogens: A Bibliometric Mapping of Diagnostic Platforms, Resistance Markers, and Antimicrobial Resistance Research Trends.
Antimicrobial resistance (AMR) constrains effective treatment and carries implications for infection control, surveillance, and public health. The World Health Organization (WHO) priority bacterial pathogen framework has intensified the need for diagnostic innovation by redefining research priorities around organisms combining high disease burden with complex resistance profiles. Molecular diagnostics have accordingly moved beyond culture-based workflows, integrating rapid pathogen identification, resistance-marker detection, genomic surveillance, and clinical decision support. The present study conducted a bibliometric mapping of the literature on WHO priority pathogens. Rather than addressing resistance at a general level or a single pathogen or technology, it integrates priority pathogens, molecular platforms, and resistance markers within a single framework, tracing their joint thematic and temporal evolution along an explicit pathogen-platform-marker axis. Scopus-indexed articles and reviews (2000-2025) were retrieved, yielding 1746 publications after screening adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Analyses used Bibliometrix/Biblioshiny, R, and VOSviewer. The literature expanded markedly after 2018, led by China and the United States. Methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis, Enterococcus faecium, and the Enterobacterales-carbapenemase axis constituted the principal thematic cores, whereas conventional polymerase chain reaction (PCR)/nucleic acid amplification testing (NAAT) and whole-genome sequencing were the dominant platforms. Overall, the field has evolved from pathogen detection into an AMR-centered translational domain encompassing resistance prediction, genomic epidemiology, surveillance, and clinical decision support. Diagnostic development, stewardship, and surveillance depend on hybrid workflows coupling rapid marker-targeted assays with genome-based characterization, delivering actionable resistance within clinically meaningful timeframes, and extending coverage to underrepresented pathogens and platforms.
Humans↗
Experimental evolution of a pathogen confronted with innate immune memory increases variation in virulence.
Understanding the drivers and mechanisms of virulence evolution is still a major goal of evolutionary biologists and epidemiologists. Theory predicts that the way virulence evolves depends on the balance between the benefits and costs it provides to pathogen fitness. Additionally, host responses to infections, such as resistance or tolerance, play a critical role in shaping virulence evolution. But, while the evolution of pathogens has been traditionally studied under the selection pressure of host adaptive immunity, less is known about their evolution when confronted to simpler and less effective forms of immunity such as immune priming. In this study, we used a well-established insect model for immune priming - red flour beetles and their bacterial pathogen Bacillus thuringiensis tenebrionis - to test how this form of innate immune memory drives the pathogen evolution. Through controlled experimental evolution of the pathogen in primed versus non-primed hosts, we found no change in average virulence after eight selection cycles in primed host. Nonetheless, we observed a notable rise in the variability of virulence, defined as the ability to kill hosts, among independent pathogen lines that evolved in primed hosts, and the bacteria were unable to develop resistance to host priming. Whole genome sequencing revealed increased activity in the bacterial mobilome (prophages and plasmids). Expression of the Cry toxin - a well-known virulence factor - was linked to evolved differences in copy number variation of the cry-carrying plasmid, though this did not correlate directly with virulence. These findings highlight that innate immune memory can drive variability in pathogen traits, which may favor adaptation to variable environments. This underscores the need to consider pathogen evolution in response to innate immune memory when applying these mechanisms in medicine, aquaculture, pest control, and insect mass production.
Animals↗
Frequency and clinical features of germline pathogenic variants in sarcoma: a case-control study.
BACKGROUND: Germline multigene panel testing is not yet integrated into standard care for patients with sarcoma. This study aimed to assess the frequency and distribution of germline pathogenic variants in patients with sarcoma compared with cancer-free controls and identify differences between patients with and without germline pathogenic variants. METHODS: This retrospective cohort included 488 sarcoma patients and 2440 cancer-free controls matched 1:5 by age, sex, and ethnicity. Multigene panel testing was performed between 2016 and 2024 at a single germline testing laboratory. The frequency of germline pathogenic variants in selected genes was compared using Fisher exact test with odds ratios (ORs) and 95% confidence intervals. Additionally, within the case-only cohort, clinical characteristics were evaluated to assess associations with the presence of germline pathogenic variants in any gene. RESULTS: Among 488 patients with sarcoma, 67.8% (n = 331) were female, with a median age at sarcoma diagnosis of 47 years (range = 0.5-87.5 years). Cases had a higher frequency of germline pathogenic variants compared with controls (26.2% vs 10.5%; OR = 3.05, P < .001). We observed a higher frequency of germline pathogenic variants in TP53, BRCA2, CHEK2, NF1, SDHA, BRIP1, POT1, RB1, and CDH1 among patients with sarcoma compared with controls. Age at sarcoma diagnosis did not differ between groups. CONCLUSIONS: This study confirms the high detection rate of germline pathogenic variants in patients with sarcoma and describes several associated genes. These findings indicate that age at sarcoma diagnosis may not reliably predict germline pathogenic variants. Expanding germline testing for patients with sarcoma would enhance personalized treatment strategies and familial risk assessment.
Humans↗
Spray-induced gene silencing for disease control is dependent on the efficiency of pathogen RNA uptake.
Recent discoveries show that fungi can take up environmental RNA, which can then silence fungal genes through environmental RNA interference. This discovery prompted the development of Spray-Induced Gene Silencing (SIGS) for plant disease management. In this study, we aimed to determine the efficacy of SIGS across a variety of eukaryotic microbes. We first examined the efficiency of RNA uptake in multiple pathogenic and non-pathogenic fungi, and an oomycete pathogen. We observed efficient double-stranded RNA (dsRNA) uptake in the fungal plant pathogens Botrytis cinerea, Sclerotinia sclerotiorum, Rhizoctonia solani, Aspergillus niger and Verticillium dahliae, but no uptake in Colletotrichum gloeosporioides, and weak uptake in a beneficial fungus, Trichoderma virens. For the oomycete plant pathogen, Phytophthora infestans, RNA uptake was limited and varied across different cell types and developmental stages. Topical application of dsRNA targeting virulence-related genes in pathogens with high RNA uptake efficiency significantly inhibited plant disease symptoms, whereas the application of dsRNA in pathogens with low RNA uptake efficiency did not suppress infection. Our results have revealed that dsRNA uptake efficiencies vary across eukaryotic microbe species and cell types. The success of SIGS for plant disease management can largely be determined by the pathogen's RNA uptake efficiency.
Ascomycota↗
Capsular Polysaccharide Is Essential for the Virulence of the Antimicrobial-Resistant Pathogen Enterobacter hormaechei.
Nosocomial infections caused by multidrug-resistant (MDR) Enterobacter cloacae complex (ECC) pathogens are on the rise. However, the virulence strategies employed by these pathogens remain elusive. Here, we study the interaction of ECC clinical isolates with human serum to define how this pathogen evades the antimicrobial action of complement, one of the first lines of host-mediated immune defense. We identified a small number of serum-sensitive strains, including Enterobacter hormaechei strain NR3055, which we exploited for the in vitro selection of serum-resistant clones. Comparative genomics between the serum-sensitive NR3055 strain and the isolated serum-resistant clones revealed a premature stop codon in the wzy gene of the capsular polysaccharide biosynthesis locus of NR3055. The complementation of wzy conferred serum resistance to NR3055, prevented the deposition of complement proteins on the bacterial surface, inhibited phagocytosis by human neutrophils, and rendered the bacteria virulent in a mouse model of peritonitis. Mice exposed to a nonlethal dose of encapsulated NR3055 were protected from subsequent lethal infections by encapsulated NR3055, whereas mice that were previously exposed to unencapsulated NR3055 succumbed to infection. Thus, capsule is a key immune evasion determinant for E. hormaechei, and it is a potential target for prophylactics and therapeutics to combat these increasingly MDR human pathogens. IMPORTANCE Infections caused by antimicrobial resistant bacteria are of increasing concern, especially those due to carbapenem-resistant Enterobacteriaceae pathogens. Included in this group are species of the Enterobacter cloacae complex, regarding which there is a paucity of knowledge on the infection biology of the pathogens, despite their clinical relevance. In this study, we combine techniques in comparative genomics, bacterial genetics, and diverse models of infection to establish capsule as an important mechanism of Enterobacter pathogens to resist the antibacterial activity of serum, a first line of host defense against bacterial infections. We also show that immune memory targeting the Enterobacter capsule protects against lethal infection. The further characterization of Enterobacter infection biology and the immune response to infection are needed for the development of therapies and preventative interventions targeting these highly antibiotic resistant pathogens.
Humans↗
Patterns of antimicrobial resistance genes in pathogens across One Health sectors in Ireland: an in silico approach.
As part of a rapid risk assessment, an in silico approach was used to detect antimicrobial resistance (AMR) in pathogenic isolates from humans, animals, and the environment. A total of 11,670 genomic data sets were retrieved from the NCBI Pathogen Detection system for Ireland, which represented 47 pathogenic species, including Salmonella enterica, Escherichia coli/Shigella spp., Staphylococcus aureus, Klebsiella pneumoniae, and Enterococcus faecium. Identifying the most critical pathogenic strains over time is essential, as these organisms significantly contribute to mortality, morbidity, and hospitalization. The analysis identified 799 antimicrobial resistance genes (ARGs), including their allelic diversity, 117 plasmid replicons, and 274 virulence factors. Several critical ARGs, particularly those conferring resistance to beta-lactams, aminoglycosides, quinolones, and colistin, were common across isolates originating from human, animal, and environmental sources, suggesting shared resistance profiles across One Health sectors. Klebsiella pneumoniae, E. coli/Shigella spp., S. enterica, and S. aureus were the dominant hosts of these ARGs and associated mobile genetic elements. Increasing resistance across major antibiotic classes aligned with trends reported across other European countries. This study provides a national-scale in silico comparison of AMR across pathogens and One Health sectors using publicly available genomic data. The findings help reinforce Ireland's AMR surveillance by showing which resistance genes are present and how they spread across critical pathogens in humans, animals, and the environment. These findings highlight the urgent need for improved antibiotic stewardship and integrated One Health surveillance to limit the emergence and spread of AMR.IMPORTANCEAntimicrobial resistance (AMR) is a growing threat to human, animal, and environmental health. This study used publicly available genomic data to identify antimicrobial resistance genes (ARGs) in key bacterial pathogens circulating in Ireland. By analyzing over 11,000 genomes from humans, animals, and the environment, we found that several dangerous resistance genes, including those against last-resort antibiotics, were widespread across different sources. The study highlights which bacteria and resistance genes are most critical and how they may spread between humans, animals, and the environment. These insights provide a national snapshot of AMR, supporting more effective monitoring and prevention strategies. By revealing patterns of resistance and modes of transmission, our findings underscore the importance of coordinated antibiotic stewardship and One Health approaches to slow the emergence and spread of resistant infections, protecting public health and ensuring antibiotics remain effective.
Humans↗
Diversification of an emerging bacterial plant pathogen; insights into the global spread of Xanthomonas euvesicatoria pv. perforans.
Emerging and re-emerging plant diseases continue to present multifarious threats to global food security. Considerable recent efforts are therefore being channeled towards understanding the nature of pathogen emergence, their spread and evolution. Xanthomonas euvesicatoria pv. perforans (Xep), one of the causal agents of bacterial spot of tomato, rapidly emerged and displaced other bacterial spot xanthomonads in many tomato production regions around the world. In less than three decades, it has become a dominant xanthomonad pathogen in tomato production systems across the world and presents a compelling example for understanding diversification of recently emerged bacterial plant pathogens. Although Xep has been continuously monitored in Florida since its discovery, the global population structure and evolution at the genome-scale is yet to be fully explored. The objectives of this work were to determine genetic diversity globally to ascertain if different tomato production regions contain genetically distinct Xep populations, to examine genetic relatedness of strains collected in tomato seed production areas in East Asia and other production regions, and to evaluate variation in type III secretion effectors, which are critical pathogenicity and virulence factors, in relationship to population structure. We used genome data from 270 strains from 13 countries for phylogenetic analysis and characterization of type III effector gene diversity among strains. Our results showed notable genetic diversity in the pathogen. We found genetically similar strains in distant tomato production regions, including seed production regions, and diversification over the past 100 years, which is consistent with intercontinental dissemination of the pathogen in hybrid tomato production chains. Evolution of the Xep pangenome, including the acquisition and loss of type III secreted effectors, is apparent within and among phylogenetic lineages. The apparent long-distance movement of the pathogen, together with variants that may not yet be widely distributed, poses risks of emergence of new variants in tomato production.
Xanthomonas↗
Genomic characterization and pathogenicity of ruminant Listeria monocytogenes isolates in a murine oral infection model.
Listeria monocytogenes is a major foodborne pathogen; its ruminant isolates display zoonotic characteristics, causing similar clinical signs in humans, including abortion and encephalitis. However, data on whole genome sequencing and pathogenicity of ruminant L. monocytogenes isolates remain sparse. This study aimed to analyze the genotypic characteristics of L. monocytogenes isolates from ruminants with listeriosis. Furthermore, we assessed the in vivo pathogenicity of four ruminant L. monocytogenes isolates, characterized via whole-genome sequencing-based genetic clustering, in orogastrically inoculated mice. The isolate LM18 (serotype 1/2b, ST224, SL6178) had the lowest lethal dose compared to the other three isolates including previous hypervirulence type (serotype 4b, ST1, SL1) and caused secondary bacteremia in lungs, with sustained bacterial loads in the spleen and liver. Genomic (listeria pathogenicity island -1 and -3) and virulence gene (actA and llsX) mutation analyses associated with virulence suggested from well-recognized studies could not elucidate the virulence of the isolates. SSI-1, which only exists in the isolate LM18 (serotype 1/2b, ST224, SL6178), may help L. monocytogenes survive in the gastrointestinal environment, thereby affecting its virulence. Further research should investigate the role of SSI-1 in the pathogenicity of L. monocytogenes. Moreover, additional studies utilizing larger datasets of ruminant isolates are required to validate our genotypic characterization and to obtain a comprehensive picture of further genotypic differences crucial for L. monocytogenes pathogenicity.
Animals↗