Comparative transcriptional profiling of the early host response to infection by typhoidal and non-typhoidal Salmonella serovars in human intestinal organoids

Salmonella enterica represents over 2500 serovars associated with a wide-ranging spectrum of disease; from self-limiting gastroenteritis to invasive infections caused by non-typhoidal serovars (NTS) and typhoidal serovars, respectively. Host factors strongly influence infection outcome as malnourished or immunocompromised individuals can develop invasive infections from NTS, however, comparative analyses of serovar-specific host responses have been constrained by reliance on limited model systems. Here we used human intestinal organoids (HIOs), a three-dimensional “gut-like” in vitro system derived from human embryonic stem cells, to elucidate similarities and differences in host responses to NTS and typhoidal serovars. HIOs discriminated between the two most prevalent NTS, Salmonella enterica serovar Typhimurium (STM) and Salmonella enterica serovar Enteritidis (SE), and typhoidal serovar Salmonella enterica serovar Typhi (ST) in epithelial cell invasion, replication and transcriptional responses. Pro-inflammatory signaling and cytokine output was reduced in ST-infected HIOs compared to NTS infections, consistent with early stages of NTS and typhoidal diseases. While we predicted that ST would induce a distinct transcriptional profile from the NTS strains, more nuanced expression profiles emerged. Notably, pathways involved in cell cycle, metabolism and mitochondrial functions were downregulated in STM-infected HIOs and upregulated in SE-infected HIOs. These results correlated with suppression of cellular proliferation and induction of host cell death in STM-infected HIOs and in contrast, elevated levels of reactive oxygen species production in SE-infected HIOs. Collectively, these results suggest that the HIO model is well suited to reveal host transcriptional programming specific to infection by individual Salmonella serovars, and that individual NTS may provoke unique host epithelial responses during intestinal stages of infection.

Salmonella enterica is the major causative agent of bacterial infections associated with contaminated food and water. Salmonella enterica consists of over 2500 serovars of which Typhimurium (STM), Enteritidis (SE) and Typhi (ST) are the three major serovars with medical relevance to humans. These serovars elicit distinctive immune responses and cause different diseases in humans, including self-limiting diarrhea, gastroenteritis and typhoid fever. Differences in the human host response to these serovars are likely to be a major contributing factor to distinct disease outcomes but are not well characterized, possibly due to the limitations of human-derived physiological infection models. Distinct from immortalized epithelial cell culture models, human intestinal organoids (HIOs) are three-dimensional structures derived from embryonic stem cells that differentiate into intestinal mesenchymal and epithelial cells, mirroring key organizational aspects of the intestine. In this study, we used HIOs to monitor transcriptional changes during early stages of STM, SE and ST infection. Our comparative analysis showed that HIO inflammatory responses are the dominant response in all infections, but ST infection induces the weakest upregulation of inflammatory mediators relative to the other serovars. In addition, we identified several cellular processes, including cell cycle and mitochondrial functions, that were inversely regulated between STM and SE infection despite these serovars causing similar localized intestinal infection in humans. Our findings reinforce HIOs as an emerging model system to study Salmonella serovar infection and define global host transcriptional response profiles as a foundation for understanding human infection outcomes.

Cellular Activity of Salmonella Typhimurium ArtAB Toxin and Its Receptor-Binding Subunit

Salmonellosis is among the most reported foodborne illnesses in the United States. The Salmonellaenterica Typhimurium DT104 phage type, which is associated with multidrug-resistant disease in humans and animals, possesses an ADP-ribosylating toxin called ArtAB. Full-length artAB has been found on a number of broad-host-range non-typhoidal Salmonella species and serovars. ArtAB is also homologous to many AB₅ toxins from diverse Gram-negative pathogens, including cholera toxin (CT) and pertussis toxin (PT), and may be involved in Salmonella pathogenesis, however, in vitro cellular toxicity of ArtAB has not been characterized. artAB was cloned into E. coli and initially isolated using a histidine tag (ArtABHIS) and nickel chromatography. ArtABHIS was found to bind to African green monkey kidney epithelial (Vero) cells using confocal microscopy and to interact with glycans present on fetuin and monosialotetrahexosylganglioside (GM1) using ELISA. Untagged, or native, holotoxin (ArtAB), and the pentameric receptor-binding subunit (ArtB) were purified from E. coli using fetuin and d-galactose affinity chromatography. ArtAB and ArtB metabolic and cytotoxic activities were determined using Vero and Chinese hamster ovary (CHO) epithelial cells. Vero cells were more sensitive to ArtAB, however, incubation with both cell types revealed only partial cytotoxicity over 72 h, similar to that induced by CT. ArtAB induced a distinctive clustering phenotype on CHO cells over 72 h, similar to PT, and an elongated phenotype on Vero cells, similar to CT. The ArtB binding subunit alone also had a cytotoxic effect on CHO cells and induced morphological rounding. Results indicate that this toxin induces distinctive cellular outcomes. Continued biological characterization of ArtAB will advance efforts to prevent disease caused by non-typhoidal Salmonella.

How Pathogens Feel and Overcome Magnesium Limitation When in Host Tissues

Host organisms utilize nutritional immunity to limit the availability of nutrients essential to an invading pathogen. Nutrients may include amino acids, nucleotide bases, and transition metals, the essentiality of which varies among pathogens. The mammalian macrophage protein Slc11a1 (previously Nramp1) mediates resistance to several intracellular pathogens. Slc11a1 is proposed to restrict growth of Salmonella enterica serovar Typhimurium in host tissues by causing magnesium deprivation. This is intriguing because magnesium is the most abundant divalent cation in all living cells. A pathogen's response to factors such as Slc11a1 that promote nutritional immunity may therefore reflect what the pathogen 'feels' in its cytoplasm, rather than the nutrient concentration in host cell compartments.

Infection-generated electric field in gut epithelium drives bidirectional migration of macrophages

Many bacterial pathogens hijack macrophages to egress from the port of entry to the lymphatic drainage and/or bloodstream, causing dissemination of life-threatening infections. However, the underlying mechanisms are not well understood. Here, we report that Salmonella infection generates directional electric fields (EFs) in the follicle-associated epithelium of mouse cecum. In vitro application of an EF, mimicking the infection-generated electric field (IGEF), induces directional migration of primary mouse macrophages to the anode, which is reversed to the cathode upon Salmonella infection. This infection-dependent directional switch is independent of the Salmonella pathogenicity island 1 (SPI-1) type III secretion system. The switch is accompanied by a reduction of sialic acids on glycosylated surface components during phagocytosis of bacteria, which is absent in macrophages challenged by microspheres. Moreover, enzymatic cleavage of terminally exposed sialic acids reduces macrophage surface negativity and severely impairs directional migration of macrophages in response to an EF. Based on these findings, we propose that macrophages are attracted to the site of infection by a combination of chemotaxis and galvanotaxis; after phagocytosis of bacteria, surface electrical properties of the macrophage change, and galvanotaxis directs the cells away from the site of infection.

Salmonella spv locus suppresses host innate immune responses to bacterial infection

Salmonella enterica serovar typhimurium (S. typhimurium) is globally distributed and causes massive morbidity and mortality in humans and animals. S. typhimurium carries Salmonella plasmid virulence (spv) locus, which is highly conserved and closely related to bacterial pathogenicity, while its exact role in host immune responses during infection remains to be elucidated. To counteract the invaders, the host has evolved numerous strategies, among which the innate immunity and autophagy act as the first defense. Recently, zebrafish has been universally accepted as a valuable and powerful vertebrate model in analyzing bacteria-host interactions. To investigate whether spv locus enhances the virulence of Salmonella by exerting an effect on the host early defense, zebrafish larvae were employed in this study. LD₅₀ of S. typhimurium to zebrafish larvae and bacterial dissemination were analyzed. Sudan black B and neutral red staining were performed to detect the responses of neutrophils and macrophages to Salmonella infection. Autophagy agonist Torin1 and inhibitor Chloroquine were used to interfere in autophagic flux, and the protein level of Lc3 and p62 were measured by western blotting. Results indicated that spv locus could decrease the LD₅₀ of S. typhimurium to zebrafish larvae, accelerate the reproduction and dissemination of bacteria by inhibiting the function of neutrophils and macrophages. Moreover, spv locus restrained the formation of autophagosomes in the earlier stage of autophagy. These findings suggested the virulence of spv locus involving in suppressing host innate immune responses for the first time, which shed new light on the role of spv operon in Salmonella pathogenicity.

Interferon-γ in Salmonella pathogenesis: New tricks for an old dog

Salmonella enterica is a facultative intracellular bacterium that is the leading cause of food borne illnesses in humans. The cytokine IFN-γ has well-established antibacterial properties against Salmonella and other intracellular microbes, for example its capacity to activate macrophages, promote phagocytosis, and destroy phagocytosed microbes by free radical-driven toxification of phagosomes. But IFN-γ induces the expression of hundreds of uncharacterized genes, suggesting that this cytokine deploys additional antimicrobial strategies that await discovery. Recently, one such mechanism, mediated by a family of IFN-inducible small GTPases called Guanylate Binding Proteins (GBPs) has been uncovered. GBPs were shown to facilitate the pyroptotic clearance of Salmonella from infected macrophages by rupturing the protective intracellular vacuole this microbe forms around itself. Once this protective vacuole is lost, exposed Salmonella activates pyroptosis, which destroys the infected cell. In this review, we summarize such emerging roles for IFN-γ in restricting Salmonella pathogenesis.

Salmonella plasmid virulence gene spvB enhances bacterial virulence by inhibiting autophagy in a zebrafish infection model

Salmonella enterica serovar typhimurium (S. typhimurium) is a facultative intracellular pathogen that can cause gastroenteritis and systemic infection in a wide range of hosts. Salmonella plasmid virulence gene spvB is closely related to bacterial virulence in different cells and animal models, and the encoded protein acts as an intracellular toxin required for ADP-ribosyl transferase activity. However, until now there is no report about the pathogenecity of spvB gene on zebrafish. Due to the outstanding advantages of zebrafish in analyzing bacteria-host interactions, a S. typhimurium infected zebrafish model was set up here to study the effect of spvB on autophagy and intestinal pathogenesis in vivo. We found that spvB gene could decrease the LD50 of S. typhimurium, and the strain carrying spvB promoted bacterial proliferation and aggravated the intestinal damage manifested by the narrowed intestines, fallen microvilli, blurred epithelium cell structure and infiltration of inflammatory cells. Results demonstrated the enhanced virulence induced by spvB in zebrafish. In spvB-mutant strain infected zebrafish, the levels of Lc3 turnover and Beclin1 expression increased, and the double-membraned autophagosome structures were observed, suggesting that spvB can inhibit autophagy activity. In summary, our results indicate that S. typhimurium strain containing spvB displays more virulence, triggering an increase in bacterial survival and intestine injuries by suppressing autophagy for the first time. This model provides novel insights into the role of Salmonella plasmid virulence gene in bacterial pathogenesis, and can help to further elucidate the relationship between bacteria and host immune response.

Thymic function is maintained during Salmonella-induced atrophy and recovery

Thymic atrophy is a frequent consequence of infection with bacteria, viruses, and parasites and is considered a common virulence trait between pathogens. Multiple reasons have been proposed to explain this atrophy, including premature egress of immature thymocytes, increased apoptosis, or thymic shutdown to prevent tolerance to the pathogen from developing. The severe loss in thymic cell number can reflect an equally dramatic reduction in thymic output, potentially reducing peripheral T cell numbers. In this study, we examine the relationship between systemic Salmonella infection and thymic function. During infection, naive T cell numbers in peripheral lymphoid organs increase. Nevertheless, this occurs despite a pronounced thymic atrophy caused by viable bacteria, with a peak 50-fold reduction in thymocyte numbers. Thymic atrophy is not dependent upon homeostatic feedback from peripheral T cells or on regulation of endogenous glucocorticoids, as demonstrated by infection of genetically altered mice. Once bacterial numbers fall, thymocyte numbers recover, and this is associated with increases in the proportion and proliferation of early thymic progenitors. During atrophy, thymic T cell maturation is maintained, and single-joint TCR rearrangement excision circle analysis reveals there is only a modest fall in recent CD4(+) thymic emigrants in secondary lymphoid tissues. Thus, thymic atrophy does not necessarily result in a matching dysfunctional T cell output, and thymic homeostasis can constantly adjust to systemic infection to ensure that naive T cell output is maintained.

D-Lactic acidosis 25 years after bariatric surgery due to Salmonella enteritidis

D-Lactic acidosis is a rare complication that occurs in patients with short bowel syndrome due to surgical intestine resection for treatment of obesity. The clinical presentation is characterized by neurologic symptoms and high anion gap metabolic acidosis. The incidence of this syndrome is unknown, probably because of misdiagnosis and sometimes symptoms may be incorrectly attributed to other causes. Therapy is based on low carbohydrate diet, sodium bicarbonate intravenous, rehydratation, antiobiotics, and probiotics that only produce L-lactate. In the case we describe, D-lactic acidosis encephalopathy occurred 25 y after bypass jejunoileal, due to Salmonella enteriditis infection.

Clinical features of gastrointestinal salmonellosis in children in Bangkok, Thailand

This retrospective descriptive study was conducted at Queen Sirikit National Institute of Child Health (QSNICH), Bangkok, Thailand to describe the clinical features of gastrointestinal salmonellosis in children. The medical records of 134 patients admitted to QSNICH in 2009 who had a positive stool culture for Salmonella spp were reviewed. Demographic, clinical, laboratory, treatment, culture and antimicrobial sensitivity data were collected and analyzed. The mean age of the patients was 22.9 months (range 0.5 to 158 months); 76.9% were < 2 years old. The male to female ratio was 1.5:1. Salmonella B was most commonly found serogroup (47%). The common clinical manifestations included diarrhea (99.3%), fever (93.3%), dehydration (64.9%) and nausea/vomiting (48.5%). Most of the Salmonella isolates were sensitive to a fluoroquinolone and many were sensitive to Cotrimoxazole, but few were sensitive to ampicillin. There were no significant differences in the clinical manifestations and drug sensitivities of the different Salmonella serogroups, except convulsions were more common in Salmonella E infected patients (p = 0.04) and more Salmonella C isolates were sensitive to ampicillin (p = 0.04). There was no significant correlation between clinical course and antimicrobial treatment, except the duration of diarrhea was significantly longer in patients who received antimicrobial treatment (mean 6.1, SD 4.7 days vs mean 4.2, SD 2.1 days) (p = 0.03). Three patients had Salmonella bacteremia. Three patients died but not directly due to Salmonella infection.

The renal cyst infection caused by Salmonella enteritidis in a patient with autosomal dominant polycystic kidney disease: how did this pathogen come into the renal cysts?

A 40-year-old Japanese man was admitted to our hospital for investigation of fever and right flank pain starting after watery diarrhea. Salmonella enteritidis was cultured from samples of stool and blood. Although his diarrhea subsided soon, high fever persisted and flank pain got worse. Magnetic resonance imaging (MRI) revealed four areas of abnormal intensity in renal cysts and computed tomography showed the same findings. Renal cysts infection was diagnosed. After ultrasound-guided aspiration of these cysts, his fever subsided. Culture of each aspirate grew Salmonella enteritidis. Although the route of cyst infection in ADPKD generally remains unclear, the clinical course of our patient may indicate that gastrointestinal tract infection progressed to renal cyst infection when bacteremia occurred due to bacterial translocation.

[Genetic mechanisms of Salmonella enteritidis biodiversity and clinical features of salmonellosis]

AIM

To assess prevalence of fragments of Escherichia coli pathogenicity islands in Salmonella enteritidis strains as well as to study clinical signs of disease caused by these strains in adults.

MATERIALS AND METHODS

Ninety-six patients with salmonellosis were studied. Ninety strains of S. enteritidis were isolated and tested by PCR for the presence of genes associated with pathogenicity islands of E. coli: hlyA, hlyB, sfaG, and sfaA.

RESULTS

It was determined that DNA fragments homologous to pathogenicity islands of E. coli were present in 87 (96.7%) of S. enteritidis clinical isolates. Disease caused by Salmonella strains which possess only sfaG was mostly mild--7 (33.3%), whereas strains which had sfaG with fragments of hlyA and/or hlyB caused severe disease--7 (50%). sfaA fragments were found mostly in combination with other genes. In such cases the disease was mostly severe--6 (42.8%).

CONCLUSION

Correlation between presence of E. coli pathogenicity islands in Salmonella spp., their antibiotic resistance and severity of infection was established.

Cases of Salmonella Urbana in Finland, the Czech Republic and Latvia, January-February 2010

A cluster of 14 cases of Salmonella Urbana cases in Finland, the Czech Republic and Latvia were identified in January-February, 2010. The majority of cases (11) were male and children under 16 years of age. The investigation is currently ongoing and comparison of pulsed-field gel electrophoresis (PFGE) profiles of the isolates suggests that the cases may have a common source of infection.

First report of a Salmonella enterica serovar Weltevreden outbreak on Reunion Island, France, August 2007

An outbreak of gastroenteritis involving 26 guests of a wedding dinner occurred in August 2007 in Réunion Island, a French Overseas Department. Salmonella was isolated in 61.5% of cases and the two isolates serotyped were of serovar Weltevreden. We believe this to be the first food-borne outbreak due to S. enterica serovar Weltevreden described in Réunion Island. The epidemiological and environmental investigations of this outbreak did not provide enough evidence to identify a single vehicle of infection. It is necessary to improve surveillance of salmonellosis by multidisciplinary cooperation between clinicians, epidemiologists, microbiologists and veterinarians on Réunion Island.

Nontyphoidal Salmonella bacteremia in previously healthy children: analysis of 199 episodes

BACKGROUND

Nontyphoidal Salmonella (NTS) bacteremia is not rare in otherwise healthy children in Taiwan. Few studies described the clinical manifestations and outcomes of NTS bacteremia in previously healthy children.

METHODS

Children with blood culture positive for NTS treated at Chang Gung Children's Hospital between May 1996 and June 2003 were identified from the microbiology logbook. Patients who had underlying events or concomitant diseases were excluded.

RESULTS

We evaluated 199 patients. One hundred and eighteen (59.3%) were male children and 184 (92.5%) were between 3 months and 5 years of age. Fever (97.0%) and diarrhea (79.9%) were the most common initial presentations. Leukocytosis (leukocyte >15,000/mm) and elevated serum C-reactive protein concentration (> or =10 mg/L) were present in 14.6% and 79.4% of the patients, respectively. Eighty-three percent of 184 patients with antibiotic treatment received a third- or fourth-generation cephalosporin as definitive antibiotic therapy. Focal suppurative infections were present in 5 children (2.5%) on initial evaluation, and included meningitis in 2 and osteomyelitis in 3. Neither metastatic complications nor clinically recurrent diseases were found during a follow-up period of at least 12 months after treatment. No fatalities occurred in this series.

CONCLUSIONS

In healthy children, NTS bacteremia was relatively benign and extraintestinal focal suppurative infections were infrequently seen. Less than 10 days of appropriate antibiotic treatment is probably adequate for those without a suppurative focus of infection.

Change of serotype pattern of Group D non-typhoidal Salmonella isolated from pediatric patients in southern Taiwan

BACKGROUND AND PURPOSE

Group D non-typhoidal Salmonella infection is increasing in Taiwan. This study aimed to investigate the changing serotypes and antibiotic resistance of childhood group D Salmonella infection.

METHODS

From 1998 through 2004, children (<16 years) infected with group D Salmonella were retrospectively reviewed. Demographic data, clinical and laboratory features, and risk factors of bacteremia were analyzed. Enrolled patients were classified as acute gastroenteritis with bacteremia (Group I) and acute gastroenteritis without bacteremia (Group II). The minimal inhibitory concentrations were determined by agar dilution method. Genotyping was performed by use of pulsed-field gel electrophoresis (PFGE).

RESULTS

Eighty one children (Group I, n = 15; Group II, n = 66) were enrolled with a mean (+/- standard deviation) age of 3.1 +/- 2.6 years. Group I patients were younger and had a longer duration of fever prior to admission (> or =5 days, 40% vs 9.2%; p=0.003) and total fever duration (8.3 vs 4.1 days, p<0.001) than Group II. Salmonella enterica serotype Enteritidis (80%) was the most common serotype, followed by Salmonella Panama (7%). The antibiotic resistance rates of S. Enteritidis were: tetracycline (36.5%), trimethoprim-sulfamethoxazole (25.4%), ampicillin (14.3%), and chloramphenicol (12.7%). S. Panama was associated with a higher rate of bacteremia. All strains were susceptible to quinolone and third-generation cephalosporins. PFGE study showed a single genotype of S. Enteritidis and diverse genotypes of S. Panama circulating in the area.

CONCLUSIONS

S. Enteritidis was the predominant serotype of group D Salmonella that caused pediatric infection in southern Taiwan during the study period from 1998 to 2004. S. Panama is associated with higher rates of bacteremia and antimicrobial resistance.

Extraintestinal focal infections in adults with Salmonella enterica serotype Choleraesuis bacteremia

BACKGROUND AND PURPOSE

Salmonella enterica serotype Choleraesuis, which is associated with severe human infections and multidrug resistance, poses a serious problem in Taiwan. The aim of the study was to investigate the epidemiology and clinical features of S. Choleraesuis bacteremia.

METHODS

Medical records and antimicrobial susceptibility of blood isolates were investigated for 43 adults (> or =18 years old) with S. Choleraesuis bacteremia from 1999 to 2005.

RESULTS

The proportion of S. Choleraesuis in non-typhoidal Salmonella bacteremia increased in the latter three years (2003-2005). The elderly with aged-related disorders, and younger patients receiving immunosuppressive therapy for their underlying diseases were two high-risk groups. Twenty cases (47%) had extraintestinal focal infections, including 10 cases of mycotic aneurysm, six of osteomyelitis, and 4 pleuropulmonary infections. Univariate analysis revealed that age > or =50 years was associated with occurrence of endovascular infection (p=0.008), while immunosuppressive therapy was negatively associated with endovascular infection (p=0.043). Significant resistance to first-line antimicrobial agents (i.e., ampicillin, trimethoprim-sulfamethoxazole or chloramphenicol) was noted. All strains were resistant to nalidixic acid, and 56% were resistant to ciprofloxacin. Few (<5%) isolates were resistant to ceftriaxone, and all were susceptible to cefepime, aztreonam, imipenem, meropenem and ertapenem. Multivariate analysis showed that shock (odds ratio [OR], 20.6; 95% confidence interval [CI], 1.8-239.4; p=0.016) and apyrexia (OR, 36.2; 95% CI, 3.7-358.2; p=0.002) were independent risk factors for mortality.

CONCLUSION

S. Choleraesuis bacteremia was usually complicated with extraintestinal focal infections in the elderly. With a high level of resistance among S. Choleraesuis, fluoroquinolones should be avoided for critically ill patients with suspected Salmonella bacteremia.

Non-typhoidal Salmonella bacteremia in adults

BACKGROUND AND PURPOSE

Very few studies have examined prognostic factors in adult patients with non-typhoidal Salmonella (NTS) bacteremia. The purpose of this study was to identify the prognostic factors of these patients.

METHODS

A total of 79 episodes of NTS bacteremia were identified in 73 patients between January 2001 and December 2003. Susceptibilities to various antimicrobials were determined using disk-diffusion tests and National Committee for Clinical Laboratory Standards criteria. Multiple logistic regression was used to evaluate the relationship between patients' characteristics and covariates of mortality.

RESULTS

There were only 5 episodes (6%) of gastroenteritis, two of which were due to Salmonella septicemia contracted abroad. Potentially predisposing factors were identifiable in 51 episodes (65%). Infections in 24 patients (30%) were due to serogroup B Salmonella and in 22 patients (28%), to serogroup C Salmonella. A logistic regression analysis selected two variables as independently influencing prognosis: coma (p=0.006) and septic shock (p=0.002).

CONCLUSIONS

Thus, most adult patients with NTS bacteremia do not develop gastroenteritis. Patients in shock or coma have poor prognosis, and susceptibility to third-generation cephalosporins, cefepime, and carbapenem is high.

Functional characteristics of the porcine colonic epithelium following transportation stress and Salmonella infection

OBJECTIVE

Stressful life events and infections contribute to gut disorders such as irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD). We used a pig model to analyse whether this could be linked to altered mediator sensitivity of the epithelial lining.

MATERIAL AND METHODS

Uninfected control pigs or pigs with subclinical Salmonella (S.) typhimurium DT 104 infection were killed either without (ConRest, InfRest) or with prior 8-h transportation (ConTrans, InfTrans). Short-circuit current (I(sc)), tissue conductance (G(t)) and release of mast cell mediators were monitored in isolated colonic epithelia mounted in Ussing chambers. Epithelia were exposed to histamine (100 microM, mucosally), substance P (SP; 1 microM, serosally), calcimycin A23187 (1 microM, serosally) and theophylline (10 mM, bilaterally). Transepithelial flux of histamine and colonic activities of histamine N-methyltransferase (HMT) and diamine oxidase (DAO) were determined.

RESULTS

S. infection decreased baseline I(sc), G(t) and histamine fluxes, while transportation had no effect on these values. Mucosal histamine increased I(sc) only in ConTrans pigs. This was not associated with increased mucosal-to-serosal flux of histamine but with a 2-fold increased DAO activity. Serosal SP increased I(sc) only in transported animals, but the increase was six times higher in ConTrans versus InfTrans pigs. Effectiveness of SP was not dependent on the release of histamine or prostaglandin D2. A23187 and theophylline elicited increases in I(sc) that were not different between treatments.

CONCLUSIONS

Transportation stress facilitates secretory responses of the colonic epithelium to SP and luminal histamine. This is suppressed by subclinical S. infection. Effects of S. infection on porcine colon resemble, in part, the known effects of an oral S. endotoxin application.

Gas-forming splenic abscess due to Salmonella enterica serotype Enteritidis in a chronically hemodialyzed patient

We describe a diabetic patient who was chronically hemodialyzed due to end-stage renal disease and developed a gas-forming splenic abscess and bacteremia caused by Salmonella enterica serotype Enteritidis. Fever persisted despite urgent splenectomy and intravenous ceftriaxone and metronidazole for 14 days. He recovered completely after intravenous ciprofloxacin/metronidazole treatment for a further 14 days. The isolate was susceptible to ciprofloxacin and ceftriaxone and did not exhibit extended-spectrum beta-lactamase phenotype.

Differential requirement of P2X7 receptor and intracellular K+ for caspase-1 activation induced by intracellular and extracellular bacteria

Interleukin-1beta (IL-1beta) is a pro-inflammatory cytokine that plays an important role in host defense and inflammatory diseases. The maturation and secretion of IL-1beta are mediated by caspase-1, a protease that processes pro-IL-1beta into biologically active IL-1beta. The activity of caspase-1 is controlled by the inflammasome, a multiprotein complex formed by NLR proteins and the adaptor ASC, that induces the activation of caspase-1. The current model proposes that changes in the intracellular concentration of K(+) potentiate caspase-1 activation induced by the recognition of bacterial products. However, the roles of P2X7 receptor and intracellular K(+) in IL-1beta secretion induced by bacterial infection remain unknown. Here we show that, in response to Toll-like receptor agonists such as lipopolysaccharide or infection with extracellular bacteria Staphylococcus aureus and Escherichia coli, efficient caspase-1 activation is only triggered by addition of ATP, a signal that promotes caspase-1 activation through depletion of intracellular K(+) caused by stimulation of the purinergic P2X7 receptor. In contrast, activation of caspase-1 that relies on cytosolic sensing of flagellin or intracellular bacteria did not require ATP stimulation or depletion of cytoplasmic K(+). Consistently, caspase-1 activation induced by intracellular Salmonella or Listeria was unimpaired in macrophages deficient in P2X7 receptor. These results indicate that, unlike caspase-1 induced by Toll-like receptor agonists and ATP, activation of the inflammasome by intracellular bacteria and cytosolic flagellin proceeds normally in the absence of P2X7 receptor-mediated cytoplasmic K(+) perturbations.

Matrix metalloproteinase-9 regulates MUC-2 expression through its effect on goblet cell differentiation

BACKGROUND & AIMS

We recently demonstrated that epithelial-derived matrix metalloproteinase (MMP) 9 up-regulated during inflammatory bowel disease is a critical mediator of tissue damage during colitis. MMP-9 null mice (MMP-9(-/-)) develop dramatically reduced inflammatory response to luminally administered colitic agents in the face of intact systemic immune response and inflammatory cell recruitment, suggesting protected epithelial barrier in these mice. In this study, we sought to address the role and mechanism by which MMP-9 influences barrier protective function.

METHODS

Wild-type and MMP-9(-/-) mice were used for in vivo studies, and the goblet cell line HT29-cl.16E and the enterocyte cell line Caco2-BBE were used for in vitro studies.

RESULTS

Compared with wild-type mice, MMP-9(-/-) mice had an increased number of goblet cells and MUC-2 expression. In addition, KLF-4 and Elf-3, transcription factors involved in terminal differentiation of goblet cells were up-regulated, whereas notch intracellular domain (NICD; activated Notch-1) was down-regulated in MMP-9(-/-) mice. These findings suggest altered epithelial cell differentiation in MMP-9(-/-) mice. Temporal expression of MMP-9 inversely correlated with MUC-2 expression during maturation of goblet cells. MMP-9 over expression inhibited goblet cell differentiation in vitro. Conversely, MMP-9 gene silencing in Caco2-BBE cells resulted in a change in their phenotype toward goblet cells. Finally, MMP-9 over expression or silencing in goblet cells increased or decreased Salmonella typhimurium adherence, respectively.

CONCLUSIONS

MMP-9 regulates goblet cell differentiation in colon. The effect of MMP-9 on goblet cells could contribute to alteration in mucosal defense leading to inflammation. Together, our data uncover a novel function of MMP-9 in intestinal epithelial cells.

[Impact of the clinical course of salmonella infection in the period of early convalescence on the endotoxin-induced apoptosis of peripheral blood cells]

The sensitivity of granulocytes, monocytes, and lymphocytes to endotoxin-induced apoptosis S. enteritidis liposaccharides (LS) (100 and 1000 ng/ml) was studied in patients during early convalescence with the prior gastrointestinal form of salmonellosis in relation to the course of the disease. An ApoAlert DNA test system (BD, Biosciences) was used to identify apoptotic cells containing fragmented DNA sites by the Tunel method. According to the severity of a clinical course of Salmonella infection, there was suppression of early endotoxin-induced apoptosis of granulocytes and monocytes, a reduction in the rate of lymphocytic apoptosis, as well as an increase in granulocytic sensitivity to the suboptimum doses of LS (100 ng/ml). At the same time, there was no clear dose-dependent relationship of induction of an apoptotic response in the population of monocytes and lymphocytes. A correlation between endotoxin-induced apoptosis of granulocytes, monocytes, and lymphocytes was found in patients with mild Salmonella infection and in the control group.

What is the role of Toll-like receptors in bacterial infections?

Innate immunity relies on signalling by Toll-like receptors (TLRs) to alert the immune system of the presence of invading bacteria. TLR activation leads to the release of cytokines that allow for effective innate and adaptive immune responses. However, the contribution of different TLRs depends on the site of the infection and the pathogen. This review will describe the involvement of TLRs in the development of three different bacterial infections as well as our current understanding of the role of TLRs during microbial pathogenesis.

Case report: parotid abscess due to Salmonella enterica serovar Enteritidis in an immunocompetent adult

There are reports of increasing incidence of focal extra-intestinal infections from non-typhoidal salmonellae during the past two decades. We present the first case of a parotid abscess caused by Salmonella enterica serovar Enteritidis (S. Enteritidis) in an apparently immunocompetent adult without other abnormality of the parotid glands. A 58-year-old man was admitted to our hospital because of a 3-day history of fever and painful swelling of the right parotid gland. His medical history was unremarkable. A CT scan revealed an abscess of the right parotid. S. Enteritidis was isolated from a sample of fluid aspirated from the parotid abscess under ultrasound guidance. The stool, urine, and blood cultures were negative. The patient was treated with ciprofloxacin 500 mg per os every 12 h for 10 days, with complete remission of symptoms. The infection did not recur during 3 years of follow up. Our case report adds to the literature regarding the extra-intestinal infections with S. Enteritidis, a common non-typhoidal salmonellosis.

In silico model as a tool for interpretation of intestinal infection studies

In nutrition research the number of human in vivo experiments is limited because of the many restrictions and the high costs of testing in humans. Up to now predictive computer models aiming to enhance research have been rare or too complex, with many nonmeasurable adjustable parameters. This study aimed to develop a basic physicochemical computer model for a first quantitative interpretation of results obtained from in vivo intestinal experiments with bacteria. This new modeling approach is validated with results obtained from gut infection studies in vivo. The design of the model is described, and its ability to reproduce experimental data is evaluated. The model predictions are compared with new experimental data. The phenomena that take place in the gastrointestinal tract are summarized by model constants for growth, adherence, and release of bacteria. Although the model is far from describing all details and many processes in the intestine are combined, the model calculation results lead to reasonable conclusions and interesting hypotheses. One of these hypotheses concluded from the model outcomes is that Escherichia coli bacteria have a much lower intestinal growth rate in humans than in rats. Extra laboratory validation experiments proved the reliability of this hypothesis predicted by the model. In addition, the known protective effect of dietary calcium and detrimental effect of clindamycin on the growth and adherence of Salmonella bacteria could be quantified. From these results it is clear that the model enhances the interpretation of in vivo gastrointestinal experiments and will facilitate research trajectories towards new functional foods that improve resistance to pathogenic bacteria in humans.

[A case of a child who developed Cushing reflex after a clinical diagnosis of brain death]

The author presents a case of brain death caused by salmonella encephalopathy in a 1-year-old girl. The patient suffered from fever, convulsive status, and coma. On the 5th day, her respiration was arrested. At that time, we confirmed the absence of brainstem reflexes. An electroencephalogram (EEG) showed a flat pattern. Only wave I was recordable in auditory brainstem responses (ABR). On the 6th day, we obtained a flat EEG and a disappearance of all components of ABR. A simultaneous elevation of her heart rate and blood pressure was observed 14 to 18 hours after the respiratory arrest. This phenomenon was equivalent to the Cushing reflex, which represents an autoregulation against increased intracranial pressure. Our case suggested that the activity of a part of the brainstem was preserved in spite of the absence of activities in EEG, ABR and brainstem reflexes at 14 hours after the onset of apnea.

Septic arthritis in patients with systemic lupus erythematosus: salmonella and nonsalmonella infections compared

OBJECTIVES

To assess the clinical characteristics and outcome of systemic lupus erythematosus (SLE) with septic arthritis.

METHODS

In this 20-year retrospective study, we reviewed the charts of SLE patients with septic arthritis confirmed by synovial fluid analysis and culture. To identify risk factors for septic arthritis, data of SLE patients with septic arthritis were compared with data of 100 hospitalized SLE patients without septic arthritis.

RESULTS

There were 10,732 inpatient records of 3,127 SLE patients; 29 SLE patients had septic arthritis. Their ages ranged from 14 to 68 years (mean, 35.1 +/- 14.1 years). The mean SLE duration before septic arthritis onset was 30.6 months. All patients received corticosteroids; 93% had active disease (SLEDAI > or = 4). Compared with controls, avascular necrosis (AVN) of the femoral head was the most common predisposing articular disease (Odds ratio, 3.799;CI, 1.59 to 9.05). Of the 29 patients, 17 (59%) had salmonella infections and 12 (41%) had other infections. Salmonella-infected patients were younger (28.7 +/- 10.4 years) than those with nonsalmonella infections (44.1 +/- 14.0 years; P = 0.002). The hip was the most commonly affected joint, especially in the salmonella group, followed by the knees and ankles. Salmonella-infected patients were more prone to oligo-articular septic arthritis. The overall mortality rate was 10%.

CONCLUSIONS

Salmonella enteritidis B is the most common pathogen causing septic arthritis in younger SLE patients. Septic arthritis tended to be oligo-articular and involve the hip joint. AVN of the femoral head was the most common predisposing articular disease. Once septic arthritis is suspected, culture specimens should be collected and appropriate antibiotics given immediately.

Severity of infection and seasonal variation of non-typhoid Salmonella occurrence in humans

Non-typhoid Salmonella infections may present as severe gastroenteritis necessitating hospitalization and some patients become septic with bacteraemia. We hypothesized that the seasonal variation of non-typhoid Salmonella occurrence in humans diminishes with increased severity of infection. We examined the seasonal variation of non-typhoid Salmonella infections in three patient groups with differing severity of infection: outpatients treated for gastroenteritis (n=1490); in-patients treated for gastroenteritis (n=492); and in-patients treated for bacteraemia (n=113). The study was population-based and included all non-typhoid Salmonella patients in a Danish county from 1994 to 2003. A periodic regression model was used to compute the peak-to-trough ratio for the three patient groups. The peak-to-trough ratios were 4.3 [95% confidence interval (CI) 3.6-5.0] for outpatients with gastroenteritis, 3.2 (95% CI 2.4-4.2) for in-patients with gastroenteritis, and 1.6 (95% CI 1.0-2.8) for in-patients with bacteraemia. We conclude that the role of seasonal variation diminishes with increased severity of non-typhoid Salmonella infection.

Non-Typhi Salmonella gastroenteritis in children presenting to the emergency department: characteristics of patients with associated bacteraemia

The records of children with Salmonella gastroenteritis only (n = 97), and those with associated bacteraemia (n = 64), seen in one medical centre during a 12-year period, were analysed retrospectively. Mean patient age was 2.24 +/- 2.8 years (range, 0.05-16 years), and 49% were male. Children with bacteraemia presented after a longer duration of symptoms (7.0 +/- 6.9 vs. 3.9 +/- 4.6 days, p 0.0002), and had higher erythrocyte sedimentation rates (45 +/- 22 vs. 33 +/- 22 mm/h, p < 0.02) and lactate dehydrogenase values (924 +/- 113 vs. 685 +/- 165 IU/L, p 0.001). There was a trend in bacteraemic children towards immunosuppression (6.3% vs. 1.0%, p 0.08) and a lower number of siblings (2.9 +/- 1.9 vs. 3.8 +/- 2.7, p 0.063). Non-bacteraemic children had a more severe clinical appearance, and a higher percentage had a moderate to bad general appearance (51.5 vs. 29.7%, p < 0.01), with dehydration (37.1 vs. 18.8%, p 0.02) and vomiting (58.8 vs. 39.0%, p 0.02). Laboratory dehydration indicators were also markedly worse in non-bacteraemic children, with urine specific gravity of 1020 +/- 9.4 vs. 1013 +/- 9.0 (p 0.0002), base excess of - 4.2 +/- 3.0 vs. - 2.5 +/- 3.4 mEq/L (p 0.01), and blood urea nitrogen of 10.1 +/- 7.0 vs. 7.4 +/- 4.5 mg% (p 0.002). Thus, the clinical presentation of bacteraemic children was more gradual, and associated gastroenteritis and dehydration was less pronounced. These findings may contribute in part to the inadvertent discharge of bacteraemic children from the emergency department.

Integrones de clase 1 en aislados de Salmonella enterica productores de diferentes tipos de betalactamasas recogidos en la región sanitaria de Tortosa

OBJECTIVE

To assess the frequency of class 1 integrons among isolates of Salmonella enterica producing different types of beta-lactamases from the health region of Tortosa, and to attempt to establish the resistance genes located within their variable regions.

METHODS

The presence of class 1 integrons and of aadA1, aadA2, dfrA1, tem-1, oxa-1 and pse-1 resistance genes within their variable regions was investigated by PCR in 100 ampicillin-resistant isolates of S. enterica (30 S. enteritidis, 56 S. Typhimurium and 14 from other serotypes) consecutively recovered in our laboratory between 2000 and 2001. Beta-lactamases were characterized by isoelectric focusing and PCR.

RESULTS

a) 6/57 TEM-1 producing isolates carried integrons: 1 S. ser Panama, 2 S. ser Enteritidis and 1 S. ser Typhimurium (1600 pb/aadA1-dfrA1); 1 S. ser Panama (1600 pb/aadA2-dfrA1); 1 S. ser Grumpensis (1500 pb 1 1700 pb; aadA2 and ??) b) All OXA-1 producing isolates (20 S. ser Typhimurium) bore an integron of 2000 pb/aadA1-oxa-1; c) All PSE-1 producing isolates (22 S. ser Typhimurium, most of them 104 phage type, and 1 S. enterica immobile [4,12:-:-]) harbored 2 integrons (1000 pb/aadA1 and 1,00 pb/pse-1).

CONCLUSION

The presence of class 1 integrons carrying oxa-1 or pse-1 resistance genes in all the OXA-1-producing and PSE-1-producing isolates investigated could have contributed to their spread and explain the increase in frequency of multiresistant S. ser Typhimurium isolates harboring these enzymes seen in the health region of Tortosa. In addition, we report the first isolate of S. ser enterica serotype Grumpensis harboring integrons.

[Molecular mechanism for pathogenicity of Salmonella sp]

Salmonella is a Gram negative bacillus that behaves like a facultative intracellular pathogen. Its environment is the human and animal gastrointestinal tracts, it is never found like a normal microbiota. It is associated with gastrointestinal problems, septicaemic disease and abortion, due to its cellular invasion capacity and its intraphagocytic survival. Nowadays, it is known that Salmonella contains five pathogenicity islands. Several genes involved in the cellular invasion of nonphagocytic cells such as epithelial cells, apoptosis of macrophages, activation of routes of MAP kinases and transcription factors are located in centisome 63, constituting the pathogenicity island 1 (SPI-1). The SPI-2 and SPI-3 islands control the intracellular survival and replication. The SPI-4 island encodes a putative type I secretion system and its believed that it participates in the intracellular survival. Finally, the SPI-5 island encodes for factors involved in the fluid secretion and inflammatory reaction in the intestinal mucosa. Due to a coordinated and precise regulation of the Salmonella genes, it allows for adaptation to environmental changes that occur during an inflammatory process.

Pathogen-induced actin filament rearrangement in infectious diseases

Host defence mechanisms involve the establishment and maintenance of numerous barriers to infectious microbes, including skin and mucosal surfaces, connective tissues, and a sophisticated immune system to detect and destroy invaders. Defeating these defence mechanisms and breaching the cell membrane barrier is the ultimate challenge for most pathogens. By invading the host and, moreover, by penetrating into individual host cells, pathogens gain access to a protective niche, not only to avoid immune clearance, but also to replicate and to disseminate from cell to cell within the infected host. Many pathogens are accomplishing these challenges by exploiting the actin cytoskeleton in a highly sophisticated manner as a result of having evolved common as well as unique strategies.

Caenorhabditis elegans-based screen identifies Salmonella virulence factors required for conserved host-pathogen interactions

A Caenorhabditis elegans-Salmonella enterica host-pathogen model was used to identify both novel and previously known S. enterica virulence factors (HilA, HilD, InvH, SptP, RhuM, Spi4-F, PipA, VsdA, RepC, Sb25, RfaL, GmhA, LeuO, CstA, and RecC), including several related to the type III secretion system (TTSS) encoded in Salmonella pathogenicity island 1 (SPI-1). Mutants corresponding to presumptive novel virulence-related genes exhibited diminished ability to invade epithelial cells and/or to induce polymorphonuclear leukocyte migration in a tissue culture model of mammalian enteropathogenesis. When expressed in C. elegans intestinal cells, the S. enterica TTSS-exported effector protein SptP inhibited a conserved p38 MAPK signaling pathway and suppressed the diminished pathogenicity phenotype of an S. enterica sptP mutant. These results show that C. elegans is an attractive model to study the interaction between Salmonella effector proteins and components of the innate immune response, in part because there is a remarkable overlap between Salmonella virulence factors required for human and nematode pathogenesis.

Salmonella enterica serotype Choleraesuis: epidemiology, pathogenesis, clinical disease, and treatment

Nontyphoid Salmonella strains are important causes of reportable food-borne infection. Among more than 2,000 serotypes, Salmonella enterica serotype Choleraesuis shows the highest predilection to cause systemic infections in humans. The most feared complication of serotype Cholearesuis bacteremia in adults is the development of mycotic aneurysm, which previously was almost uniformally fatal. The advances in diagnostic techniques, surgical care, and antimicrobial therapy have greatly improved the survival of these patients. However, the recent emergence of serotype Choleraesuis that is resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, and, notably, fluoroquinolone antibiotics has aroused concern about the use of these agents for the empirical treatment of systemic infection caused by this organism. In view of the serious implications of the situation, the chain of transmission and mechanism of resistance should be carefully studied to reduce the spread of infection and threat to human health. To date, there are no vaccines available to prevent serotype Choleraesuis infections in humans. The availability, in the near future, of the genome sequence of serotype Cholearesuis will facilitate the development of effective vaccines as well as the discovery of new targets for novel antimicrobial agents.

Modulation of chloride secretory responses and barrier function of intestinal epithelial cells by the Salmonella effector protein SigD

The Salmonella effector protein SigD is an inositol phosphate phosphatase that inhibits phosphatidylinositol 3-kinase-dependent signaling. Because epidermal growth factor (EGF) inhibits chloride secretion via phosphatidylinositol 3-kinase, we explored whether Salmonella infection might modify the inhibitory effect of EGF. As expected, EGF inhibited chloride secretion induced by carbachol in T(84) epithelial cells. Infection with wild-type (WT) but not sigD(-) mutant S. typhimurium SL1344 decreased CCh-stimulated chloride secretion. Moreover, WT but not sigD(-) Salmonella reduced the inhibitory effect of EGF on carbachol-stimulated chloride secretion. Complementation of sigD restored the ability of mutant Salmonella to reverse the inhibitory effect of EGF. EGF-induced EGF receptor phosphorylation was similar in cells infected with either WT or mutant Salmonella, and neither WT nor sigD(-) Salmonella altered recruitment of the p85 subunit of phosphatidylinositol 3-kinase to EGF receptor, implying that SigD acts downstream of these signaling events. Furthermore, transepithelial resistance fell more rapidly in cells infected with WT vs. sigD(-) Salmonella, indicating an early role for SigD in reducing barrier function, perhaps via activation of protein kinase C. We conclude that the Salmonella bacterial effector protein SigD may play critical roles in the pathogenesis of disease caused by this microorganism.

Prior antimicrobial agent use increases the risk of sporadic infections with multidrug-resistant Salmonella enterica serotype Typhimurium: a FoodNet case-control study, 1996-1997

Several strains of multidrug-resistant (MDR) Salmonella serotype Typhimurium, including MDR S. Typhimurium definitive type 104, cause almost 10% of Salmonella infections among humans in the United States. To determine the risk factors for acquiring sporadic MDR S. Typhimurium infection, we conducted a population-based, case-control study using data from the Foodborne Diseases Active Surveillance Network (FoodNet) during 1996-1997. S. Typhimurium isolates from 5 FoodNet surveillance areas (California, Connecticut, Georgia, Minnesota, and Oregon) were tested for antimicrobial resistance and phage typing. Telephone interviews were conducted with ill persons and matched control subjects. Compared with both control subjects and patients infected with pansensitive strains of S. Typhimurium, patients with MDR S. Typhimurium infection were significantly more likely to have received an antimicrobial agent, particularly an agent to which the Salmonella isolate was resistant, during the 4 weeks preceding illness onset. Prudent antimicrobial agent use among humans and among veterinarians and food-animal producers is necessary to reduce the burden of drug-resistant salmonellosis in humans.

Salmonella enterica serotype Choleraesuis infection in a medical center in northern Taiwan

This retrospective study was conducted in order to determine the clinical and microbiologic features of infection with Salmonella enterica serotype Choleraesuis. Between March 1999 and December 2002, 55 patients with 66 isolates were enrolled for analysis. The ratio of males to females was 2.2:1. Most patients were older than 60 years (56%) and had underlying diseases (78%), such as diabetes mellitus, malignancy, and peptic ulcer. Fever (85%) was the most common clinical manifestation, followed by abdominal pain/fullness (31%). The gastrointestinal manifestations, including nausea/vomiting or diarrhea, accounted for only 13% and 11% of patients, respectively. S. enterica serotype Choleraesuis was extremely invasive, with a high predilection to cause bacteremia (78% of the isolates were from blood). Various types of metastatic focal infections were found, including infected arterial aneurysm, osteomyelitis, septic arthritis, urinary tract infection and wound infection. The crude mortality rate was 18% (10 deaths in 55 cases). Nearly all isolates were susceptible to the third-generation cephalosporins. A higher resistance rate to commonly used antimicrobial agents was found with ampicillin (85%, 56/66), trimethoprim-sulfamethoxazole (81%, 40/49), chloramphenicol (96%, 47/49), and ciprofloxacin (49%, 30/61). In view of the emergence of fluoroquinolone resistance, the third-generation cephalosporins appear to be the best choice for treatment of invasive infections caused by this organism.

Impairment of glucose metabolism in hearts from rats treated with endotoxin

OBJECTIVE

In patients and animals with sepsis or critical illness, the mechanical function of the heart is often impaired. Although these conditions are accompanied by dramatic metabolic and hormonal changes, little is known about alterations of cardiac metabolism. In this study, we assessed the impact of an endotoxin-induced inflammation on cardiac glucose utilization.

METHODS

Bacterial endotoxin (1 mg/kg lipopolysaccharide from Salmonella typhimurium, LPS) was injected intravenously to rats. Six hours after LPS application, hearts were isolated and perfused in the Langendorff mode.

RESULTS

Left ventricular pressure was reduced by 50% in hearts from LPS-treated rats, compared to those from saline-injected control animals. With glucose as the sole fuel, there was no difference in glycolysis between the groups. However, on addition of beta-hydroxybutyrate (an alternative fuel which inhibits phosphofructokinase via an increased citrate level), the glycolytic rate in the LPS group was 44 and 48% lower (in basal, and insulin-stimulated conditions, respectively; P<0.01) than in control hearts. At the end of perfusions with beta-hydroxybutyrate and insulin, the cardiac citrate content was 40% higher in LPS vs. controls (P<0.001). In addition to the reduced glycolysis, the insulin-dependent increase of cardiac glycogen was 77% smaller in LPS hearts. The difference between LPS and control glycolysis was abolished if the hearts were perfused with the ceramidase inhibitor N-oleyl-ethanolamine (5 microM), and also with the cyclooxygenase-2 inhibitor NS-398 (10 microM), or the thromboxane A2 receptor antagonist SQ-29548 (1 microM).

CONCLUSION

The inflammatory reaction caused by endotoxin impairs cardiac glucose metabolism (and in particular, the action of insulin) in at least two ways: through the exacerbation of the counterregulatory effect of alternative fuels on glycolysis, and through a reduction in net glycogen synthesis. Impairment of glycolysis may be mediated by a sphingomyelin derivative, and COX-2-derived thromboxane A2.

Clinical tuberculosis in 2 of 3 siblings with interleukin-12 receptor beta1 deficiency

We describe 3 siblings with interleukin-12 receptor beta1 (IL-12Rbeta1) deficiency, a known genetic etiology of clinical disease caused by infection with poorly virulent mycobacteria, such as mycobacteria found in bacille Calmette-Guérin (BCG) vaccines and environmental nontuberculous mycobacteria (NTM). One child had disseminated tuberculosis, the second had extraintestinal salmonellosis and pulmonary tuberculosis, and the third remained asymptomatic. IL-12Rbeta1 deficiency should be considered as a diagnosis in patients with severe salmonellosis or tuberculosis, even if they do not have disease due to BCG or NTM.

Luminal salmonella endotoxin affects epithelial and mast cell function in the proximal colon of pigs

BACKGROUND

Salmonellosis and systemic endotoxaemia affect intestinal function. However, little is known about the functional importance of luminal Salmonella (S.) endotoxin during intestinal infection.

METHODS

Pigs were either given or not given lipopolysaccharide (LPS, 30 mg day(-1)) of S. Typhimurium DT-104 orally for 14 days. Blood samples were taken weekly. After slaughter (day 14), epithelia of the proximal colon were investigated in Ussing chambers. Bacterial translocations to lung, liver, spleen and several lymph nodes were determined by culture.

RESULTS

Endotoxin feeding increased plasma C-reactive protein (CRP) and histamine levels without evoking clinical signs. Postmortem, proximal colonic epithelia of LPS-treated animals showed both a decreased histamine release after mast cell stimulation with A23187 and a smaller increase in short-circuit current after A23187 application. Addition of the nitric oxide donor, sodium nitroprusside (SNP), also elicited lower increases in short-circuit current in the proximal colon of endotoxin-treated pigs. Endotoxin pre-feeding decreased colonic ion conductance, although mannitol and histamine fluxes were high in some epithelia of this group. Luminal Salmonella endotoxin increased bacterial translocation to proximal jejunal lymph nodes. LPS applied to colonic epithelia in vitro had no electrophysiological effects.

CONCLUSIONS

Luminal endotoxin elicits an acute phase response and affects intestinal electrolyte transport and mast cell function. Furthermore, LPS induces epithelial spots of increased mannitol permeability that could be identical to spots of enhanced bacterial translocation.