Bacterial translocation in the rat model of lectin induced diarrhoea

Citrobacter freundii infection after acute necrotizing pancreatitis in a patient with a pancreatic pseudocyst: a case report

Introduction

Infections are the most frequent and severe complications of acute necrotizing pancreatitis with a mortality rate of up to 80 percent. Although experimental and clinical studies suggest that the microbiologic source of pancreatic infection could be enteric, information in this regard is controversial.

Case presentation

We describe a Citrobacter freundii isolation by endoscopy ultrasound fine needle aspiration in a 80-year-old Caucasian man with pancreatic pseudocyst after acute necrotizing pancreatitis.

Conclusion

Our case report confirms that this organism can be recovered in patients with a pancreatic pseudocyst. On-site cytology feedback was crucial to the successful outcome of this case as immediate interpretation of the fine needle aspiration sample directed the appropriate cultures and, ultimately, the curative therapy. To the best of our knowledge, this is the first reported case of isolated pancreatic C. freundii diagnosed by endoscopy ultrasound fine needle aspiration.

Efficacy of various dietary calcium salts to improve intestinal resistance to Salmonella infection in rats

Previous animal and human studies have shown protective effects of Ca on the resistance to enteropathogenic infections. Most interventions were performed with calcium phosphate and little is known about the protective effect of other dietary sources of Ca. Therefore, we investigated the efficacy of several Ca salts to enhance intestinal resistance to Salmonella enteritidis infection. Rats (n 7–8 per group) were fed a high-fat, Western human-style, purified diet with a low Ca content (20 mmol calcium phosphate/kg; negative control group) or the same diet supplemented with either (extra) calcium phosphate, milk Ca, calcium chloride or calcium carbonate (total of 100 mmol Ca supplement/kg). Diets contained Cr-EDTA for assessment of incremental changes in intestinal permeability. After an adaptation period of 2 weeks, animals were orally infected with S. enteritidis to mimic a human-relevant foodborne infection. Ca supplement-induced changes on faecal lactobacilli and enterobacteria were studied before infection. Changes in intestinal permeability were determined by measuring urinary Cr with time. Persistence of Salmonella was determined by studying faecal excretion of this pathogen in time. Overall, all Ca salts increased resistance towards Salmonella. After infection, body weight gain and food intake were higher in the calcium phosphate group. Calcium phosphate and milk Ca decreased faecal enterobacteria before infection. All Ca salts decreased infection-induced intestinal permeability and persistence of Salmonella. Calcium phosphate, milk Ca, calcium carbonate and calcium chloride are able to enhance the intestinal resistance to Salmonella in rats.

Detection and identification of bacterial DNA in serum from patients with acute pancreatitis

BACKGROUND AND AIMS

Bacterial infections are common complications in patients with acute pancreatitis, and translocation of bacteria from the intestinal lumen is probably the first step in the pathogenesis of these infections. As blood cultures in afebrile patients are usually negative, more sensitive methods to investigate this hypothesis in patients are needed. Our group has recently developed a method to detect the presence of bacterial DNA in biological fluids, and we aimed to detect bacterial DNA in patients with acute pancreatitis, as molecular evidences of bacterial translocation.

METHODS

Samples of blood were obtained on three consecutive days within the first six days after admission. Bacterial DNA was detected using a polymerase chain reaction based method, and an automated DNA nucleotide sequencing process allowed identification of bacteria species.

RESULTS

Thirty one consecutively admitted patients with acute pancreatitis were studied. Bacterial DNA was detected in six patients (19.3%), and the sequencing process allowed identification of Citrobacter freundii and Pseudomonas aeruginosa. In two patients the same bacteria detected at admission was detected 24 hours later (above 99.9% homology of nucleotide sequence). Basic clinical and biochemical characteristics were similar among patients with or without the presence of bacterial DNA.

CONCLUSION

Detection of gram negative bacteria derived bacterial DNA in our series supports the contention that bacterial translocation is a systemic process in approximately 20% of patients with acute pancreatitis that does not seem to be related to the severity of the episode or immediate development of infection.

Effects of dietary lectins on ion transport in epithelia

Phytohemagglutinins are widely distributed in common food items. They constitute a heterogeneous group of proteins, which are often resistant to proteolysis in the gastrointestinal tract. Upon binding to the luminal membrane of intestinal cells, they can interfere with digestive, protective or secretory functions of the intestine. Phytohemagglutinins present in red kidney beans and jackbeans have been shown to induce diarrhea and hypersecretion in human airways, but the underlying mechanisms remain obscure. We examined how agglutinins from wheat germ (WGA), soy bean (SBA), red kidney beans (Pha-E, Pha-L), and jackbeans (Con-A) affect ion transport in mouse airways and large intestine using Ussing chamber techniques. We found that Pha-E, Pha-L, and Con-A but not WGA and SBA inhibit electrogenic Na(+) absorption dose dependently in both colon and trachea. The inhibitory effects of Con-A on Na(+) absorption were suppressed by the sugar mannose, by inhibition of phospholipase C (PLC) and protein kinase C (PKC). Thus, nutritional phytohemagglutinins block salt absorption in a PLC- and PKC-dependent manner, probably by inhibition of the epithelial Na(+) channel (ENaC). This effect may be therapeutically useful in patients suffering from cystic fibrosis.

Dietary fructo-oligosaccharides and lactulose inhibit intestinal colonisation but stimulate translocation of salmonella in rats

BACKGROUND AND AIMS

It is frequently assumed that dietary non-digestible carbohydrates improve host resistance to intestinal infections by stimulating the protective gut microflora. However, compelling scientific evidence from in vivo infection studies is lacking. Therefore, we studied the effect of several non-digestible carbohydrates on the resistance of rats to Salmonella enteritidis infection.

METHODS

Rats (n=8 per group) were fed "humanised" purified diets containing 4% lactulose, fructo-oligosaccharides (FOS), resistant starch, wheat fibre, or cellulose. After an adaptation period of 2 weeks the animals were orally infected with S enteritidis. Supplement induced changes in faecal biochemical and microbiological parameters were studied before infection. Colonisation of salmonella was determined by studying the faecal excretion of this pathogen and translocation by analysis of urinary nitric oxide metabolites over time and classical organ cultures. Intestinal mucosal myeloperoxidase activity was determined to quantify intestinal inflammation after infection.

RESULTS

Despite stimulation of intestinal lactobacilli and bifidobacteria and inhibition of salmonella colonisation, FOS and lactulose significantly enhanced translocation of this pathogen. These supplements also increased cytotoxicity of faecal water and faecal mucin excretion, which may reflect mucosal irritation. In addition, caecal and colonic, but not ileal, mucosal myeloperoxidase activity was increased in infected rats fed FOS and lactulose. In contrast, cellulose, wheat fibre, and resistant starch did not affect the resistance to salmonella.

CONCLUSIONS

In contrast to most expectations, FOS and lactulose impair the resistance of rats to intestinal salmonella infection. Obviously, stimulation of the endogenous lactobacilli and bifidobacteria is no guarantee of improved host defence against intestinal infections.

Gastrointestinal disorders of the critically ill. Bacterial translocation in the gut

The human gastrointestinal tract is colonized by a dense population of microorganisms, referred to as the bacterial flora. Although the gut provides a functional barrier between these organisms and the host, bacterial translocation is a common event in the healthy person. However, in critically ill patients, with various underlying diseases, this bacterial translocation may lead to infections and consequently to a further reduction in general health status. The mechanism of bacterial translocation is widely, and somehow controversially investigated in vitro and in animal models. In human studies, several diseases have been associated with bacterial translocation. However, methodological shortcomings, insufficient populations and conflicting results leave many open questions. This is also reflected in the various published therapeutic strategies. To overcome this problem more investigations in humans are needed, especially in techniques for detecting bacterial translocation.

Vitamin A, infection, and immune function

In populations where vitamin A availability from food is low, infectious diseases can precipitate vitamin A deficiency by decreasing intake, decreasing absorption, and increasing excretion. Infectious diseases that induce the acute-phase response also impair the assessment of vitamin A status by transiently depressing serum retinol concentrations. Vitamin A deficiency impairs innate immunity by impeding normal regeneration of mucosal barriers damaged by infection, and by diminishing the function of neutrophils, macrophages, and natural killer cells. Vitamin A is also required for adaptive immunity and plays a role in the development of T both-helper (Th) cells and B-cells. In particular, vitamin A deficiency diminishes antibody-mediated responses directed by Th2 cells, although some aspects of Th1-mediated immunity are also diminished. These changes in mucosal epithelial regeneration and immune function presumably account for the increased mortality seen in vitamin A-deficient infants, young children, and pregnant women in many areas of the world today.

Ammonia and glutamine metabolism during liver insufficiency: the role of kidney and brain in interorgan nitrogen exchange

BACKGROUND

During liver failure, urea synthesis capacity is impaired. In this situation the most important alternative pathway for ammonia detoxification is the formation of glutamine from ammonia and glutamate. Information is lacking about the quantitative and qualitative role of kidney and brain in ammonia detoxification during liver failure.

METHODS

This review is based on own experiments considered against literature data.

RESULTS AND CONCLUSIONS

Brain detoxifies ammonia during liver failure by ammonia uptake from the blood, glutamine synthesis and subsequent glutamine release into the blood. Although quantitatively unimportant, this may be qualitatively important, because it may influence metabolic and/or neurotransmitter glutamate concentrations. The kidney plays an important role in adaptation to hyperammonaemia by reversing the ratio of ammonia excreted in the urine versus ammonia released into the blood from 0.5 to 2. Thus, the kidney changes into an organ that netto removes ammonia from the body as opposed to the normal situation in which it adds ammonia to the body pools.