Dengue virus (DENV), from the Flaviviridae family, is the causative agent of dengue fever and poses a significant global health challenge. The virus primarily affects the vascular system and liver; however, a growing body of evidence suggests its involvement in the gastrointestinal (GI) tract, contributing to clinical symptoms such as abdominal pain, vomiting, and diarrhea. However, the mechanisms underlying DENV infection in the digestive system remain largely unexplored. Prior research has detected viral RNA in the GI tissue of infected animals; however, whether the dengue virus can directly infect human enterocytes remains unclear. In this study, we examine the infectivity of human intestinal cell lines to the dengue virus and their subsequent response. We report that the Caco-2 cell line, a model of human enterocytes, is susceptible to infection and capable of producing viruses. Notably, differentiated Caco-2 cells exhibited a lower infection rate yet a higher level of virus production than their undifferentiated counterparts. These findings suggest that human intestinal cells are a viable target for the dengue virus, potentially elucidating the GI symptoms observed in dengue fever and offering a new perspective on the pathogenetic mechanisms of the virus.

Salmonella enterica serotype Cerro (S. Cerro) is an emerging Salmonella serotype isolated from cattle, but the association of S. Cerro with disease is not well understood. While comparative genomic analyses of bovine S. Cerro isolates have indicated mutations in elements associated with virulence, the correlation of S. Cerro fecal shedding with clinical disease in cattle varies between epidemiologic studies. The primary objective of this study was to characterize the infection-relevant phenotypes of S. Cerro fecal isolates obtained from neonatal calves born on a dairy farm in Wisconsin, USA. The S. Cerro isolates varied in biofilm production and sensitivity to the bile salt deoxycholate. All S. Cerro isolates were sensitive to sodium hypochlorite, hydrogen peroxide, and acidic shock. However, S. Cerro isolates were resistant to nitric oxide stress. Two S. Cerro isolates were unable to compete with S. Typhimurium during infection of calf ligated intestinal loops, indicating decreased fitness in vivo. Together, our data suggest that S. Cerro is sensitive to some innate antimicrobial defenses present in the gut, many of which are also used to control Salmonella in the environment. The observed phenotypic variation in S. Cerro isolates from a single farm suggest phenotypic plasticity that could impact infectious potential, transmission, and persistence on a farm.IMPORTANCESalmonella enterica is a zoonotic pathogen that threatens both human and animal health. Salmonella enterica serotype Cerro is being isolated from cattle at increasing frequency over the past two decades; however, its association with clinical disease is unclear. The goal of this study was to characterize infection-relevant phenotypes of S. Cerro isolates obtained from dairy calves from a single farm. Our work shows that there can be variation among temporally related S. Cerro isolates and that these isolates are sensitive to killing by toxic compounds of the innate immune system and those used for environmental control of Salmonella. This work contributes to our understanding of the pathogenic potential of the emerging pathogen S. Cerro.

UNASSIGNED: Gastrointestinal (GI) infections result in 17 million cases annually, with foodborne illness costing the National Health Service (NHS) £60m per year. The burden of GI infection is unequally distributed, with greater impact in more socioeconomically disadvantaged groups and areas. Local authorities (LA) provide vital services that protect public health and wellbeing. The impact of funding cuts to local services and their effect on public health is an area of concern. Environmental and regulatory (ER) services are responsible for roles such as food safety and infectious disease control. This study aims to understand the impact of local funding cuts on ER and GI infection outcomes.
UNASSIGNED: We will conduct an ecological longitudinal study in England from 2010-2019 at the LA level to examine how changes in ER expenditure overtime have impacted ER and GI infection outcomes. Data will be gathered on food hygiene enforcement, food hygiene compliance levels, GI infection hospitalisation, NHS 111 calls relating to GI infection symptoms, GI infection pathogen data, deprivation, and population density. Measures will be aggregated to LA level and statistical analysis will be carried out.
UNASSIGNED: University of Liverpool Ethics committee have confirmed ethical approval will not be required. All data will be aggregated and anonymised, therefore only data sharing agreements will be required. Findings will be disseminated to the stakeholder group in addition to outputs through conferences and publications. These findings will help understand impact of key services on public health and should inform government and public health policy and strategy.

Salmonella enterica serovar Typhimurium (S. Typhimurium) infection triggers an inflammatory response that changes the concentration of metabolites in the gut impacting the luminal environment. Some of these environmental adjustments are conducive to S. Typhimurium growth, such as the increased concentrations of nitrate and tetrathionate or the reduced levels of Clostridia-produced butyrate. We recently demonstrated that S. Typhimurium can form biofilms within the host environment and respond to nitrate as a signaling molecule, enabling it to transition between sessile and planktonic states. To investigate whether S. Typhimurium utilizes additional metabolites to regulate its behavior, our study delved into the impact of inflammatory metabolites on biofilm formation. The results revealed that lactate, the most prevalent metabolite in the inflammatory environment, impedes biofilm development by reducing intracellular c-di-GMP levels, suppressing the expression of curli and cellulose, and increasing the expression of flagellar genes. A transcriptomic analysis determined that the expression of the de novo purine pathway increases during high lactate conditions, and a transposon mutagenesis genetic screen identified that PurA and PurG, in particular, play a significant role in the inhibition of curli expression and biofilm formation. Lactate also increases the transcription of the type III secretion system genes involved in tissue invasion. Finally, we show that the pyruvate-modulated two-component system BtsSR is activated in the presence of high lactate, which suggests that lactate-derived pyruvate activates BtsSR system after being exported from the cytosol. All these findings propose that lactate is an important inflammatory metabolite used by S. Typhimurium to transition from a biofilm to a motile state and fine-tune its virulence.IMPORTANCEWhen colonizing the gut, Salmonella enterica serovar Typhimurium (S. Typhimurium) adopts a dynamic lifestyle that alternates between a virulent planktonic state and a multicellular biofilm state. The coexistence of biofilm formers and planktonic S. Typhimurium in the gut suggests the presence of regulatory mechanisms that control planktonic-to-sessile transition. The signals triggering the transition of S. Typhimurium between these two lifestyles are not fully explored. In this work, we demonstrated that in the presence of lactate, the most dominant host-derived metabolite in the inflamed gut, there is a reduction of c-di-GMP in S. Typhimurium, which subsequently inhibits biofilm formation and induces the expression of its invasion machinery, motility genes, and de novo purine metabolic pathway genes. Furthermore, high levels of lactate activate the BtsSR two-component system. Collectively, this work presents new insights toward the comprehension of host metabolism and gut microenvironment roles in the regulation of S. Typhimurium biology during infection.

Infection with the apicomplexan parasite Cryptosporidium is a leading cause of diarrheal disease. Cryptosporidiosis is of particular importance in infants and shows a strong association with malnutrition, both as a risk factor and as a consequence. Cryptosporidium invades and replicates within the small intestine epithelial cells. This is a highly dynamic tissue that is developmentally stratified along the villus axis. New cells emerge from a stem cell niche in the crypt and differentiate into mature epithelial cells while moving toward the villus tip, where they are ultimately shed. Here, we studied the impact of Cryptosporidium infection on this dynamic architecture. Tracing DNA synthesis in pulse-chase experiments in vivo, we quantified the genesis and migration of epithelial cells along the villus. We found proliferation and epithelial migration to be elevated in response to Cryptosporidium infection. Infection also resulted in significant cell loss documented by imaging and molecular assays. Consistent with these observations, single-cell RNA sequencing of infected intestines showed a gain of young and a loss of mature cells. Interestingly, enhanced epithelial cell loss was not a function of enhanced apoptosis of infected cells. To the contrary, Cryptosporidium-infected cells were less likely to be apoptotic than bystanders, and experiments in tissue culture demonstrated that infection provided enhanced resistance to chemically induced apoptosis to the host but not bystander cells. Overall, this study suggests that Cryptosporidium may modulate cell apoptosis and documents pronounced changes in tissue homeostasis due to parasite infection, which may contribute to its long-term impact on the developmental and nutritional state of children.
OBJECTIVE: The intestine must balance its roles in digestion and nutrient absorption with the maintenance of an effective barrier to colonization and breach by numerous potential pathogens. An important component of this balance is its constant turnover, which is modulated by a gain of cells due to proliferation and loss due to death or extrusion. Here, we report that Cryptosporidium infection changes the dynamics of this process increasing both gain and loss of enterocytes speeding up the villus elevator. This leads to a much more immature epithelium and a reduction of the number of those cells typically found toward the villus apex best equipped to take up key nutrients including carbohydrates and lipids. These changes in the cellular architecture and physiology of the small intestine may be linked to the profound association between cryptosporidiosis and malnutrition.

The intestinal tract generates significant reactive oxygen species (ROS), but the role of T cell antioxidant mechanisms in maintaining intestinal homeostasis is poorly understood. We used T cell-specific ablation of the catalytic subunit of glutamate cysteine ligase (Gclc), which impaired glutathione (GSH) production, crucially reducing IL-22 production by Th17 cells in the lamina propria, which is critical for gut protection. Under steady-state conditions, Gclc deficiency did not alter cytokine secretion; however, C. rodentium infection induced increased ROS and disrupted mitochondrial function and TFAM-driven mitochondrial gene expression, resulting in decreased cellular ATP. These changes impaired the PI3K/AKT/mTOR pathway, reducing phosphorylation of 4E-BP1 and consequently limiting IL-22 translation. The resultant low IL-22 levels led to poor bacterial clearance, severe intestinal damage, and high mortality. Our findings highlight a previously unrecognized, essential role of Th17 cell-intrinsic GSH in promoting mitochondrial function and cellular signaling for IL-22 protein synthesis, which is critical for intestinal integrity and defense against gastrointestinal infections.

This study focuses on the genomic characterization of a multidrug-resistant Escherichia coli strain responsible for a severe gastrointestinal infection in a 33-year-old male. The patient initially received sulfamethoxazole/trimethoprim treatment, which proved ineffective. Fecal culture confirmed the presence of E. coli displaying a MDR profile to ampicillin, nalidixic acid, ciprofloxacin, sulfamethoxazole, trimethoprim, and tetracycline. Serotyping identified the strain as ONT:H19. Virulence analysis indicated a highly virulent profile with numerous virulence markers. Plasmid analysis uncovered various plasmids carrying both antimicrobial resistance and virulence genes. MLST assigned the strain to ST10955. Phylogenomic analysis revealed similarity to an older Brazilian isolate, suggesting the persistence of a common lineage with evolving antimicrobial resistance. This report highlights the first identification of a multidrug-resistant ST10955 E. coli strain with a wide resistome and virulence potential, emphasizing the importance of ongoing surveillance of E. coli strains due to their potential for severe infections, resistance development, and virulence.

Certain Escherichia coli (E. coli) strains are attaching and effacing (A/E) lesion pathogens that primarily infect intestinal epithelial cells. They cause actin restructuring and polymerization within the host cell to create an actin-rich protrusion below the site of adherence, termed the pedestal. Although there is clarity on the pathways initiating pedestal formation, the underlying purpose(s) of the pedestal remains ambiguous. The conservation of pedestal-forming activity across multiple pathogens and redundancy in formation pathways indicate a pathogenic advantage. However, few decisive conclusions have been drawn, given that the results vary between model systems. Some research argues that the pedestal increases the colonization capability of the bacterium. These studies utilize A/E pathogens specifically deficient in pedestal formation to evaluate adhesion and intestinal colonization following infection. There have been many proposed mechanisms for the colonization benefit conferred by the pedestal. One suggested benefit is that the pedestal allows for direct cytosolic anchoring through incorporation of the established host cortical actin, causing a stable link between the pathogen and cell structure. The pedestal may confer enhanced motility, as enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC) are better able to migrate on the surface of host cells and infect neighboring cells in the presence of the pedestal. Additionally, some research suggests that the pedestal improves effector delivery. This review will investigate the purpose of pedestal formation using evidence from recent literature and will critically evaluate the methodology and model systems. Most importantly, we will contextualize the proposed functions to reconcile potential synergistic effects.

Gastrointestinal (GI) infection is evidenced with involvement in COVID-19 pathogenesis caused by SARS-CoV-2. However, the correlation between GI microbiota and the distinct pathogenicity of SARS-CoV-2 Proto and its emerging variants remains unclear. In this study, we aimed to determine if GI microbiota impacted COVID-19 pathogenesis and if the effect varied between SARS-CoV-2 Proto and its variants. We performed an integrative analysis of histopathology, microbiomics, and transcriptomics on the GI tract fragments from rhesus monkeys infected with SARS-CoV-2 proto or its variants. Based on the degree of pathological damage and microbiota profile in the GI tract, five of SARS-CoV-2 strains were classified into two distinct clusters, namely, the clusters of Alpha, Beta and Delta (ABD), and Proto and Omicron (PO). Notably, the abundance of potentially pathogenic microorganisms increased in ABD but not in the PO-infected rhesus monkeys. Specifically, the high abundance of UCG-002, UCG-005, and Treponema in ABD virus-infected animals positively correlated with interleukin, integrins, and antiviral genes. Overall, this study revealed that infection-induced alteration of GI microbiota and metabolites could increase the systemic burdens of inflammation or pathological injury in infected animals, especially in those infected with ABD viruses. Distinct GI microbiota and metabolite profiles may be responsible for the differential pathological phenotypes of PO and ABD virus-infected animals. These findings improve our understanding the roles of the GI microbiota in SARS-CoV-2 infection and provide important information for the precise prevention, control, and treatment of COVID-19.

The role of aichivirus A1 (AiV-A1) in acute gastroenteritis remains controversial and in vitro data illustrating its pathogenesis in suitable human models are scarce. Here, we demonstrate that AiV-A1 isolate A846/88 replicates in ApoA1- (absorptive) and Ki-67-positive (proliferative) enterocytes in stem cell-derived human small intestinal epithelium (HIE) as well as in patient biopsy samples, but not in any of the tested human cell lines. The infection did not result in tissue damage and did not trigger type I and type III interferon (IFN) signalling, whereas the control, human coxsackievirus B3 (strain Nancy), triggered both IFNs. To investigate the tissue tropism, we infected a human tracheal/bronchial epithelium model (HTBE) with AiV-A1 isolates A846/88 and kvgh99012632/2010 and, as a control, with rhinovirus A2 (RV-A2). AiV-A1 isolate kvgh99012632/2010, but not isolate A846/88, replicated in HTBE and induced type III IFN and ISGs signalling. By using various pharmacological inhibitors, we elaborated that cellular entry of AiV-A1 depends on clathrin, dynamin, and lipid rafts and is strongly reliant on endosome acidification. Viral particles co-localised with Rab5a-positive endosomes and promoted leakage of endosomal content. Our data shed light on the early events of AiV-A1 infection and reveal that different isolates exhibit distinct tissue tropism. This supports its clinical importance as a human pathogen with the potential to evolve toward broader tissue specificity.