Search Results (412)

Plague remains a globally important zoonotic disease maintained in natural foci, with ongoing epizootic activity and periodic human cases reported in several regions of the world. Continuous monitoring of antimicrobial susceptibility in Yersinia pestis is essential because the emergence of resistant strains could compromise the effectiveness of currently recommended therapeutic regimens. In this study, 75 Y. pestis isolates originating from natural plague foci of Kazakhstan were investigated using an integrated approach combining phenotypic susceptibility testing, targeted molecular screening, and whole-genome sequencing (WGS)-based resistome analysis. The collection included historical clinical isolates obtained during plague outbreaks as well as more recent epizootic strains recovered from animal hosts and flea vectors. Phenotypic testing demonstrated uniformly high susceptibility to clinically relevant antimicrobial agents used for plague treatment. Targeted molecular screening by real-time PCR did not detect the analyzed resistance determinants. Genome-wide analysis based on WGS data from NCBI BioProject PRJNA1249055 did not identify acquired antimicrobial resistance genes, major resistance-associated mutations in key chromosomal loci (rpsL, gyrA, and parC), or plasmid-borne resistance determinants. Regulatory loci associated with adaptive responses were highly conserved across the analyzed genomes. The complete concordance between phenotypic, molecular, and genomic findings indicates a stable antimicrobial susceptibility profile of Y. pestis circulating in natural plague foci of Kazakhstan. These results support the continued effectiveness of current therapeutic strategies for plague and highlight the value of integrating genomic surveillance into long-term monitoring programs for this pathogen. Full article

Plague remains a significant natural focal zoonotic infection with continuing epidemiological relevance in the Republic of Kazakhstan. This study provides a comprehensive assessment of epizootological dynamics in natural plague foci during 2020–2025 through the integration of historical epidemiological data, phenotypic and molecular characterization of Yersinia pestis, and GIS-based spatial analysis. The study utilized long-term surveillance data (1920–2025), epidemiological records of human plague cases (1926–2003), phenotypic analysis of 1526 strains, and whole-genome sequencing of 75 representative isolates. Epizootological monitoring demonstrated high surveillance coverage and stable monitoring capacity, together with a marked increase in the application of molecular diagnostic methods. By 2025, both the number and isolation rate of Y. pestis strains increased substantially, while the epizootically active area expanded in 2024–2025, although the overall long-term trend in active area was not statistically significant. Despite these fluctuations, Y. pestis populations remained highly stable, with 94.9% phenotypically typical and 97.5% genotypically typical strains, and no evidence of antimicrobial resistance. Spatial autocorrelation analysis using Moran’s I revealed significant clustering of epizootics (Moran’s I = 0.1627; z = 4.39; p < 0.001), indicating non-random spatial distribution and localized zones of increased epizootic activity. No human plague cases have been recorded since 2003 during the period of sustained epidemiological surveillance and control measures. These findings highlight the potential utility of integrating spatial modeling and molecular surveillance into risk-oriented plague monitoring and control strategies. Full article

Camels are increasingly recognized as an important epizootological and epidemiological link in natural plague foci, contributing to the transmission of Yersinia pestis from wildlife to humans. In the Republic of Kazakhstan, where natural plague foci occupy up to 40% of the territory, the rapid growth of camel populations may significantly enhance epidemiological risks. The aim of this study was to perform a comprehensive assessment of the role of camels in the epizootology and epidemiology of plague based on retrospective data (1907–2003) and contemporary monitoring (2000–2025), including spatial analysis and risk zoning. A total of 64 cases of camel plague and 43 epizootic foci were identified during the historical period. More than 400 human cases, including fatal outcomes, associated with infected camels were documented, with direct contact during slaughter and meat processing accounting for 94.7% of infections. Spatial analysis and epidemiological zoning revealed a heterogeneous risk distribution, with western and southern regions representing the highest-risk areas. Serological investigation (n = 2726) showed 75.6% seropositivity, likely reflecting substantial population immunity largely associated with vaccination. Despite increasing camel population size (from 227.7 to 304.0 thousand heads in 2020–2025), vaccination coverage varied between 32.0% and 51.0%, reflecting risk-based preventive strategies. The absence of recent camel plague cases supports the effectiveness of integrated control measures, including vaccination, surveillance, and the establishment of protective zones. These findings suggest that camels remain an important component of plague transmission systems and should be systematically integrated into surveillance programs within a One Health framework. Full article

Background: Despite its typically self-limiting course, acute diarrheal disease continues to be clinically relevant from an antimicrobial resistance surveillance perspective. In-depth analyses at a national level remain limited, with available Romanian studies from the last decade focusing on individual pathogens, often relying on a restricted isolate collection. In this context, we aimed to evaluate antimicrobial resistance profiles and distribution of Salmonella spp., Campylobacter spp., Escherichia coli, Yersinia spp. and Shigella spp. Methods: Data was obtained from records from the Microbiology Laboratory of a tertiary-care hospital serving the south region of Romania, over a 3-year period. Results: Campylobacter spp. had high resistance rates to ciprofloxacin (81.65% for C. jejuni; 85.15% for C. coli) and tetracycline (44.65% for C. jejuni; 56.07% for C. coli). Erythromycin resistance remained low and stable over the study period, with no statistically significant temporal variation; however, C. coli isolates demonstrated significantly higher erythromycin (p = 0.001) and tetracycline (p = 0.008) resistance rates compared to C. jejuni. Overall Salmonella spp. resistance rate to ciprofloxacin was 46.00%, with higher resistance observed in serogroups C (63.64%) and D (52.53%) (p < 0.01). Ampicillin (AMP) resistance varied significantly across years and serogroups, with serogroup B consistently demonstrating higher resistance rates (40.48%) (p < 0.001). E. coli isolates reacting with pathotype-associated O antisera revealed high resistance levels to ampicillin (41.57%), amoxicillin–clavulanic acid (AMC) (38.73%) and sulfamethoxazole–trimethoprim (SXT) (19.25%), with low resistance levels to ciprofloxacin (9.04%) and ceftriaxone (CRO) (9.71%); no significant variation in resistance patterns was identified across years or serological pools, suggesting a relatively stable resistance profile over the study period. Yersinia spp. isolates showed no notable antimicrobial resistance levels. Shigella spp. isolates exhibited high resistance for ampicillin (78.57%), sulfamethoxazole–trimethoprim (68.75%), amoxicillin–clavulanic acid (50.00%) and ceftriaxone (35.41%). Conclusions: This study addressed a recognized gap in Romanian and Eastern European surveillance data and aims to contribute to a stronger evidence base for future epidemiological investigations and antimicrobial stewardship efforts. Resistance rates identified in our study may provide valuable information for comparison with data generated from veterinary, food and environmental surveillance programs, thereby supporting a more comprehensive understanding of antimicrobial resistance (AMR) epidemiology. These findings may additionally contribute to the development of coordinated strategies aimed at mitigating the emergence and spread of AMR. Full article

Proteins are the most common targets for antibody discovery and vaccine development, but their sequence variability can limit the breadth of resulting antigens. Lipids represent an alternative class of antigens due to their structural conservation and roles in host–pathogen interactions. Here, we describe the development and optimization of an in vitro antibody selection workflow using lipid-containing nanodiscs as antigen presentation platforms to enable phage and yeast display selections under conditions adapted for these non-protein targets. Lipopolysaccharide (LPS) nanodiscs were first used as a model system to evaluate selection strategies, including competitive and subtractive approaches to reduce non-specific binders, yielding peptide and single-chain variable fragment (scFv) binders that were affinity matured to improve binding signals. The same approach was subsequently used to select scFv antibodies that recognize lipid nanodiscs prepared from Yersinia pestis membrane lipid extracts. These antibodies show binding to lipid nanodiscs derived from Y. pestis, with evidence of selectivity relative to control nanodiscs. Overall, this work establishes a workflow for antibody selection against lipid-containing nanodisc antigens and highlights practical considerations associated with these targets. The approach may be useful for generating affinity reagents to membrane-associated lipids, although further characterization is required to define antigen specificity and functional activity. Full article

Yersinia pestis is the causative agent of bubonic plague, a zoonotic disease that is primarily transmitted by infectious fleas. Plague is endemic in regions around the world, including the United States, where optimal climate conditions support a stable, enzootic sylvatic transmission cycle. Epizootic outbreaks periodically occur with rapid spread of disease that increases the risk of human exposure. As fleas are ectotherms that are responsive to environmental conditions, it is likely that transmission efficiency varies under different ecological conditions, with optimal conditions capable of supporting rapid spread of disease while sub-optimal conditions may promote lower levels of transmission. To test this, we experimentally infected Xenopsylla cheopis with Y. pestis using a membrane feeder in order to define the impact of varying temperature, humidity and mammalian blood sources on infection and transmission. We show that environmental factors and host blood source are key factors influencing colonization, bacterial aggregation, and transmission rates, with variation in the responses seen depending on the experimental conditions. The combined data illustrate the impact of ecological factors on Y. pestis flea infection and suggests that optimal conditions involving the vector–host–pathogen interface are needed for enhanced transmission rates and the rapid spread of infection that occurs during epizootic outbreaks. Full article

To determine whether Yersinia pestis (Y. pestis) signals were present in the soil, 78 soil samples were collected from 10 counties identified as Rattus tanezumi plague foci and another six counties in non-foci areas in Yunnan, China, from August 2024 to May 2025. Nucleic acids were extracted using the DNeasy PowerSoil Pro Kit (Qiagen) and detected with a Bio-Rad QX200 droplet digital PCR (ddPCR) system targeting two Y. pestis genes (caf1 and ypo0392). Our sampling design also considered two additional dimensions: nine soil types and three habitat types. The raw data obtained from ddPCR were copy numbers. A gene was considered positive when its copy number exceeded the limit of detection (LoD). A sample was considered positive if the copy number of ypo0392 exceeded its LoD (regardless of caf1), or if both genes exceeded their respective LoDs. No correlation was detected between the positivity rate of Y. pestis and the division of sampling sites into plague focus and non-focus regions (p = 0.758). Similarly, the Mann–Whitney U test revealed non-significant differences in pathogen copy number across the two site categories, with p = 0.603 for the caf1 gene and p = 0.372 for the ypo0392 gene. No statistical difference in positivity rate was found for either soil types or habitat types. However, for both the grouping variables, a statistical difference in copy number was observed. Our results indicated that quantifying nucleic acid abundance by copy number provided richer information than a simple positive/negative determination. The detection of Y. pestis signals was associated with soil type, rather than with whether an area was classified as a focus or non-focus region. Accordingly, future research on the preservation mechanism of Y. pestis should not be restricted to the concept of natural foci but should adopt a broader perspective. Full article

The flea-borne transmission of Yersinia pestis relies on biofilm formation and metabolic adaptation within the insect gut. The pentose phosphate pathway (PPP) is central to these processes, yet the contribution of its non-oxidative branch remains poorly defined. Here, we investigated the roles of transketolase (TktA) and transaldolase (TalB) in plague bacillus physiology, metabolism, and flea colonization. TktA was essential for growth, preventing assessment of its role in biofilm formation and in vivo colonization. In contrast, TalB was dispensable for growth but required for optimal biofilm formation. In fleas, the ΔtalB mutant colonized the proventriculus but displayed a lower bacterial load than the wild-type strain at later time points, indicating a defect in sustained colonization. Metabolomic analyses revealed that disruption of tktA severely impairs PPP-associated metabolism, whereas loss of talB is associated with disruption of nucleotide homeostasis, carbon redistribution toward glycolysis, and a redox imbalance. These findings demonstrate a functional partitioning of the non-oxidative PPP and identify it as a key metabolic control node linking metabolism to colonization dynamics in Y. pestis. Full article

Three pathogenic species of the genus Yersinia, including Plague-associated Yersinia pestis, Yersinia pseudotuberculosis, and Yersinia enterocolitica, are commonly associated with human infection. Current qPCR detection methods are mainly limited to the identification of one or two Yersinia species in a single reaction tube, while multiplex assays for multiple genera have been more commonly reported. Therefore, the present study aimed to establish a multiplex TaqMan qPCR assay for the simultaneous detection of these three pathogenic Yersinia species. Primer and probe sets were designed based on the inv gene for Y. pseudotuberculosis, the caf1 gene for Y. pestis, and the foxA gene for Y. enterocolitica. Under the optimized reaction conditions, the standard curve slopes for the caf1, inv, and foxA genes were −3.046, −2.968, and −2.948, respectively. The correlation coefficients (R²) ranged from 0.993 to 0.996, while the amplification efficiencies ranged from 109% to 115%. The limits of detection (LOD) were determined to be 5 × 10² copies/μL for inv (FAM), 1 × 10¹ copies/μL for caf1 (ROX), and 1 × 10¹ copies/μL for foxA (CY5). The sensitivity of the multiplex qPCR assay was 10- to 100-fold higher than that of conventional PCR, depending on the target. Specificity experiments demonstrated that no cross-reactivity was observed with non-target bacteria, including Francisella tularensis, Brucella spp., Vibrio cholerae, Salmonella Typhi, and Shigella spp. The intra-assay coefficients of variation (CVs) ranged from 0.13% to 0.79%, whereas the inter-assay CVs ranged from 0.62% to 2.61%. Among 173 spleen samples collected from wild rodents, no positive signal for Y. pestis or Y. pseudotuberculosis was detected. In contrast, Y. enterocolitica was detected in three samples (1.73%, 3/173). In conclusion, the multiplex qPCR assay developed in this study provides a sensitive and specific tool for the simultaneous detection of three pathogenic Yersinia species and has the potential to improve detection efficiency in clinical and epidemiological investigations. Full article

Based on phylogenetic analysis of whole-genome sequencing of Yersinia pestis 2.MED1 strains of the medieval biovar, combined with epizootic, epidemiological, and climatic data over a 100-year period, we have reconstructed the most probable directions of distribution of plague in Eastern Europe and Central Asia (EECA) in the 20th and 21st centuries. The data suggest the important role of three great lakes—the Caspian, Aral, and Balkhash—in the circulation and preservation of Y. pestis 2.MED1 in EECA. Three main directions of Y. pestis 2.MED1 expansion have been identified: Caspian (Caspian Sea region foci, 1912–1945; Caucasus, 1953–1986), North Aral (Northern Aral Sea region foci, 1945–1959; Caspian Sea region foci, 1945–2015; Pre-Caucasus, 1999–2003; Karakum, 1949–1965) and Central Asian (Kyzylkum, 1924, 1983–2020; Balkhash foci, 1939–2020; Northern Aral Sea region foci, 1967–2020; Eastern Caspian Sea region foci, 1968–1985). Favorable climatic conditions in the Caspian Sea region, the Northern Aral Sea region, and the Balkhash region in the 20th and 21st centuries contributed to the rapid formation of stable natural plague foci and the long-term persistence of Y. pestis 2.MED1 strains of the medieval biovar, with their further introduction into other foci of EECA. Periodic introductions of the pathogen are one of the reasons for the plague re-emergence and activation of plague foci in the EECA region. Full article

This review provides a comprehensive overview of the genetic diversity and epidemiological potential of Yersinia pestis in Kazakhstan’s natural plague foci, emphasizing the link between genotypic variation and outbreak capacity. Integrating historical epidemiological records with contemporary microbiological and genomic data (including PCR, VNTR/MLVA, SNP analysis, and whole-genome sequencing), we evaluate core and accessory genome variations. The data reveal substantial regional heterogeneity. High-risk desert foci (Caspian and Aral regions) are dominated by the Medievalis biovar, including atypical genovariants lacking canonical markers. Conversely, high-mountain foci (Sarydzhaz, Talas) harbor the Antiqua and Talas biovars, primarily linked to enzootic circulation. Notably, the Ili River focus exhibits extreme genomic variability, featuring strains with plesiomorphic traits. Furthermore, the widespread distribution of mobile elements like the cryptic plasmid pCKF suggests significant horizontal transfer contributing to pathogen adaptation. Ultimately, Central Asian plague dynamics are driven by complex evolutionary and ecological interactions. Given climate change and expanding human–wildlife interfaces, continuous genomic and ecological surveillance is essential for the early detection of high-risk Y. pestis genovariants and improving public health preparedness. Full article

Yersinia enterocolitica strains of biotype 4 (BT4) are the most prevalent in human cases in France, followed by biotype 2 (BT2). We evaluated four BT4 porcine (P) isolates and four BT2 bovine (B) isolates for their ability to survive at 4 °C in culture broth and on meat, exhibit motility at 4 °C and 12 °C, adhere to stainless steel at 12 °C, resist five biocides, and infect human intestinal Caco-2 cells. The objective was to determine whether animal isolates that genetically cluster with human (H) isolates (P+H+, B+H+) differ phenotypically from non-clustering isolates (P+H−, B+H−), based on core genome multi-locus sequence typing (cgMLST) using allelic distance thresholds of ≤5 for BT4 and ≤3 for BT2 isolates. No significant difference was observed for BT4 between P+H+ and P+H− isolates, nor for BT2 between B+H+ and B+H− isolates, for any test, except for motility. Porcine isolates clustering with human isolates (H+) exhibited a significantly reduced motility compared with non-clustering isolates (H−) (p-value < 0.05). In contrast, bovine isolates clustering with human isolates (H+) showed a significantly higher motility than non-clustering isolates (H−). Motility plays a role in the early stages of biofilm formation but is not directly involved in virulence, as Y. enterocolitica becomes non-motile at 37 °C. Animal isolates that did not cluster with human isolates displayed traits enabling their transmission along the food chain, suggesting potential low-level human exposure, asymptomatic carriage, or links to unreported infections. Full article

The plague, caused by Yersinia pestis, has resulted in significant mortality over the past century. Despite advances in antimicrobial therapy, plague remains a re-emerging infectious disease with ongoing outbreaks and increasing concerns regarding antimicrobial resistance. Today, plague cases are still being reported, and the loss of effectiveness of treatment methods remains a major challenge. Therefore, effective treatment strategies are needed. In this study, we aimed to develop aptamers specific to Yersinia outer protein M (YopM), a key immunosuppressive protein that is essential for virulence. Our goal was to develop an aptamer that binds to YopM and inhibits its interaction with the human DEAD-box helicase 3 (DDX3) protein. YopM-DDX3 protein interaction was targeted because of its key role in nucleocytoplasmic shuttling of YopM. To achieve this, we developed the YopM16 aptamer using magnetic bead-based (Systematic Evolution of Ligands by Exponential Enrichment) (SELEX). The selected YopM16 aptamer exhibited a half-maximal inhibitory concentration(IC₅₀) value of 103.3 ± 2 nM and effectively inhibited the interaction between YopM and DDX3. The inhibitory effect of the aptamer on protein interaction was confirmed using a pull-down assay and colorimetric test. Given that protein–protein interaction surfaces are considered undruggable, YopM16 is a promising inhibitor with the potential to serve as a molecular tool to investigate the virulence mechanism of YopM, as well as a novel antibacterial agent upon validation of its inhibition in cellular models. Full article

The Third Plague Pandemic originated in 19th-century Yunnan, China, yet the confluence of factors that enabled the pandemic strain Yersinia pestis 1.ORI to emerge and spread globally remains unclear. Using a One Health framework, this study investigates how human-driven ecological and socioeconomic changes disrupted zoonotic barriers in Yunnan. We conduct an interdisciplinary historical analysis, triangulating evidence from Qing dynasty gazetteers, environmental reconstructions, and biological data on plague ecology, including host–vector dynamics, to model conditions for spillover and spread and to build a convergent, validated case. The analysis identifies a mid-19th-century convergence that created a high-risk interface: widespread deforestation from mining and agriculture, rapid population growth, increased synanthropic rat densities, and the turmoil of the Panthay Rebellion. Socioeconomic stressors—labour migration into mining valleys, currency devaluation undermining food security, and comorbidities such as malnutrition, heavy metal contamination, and opium use—may have further increased host susceptibility. This socio-ecological context catalysed spillover and establishment of the 1.ORI strain in commensal rat populations. The findings show the pandemic’s origin reflects spatiotemporal convergence rather than a single cause, while noting uncertainty in quantifying historical ecological and health parameters; the case offers a framework for assessing contemporary pandemic risks. It underscores how layered pressures operate across timescales. Full article

Yersinia pestis is the etiological agent of plague, a severe and often fatal disease in humans when left untreated. Because of the high genetic clonality of Y. pestis, high-resolution genotyping assays are necessary to differentiate between individual strains. Here, we report on the development and validation of a robust and reproducible core-genome multilocus sequence typing (cgMLST) assay for Y. pestis comprising 3139 gene targets, enabling high-resolution typing at the strain level. The assay was validated using 222 publicly available Y. pestis genomes, including 45 recently sequenced outbreak isolates from Madagascar and 21 isolates from Mongolia. The cgMLST analysis revealed primary clustering aligned with known biovar-associated branches and sub-branches. Additional geographically structured sub-clusters illustrate its application for regional diversification analysis. Yersinia pestis strains from different geographic regions were clearly distinguished, consistent with spatial clustering. Within the analyzed dataset, closely related or epidemiologically linked strains differed by zero to three alleles, suggesting this range as an operational reference for identifying highly similar isolates. The cgMLST showed clustering patterns concordant with previously described single-nucleotide polymorphism (SNP) assays. It therefore provides a standardized high-resolution typing approach, with demonstrated applicability for outbreak investigations, source tracking, and comparative genomic surveillance of Y. pestis. Full article