Role of bacterial infection in diet-induced acute pancreatitis in mice

The Effects of Total Colectomy on Bacterial Translocation in a Model of Acute Pancreatitis

Prevention of secondary infection is currently the main goal of treatment for acute necrotizing pancreatitis. Colon was considered as the main origin of secondary infection. Our aim was to investigate whether prophylactic total colectomy would reduce the rate of bacterial translocation and infection of pancreatic necrosis. Forty-two Sprague-Dawley rats were used. Pancreatitis was created by ductal infusion of sodium taurocholate. Rats were divided into four groups: group-1, laparotomy + pancreatic ductal infusion of saline; group-2, laparotomy + pancreatic ductal infusion of sodium taurocholate; group-3, total colectomy + pancreatic ductal infusion of saline; and group-4, total colectomy + pancreatic ductal infusion of sodium taurocholate. Forty-eight hours later, tissue and blood samples were collected for microbiological and histopathological analysis. Total colectomy caused small bowel bacterial overgrowth with gram-negative and gram-positive microorganisms. Bacterial count of gram-negative rods in the small intestine and pancreatic tissue in rats with colectomy and acute pancreatitis were significantly higher than in rats with acute pancreatitis only (group-2 versus group-4; small bowel, p = <0.001; pancreas, p = 0.002). Significant correlation was found between proximal small bowel bacterial overgrowth and pancreatic infection (r = 0,836, p = 0.001). In acute pancreatitis, prophylactic total colectomy (which can mimic colonic cleansing and reduction of colonic flora) induces small bowel bacterial overgrowth, which is associated with increased bacterial translocation to the pancreas.

Study of the protective effects of dexamethasone on ileum mucosa injury in rats with severe acute pancreatitis

OBJECTIVES

To study the protecting effects of dexamethasone on ileum mucosa injury of rats with severe acute pancreatitis (SAP).

METHODS

The SAP rats were prepared by improved Aho's methods. The plasma endotoxin and inflammatory mediators in serum were determined. The rat mortality, pathological changes of terminal ileum, nuclear factor kappa B (NF-kappaB), apoptotic indexes, and apoptotic related protein expression were observed.

RESULTS

The plasma endotoxin, inflammatory mediators, and NF-kappaB protein expression as well as pathological scores of the treatment group of ileum mucosa were lower than those of the model group at different time points. P selectin in model group significantly exceeded the dexamethasone treatment group at 3 and 6 hours (P < 0.01, P < 0.05). Caspase-3 protein expression in dexamethasone treatment group significantly exceeded the model group at 3 and 6 hours (P < 0.05), and apoptotic indexes were higher than those of the model group at 6 hours (P < 0.05), but Bax protein has shown no marked difference among groups.

CONCLUSIONS

Dexamethasone can reduce the endotoxin level and inflammatory mediators and down-regulate NF-kappaB protein expression of ileum mucosa, and ileum mucosa epithelial cell apoptosis induction was involved as well. The tissue microarrays technique is of advantage in SAP study.

Prophylactic antibiotics and pancreatic necrosis

Recent controlled clinical studies suggest a positive effect of early antibiotic treatment on late morbidity and mortality in severe acute pancreatitis. In contrast, widespread use of antibiotics may lead to an increased number of fungal infections and multiresistant bacteria. Optimal choice, duration, and route of administration of the antibiotic agent(s) are far from being established. The additional administration of an antifungal agent with prophylactic intention cannot be supported by the currently available data.

Infected bile-induced acute pancreatitis in rabbits. The role of bacteria

CONCLUSIONS

Bacteria species commonly found in bile of patients with choledocholithiasis render human bile toxic to the pancreas. The severity of infected bile-induced acute pancreatitis depends on the bacterial species. Infected bile-induced acute pancreatitis turns into a sterile inflammation within 10 d.

BACKGROUND

Flow of bile into the pancreatic duct was proposed to cause some forms of gallstone pancreatitis. The development of bile-induced acute pancreatitis at physiologic ductal pressure is known to depend on the bacterial infection of bile. In this study, we investigated the effect of a variety of bacteria species commonly found in bile of patients with choledocholithiasis upon the pancreatic toxicity of human bile. The time-course of pancreatic infection in infected bile-induced acute pancreatitis was also analyzed.

METHODS

In rabbits, the pancreatic duct was kept obstructed throughout the experiment. After 24 h, 50 microL of pancreatic juice was obtained from the congested pancreatic duct and replaced with the same quantity of infected human bile. Bile contained bacteria (10(7) microorganisms/microL) of species frequently found in choledochal secretions of patients with gallstone disease. Effects on pancreatic morphology were studied after 48 h. In another experiment, the number of Escherichia coli/mg of pancreatic tissue was determined in a time sequence study following exposure of the rabbit pancreatic duct to 50 microL E. coli-infected bile (10(7) microorganisms/mL) and temporary (12 h) or permanent duct obstruction.

RESULTS

Sterile bile was not harmful to the pancreas. Infected bile caused an interstitial-edematous pancreatitis with occasional acinar necrosis. The severity of acute pancreatitis depended on the bacterial species. Following pancreatic duct exposure to E. coli-infected bile, there was complete clearance of the bacteria from the gland with a concomitant interstitial leukocyte infiltration within a period of 2-10 d.

Pathogenesis and prevention of early pancreatic infection in experimental acute necrotizing pancreatitis

OBJECTIVE

The authors test antibiotic strategies aimed at either mitigating bacterial translocation from the gut or delivering antibiotics specifically concentrated by the pancreas for prevention of early secondary infection after acute necrotizing pancreatitis.

BACKGROUND

Infection currently is the principal cause of death after severe pancreatitis. The authors have shown that the risk of bacterial infection correlates directly with the degree of tissue injury in a rodent model of pancreatitis. Bacteria most likely arrive by translocation from the colon.

METHODS

Severe acute necrotizing pancreatitis was induced in rats by a combination of low-dose controlled intraductal infusion of glycodeoxycholic acid superimposed on intravenous cerulein hyperstimulation. At 6 hours, animals were randomly allocated to five treatment groups: controls, selective gut decontamination (oral antibiotics and cefotaxime), oral antibiotics alone, cefotaxime alone, or imipenem. At 96 hours, surviving animals were killed for quantitative bacterial study of the cecum, pancreas, and kidney.

RESULTS

The 96-hour mortality (35%) was unaffected by any treatment regimen. Cecal gram-negative bacteria were significantly reduced only by the oral antibiotics. Pancreatic infection was significantly reduced by full-gut decontamination and by imipenem, but not by oral antibiotics or by cefotaxime alone. Renal infection was reduced by both intravenous antibiotics.

CONCLUSIONS

Early pancreatic infection after acute necrotizing pancreatitis can be reduced with a full-gut decontamination regimen or with an antibiotic concentrated by the pancreas (imipenem) but not by unconcentrated antibiotics of similar spectrum (cefotaxime) or by oral antibiotics alone. These findings suggest that 1) both direct bacterial translocation from the gut and hematogenous seeding interplay in pancreatic infection while hematogenous seeding is dominant at extrapancreatic sites and 2) imipenem may be useful in clinical pancreatitis.

Controlled clinical trial of selective decontamination for the treatment of severe acute pancreatitis

OBJECTIVE

A randomized, controlled, multicenter trial was undertaken in 102 patients with objective evidence of severe acute pancreatitis to evaluate whether selective decontamination reduces mortality.

SUMMARY BACKGROUND DATA

Secondary pancreatic infection is the major cause of death in patients with acute necrotizing pancreatitis. Controlled clinical trials to study the effect of selective decontamination in such patients are not available.

METHODS

Between April 22, 1990 and April 19, 1993, 102 patients with severe acute pancreatitis were admitted to 16 participating hospitals. Patients were entered into the study if severe acute pancreatitis was indicated, on admission, by multiple laboratory criteria (Imrie score > or = 3) and/or computed tomography criteria (Balthazar grade D or E). Patients were randomly assigned to receive standard treatment (control group) or standard treatment plus selective decontamination (norfloxacin, colistin, amphotericin; selective decontamination group). All patients received full supportive treatment, and surveillance cultures were taken in both groups.

RESULTS

Fifty patients were assigned to the selective decontamination group and 52 were assigned to the control group. There were 18 deaths in the control group (35%), compared with 11 deaths (22%) in the selective decontamination group (adjusted for Imrie score and Balthazar grade: p = 0.048). This difference was mainly caused by a reduction of late mortality (> 2 weeks) due to significant reduction of gram-negative pancreatic infection (p = 0.003). The average number of laparotomies per patient was reduced in patients treated with selective decontamination (p < 0.05). Failure of selective decontamination to prevent secondary gram-negative pancreatic infection with subsequent death was seen in only three patients (6%) and transient gram-negative pancreatic infection was seen in one (2%). In both groups of patients, all gram-negative aerobic pancreatic infection was preceded by colonization of the digestive tract by the same bacteria.

CONCLUSION

Reduction of gram-negative colonization of the digestive tract, preventing subsequent pancreatic infection by means of selective decontamination, significantly reduces morbidity and mortality in patients with severe acute necrotizing pancreatitis.

Time course of bacterial infection of the pancreas and its relation to disease severity in a rodent model of acute necrotizing pancreatitis

BACKGROUND

Bacterial infection of pancreatic necrosis is thought to be a major determinant of outcome in acute necrotizing pancreatitis. The determinants and possibilities for prophylaxis are unknown and difficult to study in humans.

OBJECTIVE

The time course of bacterial infection of the pancreas in a rodent model of acute necrotizing pancreatitis was characterized. The authors ascertained if there is a correlation with the degree of necrosis.

METHODS

Acute pancreatitis (AP) of graded severity was induced under sterile conditions by an intravenous infusion of cerulein (5 micrograms/kg/hr) for 6 hours (mild AP), or a combination of intravenous cerulein with an intraductal infusion of 10-mM glycodeoxycholic acid (0.2 mL for 2 min for moderate AP, 0.5 mL for 10 min for severe AP). Sham-operated animals (intravenous and intraductal NaCl 0.9%) served as controls. Ninety-six hours after induction, animals were killed for quantitative bacterial examination and histologic scoring of necrosis. In addition, groups of animals with severe AP were investigated at 12, 24, 48, 96, and 144 hours.

RESULTS

No significant pancreatic necrosis was found in control animals (0.3 +/- 0.1) or animals with mild AP (0.6 +/- 0.1) killed at 96 hours. Necrosis scores were 1.1 +/- 0.2 for animals with moderate AP and 1.9 +/- 0.2 for animals with severe AP. Control animals did not develop significant bacterial infection of the pancreas (> or = 10(3) CFU/g). At 96 hours, the prevalence of infection was 37.5% in animals with mild AP and 50% in animals with moderate AP. In animals with severe AP, infection of the pancreas increased from 33% in the first 24 hours to 75% between 48 and 96 hours (p < 0.05). The bacterial counts and the number of different species increased with time and was maximal (> 10(11) CFU/g) at 96 hours.

CONCLUSION

Bacterial infection of the pancreas in rodent AP increases during the first several days, and its likelihood correlates with the severity of the disease. This model, which closely mimics the features of human acute pancreatitis, provides a unique opportunity to study the pathogenesis of infected necrosis and test therapeutic strategies.

Early increase in intestinal permeability in patients with severe acute pancreatitis: correlation with endotoxemia, organ failure, and mortality

Sepsis accounts for 80% of deaths from acute pancreatitis. This study aimed to investigate early changes in intestinal permeability in patients with acute pancreatitis, and to correlate these changes with subsequent disease severity and endotoxemia. The renal excretion of enterally administered polyethylene glycol (PEG) 3350 and PEG 400 was measured within 72 hours of onset of acute pancreatitis to determine intestinal permeability. Severity was assessed on the basis of APACHE II scores and C-reactive protein measurements. Serum endotoxin and antiendotoxin antibodies were measured on admission. Eight-five patients with acute pancreatitis (mild in 56, severe in 29) and 25 healthy control subjects were studied. Urinary excretion of PEG 3350 (median) was significantly greater in patients who had severe attacks (0.61%) compared to those with mild disease (0.09%) and health control subjects (0.12%) (P <0. 0001), as was the permeability index (PEG 3350/400 excretion) (P <0. 00001). The permeability index was significantly greater in patients who subsequently developed multiple organ system failure and/or died compared with other severe cases (0.16 vs. 0.04) (P = 0.0005). The excretion of PEG 3350 correlated strongly with endotoxemia (r = 0.8; P = 0.002). Early increased intestinal permeability may play an important role in the pathophysiology of severe acute pancreatitis. Therapies that aim to restore intestinal barrier function may improve outcome.