Intestinal bacterial overgrowth and bacterial translocation in cirrhotic rats with ascites

Diagnosis of small intestinal bacterial overgrowth in patients with cirrhosis of the liver: poor performance of the glucose breath hydrogen test

BACKGROUND/AIMS

Small intestinal bacterial overgrowth is known to occur in association with cirrhosis of the liver and studies are needed to assess its pathophysiological role. The glucose breath hydrogen test as an indirect test for small intestinal bacterial overgrowth has been applied to patients with cirrhosis but has not yet been validated against quantitative culture of jejunal secretion in this particular patient population.

METHODS

Forty patients with cirrhosis underwent glucose breath hydrogen test and jejunoscopy. Jejunal secretions were cultivated quantitatively for aerobe and anaerobe microorganisms.

RESULTS

Small intestinal bacterial overgrowth was detected by culture of jejunal aspirates in 73% of patients, being associated with age and the administration of acid-suppressive therapy. The glucose breath hydrogen test correlated poorly with culture results, sensitivity and specificity ranging from 27%-52% and 36%-80%, respectively.

CONCLUSIONS

In patients with cirrhosis, the glucose breath hydrogen test correlates poorly with the diagnostic gold standard for small intestinal bacterial overgrowth. Until other non-invasive tests have been validated, studies addressing the role of small intestinal bacterial overgrowth in patients with cirrhosis should resort to microbiological culture of jejunal secretions.

Effect of cisapride on intestinal bacterial overgrowth and bacterial translocation in cirrhosis

Deranged intestinal motility, which occurs in cirrhosis, may facilitate the development of intestinal bacterial overgrowth (IBO), which can lead to bacterial translocation (BT). To assess the effect of cisapride on IBO and BT in cirrhosis, cirrhotic rats received cisapride or a placebo for 7 days, and measurements of jejunal bacterial content and BT studies were performed. In addition, jejunal fluid from 46 cirrhotic patients was obtained for quantitative bacterial culture. Those patients in whom gram-negative IBO was detected were randomized to receive or not to receive cisapride (20 mg twice per day) for 1 week. Cisapride significantly reduced IBO in cirrhotic rats. In addition, no BT was documented in treated animals, whereas it occurred in 40% in nontreated cirrhotic rats. Total IBO was documented in 23 of 46 cirrhotic patients, which was caused by gram-negative organisms in 10 cases. Orocecal transit time (OCT) significantly decreased after cisapride therapy, and was associated with the abolishment of bacterial overgrowth caused by gram-negative organisms in 4 out of 5 treated patients, whereas it persisted in nontreated cases. Cisapride administration to cirrhotic rats resulted in a reduction of the IBO, which is associated with a marked decrease in BT. On the other hand, cisapride facilitates the abolition of IBO caused by gram-negative organisms in cirrhotic patients.

Systemic bacterial invasion induced by sleep deprivation

Profound sleep disruption in humans is generally believed to cause health impairments. Through comparative research, specific physical effects and underlying mechanisms altered by sleep deprivation are being elucidated. Studies of sleep-deprived animals previously have shown a progressive, chronic negative energy balance and gradual deterioration of health, which culminate in fatal bloodstream infection without an infectious focus. The present study investigated the conditions antecedent to advanced morbidity in sleep-deprived rats by determining the time course and distribution of live microorganisms in body tissues that are normally sterile. The tissues cultured for microbial growth included the blood, four major organs, six regional lymph nodes, the intestine, and the skin. The principal finding was early infection of the mesenteric lymph nodes by bacteria presumably translocated from the intestine and bacterial migration to and transient infection of extraintestinal sites. Presence of pathogenic microorganisms and their toxins in tissues constitutes a septic burden and chronic antigenic challenge for the host. Bacterial translocation and pathogenic sequelae provide mechanisms by which sleep deprivation appears to adversely affect health.

Effect of propranolol on the factors promoting bacterial translocation in cirrhotic rats with ascites

Bacterial translocation appears to be an important mechanism in the pathogenesis of spontaneous infections in cirrhosis. Cirrhotic patients are commonly treated with beta-adrenoceptor blockers, but the impact of this treatment in the factors promoting bacterial translocation has not been investigated. This study was aimed at investigating in cirrhotic rats with ascites the effect of propranolol on intestinal bacterial load, transit, and permeability of the bowel and on the rate of bacterial translocation. Bacterial translocation to mesenteric lymph nodes and intestinal bacterial overgrowth, permeability (urinary excretion of (99m)Tc-diethylenetriaminepentaacetic acid [(99m)Tc-DTPA]), and transit (geometric center ratio of (51)Cr) were assessed in 29 rats with carbon tetrachloride (CCl(4)) cirrhosis and 20 controls. These variables were then measured in 12 placebo- and in 13 propranolol-treated ascitic cirrhotic rats. Bacterial translocation was present in 48% of the cirrhotic rats and in none of the controls. Cirrhotic rats with intestinal bacterial overgrowth had a significantly higher rate of translocation and slower intestinal transit than those without it. Among the 15 rats with overgrowth and a (99m)Tc-DTPA excretion greater than 10%, 15 had translocation and 2 had bacterial peritonitis. Only 1 of the 14 rats with either intestinal overgrowth or a (99m)Tc-DTPA excretion greater than 10% presented translocation. Compared with the placebo group, propranolol-treated animals had significantly lower portal pressure, faster intestinal transit, and lower rates of bacterial overgrowth and translocation. In ascitic cirrhotic rats, bacterial translocation results from intestinal overgrowth and severe damage to gut permeability. In this setting, intestinal overgrowth is associated with intestinal hypomotility. Propranolol accelerates the intestinal transit, decreasing the rates of bacterial overgrowth and translocation.

Spontaneous Bacterial Peritonitis

A suspicion, even if low, of spontaneous bacterial peritonitis (SBP) should prompt a diagnostic paracentesis to be performed on presentation. Empiric antibiotic therapy with a third-generation cephalosporin should commence upon demonstration of over 250 granulocytes/mm(3) in ascitic fluid. Treatment for 5 days in uncomplicated SBP is sufficient; persistent symptoms and/or ascites fluid showing persistent granulocytosis (over 250 cells/mm(3)) should be handled by broadening of antibiotic spectrum and searching for secondary causes of peritonitis. Antibiotic prophylaxis for cirrhotic patients with ascites and acute gastrointestinal hemorrhage and in those with a prior history of SBP is indicated.

Bacterial translocation in cirrhotic rats stimulates eNOS-derived NO production and impairs mesenteric vascular contractility

Nitric oxide (NO) has been implicated in the arterial vasodilation and associated vascular hyporesponsiveness to vasoconstrictors observed in liver cirrhosis. Bacteria, potent activators of NO and TNF-alpha synthesis, are found in the mesenteric lymph nodes (MLNs) of ascitic cirrhotic rats. Here, we investigated the impact of bacterial translocation (BT) to MLNs on TNF-alpha production, vascular NO release, and contractility in the mesenteric vasculature of ascitic cirrhotic rats. Vascular response to the alpha-adrenoagonist methoxamine, which is diminished in the superior mesenteric arterial beds of cirrhotic rats, is further blunted in the presence of BT. BT promoted vascular NO release in cirrhotic rats, an effect that depended on pressure-induced shear stress and was blocked by the NO inhibitor N(omega)-nitro-L-arginine. Removing the endothelium had the same effect. Endothelial NO synthase (eNOS), but not the inducible isoform (iNOS), was present in mesenteric vasculature of cirrhotic rats with and without BT, and its expression was enhanced compared with controls. TNF-alpha was induced in MLNs by BT and accumulated in parallel in the serum. This TNF-alpha production was associated with elevated levels of tetrahydrobiopterin (BH(4)), a TNF-alpha-stimulated cofactor and enhancer of eNOS-derived NO biosynthesis and NOS activity in mesenteric vasculature. These findings establish a link between BT to MLNs and increased TNF-alpha production and elevated BH(4) levels enhancing eNOS-derived NO overproduction, further impairing contractility in the cirrhotic mesenteric vasculature.

Trichloroethylene activates CD4+ T cells: potential role in an autoimmune response

Trichloroethylene is an industrial solvent and has become a major environmental contaminant. Autoimmune-prone MRL +/+ mice were treated for up to 22 weeks with trichloroethylene in the drinking water (0, 2.5, and 5.0 mg/mL) in order to study the immunoregulatory effects of this environmental toxicant. After only 4 weeks of treatment, trichloroethylene was shown to promote the expansion of CD4+ T cells that expressed a memory/activation phenotype (i.e., CD44hi CD45RBlo) and secreted high levels of IFN-gamma, but not IL-4. In addition, trichloroethylene treatment accelerated the development of an autoimmune response in the MRL +/+ mice as evidenced by an earlier appearance of antinuclear antibodies and increased levels of total IgG2a. MRL +/+ mice treated with trichloroethylene for 22 weeks also contained antibodies specific for trichloroethylene adducts, suggesting the activation of trichloroethylene-specific T cells. The results suggest that trichloroethylene can stimulate antigen nonspecific as well as specific T cells that are capable of promoting autoimmunity in genetically predisposed individuals.

Development of quinolone-resistant strains of Escherichia coli in stools of patients with cirrhosis undergoing norfloxacin prophylaxis: clinical consequences

BACKGROUND/AIM

Norfloxacin prophylaxis decreases the incidence of bacterial infections in high-risk cirrhotic patients, but may promote the development of quinolone-resistant gram-negative bacteria in stools, and eventually lead to infections due to these bacteria. The aim of the study was to evaluate the prevalence of quinolone-resistant strains of E. coli in stools on admission, and the characteristics of any nosocomial infections.

METHODS

Eighty-three consecutively hospitalized cirrhotic patients were included in this prospective study. The presence of quinolone-resistant strains of E. coli in stools on admission, and the characteristics of any nosocomial infections were recorded.

RESULTS

Fourteen out of 83 patients (16.8%) showed quinolone-resistant E. coli in stools (Group I), and 69 did not (Group II). Thirteen out of 14 from Group I (92.8%) and 17/69 (24.6) from Group II had received primary or secondary prophylaxis with norfloxacin (p<0.001). During hospitalization, 12/12 (100%) of patients from Group I and 25/66 (37.8%) of patients from Group II underwent norfloxacin prophylaxis. Three bacterial infections in patients from Group I, 3 from Group II patients receiving norfloxacin and 16 from Group II patients not receiving norfloxacin were recorded (p<0.05). No infections due to quinolone-resistant E. coli were observed in patients colonized with these bacteria. Treatment with norfloxacin induced the development of quinolone-resistant E. coli in 6/14 (42.8%) patients in a mean time of 18.5+/-9.8 days.

CONCLUSIONS

The development of quinolone-resistant strains of E. coli is significantly associated with previous administration of norfloxacin prophylaxis. However, in our series this fact is not associated with an increased incidence of quinolone-resistant E. coli or other gram-negative infections.

Infections caused by Escherichia coli resistant to norfloxacin in hospitalized cirrhotic patients

Selective intestinal decontamination with norfloxacin is useful to prevent bacterial infections in several groups of cirrhotic patients at high risk of infection. However, the emergence of infections caused by Escherichia coli resistant to quinolones has recently been observed in cirrhotic patients undergoing prophylactic norfloxacin. Our aim is to determine the characteristics of the infections caused by E. coli resistant to norfloxacin in hospitalized cirrhotic patients. One hundred and six infections caused by E. coli in 99 hospitalized cirrhotic patients were analyzed and distributed into two groups: group I (n = 67), infections caused by E. coli sensitive to norfloxacin, and group II (n = 39), infections caused by E. coli resistant to norfloxacin. The clinical and analytical characteristics at diagnosis of the infection were similar in both groups. Previous prophylaxis with norfloxacin was more frequent in group II (15/67, 22.4% vs. 32/39, 82%, P <.0001), as a result of a higher number of patients submitted to continuous long-term prophylaxis in this group, whereas previous short-term prophylaxis was similar in both groups. Infections were more frequently nosocomial-acquired in group II than in group I (17/67, 25.3% vs. 20/39, 51.2%, P =.01). The type of infections was similar in both groups: urinary tract infections 38 in group I and 24 in group II, spontaneous bacterial peritonitis 8 and 2, spontaneous bacteremia 4 and 4, and bacterascites 1 and 0, respectively (pNS). Mortality during hospitalization was similar in the two groups (4/67, 5.9% vs. 5/39, 12.8%, pNS). None of the E. coli resistant to norfloxacin were also resistant to cefotaxime and only one of them was resistant to amoxicillin-clavulanic acid. Prophylaxis with norfloxacin, usually continuous long-term prophylaxis, favors the development of infections caused by norfloxacin-resistant E. coli. Long-term antibiotic prophylaxis should therefore be restricted to highly selected groups of cirrhotic patients at high-risk of infection. Infections caused by E. coli resistant to norfloxacin show a severity similar to those caused by sensitive E. coli. No significant associated resistance between norfloxacin and the antibiotics most frequently used in the treatment of bacterial infections in cirrhotic patients has been observed.

Small intestine dysmotility and bacterial overgrowth in cirrhotic patients with spontaneous bacterial peritonitis

Patients with bacterial overgrowth of the small intestine developed spontaneous bacterial peritonitis (SBP) more frequently than patients without bacterial overgrowth of the small intestine. The objective of this study was to determine whether the incidences of small intestine dysmotility and bacterial overgrowth are higher in cirrhotic patients with a history of SBP than in cirrhotic patients without SBP. Forty cirrhotic patients were enrolled in this study. There were 20 patients with a history of SBP and 20 patients without a history of SBP. Small intestine bacterial overgrowth was diagnosed by breath hydrogen test. Small intestine motility was recorded, by a 3-channel solid-state manometric catheter, for 24 hours. There were no statistical differences in age or sex between the two groups. The Child-Pugh scores in the SBP group were higher than in the non-SBP group (10.5 +/- 2.1 vs. 8.1 +/- 1.9, P < .01). The incidence of bacterial overgrowth of the small intestine was higher in the SBP group than in the non-SBP group (70% vs. 20%, P < .01). The amplitude and duration of migrating motor complex (MMC) activity fronts, as well as the number of clusters per hour, were similar in both groups. However, the frequency of MMC activity fronts was higher in the non-SBP group than in the SBP group (4.8 +/- 2.3/24 hours vs. 3.5 +/- 1.2/24 hours, P < .05). In addition, the MMC velocity was significantly higher in the non-SBP group (8.3 +/- 2.6 vs. 5.3 +/- 2.1 cm/min, P < .01). The incidence of bacterial overgrowth of the small intestine was higher in cirrhotic patients with history of SBP than in those without SBP. Small intestine motility dysfunction was more severe in cirrhotic patients with history of SBP. Impaired motility of the small intestine, causing bacterial overgrowth of the small intestine, may be one of the explanations for recurrent SBP in cirrhotic patients.