Histopathological analysis of Salmonella chronic carriage in the mouse hepatopancreatobiliary system

Bacterial Infections and Cancer: Exploring This Association And Its Implications for Cancer Patients

Bacterial infections are common in the etiology of human diseases owing to the ubiquity of bacteria. Such infections promote the development of periodontal disease, bacterial pneumonia, typhoid, acute gastroenteritis, and diarrhea in susceptible hosts. These diseases may be resolved using antibiotics/antimicrobial therapy in some hosts. However, other hosts may be unable to eliminate the bacteria, allowing them to persist for long durations and significantly increasing the carrier's risk of developing cancer over time. Indeed, infectious pathogens are modifiable cancer risk factors, and through this comprehensive review, we highlight the complex relationship between bacterial infections and the development of several cancer types. For this review, searches were performed on the PubMed, Embase, and Web of Science databases encompassing the entirety of 2022. Based on our investigation, we found several critical associations, of which some are causative: Porphyromonas gingivalis and Fusobacterium nucleatum are associated with periodontal disease, Salmonella spp., Clostridium perfringens, Escherichia coli, Campylobacter spp., and Shigella are associated with gastroenteritis. Helicobacter pylori infection is implicated in the etiology of gastric cancer, and persistent Chlamydia infections present a risk factor for the development of cervical carcinoma, especially in patients with the human papillomavirus (HPV) coinfection. Salmonella typhi infections are linked with gallbladder cancer, and Chlamydia pneumoniae infection is implicated in lung cancer, etc. This knowledge helps identify the adaptation strategies used by bacteria to evade antibiotic/antimicrobial therapy. The article also sheds light on the role of antibiotics in cancer treatment, the consequences of their use, and strategies for limiting antibiotic resistance. Finally, the dual role of bacteria in cancer development as well as in cancer therapy is briefly discussed, as this is an area that may help to facilitate the development of novel microbe-based therapeutics as a means of securing improved outcomes.

Inflammatory Monocytes Promote Granuloma-Mediated Control of Persistent Salmonella Infection

Persistent infections generally involve a complex balance between protective immunity and immunopathology. We used a murine model to investigate the role of inflammatory monocytes in immunity and host defense against persistent salmonellosis. Mice exhibit increased susceptibility to persistent infection when inflammatory monocytes cannot be recruited into tissues or when they are depleted at specific stages of persistent infection. Inflammatory monocytes contribute to the pathology of persistent salmonellosis and cluster with other cells in pathogen-containing granulomas. Depletion of inflammatory monocytes during the chronic phase of persistent salmonellosis causes regression of already established granulomas with resultant pathogen growth and spread in tissues. Thus, inflammatory monocytes promote granuloma-mediated control of persistent salmonellosis and may be key to uncovering new therapies for granulomatous diseases.

Activation of activator protein-1-fibroblast growth factor 21 signaling attenuates Cisplatin hepatotoxicity

Fibroblast growth factor (Fgf/FGF) 21, which plays important roles in sugar, lipid and energy metabolism, has been accepted as a mito-stress marker gene. We recently reported that FGF21 expression can be up-regulated via activation of aryl hydrocarbon receptor (AhR) or glucocorticoid receptor (GR) and that FGF21 plays important cytoprotective roles. Cisplatin (cis-diamminedichloroplatinum, CDDP) is a widely used chemotherapeutic drug. Numerous adverse effects including hepatotoxicity have been noted during CDDP therapy. It is known that CDDP can induce mitochondrial dysfunction. The studies were designed to determine the regulation of Fgf/FGF21 expression by CDDP, and to characterize the underlying mechanisms of its regulation, as well as to determine the impact of gain or loss of Fgf/FGF21 function on the progression of CDDP hepatotoxicity. Our results showed that CDDP and phorbol ester induced mRNA and protein expression of Fgf/FGF21 and β-Klotho, two essential components of Fgf21 signaling, in mouse livers and cultured mouse/human hepatocytes. Luciferase reporter assays and ChIP-qPCR assays demonstrated that the cJun-AP-1 activation is responsible for CDDP- and phorbol ester-induced Fgf/FGF21 expression. Such induction is abolished after cotreated with AP-1 inhibitor SR11302. In addition, CDDP produces more severe liver injury in Fgf21-null than wild-type mice. Pre-treatment of GR activator dexamethasone or AhR activator β-Naphthoflavone, both of which can induce Fgf21 expression, attenuated CDDP-induced hepatotoxicity in vivo and in vitro. In conclusion, Fgf/FGF21-β-Klotho signaling can be activated via AP-1 activation. Gain of Fgf/FGF21 function attenuates the progression of CDDP hepatotoxicity, which may be considered clinically to improve CDDP therapy.

Molecular determinants of peaceful coexistence versus invasiveness of non-Typhoidal Salmonella: Implications in long-term side-effects

The genus Salmonella represents a wide range of strains including Typhoidal and Non-Typhoidal Salmonella (NTS) isolates that exhibit illnesses of varied pathophysiologies. The more frequent NTS ensues a self-limiting enterocolitis with rare occasions of bacteremia or systemic infections. These self-limiting Salmonella strains are capable of subverting and dampening the host immune system to achieve a more prolonged survival inside the host system thus leading to chronic manifestations. Notably, emergence of new invasive NTS isolates known as invasive Non-Typhoidal Salmonella (iNTS) have worsened the disease burden significantly in some parts of the world. NTS strains adapt to attain persister phenotype intracellularly and cause relapsing infections. These chronic infections, in susceptible hosts, are also capable of causing diseases like IBS, IBD, reactive arthritis, gallbladder cancer and colorectal cancer. The present understanding of molecular mechanism of how these chronic infections are manifested is quite limited. The current work is an effort to review the prevailing knowledge emanating from a large volume of research focusing on various forms of NTS infections including those that cause localized, systemic and persistent disease. The review will further dwell into the understanding of how this pathogen contributes to the associated long term sequelae.

Association of Microbial Dysbiosis with Gallbladder Diseases Identified by Bile Microbiome Profiling

BACKGROUND

Cholecystitis is an important risk factor for gallbladder cancer, but the bile microbiome and its association with gallbladder disease has not been investigated fully. We aimed to analyze the bile microbiome in normal conditions, chronic cholecystitis, and gallbladder cancer, and to identify candidate bacteria that play an important role in gallbladder carcinogenesis.

METHODS

We performed metagenome sequencing on bile samples of 10 healthy individuals, 10 patients with chronic cholecystitis, and 5 patients with gallbladder cancer, and compared the clinical, radiological, and pathological characteristics of the participants.

RESULTS

No significant bacterial signal was identified in the normal bile. The predominant dysbiotic bacteria in both chronic cholecystitis and gallbladder cancer were those belonging to the Enterobacteriaceae family. Klebsiella increased significantly in the order of normal, chronic cholecystitis, and gallbladder cancer. Patients with chronic cholecystitis and dysbiotic microbiome patterns had larger gallstones and showed marked epithelial atypia, which are considered as precancerous conditions.

CONCLUSION

We investigated the bile microbiome in normal, chronic cholecystitis, and gallbladder cancer. We suggest possible roles of Enterobacteriaceae, including Klebsiella, in gallbladder carcinogenesis. Our findings reveal a possible link between a dysbiotic bile microbiome and the development of chronic calculous cholecystitis and gallbladder cancer.

Autoimmune-prone lpr mice exhibit a prolonged but lethal infection with an attenuated Salmonella Typhimurium strain

Autoimmunity can potentially pre-dispose to, exacerbate or ameliorate pathogenic infections. The current study was designed to compare and understand the infection outcomes with Salmonella enterica serovar Typhimurium ATCC 14028s (S. Typhimurium) wild type (WT) and attenuated ΔrpoS strains, in autoimmune-prone lpr mice. C57BL/6 (B6) and B6/lpr (lpr) 6-8 weeks old mice were orally infected with S. Typhimurium WT and ΔrpoS strains. Disease outcomes were assessed with respect to survival, organ bacterial load, tissue damage and inflammation in infected mice. The acute infection stage (day 4) was examined and compared to the later stages (up to day 12) post ΔrpoS infection. S. Typhimurium WT exhibited an acute and lethal infection in both B6 and lpr mice. However, the ΔrpoS strain exhibited prolonged infection with reduced mortality in B6 mice but complete mortality in lpr mice. During late infection, bacterial load and serum IFNγ levels were higher in the ΔrpoS strain infected lpr mice compared to B6 mice. The ΔrpoS strain infected lpr mice also exhibited greater bacterial faecal shedding and greater tissue histopathological changes. Interestingly, ΔrpoS-infected B6 mice displayed minimal microbial load in the brain; however, sustained brain bacterial load was observed in ΔrpoS-infected lpr mice, corresponding to abnormal gait. Overall, S. Typhimurium ΔrpoS is competent in establishing infection but compromised in sustaining it. Nonetheless, lpr mice are less efficient in controlling this attenuated infection. The findings from the study demonstrate that genetic pre-disposition to autoimmunity is sufficient for greater host susceptibility to infection by attenuated S. Typhimurium strains.

Understanding Infection-Induced Thrombosis: Lessons Learned From Animal Models

Thrombosis is a common consequence of infection that is associated with poor patient outcome. Nevertheless, the mechanisms by which infection-associated thrombosis is induced, maintained and resolved are poorly understood, as is the contribution thrombosis makes to host control of infection and pathogen spread. The key difference between infection-associated thrombosis and thrombosis in other circumstances is a stronger inflammation-mediated component caused by the presence of the pathogen and its products. This inflammation triggers the activation of platelets, which may accompany damage to the endothelium, resulting in fibrin deposition and thrombus formation. This process is often referred to as thrombo-inflammation. Strikingly, despite its clinical importance and despite thrombi being induced to many different pathogens, it is still unclear whether the mechanisms underlying this process are conserved and how we can best understand this process. This review summarizes thrombosis in a variety of models, including single antigen models such as LPS, and infection models using viruses and bacteria. We provide a specific focus on Salmonella Typhimurium infection as a useful model to address all stages of thrombosis during infection. We highlight how this model has helped us identify how thrombosis can appear in different organs at different times and thrombi be detected for weeks after infection in one site, yet largely be resolved within 24 h in another. Furthermore, we discuss the observation that thrombi induced to Salmonella Typhimurium are largely devoid of bacteria. Finally, we discuss the value of different therapeutic approaches to target thrombosis, the potential importance of timing in their administration and the necessity to maintain normal hemostasis after treatment. Improvements in our understanding of these processes can be used to better target infection-mediated mechanisms of thrombosis.

Establishment of Chronic Typhoid Infection in a Mouse Carriage Model Involves a Type 2 Immune Shift and T and B Cell Recruitment to the Gallbladder

The existence of chronic typhoid carriers has been in the public eye for over 100 years in part because of the publicity around Typhoid Mary. Additionally, it has been known for decades that the gallbladder is the main site of persistence and recently that gallstones play a key role. Despite this, very little is known about the physiological conditions that allow Salmonella enterica serovar Typhi to persist in the gallbladder. In this study, we analyze the transcriptional profile of the gallbladder in a mouse model of chronic carriage. We found a shift from an early proinflammatory immune response toward a later anti-inflammatory response, which could explain the stalemate that allows Salmonella persistence. Interestingly, we found a 10-fold increase in the number of Salmonella-specific T cells in mice with gallstones. This work moves us closer to understanding the mechanistic basis of chronic carriage, with a goal toward eradication of the disease.

Typhoid fever, caused primarily by Salmonella enterica serovar Typhi (S. Typhi), is a life-threatening systemic disease responsible for significant morbidity and mortality worldwide. Three to 5% of individuals infected with S. Typhi become chronic carriers due to bacterial persistence in the gallbladder. We have demonstrated that Salmonella forms biofilms on gallstones to establish gallbladder carriage. However, an in-depth molecular understanding of chronic carriage in the gallbladder, from the perspective of both the pathogen and host, is poorly defined. To examine the dynamics of the gallbladder in response to Salmonella infection, we performed transcriptional profiling in the mouse gallbladder at early (7 days) and chronic (21 days) time points. Transcriptome sequencing (RNA-Seq) revealed a shift from a Th1 proinflammatory response at 7 days postinfection (dpi) toward an anti-inflammatory Th2 response by 21 dpi, characterized by increased levels of immunoglobulins and the Th2 master transcriptional regulator, GATA3. Additionally, bioinformatic analysis predicted the upstream regulation of characteristic Th2 markers, including interleukin-4 (IL-4) and Stat6. Immunohistochemistry and fluorescence-activated cell sorter (FACS) analysis confirmed a significant increase in lymphocytes, including T and B cells, at 21 dpi in mice with gallstones. Interestingly, the levels of Salmonella-specific CD4 T cells were 10-fold higher in the gallbladder of mice with gallstones at 21 dpi. We speculate that the biofilm state allows Salmonella to resist the initial onslaught of the Th1 inflammatory response, while yet undefined events influence a switch in the host immunity toward a more permissive type 2 response, enabling the establishment of chronic infection.

Pathoadaptive Alteration of Salmonella Biofilm Formation in Response to the Gallbladder Environment

Typhoid fever, a human-specific disease, is primarily caused by the pathogen Salmonella enterica serovar Typhi. It is estimated that 3 to 5% of people infected with typhoid fever become chronic carriers. Studies have demonstrated that a mechanism of chronic carriage involves biofilm formation on gallstone surfaces. In the course of a previous study using a chronic carriage mouse model, a Salmonella enterica serovar Typhimurium isolate was recovered from a mouse gallstone that exhibited a 2-fold increase in biofilm formation over the wild type. In order to identify the gene(s) responsible for the phenotype, the genomic sequences of this isolate and others were determined and compared. These sequences identified single nucleotide polymorphisms (SNPs) in 14 genes. Mutations in the most promising candidates, envZ and rcsB, were created, but neither showed increased biofilm-forming ability separately or in combination. The hyperbiofilm isolate did, however, present variations in cellular appendages observable using different techniques and a preferential binding to cholesterol. The isolate was also examined for systemic virulence and the ability to colonize the gallbladder/gallstones in a mouse model of chronic infection, demonstrating a systemic virulence defect and decreased gallbladder/gallstone colonization. Finally, to determine if the appearance of hyperbiofilm isolates could be replicated in vitro and if this was a common event, wild-type Salmonella spp. were grown long term in vitro under gallbladder-mimicking conditions, resulting in a high proportion of isolates that replicated the hyperbiofilm phenotype of the original isolate. Thus, Salmonella spp. acquire random mutations under the gallbladder/gallbladder-simulating conditions that may aid persistence but negatively affect systemic virulence.IMPORTANCE Chronic carriers are the main reservoirs for the spread of typhoid fever in regions of endemicity. Salmonella Typhi forms biofilms on gallstones in order to persist. A strain with enhanced biofilm-forming ability was recovered after a nine-month chronic-carriage mouse study. After sequencing this strain and recreating some of the mutations, we could not duplicate the phenotype. The isolate did show a difference in flagella, a preference to bind to cholesterol, and a systemic virulence defect. Finally, gallbladder conditions were simulated in vitro After 60 days, there was a 4.5-fold increase in hyperbiofilm isolates when a gallstone was present. These results indicate that Salmonella spp. can undergo genetic changes that improve persistence in gallbladder albeit at the cost of decreased virulence.

Terminal Deoxynucleotidyl Transferase Is Not Required for Antibody Response to Polysaccharide Vaccines against Streptococcus pneumoniae and Salmonella enterica Serovar Typhi

B cell antigen receptor (BCR) diversity increases by several orders of magnitude due to the action of terminal deoxynucleotidyl transferase (TdT) during V(D)J recombination. Unlike adults, infants have limited BCR diversity, in part due to reduced expression of TdT. Since human infants and young mice respond poorly to polysaccharide vaccines, such as the pneumococcal polysaccharide vaccine Pneumovax23 and Vi polysaccharide (ViPS) of Salmonella enterica serovar Typhi, we tested the contribution of TdT-mediated BCR diversity in response to these vaccines. We found that TdT^+/- and TdT^-/- mice generated comparable antibody responses to Pneumovax23 and survived Streptococcus pneumoniae challenge. Moreover, passive immunization of B cell-deficient mice with serum from Pneumovax23-immunized TdT^+/- or TdT^-/- mice conferred protection. TdT^+/- and TdT^-/- mice generated comparable levels of anti-ViPS antibodies and antibody-dependent, complement-mediated bactericidal activity against S Typhi in vitro To test the protective immunity conferred by ViPS immunization in vivo, TdT^+/- and TdT^-/- mice were challenged with a chimeric Salmonella enterica serovar Typhimurium strain expressing ViPS, since mice are nonpermissive hosts for S Typhi infection. Compared to their unimmunized counterparts, immunized TdT^+/- and TdT^-/- mice challenged with ViPS-expressing S Typhimurium exhibited a significant reduction in the bacterial burden and liver pathology. These data suggest that the impaired antibody response to the Pneumovax23 and ViPS vaccines in the young is not due to limited TdT-mediated BCR diversification.

An Unmutated IgM Response to the Vi Polysaccharide of Salmonella Typhi Contributes to Protective Immunity in a Murine Model of Typhoid

T cell-dependent B cell responses typically develop in germinal centers. Abs generated during such responses are isotype switched and have a high affinity to the Ag because of somatic hypermutation of Ab genes. B cell responses to purified polysaccharides are T cell independent and do not result in the formation of bona fide germinal centers, and the dominant Ab isotype produced during such responses is IgM with very few or no somatic mutations. Activation-induced cytidine deaminase (AID) is required for both somatic hypermutation and Ig isotype switching in humans and mice. To test the extent to which unmutated polysaccharide-specific IgM confers protective immunity, we immunized wildtype and AID^-/- mice with either heat-killed Salmonella enterica serovar Typhi (S. Typhi) or purified Vi polysaccharide (ViPS). We found that wildtype and AID^-/- mice immunized with heat-killed S. Typhi generated similar anti-ViPS IgM responses. As expected, wildtype, but not AID^-/- mice generated ViPS-specific IgG. However, the differences in the Ab-dependent killing of S. Typhi mediated by the classical pathway of complement activation were not statistically significant. In ViPS-immunized wildtype and AID^-/- mice, the ViPS-specific IgM levels and S. Typhi bactericidal Ab titers at 7 but not at 28 d postimmunization were also comparable. To test the protective immunity conferred by these immunizations, mice were challenged with a chimeric S. Typhimurium strain expressing ViPS. Compared with their naive counterparts, immunized wildtype and AID^-/- mice exhibited significantly reduced bacterial burden regardless of the route of infection. These data indicate that an unmutated IgM response to ViPS contributes to protective immunity to S. Typhi.

Effect of Various Inoculum Levels of Multidrug-Resistant Salmonella enterica Serovar Heidelberg (2011 Ground Turkey Outbreak Isolate) on Cecal Colonization, Dissemination to Internal Organs, and Deposition in Skeletal Muscles of Commercial Turkeys after Experimental Oral Challenge

Salmonella enterica serovar Heidelberg (S. Heidelberg) is a major foodborne pathogen colonizing poultry. The pathogen is associated with a significant number of foodborne outbreaks through contaminated poultry meat, including turkeys. Recently, multidrug-resistant (MDR) strains of S. Heidelberg have emerged as a threat to human public health in the United States. The objective of this study was to determine the cecal colonization, dissemination to internal organs, and the potential for skeletal muscle deposition of an MDR S. Heidelberg isolate from the 2011 ground turkey outbreak in the United States after the experimental oral challenge of poults (young turkeys) and adult turkey hens. In the poult study, two separate experiments using day-old, straight-run, commercial hybrid converter poults were randomly assigned to five challenge groups (0, 10∧2, 10∧4, 10∧6, 10∧8 CFU groups; 12 poults/group; N = 60/experiment) and a week after, treatment groups were challenged separately with 0-, 2-, 4-, 6-, and 8- log10 CFU of S. Heidelberg orally. After 14 days post-challenge, the poults were euthanized, and samples were collected to determine MDR S. Heidelberg colonization in the cecum, dissemination to liver and spleen, and deposition in the thigh, drumstick, and breast muscles. A similar experimental design was followed for the adult turkey hens. In two separate experiments, 11-week-old commercial Hybrid Converter turkey hens (4 hens/group; N = 20/experiment) were challenged with MDR S. Heidelberg and on day 16 post-challenge, birds were euthanized and samples were collected to determine Salmonella populations in the samples. The results indicated that, in turkey poults, the recovery of MDR S. Heidelberg was highest in the cecum followed by spleen, liver, thigh, drumstick, and breast. All tested inoculum levels resulted in more than 3.5 log10 CFU/g colonization in the poult cecum. The cecal colonization, dissemination to internal organs, and tissue deposition of MDR S. Heidelberg were high in poults. The pathogen recovery from the cecum of adult turkey hens ranged from 37.5 to 62.5% in the challenge groups. The results signify the importance of controlling MDR S. Heidelberg in turkeys at the farm level to improve the safety of turkey products.

Presence of Salmonella AvrA in colorectal tumor and its precursor lesions in mouse intestine and human specimens

Evidence directly supporting an association between Salmonella infection and colorectal cancer in human subjects is sparse. It has been well recognized that Salmonella infection increases the risk of gallbladder cancer. AvrA, a bacterial protein from Salmonella enterica, plays a crucial role in establishing chronic infection. To our knowledge, the presence of the bacterial AvrA has never been studied in human samples. Here, we demonstrated the presence and cellular localization of AvrA in inflamed, colorectal tumor and its precursor lesions, using both animal experimental infection models and human clinical specimens. We performed a newly developed AvrA serological assay and to determine the presence of anti-Salmonella AvrA antibody in chronic infected mouse serum samples. Further, we tested the presence of AvrA gene in healthy human fecal samples, in order to advance etiological studies of Salmonella AvrA in human population. Our study suggests a potential role of this bacterial protein in human colorectal cancer. Moreover, our new serological assay may serve a useful tool to identify individuals at increased risk for colorectal cancer.

Bile Acids Function Synergistically To Repress Invasion Gene Expression in Salmonella by Destabilizing the Invasion Regulator HilD

Salmonella spp. are carried by and can acutely infect agricultural animals and humans. After ingestion, salmonellae traverse the upper digestive tract and initiate tissue invasion of the distal ileum, a virulence process carried out by the type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1). Salmonellae coordinate SPI-1 expression with anatomical location via environmental cues, one of which is bile, a complex digestive fluid that causes potent repression of SPI-1 genes. The individual components of bile responsible for SPI-1 repression have not been previously characterized, nor have the bacterial signaling processes that modulate their effects been determined. Here, we characterize the mechanism by which bile represses SPI-1 expression. Individual bile acids exhibit repressive activity on SPI-1-regulated genes that requires neither passive diffusion nor OmpF-mediated entry. By using genetic methods, the effects of bile and bile acids were shown to require the invasion gene transcriptional activator hilD and to function independently of known upstream signaling pathways. Protein analysis techniques showed that SPI-1 repression by bile acids is mediated by posttranslational destabilization of HilD. Finally, we found that bile acids function synergistically to achieve the overall repressive activity of bile. These studies demonstrate a common mechanism by which diverse environmental cues (e.g., certain short-chain fatty acids and bile acids) inhibit SPI-1 expression. These data provide information relevant to Salmonella pathogenesis during acute infection in the intestine and during chronic infection of the gallbladder and inform the basis for development of therapeutics to inhibit invasion as a means of repressing Salmonella pathogenicity.

Suppurative Granulomatous Cholecystitis in a Pediatric Chronic Carrier with Salmonella enterica serotype Typhi: A Case Report and Review of Literature

Bacterial infection of Salmonella enterica serotype Typhi is rare in the United States but endemic in many developing countries. Approximately 3-5% of patients become chronic asymptomatic carriers. We describe an atypical presentation of S. enterica serotype Typhi infection in a 10-year-old male, whose cholecystechtomy and bile culture revealed chronic carrier status despite negative stool tests and the absence of gallstones. The gallbladder showed marked thickening of the wall with an intense suppurative granulomatous reaction.

Disease tolerance mediated by microbiome E. coli involves inflammasome and IGF-1 signaling

Infections and inflammation can lead to cachexia and wasting of skeletal muscle and fat tissue by as yet poorly understood mechanisms. We observed that gut colonization of mice by a strain of Escherichia coli prevents wasting triggered by infections or physical damage to the intestine. During intestinal infection with the pathogen Salmonella Typhimurium or pneumonic infection with Burkholderia thailandensis, the presence of this E. coli did not alter changes in host metabolism, caloric uptake, or inflammation but instead sustained signaling of the insulin-like growth factor 1/phosphatidylinositol 3-kinase/AKT pathway in skeletal muscle, which is required for prevention of muscle wasting. This effect was dependent on engagement of the NLRC4 inflammasome. Therefore, this commensal promotes tolerance to diverse diseases.

Salmonella chronic carriage: epidemiology, diagnosis, and gallbladder persistence

Typhoid (enteric fever) remains a major cause of morbidity and mortality worldwide, causing over 21 million new infections annually, with the majority of deaths occurring in young children. Because typhoid fever-causing Salmonella have no known environmental reservoir, the chronic, asymptomatic carrier state is thought to be a key feature of continued maintenance of the bacterium within human populations. Despite the importance of this disease to public health, our understanding of the molecular mechanisms that catalyze carriage, as well as our ability to reliably identify and treat the Salmonella carrier state, have only recently begun to advance.

The conspiracy of autophagy, stress and inflammation in acute pancreatitis

PURPOSE OF REVIEW

Acute pancreatitis is associated with alcohol abuse, gallstones and bacterial infection. Its basic cause is tissue destruction accompanied by an innate immune response, which induces epithelial stress pathways. Recent studies have focused on some of the integral cellular pathways shared between multiple pancreatitis models that also suggest new approaches to detection and treatment.

RECENT FINDINGS

Several models of pancreatitis have been associated with stress responses, such as endoplasmic reticulum and oxidative stress together with the induction of a defective autophagic pathway. Recent evidence reinforces the critical role of these cellular processes in pancreatitis. A member of the toll-like receptor family, toll-like receptor 4, which is known to contribute to disease pathology in many models of experimental pancreatitis, has been found to be a promising target for treatment of pancreatitis. Interestingly, a direct activator of toll-like receptor 4, the bacterial cell wall component in gram-negative bacteria lipopolysaccharide, contributes to the onset and severity of disease when combined with additional stressors, such as chronic alcohol feeding; however, recent studies have shown that acute infection of mice with live bacteria is alone sufficient to induce acute pancreatitis.

SUMMARY

In the last several months, the convergent roles of acinar cell stress, autophagy and proinflammatory signaling initiated by the toll-like receptors have been emphatically reinforced in the onset of acute pancreatitis.

Same species, different diseases: how and why typhoidal and non-typhoidal Salmonella enterica serovars differ

Human infections by the bacterial pathogen Salmonella enterica represent major disease burdens worldwide. This highly ubiquitous species consists of more than 2600 different serovars that can be divided into typhoidal and non-typhoidal Salmonella (NTS) serovars. Despite their genetic similarity, these two groups elicit very different diseases and distinct immune responses in humans. Comparative analyses of the genomes of multiple Salmonella serovars have begun to explain the basis of the variation in disease manifestations. Recent advances in modeling both enteric fever and intestinal gastroenteritis in mice will facilitate investigation into both the bacterial- and host-mediated mechanisms involved in salmonelloses. Understanding the genetic and molecular mechanisms responsible for differences in disease outcome will augment our understanding of Salmonella pathogenesis, host immunity, and the molecular basis of host specificity. This review outlines the differences in epidemiology, clinical manifestations, and the human immune response to typhoidal and NTS infections and summarizes the current thinking on why these differences might exist.