Pathogenicity and virulence of Yersinia.

The genus Yersinia includes human, animal, insect, and plant pathogens as well as many symbionts and harmless bacteria. Within this genus are Yersinia enterocolitica and the Yersinia pseudotuberculosis complex, with four human pathogenic species that are highly related at the genomic level including the causative agent of plague, Yersinia pestis. Extensive laboratory, field work, and clinical research have been conducted to understand the underlying pathogenesis and zoonotic transmission of these pathogens. There are presently more than 500 whole genome sequences from which an evolutionary footprint can be developed that details shared and unique virulence properties. Whereas the virulence of Y. pestis now seems in apparent homoeostasis within its flea transmission cycle, substantial evolutionary changes that affect transmission and disease severity continue to ndergo apparent selective pressure within the other Yersiniae that cause intestinal diseases. In this review, we will summarize the present understanding of the virulence and pathogenesis of Yersinia, highlighting shared mechanisms of virulence and the differences that determine the infection niche and disease severity.

Mechanism of sturgeon intestinal inflammation induced by Yersinia ruckeri and the effect of florfenicol intervention.

The mechanism by which Y. ruckeri infection induces enteritis in Chinese sturgeon remains unclear, and the efficacy of drug prevention and control measures is not only poor but also plagued with numerous issues. We conducted transcriptomic and 16 S rRNA sequencing analyses to examine the differences in the intestinal tract of hybrid sturgeon before and after Y. ruckeri infection and florfenicol intervention. Our findings revealed that Y. ruckeri induced the expression of multiple inflammatory factors, including il1ß, il6, and various chemokines, as well as casp3, casp8, and multiple tumor necrosis factor family members, resulting in pathological injury to the body. Additionally, at the phylum level, the relative abundance of Firmicutes and Bacteroidota increased, while the abundance of Plesiomonas and Cetobacterium decreased at the genus level, altering the composition of the intestinal flora. Following florfenicol intervention, the expression of multiple apoptosis and inflammation-related genes was down-regulated, promoting tissue repair. However, the flora became further dysregulated, increasing the risk of infection. In conclusion, our analysis of the transcriptome and intestinal microbial composition demonstrated that Y. ruckeri induces intestinal pathological damage by triggering apoptosis and altering the composition of the intestinal microbiota. Florfenicol intervention can repair pathological damage, but it also exacerbates flora imbalance, leading to a higher risk of infection. These findings help elucidate the molecular mechanism of Y. ruckeri-induced enteritis in sturgeon and evaluate the therapeutic effect of drugs on intestinal inflammation in sturgeon.

A TNF-IL-1 circuit controls Yersinia within intestinal pyogranulomas.

Tumor necrosis factor (TNF) is a pleiotropic inflammatory cytokine that mediates antimicrobial defense and granuloma formation in response to infection by numerous pathogens. We previously reported that Yersinia pseudotuberculosis colonizes the intestinal mucosa and induces the recruitment of neutrophils and inflammatory monocytes into organized immune structures termed pyogranulomas (PG) that control Yersinia infection. Inflammatory monocytes are essential for the control and clearance of Yersinia within intestinal PG, but how monocytes mediate Yersinia restriction is poorly understood. Here, we demonstrate that TNF signaling in monocytes is required for bacterial containment following enteric Yersinia infection. We further show that monocyte-intrinsic TNFR1 signaling drives the production of monocyte-derived interleukin-1 (IL-1), which signals through IL-1 receptors on non-hematopoietic cells to enable PG-mediated control of intestinal Yersinia infection. Altogether, our work reveals a monocyte-intrinsic TNF-IL-1 collaborative inflammatory circuit that restricts intestinal Yersinia infection.

Yersinia enterocolitica biovar 1A: An underappreciated potential pathogen in the food chain.

Yersinia enterocolitica is an underreported cause of foodborne gastroenteritis. Little is known of the diversity of Y. enterocolitica isolated from food and which food commodities contribute to human disease. In this study, Y. enterocolitica was isolated from 37/50 raw chicken, 8/10 pork, 8/10 salmon and 1/10 leafy green samples collected at retail in the UK. Up to 10 presumptive Y. enterocolitica isolates per positive sample underwent whole genome sequencing (WGS) and were compared with publicly available genomes. In total, 207 Y. enterocolitica isolates were analyzed and belonged to 38 sequence types (STs). Up to five STs of Y. enterocolitica were isolated from individual food samples and isolates belonging to the same sample and ST differed by 0-74 single nucleotide polymorphisms (SNPs). Biotype was predicted for 205 (99 %) genomes that all belonged to biotype 1A, previously described as non-pathogenic. However, around half (51 %) of food samples contained isolates belonging to the same ST as previously isolated from UK human cases. The closest human-derived isolates shared between 17 and 7978 single nucleotide polymorphisms (SNPs) with the food isolates. Extensive food surveillance is required to determine what food sources are responsible for Y. enterocolitica infections and to re-examine the role of biotype 1A as a human pathogen.

Recombinant expression of Yersinia ruckeri outer membrane proteins in Escherichia coli extracellular vesicles.

The secretion of extracellular vesicles (EVs) is a common process in Gram-negative bacteria and can be exploited for biotechnological applications. EVs pose a self-adjuvanting, non-replicative vaccine platform, where membrane and antigens are presented to the host immune system in a non-infectious fashion. The secreted quantity of EVs varies between Gram-negative bacterial species and is comparatively high in the model bacterium E. coli. The outer membrane proteins OmpA and OmpF of the fish pathogen Y. ruckeri have been proposed as vaccine candidates to prevent enteric redmouth disease in aquaculture. In this work, Y.ruckeri OmpA or OmpF were expressed in E. coli and recombinant EVs were isolated. To avoid competition between endogenous E. coli OmpA or OmpF, Y. ruckeri OmpA and OmpF were expressed in E. coli strains lacking ompA, ompF, and in a quadruple knockout strain where the four major outer membrane protein genes ompA, ompC, ompF and lamB were removed. Y.ruckeri OmpA and OmpF were successfully expressed in EVs derived from the E. coli mutants as verified by SDS-PAGE, heat modifiability and proteomic analysis using mass-spectrometry. Transmission electron microscopy revealed the presence of EVs in all E. coli strains, and increased EV concentrations were detected when expressing Y. ruckeri OmpA or OmpF in recombinant EVs compared to empty vector controls as verified by nanoparticle tracking analysis. These results show that E. coli can be utilized as a vector for production of EVs expressing outer membrane antigens from Y. ruckeri.

The implication of viability and pathogenicity by truncated lipopolysaccharide in Yersinia enterocolitica.

The fast envelope stress responses play a key role in the transmission and pathogenesis of Yersinia enterocolitica, one of the most common foodborne pathogens. Our previous study showed that deletion of the waaF gene, essential for the biosynthesis of lipopolysaccharide (LPS) core polysaccharides, led to the formation of a truncated LPS structure and induced cell envelope stress. This envelope stress may disturb the intracellular signal transduction, thereby affecting the physiological functions of Y. enterocolitica. In this study, truncated LPS caused by waaF deletion was used as a model of envelope stress in Y. enterocolitica. We investigated the mechanisms of envelope stress responses and the cellular functions affected by truncated LPS. Transcriptome analysis and phenotypic validation showed that LPS truncation reduced flagellar assembly, bacterial chemotaxis, and inositol phosphate metabolism, presenting lower pathogenicity and viability both in vivo and in vitro environments. Further 4D label-free phosphorylation analysis confirmed that truncated LPS perturbed multiple intracellular signal transduction pathways. Specifically, a comprehensive discussion was conducted on the mechanisms by which chemotactic signal transduction and Rcs system contribute to the inhibition of chemotaxis. Finally, the pathogenicity of Y. enterocolitica with truncated LPS was evaluated in vitro using IPEC-J2 cells as models, and it was found that truncated LPS exhibited reduced adhesion, invasion, and toxicity of Y. enterocolitica to IPEC-J2 cells. Our research provides an understanding of LPS in the regulation of Y. enterocolitica viability and pathogenicity and, thus, opening new avenues to develop novel food safety strategies or drugs to prevent and control Y. enterocolitica infections. KEY POINTS: • Truncated LPS reduces flagellar assembly, chemotaxis, and inositol phosphate metabolism in Y. enterocolitica. • Truncated LPS reduces adhesion, invasion, and toxicity of Y. enterocolitica to IPEC-J2 cells. • Truncated LPS regulates intracellular signal transduction of Y. enterocolitica.

Association of Yersinia Infection With Kawasaki Disease: A Prospective Multicenter Cohort Study.

BACKGROUND: Yersinia infection is known to present with Kawasaki disease (KD)-like symptoms although differentiating the 2 has been a challenge. The present study aimed to describe the clinical characteristics and prevalence of Yersinia infection presenting with KD-like symptoms. METHODS: The present, prospective, multicenter study enrolled patients who received a diagnosis of KD between January 2021 and January 2022 at 2 hospitals in Tokyo. Stool samples were collected within 3 days of the start of KD treatment, and cultures were performed for Yersinia . Clinical history and symptoms suggestive of Yersinia infection were also evaluated. RESULTS: During the study period, 141 KD patients were screened and 117 patients with evaluable stool samples were registered. Only 1 patient was positive for Yersinia pseudotuberculosis , which was detected from both stool and blood cultures. The patient was refractory to KD treatment but improved after initiation of appropriate antibiotic therapy. CONCLUSIONS: Routine screening for Yersinia is not appropriate for patients with KD and should be limited to certain patients in high-risk areas and those who are refractory to the standard KD treatment.

Effect of Dietary Origanum onites on Growth, Non Specific Immunity and Resistance against Yersinia ruckeri of Rainbow Trout ( Oncorhynchus mykiss).

Natural substances has been identified to maintain health and improve growth performance in the aquaculture. The effect of Origanum onites on growth and immune response of rainbow trout was investigated. Experimental groups (A and B) of 70 fish were separated into 10 different treatments. A groups were fed with dietary administration of O. onites essential oil (0.5 mL kg-1 and 3.0 mL kg-1) and crude powder (1.0 g kg-1 and 10.0 g kg-1) for a period of 8 weeks. Other groups (B) were vaccinated against Yersinia ruckeri at the beginning of experiment and then fed the same diets described above. Results showed that feed conversion ratio in fish fed a combination of O. onites and vaccine was statistically better than the control. NBT-positive cells, phagocytic activity, serum lysozyme activity and immunoglobulin M level were stimulated in both non vaccinated and vaccinated fish (p<0.05). Cumulative mortality in fish fed O. onites was lower than controls following challenge with Y. ruckeri. No mortality was observed in vaccinated fish fed with 0.5 mL kg-1 of O. onites. These results indicated that dietary administration of O. onites could act as an enhanced non specific immune response, growth performance and resistance to Y. ruckeri.

Exploring Yersinia ruckeri (O1 Biotype 2) infection in three early life-stages of rainbow trout.

Enteric redmouth disease (ERM) caused by the enterobacterium Yersinia ruckeri poses a significant threat to salmonid aquaculture globally. Despite decades of experimental infection studies, key knowledge gaps remain regarding the onset of disease susceptibility and mechanisms of immunity during early developmental stages, undermining disease management efforts in all susceptible life-stages. In this study, a series of immersion challenges were conducted, challenging and re-challenging rainbow trout Oncorhynchus mykiss (Walbaum) at 7, 14 and 51 d post-hatch (dph; mean weights = 0.085, 0.1 and 2.0 g respectively) to high concentrations (1.72 × 107-1.1 × 108 CFU) of Y. ruckeri at 15°C. This study indicates the hitherto unknown initial point of susceptibility to infection as the time of first ingestion of exogenous food (14 dph), and shows that individuals surviving primary challenge at 14 dph are significantly more likely to survive re-challenge at 51 dph compared with naive individuals (hazard ratio = 1.446, p = 0.032). Other key findings include large variation in mortality between different development-stages, from 21.1% at 14 dph to 81.2% at 51 dph, and novel age-dependent symptoms not reported previously. Results from this study enhance our understanding of ERM in juvenile rainbow trout and inform the development of improved aquatic animal health management strategies, thereby contributing to the productivity and sustainability of salmonid aquaculture into the future.

Yersinia ruckeri infection activates local skin and gill B cell responses in rainbow trout.

Teleost fish lack organized structures in mucosal tissues such as those of mammals, but instead contain dispersed B and T cells with the capacity to respond to external stimuli. Nonetheless, there is still a great lack of knowledge regarding how B cells differentiate to plasmablasts/plasma cells in these mucosal surfaces. To contribute to a further understanding of the mechanisms through which fish mucosal B cells are activated, in the current study, we have studied the B cell responses in the skin and gills of rainbow trout (Oncorhynchus mykiss) exposed to Yersinia ruckeri. We have first analyzed the transcription levels of genes related to B cell function in both mucosal surfaces, and in spleen and kidney for comparative purposes. In a second experiment, we have evaluated how the infection affects the presence and size of B cells in both skin and gills, as well as the presence of plasmablasts secreting total or specific IgMs. The results obtained in both experiments support the local differentiation of B cells to plasmablasts/plasma cells in the skin and gills of rainbow trout in response to Y. ruckeri. Interestingly, these plasmablasts/plasma cells were shown to secrete specific IgMs as soon as 5 days after the exposure. These findings contribute to a further understanding of how B cells in the periphery respond to immune stimulation in teleost fish.

Effects of diets rich in Agaricus bisporus polysaccharides on the growth, antioxidant, immunity, and resistance to Yersinia ruckeri in channel catfish.

To promote the application of Agaricus bisporus polysaccharides (ABPs) in channel catfish (Ictalurus punctatus) culture, we evaluated the effects of ABPs on the growth, immunity, antioxidant, and antibacterial activity of channel catfish. When the amount of ABPs was 250 mg/kg, channel catfish's weight gain and specific growth rates increased significantly while the feed coefficient decreased. We also found that adding ABPs in the feed effectively increased the activities of ACP, MDA, T-SOD, AKP, T-AOC, GSH, and CAT enzymes and immune-related genes such as IL-1ß, Hsp70, and IgM in the head kidney of channel catfish. Besides, long-term addition will not cause pathological damage to the head kidney. When the amount of ABPs was over 125 mg/kg, the protection rate of channel catfish was more than 60%. According to the intestinal transcriptome analysis, the addition of ABPs promoted the expression of intestinal immunity genes and growth metabolism-related genes and enriched multiple related KEEG pathways. When challenged by Yersinia ruckeri infection, the immune response of channel catfish fed with ABPs was intenser and quicker. Additionally, the 16S rRNA gene sequencing analysis showed that the composition of the intestinal microbial community of channel catfish treated with ABPs significantly changed, and the abundance of microorganisms beneficial to channel catfish growth, such as Firmicutes and Bacteroidota increased. In conclusion, feeding channel catfish with ABPs promoted growth, enhanced immunity and antioxidant, and improved resistance to bacterial infections. Our current results might promote the use of ABPs in channel catfish and even other aquacultured fish species.

Characterization of phenyl propiolic acid from Proteus mirabilis DMTMMR-11 and Evaluation of its mode of action against Yersinia enterocolitica (MTCC-840) an in-Vitro and in-Vivo based approach.

Foodborne illnesses are pervasive in raising public health concerns in both developed and developing nations. Yersinia enterocolitica a zoonotic bacterial species that causes food-transmitted infections, and gastroenteritis, is its most prevalent clinical manifestation. This study aims to investigate the differences, dependencies, and inhibitory mechanisms between the host and the microbiome. Proteus mirabilis DMTMMR-11, the bacterium found in the human gastrointestinal tract was used for the extraction of intracellular metabolite, because of its beneficial effects on the normal flora of the human gut. Phenyl propiolic acid was identified as the dominant compound in the metabolite after characterization using FT-IR, NMR, and LC-MS-MS. To assess its inhibitory mechanism against Yersinia enterocolitica, the pathogen was subjected to biological characterization by MBC and MIC, resulting in the rate of inhibition at 50 µg/ml. Anti-bacterial curve supports the inhibited growth of Y. enterocolitica. Mechanism of inhibition at its cellular level was indicated by the increase in alkaline phosphate content, which drastically reduced the cell membrane and cell wall potential expanding its permeability by intruding the membrane proteins, which was observed in SEM Imaging. Phenyl propiolic acid efficiently disrupts the biofilm formation by reducing the adherence and increasing the eradication property of the pathogen by exhibiting 65% of inhibition at the minimal duration of 12h. In-vivo study was carried out through host-pathogen interaction in C. elegans, an efficient model organism assessed for its life-span, physiological, and behavioral assays.

Comprehensive Analysis of YTH Domain-Containing Genes, Encoding m6A Reader and Their Response to Temperature Stresses and Yersinia ruckeri Infection in Rainbow Trout (Oncorhynchus mykiss).

YTH domain-containing genes are important readers of N6-methyladenosine (m6A) modifications with ability to directly affect the fates of distinct RNAs in organisms. Despite their importance, little is known about YTH domain-containing genes in teleosts until now. In the present study, a total of 10 YTH domain-containing genes have been systematically identified and functionally characterized in rainbow trout (Oncorhynchus mykiss). According to the phylogenetic tree, gene structure and syntenic analysis, these YTH domain-containing genes could be classified into three evolutionary subclades, including YTHDF, YTHDC1 and YTHDC2. Of them, the copy number of OmDF1, OmDF2, OmDF3, and OmDC1 were duplicated or even triplicated in rainbow trout due to the salmonid-specific whole-genome duplication event. The three-dimensional protein structure analysis revealed that there were similar structures and the same amino acid residues that were associated with cage formation between humans and rainbow trout, implying their similar manners in binding to m6A modification. Additionally, the results of qPCR experiment indicated that the expression patterns of a few YTH domain-containing genes, especially OmDF1b, OmDF3a and OmDF3b, were significantly different in liver tissue of rainbow trout under four different temperatures (7 °C, 11 °C, 15 °C, and 19 °C). The expression levels of OmDF1a, OmDF1b and OmDC1a were obviously repressed in spleen tissue of rainbow trout at 24 h after Yersinia ruckeri infection, while increased expression was detected in OmDF3b. This study provides a systemic overview of YTH domain-containing genes in rainbow trout and reveals their biological roles in responses to temperature stress and bacterial infection.

Traceability, virulence and antimicrobial resistance of Yersinia enterocolitica in two industrial cheese-making plants.

Between 2018 and 2019, 309 environmental and food samples were collected from two industrial cheese-making plants located in Sardinia, in order to investigate Y. enterocolitica presence and to characterize the isolates. Y. enterocolitica isolates were further compared with isolates detected during a previous investigation from sheep and goat raw milk samples. Y. enterocolitica was detected in 7.4 % of the samples and the prevalence was higher, even if not significantly (P > 0.05) higher in non-food contact surface samples (10.2 %) than in food contact surface samples (3.8 %). The highest prevalence was detected in floor samples (13.5 %), followed by drain samples (7.2 %), which might serve as main harborage sites for further contamination. Y. enterocolitica was also detected in food contact surfaces, namely shelves of the Ricotta cooling room and packaging room, one cheese cutting machine surface and one raw milk filter sample. The biotype 1A isolates identified in this study were classified into six different serotypes. Additionally, a bioserotype 2/O:5,27 isolate was identified in one goat milk sample. All 1A isolates possessed the virulence genes invA and ystB while the 2/O:5,27 isolate showed the presence of ail, ystA, invA and yadA genes, thus confirming a pathogenic potential. The isolates showed intrinsic resistance to amoxicillin-clavulanic acid, ticarcillin and cefoxitin due to the presence of the blaA gene. Whole genome sequencing allowed to identify seven different sequence types among the 1A isolates, thus showing a high genetic diversity. The same Y. enterocolitica sequence type (ST3) was detected from three different areas of the same cheese-making plant, indicating a possible transfer of the microorganism along the processing lines. Y. enterocolitica contamination in cheese-making plants can pose a risk to human health. Preventive measures include the hygienic design of the plant layout and equipment, in association with proper cleaning and disinfection programmes.

Pan-genome survey of the fish pathogen Yersinia ruckeri links accessory- and amplified genes to virulence.

While both virulent and putatively avirulent Yersinia ruckeri strains exist in aquaculture environments, the relationship between the distribution of virulence-associated factors and de facto pathogenicity in fish remains poorly understood. Pan-genome analysis of 18 complete genomes, representing established virulent and putatively avirulent lineages of Y. ruckeri, revealed the presence of a number of accessory genetic determinants. Further investigation of 68 draft genome assemblies revealed that the distribution of certain putative virulence factors correlated well with virulence and host-specificity. The inverse-autotransporter invasin locus yrIlm was, however, the only gene present in all virulent strains, while absent in lineages regarded as avirulent. Strains known to be associated with significant mortalities in salmonid aquaculture display a combination of serotype O1-LPS and yrIlm, with the well-documented highly virulent lineages, represented by MLVA clonal complexes 1 and 2, displaying duplication of the yrIlm locus. Duplication of the yrIlm locus was further found to have evolved over time in clonal complex 1, where some modern, highly virulent isolates display up to three copies.

Controlled Experimental Infection in Pigs with a Strain of Yersinia enterocolitica Harboring Genetic Markers for Human Pathogenicity: Colonization and Stability.

Yersinia enterocolitica (Ye) is one of the major causes of foodborne zoonosis. The BT4/O:3 bioserotype is most commonly isolated in human infections. Pigs are considered the main reservoir of Ye, and hence, understanding the dynamics of infection by this pathogen at the individual and group levels is crucial. In the present study, an experimental model was validated in Large White pigs infected with a BT4/O:3 strain. This study showed that Ye contamination in pigs may occur via the introduction of the bacteria not only by mouth but also by snout, with a colonization process consisting of three periods corresponding to three contamination statuses of pigs: P1, corresponding to the 24 h following ingestion or inhalation of Ye with the appearance of bacteria in tonsils or in feces; P2, from 2 days postinoculation (dpi), corresponding to expansion of Ye and colonization of the digestive system and extraintestinal organs associated with an IgG serological response; and P3, after 21 dpi, corresponding to regression of colonization with intermittent Ye detection in tonsils and feces. Although the inoculated strain persisted up to 56 dpi in all pigs, genetic variations with the loss of the gene yadA (a gene involved in human infection) and the emergence of two new multilocus variable-number tandem-repeat analysis (MLVA) profiles were observed in 33% of the 30 isolates studied. This experimental infection model of pigs by Ye provides new insights into the colonization steps in pigs in terms of bacterial distribution over time and bacterial genetic stability.

Forgotten but not gone: Yersinia infections in England, 1975 to 2020.

BackgroundYersiniosis is one of the most common food-borne zoonoses in Europe, but there are large variations in the reported incidence between different countries.AimWe aimed to describe the trends and epidemiology of laboratory-confirmed Yersinia infections in England and estimate the average annual number of undiagnosed Yersinia enterocolitica cases, accounting for under-ascertainment.MethodsWe analysed national surveillance data on Yersinia cases reported by laboratories in England between 1975 and 2020 and enhanced surveillance questionnaires from patients diagnosed in a laboratory that has implemented routine Yersinia testing of diarrhoeic samples since 2016.ResultsThe highest incidence of Yersinia infections in England (1.4 cases per 100,000 population) was recorded in 1988 and 1989, with Y. enterocolitica being the predominant species. The reported incidence of Yersinia infections declined during the 1990s and remained low until 2016. Following introduction of commercial PCR at a single laboratory in the South East, the annual incidence increased markedly (13.6 cases per 100,000 population in the catchment area between 2017 and 2020). There were notable changes in age and seasonal distribution of cases over time. The majority of infections were not linked to foreign travel and one in five patients was admitted to hospital. We estimate that around 7,500 Y. enterocolitica infections may be undiagnosed in England annually.ConclusionsFindings suggest a considerable number of undiagnosed yersiniosis cases in England, with possibly important changes in the epidemiology. The apparently low incidence of yersiniosis in England is probably due to limited laboratory testing.

Analyzing Caspase-8-Dependent GSDMD Cleavage in Response to Yersinia Infection.

Caspase-8 is best known to drive an immunologically silent form of cell death known as apoptosis. However, emerging studies revealed that upon pathogen inhibition of innate immune signalling, such as during Yersinia infection in myeloid cells, caspase-8 associates with RIPK1 and FADD to trigger a proinflammatory death-inducing complex. Under such conditions, caspase-8 cleaves the pore-forming protein gasdermin D (GSDMD) to trigger a lytic form of cell death, known as pyroptosis. Here, we describe our protocol to activate caspase-8-dependent GSDMD cleavage following Yersinia pseudotuberculosis infection in murine bone marrow-derived macrophages (BMDMs). Specifically, we describe protocols on harvesting and plating of BMDM, preparation of type 3 secretion system-inducing Yersinia, macrophage infection, lactate dehydrogenase (LDH) release assay, and Western blot analysis.

Public health implications of Yersinia enterocolitica investigation: an ecological modeling and molecular epidemiology study.

BACKGROUND: Yersinia enterocolitica has been sporadically recovered from animals, foods, and human clinical samples in various regions of Ningxia, China. However, the ecological and molecular characteristics of Y. enterocolitica, as well as public health concerns about infection in the Ningxia Hui Autonomous Region, remain unclear. This study aims to analyze the ecological and molecular epidemiological characteristics of Y. enterocolitis in order to inform the public health intervention strategies for the contains of related diseases. METHODS: A total of 270 samples were collected for isolation [animals (n = 208), food (n = 49), and patients (n = 13)], then suspect colonies were isolated and identified by the API20E biochemical identification system, serological tests, biotyping tests, and 16S rRNA-PCR. Then, we used an ecological epidemiological approach combined with machine learning algorithms (general linear model, random forest model, and eXtreme Gradient Boosting) to explore the associations between ecological factors and the pathogenicity of Y. enterocolitis. Furthermore, average nucleotide identity (ANI) estimation, single nucleotide polymorphism (SNP), and core gene multilocus sequence typing (cgMLST) were applied to characterize the molecular profile of isolates based on whole genome sequencing. The statistical test used single-factor analysis, Chi-square tests, t-tests/ANOVA-tests, Wilcoxon rank-sum tests, and Kruskal-Wallis tests. RESULTS: A total of 270 isolates of Yersinia were identified from poultry and livestock (n = 191), food (n = 49), diarrhoea patients (n = 13), rats (n = 15), and hamsters (n = 2). The detection rates of samples from different hosts were statistically different (χ2 = 22.636, P < 0.001). According to the relatedness clustering results, 270 isolates were divided into 12 species, and Y. enterocolitica (n = 187) is a predominated species. Pathogenic isolates made up 52.4% (98/187), while non-pathogenic isolates made up 47.6% (89/187). Temperature and precipitation were strongly associated with the pathogenicity of the isolates (P < 0.001). The random forest (RF) prediction model showed the best performance. The prediction result shows a high risk of pathogenicity Y. enterocolitica was located in the northern, northwestern, and southern of the Ningxia Hui Autonomous Region. The Y. enterocolitica isolates were classified into 54 sequence types (STs) and 125 cgMLST types (CTs), with 4/O:3 being the dominant bioserotype in Ningxia. The dominant STs and dominant CTs of pathogenic isolates in Ningxia were ST429 and HC100_2571, respectively. CONCLUSIONS: The data indicated geographical variations in the distribution of STs and CTs of Y. enterocolitica isolates in Ningxia. Our work offered the first evidence that the pathogenicity of isolates was directly related to fluctuations in temperature and precipitation of the environment. CgMLST typing strategies showed that the isolates were transmitted to the population via pigs and food. Therefore, strengthening health surveillance on pig farms in high-risk areas and focusing on testing food of pig origin are optional strategies to prevent disease outbreaks.

Diarrhoea-causing microorganisms are rare in adult patients undergoing diagnostic laparoscopy for suspected appendicitis: a prospective observational cohort study.

We investigated if diarrhoea-causing bacteria, including Yersinia species, could mimic the symptoms of appendicitis and lead to surgery. This prospective observational cohort study (NCT03349814) included adult patients undergoing surgery for suspected appendicitis. Rectal swabs were analysed with polymerase chain reaction (PCR) for Yersinia, Campylobacter, Salmonella, Shigella and Aeromonas spp. Blood samples were analysed routinely and with an in-house ELISA serological test for Yersinia enterocolitica antibodies. We compared patients without appendicitis and patients with appendicitis confirmed by histopathology. The outcomes included PCR-confirmed infection with Yersinia spp., serologic-confirmed infection with Y. enterocolitica, PCR-confirmed infection with other diarrhoea-causing bacteria and Enterobius vermicularis confirmed by histopathology. A total of 224 patients were included, 51 without and 173 with appendicitis, and followed for 10 days. PCR-confirmed infection with Yersinia spp. was found in one patient (2%) without appendicitis and no patients (0%) with appendicitis (p = 0.23). Serology was positive for Y. enterocolitica for the same patient without appendicitis and two patients with appendicitis (p = 0.54). Campylobacter spp. were detected in 4% vs 1% (p = 0.13) of patients without and with appendicitis, respectively. Infection with Yersinia spp. and other diarrhoea-causing microorganisms in adult patients undergoing surgery for suspected appendicitis was rare.