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PubMed2026

Differential virulence potential of different clades of multidrug-resistant Klebsiella pneumoniae ST258.

Klebsiella pneumoniae (KP) isolates belonging to multi-locus sequence type 258 (ST258) are a frequent cause of hospital-associated outbreaks and display extensive multidrug resistance. The KP ST258 lineage consists of two genetically distinct clades, called Clade 1 and Clade 2. These two clades are genetically related to one another, but are historically distinguished by having different capsular polysaccharide types. While bacteria belonging to both clades are isolated from clinical infections, Clade 2 is isolated more frequently compared to Clade 1. To investigate drivers of this difference in clade prevalence, we collected 172 clinical KP ST258 isolates from patients at a single medical center. Clinical review showed that patients infected with Clade 2 isolates were more acutely ill than Clade 1-infected patients, despite having fewer comorbidities. We also found that Clade 2 isolates were more resistant to killing by human serum, despite binding more complement protein C3 than Clade 1 isolates. Additionally, mice infected with a Clade 2 isolate had increased bacterial dissemination from the lungs to the liver and spleen than mice infected with a Clade 1 isolate, and this dissemination required an intact capsule locus. Increased dissemination in mice was not due to differential serum killing, as mouse serum was unable to kill isolates of either clade, but dissemination was associated with decreased macrophage uptake of the Clade 2 isolate. Taken together, these data suggest that KP ST258 Clade 2 is more virulent than Clade 1, although the specific mechanisms at play appear to differ between mice and humans.IMPORTANCEKP ST258 is an epidemic lineage of multidrug-resistant gram-negative bacteria that has caused numerous outbreaks in hospitals around the world. The KP ST258 population is divided into two genetically related but distinct clades, which differ primarily in their capsule type. In this study, we found that patients infected with one of the KP ST258 clades were more acutely ill than patients infected with the other clade. We also observed clade-specific differences both in killing by human serum and in bacterial dissemination in a mouse model of pneumonia. Finally, we identified important limitations in the use of mouse models to study host defenses against multidrug-resistant KP infection. Overall, this work underscores the importance of capsule composition in KP ST258 virulence, identifies differences in the host response to KP infection between mice and humans, and highlights a potential role for complement-targeting immunotherapeutics in the treatment of KP infections.

Klebsiella pneumoniae↗

PubMed2026

Differential virulence potential of different clades of multidrug-resistant Klebsiella pneumoniae ST258.

Klebsiella pneumoniae↗

PubMed2025

Unique growth and morphology properties of Clade 5 Clostridioides difficile strains revealed by single-cell time-lapse microscopy.

Clostridioides difficile is a gastrointestinal pathogen of both humans and agricultural animals and thus a major One Health threat. The C. difficile species consists of five main clades, with Clade 5 currently undergoing speciation from Clades 1-4. Clade 5 strains are highly prevalent in agricultural animals and can cause zoonotic infections, suggesting that these strains have evolved phenotypes that distinguish them from Clade 1-4 strains. Here, we compare the growth properties of Clade 5 strains to those of Clade 1-4 strains using anaerobic time-lapse microscopy coupled with automated image analysis. Our analyses indicate that Clade 5 strains grow faster and are more likely to form long chains of cells than Clade 1-4 strains. Using comparative genomic and CRISPRi analyses, we show that the chaining phenotype of Clade 5 strains is driven by the orientation of the invertible cmr switch sequence, with chaining strains exhibiting a bias to the cmr-ON state. Interestingly, Clade 5 strains with a bias towards the cmr-ON state shifted to a largely cmr-OFF state during murine infection, suggesting that the cmr-OFF state is under positive selection during infection. Collectively, our data reveal that Clade 5 strains have distinct growth properties, which may allow them to inhabit diverse ecological niches.

Journal Article↗

PubMed2025

Unique growth and morphology properties of Clade 5 Clostridioides difficile strains revealed by single-cell time-lapse microscopy.

Clostridioides difficile is a gastrointestinal pathogen of both humans and agricultural animals and thus a major One Health threat. The C. difficile species consists of five main clades, with Clade 5 currently undergoing speciation from Clades 1-4. Since Clade 5 strains are highly prevalent in agricultural animals and a frequent cause of zoonotic infections, these strains may have evolved phenotypes that distinguish them from Clade 1-4 strains. Here, we compare the growth properties of Clade 5 strains to those of Clade 1-4 strains using anaerobic time-lapse microscopy coupled with automated image analysis. Our analyses indicate that Clade 5 strains grow faster and are more likely to form long chains of cells than Clade 1-4 strains. Using comparative genomic and CRISPRi analyses, we show that the chaining phenotype of Clade 5 strains is driven by the orientation of the invertible cmr switch sequence, with chaining strains exhibiting a bias to the cmr-ON state. Interestingly, Clade 5 strains with a bias towards the cmr-ON state shifted to a largely cmr-OFF state during murine infection, suggesting that the cmr-OFF state is under positive selection during infection. Collectively, our data reveal that Clade 5 strains have distinct growth properties, which may allow them to inhabit diverse ecological niches.

Clostridioides difficile↗

PubMed2025

Emergence of clade 3 emm89 group A Streptococcus in Queensland, Australia.

The emergence of a new clade of emm89 group A Streptococcus (GAS) (clade 3) has been described in several countries. Strains in this clade have been reported to have genomic characteristics that lead to increased expression of virulence factors and may confer a selective advantage over previous emm89 strains. To investigate whether clade 3 GAS is present in the emm89 GAS population of Queensland, Australia, all emm89 GAS isolates received by the Queensland Public Health Microbiology Reference Laboratory since emm typing began in the early 2000s underwent genomic sequencing and analysis. Analysis of sequences from 293 emm89 GAS isolates demonstrated the presence of distinct genomic groups in the Queensland emm89 GAS population. Unlike emm89 GAS populations described in the UK and USA, which were mostly ST101 and ST407, there were a relatively high number of ST142 and ST812 strains in the Queensland emm89 GAS population. However, the majority of Queensland isolates belonged to clade 3, with 80% (n=233) of emm89 GAS isolated from 2006 onwards belonging to this clade. All Queensland clade 3 isolates had the reported genomic features associated with higher virulence potential including increased streptolysin O production and an acapsular phenotype. Clade 3, which has emerged to become the dominant clade of emm89 GAS in Europe and the USA, is now also the dominant clade in Queensland.

Streptococcus pyogenes↗

PubMed2025

Bacterial skin colonization with a specific Cutibacterium avidum clade as a risk factor for periprosthetic joint infections-a multicenter study.

Cutibacterium avidum is increasingly recognized as a causative agent of periprosthetic joint infections (PJIs), yet data on its pathogenic potential and distinguishing features from commensal strains remain limited. In this multicenter study, we compared 11 C. avidum isolates from PJIs with 32 isolates from healthy skin collected across four European hospitals. We investigated phylogenetic relationships, antibiotic susceptibility, biofilm formation, and bacterial fitness. Phylogenomic analysis revealed two main clades within the C. avidum population. All PJI isolates belonged exclusively to Clade 1, which also included skin isolates. Within Clade 1, gene content analysis showed no consistent genetic differences between PJI and skin isolates. All isolates exhibited moderate to strong biofilm formation, with no significant differences in either data set. Minimal inhibitory concentration (MIC) and minimal biofilm inhibitory concentration (MBIC) values were low and largely concordant, while minimal biofilm eradication concentration (MBEC) values were elevated for all antibiotics except rifampin. One isolate was resistant to clindamycin due to the erm(X) gene. Rifampin consistently showed the lowest MIC, minimal bactericidal concentration, MBIC, and MBEC values. Bacterial fitness, assessed via bacterial quantitative fitness analysis, was significantly lower in PJI isolates compared to skin isolates when all strains were analyzed (P = 0.039), but this difference was not statistically significant when restricted to Clade 1. In conclusion, C. avidum isolates are strong biofilm producers irrespective of clinical origin. PJI isolates are restricted to a single phylogenetic clade, yet lack distinct biofilm or fitness traits within that clade, suggesting that multiple Clade 1 strains may have the potential to cause PJIs. IMPORTANCE Cutibacterium avidum has long been considered a skin commensal, but it is increasingly associated with prosthetic joint infections (PJIs). Despite its clinical emergence, little is known about its virulence potential or how invasive strains differ from commensal ones. This multicenter study provides the most comprehensive comparative analysis to date, integrating phenotypic and genomic data from both PJI-associated and skin-derived isolates. We show that all isolates are strong biofilm formers and that invasive isolates exhibit reduced growth fitness-a phenotype linked to persistence and treatment failure in other pathogens. Notably, all PJI isolates belonged to a single phylogenetic clade, suggesting that specific lineages of C. avidum may be more likely to cause infection. These findings help clarify the biology of this emerging pathogen and provide a foundation for improved diagnostics, susceptibility testing, and future infection prevention and treatment strategies.

Biofilms↗

PubMed2026

Clade-dependent antifungal resistance and susceptibility in Candidozyma auris: A global scoping review.

BACKGROUND: Candidozyma auris (formerly Candida auris) is an emerging multidrug-resistant fungal pathogen that has spread globally since its first identification in 2009 and is now classified as a critical-priority pathogen by the World Health Organization. Distinct genetic clades are associated with variations in geographic distribution, antifungal susceptibility, and resistance mechanisms; however, clade-specific evidence remains fragmented. AIMS: To systematically map global evidence on clade diversity, antifungal susceptibility patterns, resistance mechanisms, and clinical implications of C. auris. METHODS: A scoping review was conducted following PRISMA-ScR guidelines. Peer-reviewed primary studies published between 2009 and September 2025 were included if they reported clade attribution and antifungal susceptibility or resistance data. PubMed/MEDLINE, Scopus, and Web of Science were searched. Two reviewers independently screened studies and extracted data using a standardized form. RESULTS: Of 2050 records identified, 105 studies met inclusion criteria, representing 29 countries and diverse study designs. Whole-genome sequencing was the most common typing method. Antifungal susceptibility varied substantially across clades. High fluconazole resistance was consistently reported (MIC 4 to >256μg/mL). Echinocandins generally retained activity, although reduced susceptibility associated with FKS1 mutations was observed. Resistance mechanisms primarily involved mutations in ERG11, FKS1, and efflux-related genes. Studies also reported challenges in healthcare-associated transmission, environmental persistence, and diagnostic misidentification. CONCLUSIONS: C. auris exhibits marked clade-dependent variability in antifungal susceptibility and resistance mechanisms. These findings support the need for clade-informed interpretation of susceptibility data, standardized surveillance, improved diagnostics, and development of novel antifungal therapies.

Antifungal Agents↗

PubMed2026

Molecular characterization and biological characteristics of a highly pathogenic recombinant ALV-J strain (HUE2023) with cross-clade gp85 recombination.

Avian leukosis virus subgroup J (ALV-J) has undergone extensive diversification into phylogenetically distinct clades, yet whether recombination between these clades within the gp85 envelope glycoprotein generates variants with altered pathogenicity has received little direct investigation. A field strain (HUE2023) was recovered from breeding roosters displaying vascular tumors. The viral genome was sequenced and subjected to phylogenetic and recombination analyses. The three-dimensional structure of gp85 was predicted with AlphaFold3; electrostatic surface potentials and surface hydrophobicity were computed using the Adaptive Poisson-Boltzmann Solver and the Eisenberg hydrophobicity scale, respectively. Pathogenicity and immunosuppressive effects were assessed in Hy-Line Brown chickens. Recombination analysis revealed that HUE2023 is an inter-clade recombinant derived from Clade 1.1 (major parent: JS14NT01) and Clade 1.2 (minor parent: JS09GY3). A single-residue deletion at position 61 within receptor-binding domain 1 (RBD-1), unique to the recombinant, induced a localized conformational rearrangement that generated a concentrated electronegative surface patch and a contiguous hydrophobic pocket not observed in either parental gp85. Animal challenge showed that HUE2023 is highly pathogenic: female chickens in the high-dose group reached only 61% survival and displayed significant growth retardation (P < 0.05) together with marked immunosuppression. The recombination in the RBD-1 led to local conformational rearrangement, resulting in a concentrated and negatively charged surface area as well as a continuous hydrophobic pocket, which were never present in any of the parental gp85 sequences. These results indicate that gp85 recombination across clades can yield variants with fundamentally altered receptor-binding surfaces and argue for integrating structural surveillance into ALV-J monitoring programmes.

Animals↗

PubMed2026

Saliva versus lesion swabs for PCR diagnosis of acute-phase clade Ib mpox in Uganda: a prospective matched hospital cohort study.

BACKGROUND: As clade Ib mpox expands through HIV-affected populations in east and central Africa, diagnostic specimen selection should balance accuracy, accessibility, and operational feasibility in outbreak settings. Here, we aimed to compare the diagnostic performance of matched plasma, saliva, genital, anal, and skin specimens during the acute rash phase of clade Ib mpox to identify clinically practical and high-yield sampling approaches for outbreak response and clinical care. METHODS: We conducted a prospective cohort study of 155 adults (median age 30 years, IQR 25-36) hospitalised at Uganda's national mpox referral hospital. The specimens were collected between March 3 and April 10, 2025, during the clade Ib outbreak. All participants were admitted with suspected mpox and were subsequently confirmed by MPXV PCR. We collected 836 clinical specimens (acid citrate dextrose plasma, saliva, genital swabs, anal swabs, and skin swabs) during the acute phase (visit 1; 14 days [SD 2] after systemic symptom onset) and at approximately 3 months (visit 2). A matched acute-phase subset (n=80) provided concurrent plasma, saliva, genital, and skin specimens for within-participant comparisons. MPXV DNA was quantified by F3L real-time quantitative PCR, and cycle threshold (Ct) values were compared using paired Wilcoxon signed-rank tests. Whole-genome sequencing of selected acute specimens confirmed clade assignment. FINDINGS: In the matched subset at visit 1, PCR positivity was high in saliva (78 [98%] of 80), skin swabs (78 [98%] of 80), and genital swabs (77 [96%] of 80). Results for the saliva closely mirrored genital and skin swab results, supporting saliva as a high-yield alternative when lesion sampling is painful, operationally difficult, or unacceptable. Plasma had substantially lower sensitivity (34 [43%] of 80) and showed poor agreement with mucocutaneous compartments. At 3 months, persistent MPXV DNA was rare (ten [9%] of 109) and clustered among people with HIV, including the only two participants with persistent plasma positivity. All sequenced genomes clustered within clade Ib. INTERPRETATION: During the established rash phase (14 days [SD 2] after onset), saliva provides diagnostic yield similar to that provided by lesion swabs for clade Ib mpox in this hospitalised cohort. These findings are restricted to this sampling window; further studies are needed to define performance in prodromal, pre-rash, and asymptomatic infection. FUNDING: CEPI through its Centralised Laboratory Network.

Adult↗

PubMed2026

Cytonuclear conflict and reticulate evolution in the Morelloid clade (Solanum, Solanaceae): Insights from genome skimming and network Phylogenomics.

The Morelloid clade (black nightshades) is one of the most strongly supported clades within the megadiverse Solanum genus. It comprises 76 globally distributed, non-spiny herbaceous and suffrutescent species. While often erroneously considered poisonous weeds, several species are economically important as orphan crops. The clade is closely related to tomato and potato but, due to a lack of focused breeding efforts, remains a putative reservoir of genetic diversity for crop improvement. Despite this potential, we lack fundamental knowledge on the evolution of the Morelloid clade. The group includes polyploid species with unknown parental origins-likely reflecting reticulate processes such as hybridization, introgression, and associated backcrossing events. Prior analyses have been unable to disentangle these processes, leaving the mechanisms underlying reticulate evolution in the Morelloid clade poorly understood. Here, we use genome skimming to produce a well-supported maximum likelihood plastid phylogeny from complete circularized plastomes and a coalescent-based species tree from combined Angiosperms353 and conserved ortholog set nuclear markers. Our dataset, composed of previously published data and deep genome skimming from herbarium samples, spans 26 Morelloid species. To investigate phylogenetic discordance, we used a nuclear phylogenetic network, multispecies coalescent simulations, a fused rooted nuclear chloroplast tree, and quantification of nuclear gene tree concordance. We show that incongruence between nuclear and plastid trees is pervasive and cannot be explained by incomplete lineage sorting alone. Instead, our results demonstrate that events consistent with repeated chloroplast capture have shaped the reticulate evolutionary history of the clade, especially among African polyploid and Pan-American diploid lineages.

Phylogeny↗

PubMed2025

Comparative Phylogenetics Reveal Clade-specific Drivers of Recombination Rate Evolution Across Vertebrates.

Meiotic recombination is an integral cellular process, required for the production of viable gametes. Recombination rate is a fundamental genomic parameter, modulating genomic responses to selection. Our increasingly detailed understanding of its molecular underpinnings raises the prospect that we can gain insight into trait divergence by examining the molecular evolution of recombination genes from a pathway perspective, as in mammals, where protein-coding changes in later stages of the recombination pathway are connected to divergence in intra-clade recombination rate. Here, we leverage increased availability of avian and teleost genomes to reconstruct the evolution of the recombination pathway across two additional vertebrate clades: birds, which have higher and more variable rates of recombination and similar divergence times to mammals, and teleost fish, which have much deeper divergence times. Rates of molecular evolution of recombination genes are highly correlated between vertebrate clades and significantly elevated compared to control panels, suggesting that they experience similar selective pressures. Avian recombination genes are significantly more likely to exhibit signatures of positive selection than other clades, unrestricted to later stages of the pathway. Signatures of positive selection in genes linked to recombination rate variation in mammalian populations and those with signatures of positive selection across the avian phylogeny are highly correlated. In contrast, teleost fish recombination genes have significantly less evidence of positive selection despite high intra-clade recombination rate variability. Gaining clade-specific understanding of patterns of variation in recombination genes can elucidate drivers of recombination rate and thus, factors influencing genetic diversity, selection efficacy, and species divergence.

Animals↗

PubMed2026

Functional unknomics of the SAR11 clade reveal hidden genetic potential underlying adaptation to bottom-up and top-down pressures.

UNLABELLED: A substantial fraction of the genes in bacteria lack detectable sequence similarity to genes with known functions. These functionally uncharacterized genes-collectively referred to as the "unknome"-represent a largely unexplored genetic repertoire harboring insights into marine bacterial ecology. In this study, we explored the function of the unknome of the SAR11 clade, the most abundant bacterial lineage in the ocean, with a particular focus on genes that provide insight into its ecology. Based on the Clusters of Orthologous Genes and Kyoto Encyclopedia of Genes and Genomes classifications, approximately 56% of SAR11 ortholog groups were classified as members of the unknome. Among the SAR11 unknome, we successfully inferred the functions of 57 ortholog groups that are conserved in the SAR11 clade by protein structure similarity searches and genomic context analyses. These ortholog groups include putative transporter components, supporting the current ecological understanding that the SAR11 clade is specialized in substrate uptake to adapt to oligotrophic marine environments. Furthermore, structural analysis indicated that the DUF2237-containing protein, enriched in marine environments, may interact with purine nucleotide-containing compounds. This may suggest the existence of unique nucleotide utilization mechanisms in marine bacteria. In addition, we identified candidate viral defense systems within the unknome, indicating that diverse defense systems are present in at least one-third of cultured SAR11 strains. The presence of these defense systems, even within streamlined SAR11 genomes, suggests that they confer significant ecological advantages. Our analyses provide insights into the genetic basis of bottom-up processes (adaptation to oligotrophic environments) and top-down processes (antiviral defense strategy) contributing to ecological success. IMPORTANCE: Many microbial genes have no experimentally established function, limiting our ability to explain how microorganisms adapt to their environments. We examined this uncharacterized gene space, or "unknome" in SAR11, the most abundant bacterial clade in the ocean, by integrating evolutionary conservation, genomic context, predicted protein structure, and environmental distribution. This approach enabled us to prioritize components of the SAR11 unknome, including a core unknome conserved across the clade and genes enriched in specific lineages, and to identify several candidates with possible ecological roles in nutrient acquisition and defense against viruses. Our results suggest that the SAR11 unknome contains important clues to the ecological success of SAR11 rather than merely reflecting incomplete annotation or gene-prediction artifacts. Our study highlights the potential value of unknome analysis for identifying ecologically relevant genes in environmental microorganisms.

Pelagibacterales↗

PubMed2026

Scalable assembly of Ascaris mitogenomes from whole-genome data reveals a novel clade.

The genus Ascaris is an important group of giant parasitic roundworms, infecting over 700 million people globally and causing substantial economic losses in domestic pigs. Whilst species of Ascaris are morphologically indistinguishable, analysis of mitochondrial loci has revealed three clades (A, B, C) broadly associated with host species and geographic distribution. The diversity within these lineages may expand with the addition of further genomic data. Here, we present a bioinformatic framework for de novo assembly of complete mitochondrial genomes (mitogenomes) from low-coverage whole-genome data through host-read depletion or mtDNA read enrichment, followed by mtDNA-specific assembly. Our approach yielded 149 high-quality Ascaris mitogenome assemblies, enabling the study of population-level diversity, including the identification of a novel clade (Clade D, designated here) associated with human samples from Ethiopia. Our analysis further revealed Clade C to comprise of pig-derived samples from Europe based on characterisation of worms isolated in Germany. The methods described here provide a scalable framework for mitogenome reconstruction with insights into roundworm population-genomic and phylogenetic studies.

Animals↗

PubMed2026

Lesion viral burden, multidrug-resistant superinfection, and HIV-associated haematological vulnerability in hospitalised clade Ib mpox: a prospective cohort study in Uganda.

BACKGROUND: Mpox has shifted to sustained human-to-human transmission across Africa, yet integrated triage incorporating viral burden, bacterial co-infection, antimicrobial resistance (AMR), HIV status, and routine biomarkers remain scarce. METHODS: At Uganda's national mpox referral hospital, we prospectively enrolled 155 adults at 14 ± 2 days post-symptom onset; mpox was confirmed by lesion-swab qPCR (F3L), with clade assignment by whole-genome sequencing in a prespecified subset (March-April 2025). Lesion viral DNA burden was estimated using qPCR cycle threshold (Ct) values. Purulent lesions underwent EUCAST-standardised culture and susceptibility testing. Routine laboratory assessments included complete blood counts, C-reactive protein, serum chemistries, HIV serostatus, and plasma HIV-1 RNA. FINDINGS: Median age was 30 years, and 73/155 (47%) had HIV infection. Multisite pain, particularly anogenital, was highly prevalent. Among 80 participants with purulent lesions selected for clinically suspected bacterial superinfection, all yielded bacterial growth; 35/80 (43.8%) were polymicrobial and predominantly multidrug-resistant Gram-negative bacilli. Susceptibility to first-line β-lactams and fluoroquinolones was low, whereas meropenem retained activity (51/61, 84%). Lesion viral burden did not differ by HIV serostatus and showed weak correlation with HIV-1 viraemia; higher burden was associated with leucocytosis, neutrophilia with left shift, elevated CRP, and hypoalbuminaemia. Genomes clustered within Clade Ib, without segregation by HIV status or clinical severity. INTERPRETATION: Hospitalised adults with acute Clade Ib mpox in Uganda exhibited high lesion viral burden, frequent multidrug-resistant bacterial co-isolation, and an inflammatory haematological profile accentuated in participants living with HIV-1. These findings support consideration of integrating diagnostic microbiology, HIV viral load assessment, and antimicrobial stewardship into mpox case-management in endemic settings. FUNDING: This study was supported by the Coalition for Epidemic Preparedness Innovations (CEPI; Project ID PRJ-8284).

Adult↗

PubMed2025

Genomic epidemiology of clade Ia monkeypox viruses circulating in the Central African Republic in 2022-24: a retrospective cross-sectional study.

BACKGROUND: The spread of monkeypox virus (Orthopoxvirus monkeypox) clade Ib from the Democratic Republic of the Congo to neighbouring countries has raised global concerns, leading to WHO declaring mpox a public health emergency on Aug 14, 2024. We applied genomic epidemiology to investigate the causes of recurrent mpox outbreaks in the Central African Republic. We aimed to determine whether frequent zoonotic spillovers or increased human-to-human transmissions are driving mpox epidemiology. METHODS: We performed a retrospective cross-sectional study of monkeypox virus genomic sequences among PCR-confirmed mpox cases detected in the Central African Republic between Feb 17, 2022, and Sept 17, 2024. We used hybridisation capture coupled to high throughput sequencing to analyse 46 samples from mpox outbreaks that occurred in eight of the 20 prefectures (14 of 35 health districts). Near-complete genomes were used for phylogenomic analyses. FINDINGS: Between Jan 10, 2022, and Sept 15, 2024, 89 mpox cases were confirmed, including 53 cases in the first 9 months of 2024. We generated 41 near-complete genomes from this period, including 33 from 2024. All new and already published monkeypox virus genomes from the Central African Republic belonged to clade Ia. These genomes spanned the phylogenetic diversity of clade Ia viruses, and most likely represented several dozen independent transmission events to humans. The monkeypox virus phylogenetic diversity was geographically structured within the country. Plausibly linked cases often showed indistinguishable genomes. Conversely, we detected identical genomes in cases that epidemiological information would suggest were independent outbreaks. Finally, we found that three distinct viruses caused cases in the capital city of Bangui in July, 2024, with all three detected on the same day (July 24, 2024). We did not detect substantial enrichment of APOBEC3 editing, suggesting limited human-to-human transmission. INTERPRETATION: The data indicate that mpox epidemiology in the Central African Republic is primarily driven by short-lived outbreaks resulting from many independent zoonotic spillover events, particularly in rural areas. Although evidence remains limited, in Bangui additional factors such as movement of people and importation of bushmeat from other regions might be introducing the virus into urban settings. Similar spillover patterns have been observed in the Democratic Republic of the Congo. The poorly understood nature of monkeypox virus reservoirs in both countries is a regional concern, as frequent spillovers increase the risk of outbreaks leading to sustained human transmission. Beyond strengthening surveillance and developing countermeasures, it is important to better understand the reservoirs and focus on reducing transmission opportunities to prevent further outbreaks. FUNDING: Pasteur Institute of Bangui, Africa CDC, AFROSCREEN, WHO, the Helmholtz Institute for One Health, and the Deutsche Forschungsgemeinschaft.

Humans↗

PubMed2026

Upsurge of pneumococcal clade I-α/CC180 serotype 3 and its association with a LytA mutation linked to immune evasion and disease potential: an observational and experimental study.

BACKGROUND: Streptococcus pneumoniae serotype 3 is one of the most prevalent serotypes that cause invasive pneumococcal disease (IPD) in children and adults worldwide. Serotype 3 is associated with vaccine failures and breakthrough episodes in children vaccinated with 13-valent pneumococcal conjugate vaccine (PCV13). In this study, we aimed to investigate potential genetic mechanisms that could explain the increase in cases of serotype 3 IPD in Spain. METHODS: We analysed the epidemiology of serotype 3 causing IPD in Spain, during 2009-23, in different age groups. Molecular characterisation was performed by whole-genome sequencing. Host-pathogen interactions of the different lineages were evaluated in terms of interaction with lung epithelial cells, biofilm formation, and capsular polysaccharide production, using opsonophagocytosis assays and mouse models of pneumonia. We used Poisson regression models to compare incidence and chi-square test calculations to identify clonal variations across vaccine periods. FINDINGS: Genomic analyses confirmed the predominance of clade I-α/clonal complex (CC) 180 in Spain, which shows increased resistance to complement-mediated immunity and phagocytosis and enhanced potential to infect lung cells. In all isolates of this lineage, we observed a single amino acid substitution (166His→Tyr) in the crucial virulence factor LytA, which increased its enzymatic activity. On evaluating the phagocytosis of mutants without LytA of the two major lineages of serotype 3 (CC180 and CC260), LytA was responsible for the increased phagocytosis-evasion pattern of clade I-α/CC180. Evaluation of individuals with IPD caused by different serotype 3 genotypes confirmed a significant (p<0·05) association between cardiac and respiratory comorbidities and infection by sequence type 180/CC180, which showed the importance of CC180 in IPD. INTERPRETATION: Our findings confirm that PCV13 reduced IPD cases caused by the susceptible CC260 lineage until CC260 was replaced by the clade I-α/CC180 lineage, which has a higher potential to cause IPD and divert the host immune system. A key mutation on LytA protein was associated with this hypervirulent phenotype. Emerging lineages jeopardise the effectiveness of pneumococcal conjugate vaccines. FUNDING: Ministerio de Ciencia e Innovación, Instituto de Salud Carlos III, and PubMLST.

Animals↗

PubMed2026

Comparison of paralog identification methods and their impact on species tree topologies in target capture phylogenomics within the Sindora clade (Detarioideae: Leguminosae).

Target capture is a common method of generating high throughput DNA sequencing data for phylogenetic reconstruction of species relationships, for which single copy genes are usually most informative. However, a pervasive problem with target capture is that putatively single copy genes may in fact be paralogs resulting from gene duplication, which are problematic for phylogenetic inference because their evolutionary history may differ from the divergence history of species. Here, we use as a case study a target enrichment dataset of 88 species of Detarioideae (Leguminosae) with a focus on the Sindora clade to examine approaches for handling paralogs, including the built-in paralog handling functions in HybPiper and CAPTUS, plus subsequent steps using Putative Paralog Detection and the tree-based Yang & Smith orthology inference approach. We compare the paralogs flagged using these methods and verify their performance with BLAST mapping against a reference genome sequence of Sindora glabra, and then subsequently compare the species tree topologies produced across these methods. Our comparisons of paralogs flagged across the Sindora clade show that the Putative Paralog Detection pipeline was the most accurate in identifying paralogs in terms of its similarity to the BLAST mapping, followed by the built-in paralog identification function of CAPTUS. However, the results we recovered for the Detarioideae subfamily suggest that the largest differences in species tree topology resulted from the use of paralog-filtered alignments (such as with the Putative Paralog Detection pipeline and the Yang & Smith orthology inference approaches) rather than just by removing the sequences of identified paralogous genes. This was the true for HybPiper-assembled datasets but was not seen in CAPTUS-assembled datasets. In all comparisons, the topological differences caused by different paralog handling methods tended to be confined to clades where processes such as hybridisation and introgression are prevalent. Our study provides a roadmap to establish the best approach to identify, eliminate or separate paralogs in the absence of a chromosomally contiguous reference genome for a study group, and highlights the importance of careful data inspection and processing in addition to understanding the extent of paralogy and paralog characteristics (e.g. sequence divergence between copies) for their study group.

Phylogeny↗

PubMed2026

Genomic and Clinicopathological Characterization of a Reassortant HPAI H5N1 (Clade 2.3.4.4b) in an Endangered Cinereous Vulture (Aegypius monachus) in South Korea, 2026.

Clade 2.3.4.4b highly pathogenic avian influenza viruses (HPAIVs) continue to circulate widely in East Asia and undergo frequent reassortment in wild birds. Raptors are regarded as spillover hosts that may be exposed through predation or scavenging, yet integrated clinicopathologic and genomic investigations in cinereous vultures remain limited. Here, we describe a fatal H5N1 HPAIV infection in a cinereous vulture (Aegypius monachus) found in South Korea on January 17, 2026. On presentation, the cinereous vulture showed severe neurologic dysfunction, including inability to stand, right-sided head tilt with pathologic nystagmus, reduced oculocephalic and palpebral reflexes, and intermittent bilateral leg tremors. The cinereous vulture died within 2 days after rescue, and a complete necropsy was performed. Hematologic and biochemical testing revealed marked heterophil predominance, severe lymphopenia, mild monocytosis, and globulin values near the upper end of the reference interval. An oropharyngeal swab tested positive for influenza A virus, and a virus isolate, designated A/Cinereous_Vulture/Korea/26-JBN47/2026(H5N1), was recovered in embryonated chicken eggs. Histopathology showed nonsuppurative encephalitis and necrotizing myocarditis, and influenza A nucleoprotein was detected immunohistochemically in neurons and cardiomyocytes. Tissue real-time RT-PCR showed the lowest cycle threshold value in the brain. Whole-genome sequencing demonstrated that 26-JBN47 belonged to clade 2.3.4.4b and contained a polybasic HA cleavage site (PLREKRRKR/GLF). Segment-level phylogenetic analysis revealed a reassortant genome constellation comprising a maintained H5N1 backbone in HA, NA, and M; low PAIV (LPAIV)-associated but H5N1-incorporated PA and NP segments; flyway-associated PB2 and NS segments; and a PB1 segment phylogenetically linked to regional LPAIV lineages. Molecular marker analysis identified multiple substitutions previously reported to be associated with receptor-binding properties, polymerase-related fitness, virulence, and host-response modulation, whereas canonical PB2 mammalian-adaptive markers were absent. These findings show that 26-JBN47 was a reassortant clade 2.3.4.4b H5N1 HPAIV associated with systemic disease and clinicopathological findings consistent with neurotropic and cardiotropic infection in a cinereous vulture. They also support the potential value of scavenging raptors as sentinels of local or regional HPAIV circulation involving reassortant viruses in East Asia.

Animals↗