José Such

Bacterial infections in cirrhosis: A position statement based on the EASL Special Conference 2013

Bacterial infections are very common and represent one of the most important reasons of progression of liver failure, development of liver-related complications, and mortality in patients with cirrhosis. In fact, bacterial infections may be a triggering factor for the occurrence of gastrointestinal bleeding, hypervolemic hyponatremia, hepatic encephalopathy, kidney failure, and development of acute-on-chronic liver failure. Moreover, infections are a very common cause of repeated hospitalizations, impaired health-related quality of life, and increased healthcare costs in cirrhosis. Bacterial infections develop as a consequence of immune dysfunction that occurs progressively during the course of cirrhosis. In a significant proportion of patients, infections are caused by gram-negative bacteria from intestinal origin, yet gram-positive bacteria are a frequent cause of infection, particularly in hospitalized patients. In recent years, infections caused by multidrug-resistant bacteria are becoming an important clinical problem in many countries. The reduction of the negative clinical impact of infections in patients with cirrhosis may be achieved by a combination of prophylactic measures, such as administration of antibiotics, to reduce the occurrence of infections in high-risk groups together with early identification and management of infection once it has developed. Investigation on the mechanisms of altered gut microflora, translocation of bacteria, and immune dysfunction may help develop more effective and safe methods of prevention compared to those that are currently available. Moreover, research on biomarkers of early infection may be useful in early diagnosis and treatment of infections. The current manuscript reports an in-depth review and a position statement on bacterial infections in cirrhosis.

Selective intestinal decontamination prevents spontaneous bacterial peritonitis

In a prospective randomized study, selective intestinal decontamination with norfloxacin was performed during hospitalization in 32 cirrhotic patients with low ascitic fluid total protein levels. The incidence of infections was compared with that in a control group of 31 nontreated cirrhotic patients of similar characteristics. We found a significantly lower incidence of infections [1/32 (3.1%) vs. 13/31 (41.9%); P less than 0.005] and spontaneous bacterial peritonitis [0/32 (0%) vs. 7/31 (22.5%); P less than 0.05] in patients receiving norfloxacin. The lower incidence of extraperitoneal infections [1/32 (3.1%) vs. 7/31 (22.5%); P = 0.052] in the treated group did not reach statistical significance. The incidence of infections [1/28 (3.6%) vs. 9/22 (40.9%); P less than 0.01] and spontaneous bacterial peritonitis [0/28 (0%) vs. 5/22 (22.7%); P less than 0.05] in cirrhotic patients admitted because of ascites was also significantly lower in the treated group. The decrease in the rate of mortality observed in the group undergoing selective intestinal decontamination did not reach statistical significance. These data show that selective intestinal decontamination is useful to prevent spontaneous bacterial peritonitis and extraperitoneal infections in hospitalized cirrhotic patients with low ascitic fluid total protein levels.

Bacterial DNA in patients with cirrhosis and noninfected ascites mimics the soluble immune response established in patients with spontaneous bacterial peritonitis

Bacterial infections and severity of associated inflammatory reaction influence prognosis in patients with advanced cirrhosis. We compared the innate immune response to bacterial DNA (bactDNA) translocation with that caused by viable bacteria translocation in patients with spontaneous bacterial peritonitis and the relationship between the cytokine response and serum levels of bactDNA. The bactDNA translocation was investigated in 226 patients with cirrhosis and noninfected ascites, 22 patients with spontaneous bacterial peritonitis, and 10 patients with ascites receiving continuous norfloxacin. Serum and ascitic fluid tumor necrosis factor α, interferon‐γ, interleukin‐12, and nitric oxide metabolites were measured via enzyme‐linked immunosorbent assay. Bacterial genomic identifications were made via amplification and sequencing of the 16S ribosomal RNA gene and digital quantization with DNA Lab‐on‐chips. The bactDNA was present in 77 noninfected patients (34%) and in all cases of spontaneous bacterial peritonitis, even in those with culture‐negative ascitic fluid. No patient receiving norfloxacin showed bactDNA translocation. Levels of all cytokines were similar in patients with bactDNA translocation or spontaneous bacterial peritonitis and significantly higher than in patients without bactDNA or in those receiving norfloxacin. Serum bactDNA concentration paralleled levels of all cytokines and nitric oxide in a series of patients with bactDNA translocation or spontaneous bacterial peritonitis followed during 72 hours. Antibiotic treatment in the series of patients with spontaneous bacterial peritonitis did not abrogate bactDNA translocation in the short term. Conclusion: bactDNA translocation‐associated cytokine response is indistinguishable from that in patients with spontaneous bacterial peritonitis and is dependent on bactDNA concentration. Norfloxacin abrogates bactDNA translocation and cytokine response. (HEPATOLOGY 2008;47:978–985.)

Pathological bacterial translocation in cirrhosis: pathophysiology, diagnosis and clinical implications.

Bacterial translocation (BT) is defined by the passage of viable indigenous bacteria from the intestinal lumen to mesenteric lymph nodes (MLNs) and other territories, and its diagnostic criteria rely on the isolation of viable bacteria in MLNs. Small intestinal overgrowth, increased intestinal permeability and immunological alterations are the main factors involved in its pathogenesis. BT is obviously difficult to identify in patients with cirrhosis, and alternative methods have been proposed instead. Bacterial DNA detection and species identification in serum or ascitic fluid has been proposed as a reliable marker of BT. Bacterial products, such as endotoxin, or bacterial DNA can translocate to extra‐intestinal sites and promote an immunological response similar to that produced by viable bacteria. Therefore, pathological BT plays an important role in the pathogenesis of the complications of cirrhosis, not only in infections, but by exerting a profound inflammatory state and exacerbating the haemodynamic derangement. This may promote in turn the development of hepatorenal syndrome, hepatic encephalopathy and other portal hypertension‐related complications. Therapeutic approaches for the prevention of BT in experimental and human cirrhosis are summarized. Finally, new investigations are needed to better understand the pathogenesis and consequences of translocation by viable bacteria (able to grow in culture), or non‐viable BT (detection of bacterial fragments with negative culture) and open new therapeutic avenues in patients with cirrhosis.

Serum and ascitic fluid bacterial DNA: A new independent prognostic factor in noninfected patients with cirrhosis

We tested the hypothesis that the presence of bacterial DNA (bactDNA) in ascitic fluid and serum is associated with decreased survival in patients with cirrhosis. In a prospective, multicenter study, we analyzed the clinical evolution of 156 patients with cirrhosis and ascites (first or recurrence) with lower than 250 polymorphonuclear cells (PMN)/μL, negative ascites bacteriological culture, and absence of other bacterial infections being admitted for evaluation of large‐volume paracentesis, according to the presence of bactDNA at admission. Survival, causes of death, and successive hospital admissions were determined during a 12‐month follow‐up period. BactDNA was detected in 48 patients. The most prevalent identified bactDNA corresponded to Escherichia coli (n = 32/48 patients, 66.6%). Patients were followed for 12 months after inclusion and in this period 34 patients died: 16 of 108 (15%) bactDNA negative versus 18 of 48 (38%) bactDNA positive (P = 0.003). The most frequent cause of death was acute‐on‐chronic liver failure in both groups (7/16 and 9/18 in patients without or with bactDNA, respectively), although more prevalent in the first month of follow‐up in patients with presence of bactDNA (0 versus 4/7). When considering patients with model for end‐stage liver disease (MELD) score less than 15, mortality was significantly higher in those with presence of bactDNA. Spontaneous bacterial peritonitis developed similarly in patients with or without bactDNA at admission. Conclusion: The presence of bactDNA in a patient with cirrhosis during an ascitic episode is an indicator of poor prognosis. This fact may be related to the development of acute‐on‐chronic liver failure at short term and does not predict the development of spontaneous bacterial peritonitis. (HEPATOLOGY 2008;48:1924‐1931.)

Bacterial DNA activates cell mediated immune response and nitric oxide overproduction in peritoneal macrophages from patients with cirrhosis and ascites

Background and aims: Translocation of intestinal bacteria to ascitic fluid is probably the first step in the development of episodes of spontaneous bacterial peritonitis in patients with cirrhosis. We have recently reported the detection of bacterial DNA in blood and ascitic fluid from patients with advanced cirrhosis, what we consider as molecular evidence of bacterial translocation. Several studies have shown the immunogenic role of bacterial DNA in vitro, and we hypothesised that the presence of bacterial DNA could activate the type I immune response in peritoneal macrophages from these patients, leading to greater cytokine synthesis (interleukin (IL)-2 and IL-12, tumour necrosis factor α, and interferon γ) and effector molecules such as nitric oxide. Methods: Peritoneal macrophages obtained from patients with cirrhosis and culture negative non-neutrocytic ascitic fluid were collected and characterised by flow cytometry. Inducible nitric oxide synthase, nitric oxide levels, and cytokine production were measured by immunoenzymometric assays in basal and harvested conditions according to the presence/absence of bacterial DNA. Results: The ability of peritoneal macrophages to synthesise nitric oxide and levels of all cytokines were significantly increased in patients with bacterial DNA. There was a positive correlation between inducible nitric oxide synthase and nitric oxide levels. Conclusions: The presence of bacterial DNA in patients with decompensated cirrhosis is associated with marked activation of peritoneal macrophages, as evidenced by nitric oxide synthesising ability, together with enhanced cytokine production.

Bacterial DNA translocation is associated with systemic circulatory abnormalities and intrahepatic endothelial dysfunction in patients with cirrhosis

Presence of bacterial DNA in noninfected patients with cirrhosis and ascites is associated with a marked inflammatory response including activation of the inducible form of nitric oxide synthase and release of nitric oxide, similar to that observed in patients with spontaneous bacterial peritonitis. Although presence of bacterial DNA is associated with an impaired prognosis, no information is available regarding its hemodynamic consequences. Systemic and hepatic hemodynamics before and after a liquid test meal were assessed in a series of 75 noninfected patients with cirrhosis (55 with ascites). Bacterial DNA was measured by polymerase chain reaction. Bacterial DNA was detected only in patients with ascites. Clinical data and liver function were similar in ascitic patients with presence (n = 21) or absence of bacterial DNA (n = 34). Bacterial‐DNA(+) patients had significantly lower mean arterial pressure (P = 0.002) and systemic vascular resistance (P = 0.03) than bacterial‐DNA(−) patients. Cardiac output, cardiopulmonary pressures, hepatic venous pressure gradient (HVPG), and hepatic blood flow were similar in both groups. Thirty minutes after the test meal, in response to increased blood flow caused by postprandial hyperemia, there was a significantly greater increase in HVPG and impaired hepatic vasorelaxation in bacterial‐DNA(+) as compared with bacterial‐DNA(−) patients, which indicates hepatic endothelial dysfunction. Indeed, the increase in HVPG after the test meal significantly correlated with serum bacterial DNA concentration. Conclusion: Presence of bacterial DNA, a marker of bacterial translocation, is associated with aggravation of peripheral vasodilation and with worsening of intrahepatic endothelial dysfunction. (HEPATOLOGY 2010;.)

Low C3 in cirrhotic ascites predisposes to spontaneous bacterial peritonitis

The risk of developing spontaneous bacterial peritonitis (SBP) in relation to the concentration of C3 in ascitic fluid (AF) has been studied prospectively in 33 patients with cirrhosis of the liver, seven of whom had one or more episodes of SBP during hospitalization. C3 concentrations in the AF of patients who developed infection (9.0 +/- 2.67 mg/dl) were significantly lower than in those who did not (18.26 +/- 8.11 mg/dl) (P less than 0.01). C4 concentrations were similar in both groups. A direct correlation was found between AF C3 and total protein concentrations (P less than 0.001). We conclude that a low C3 concentration in AF may predispose to SBP.

The detection of bacterial DNA in blood of rats with CCl4-induced cirrhosis with ascites represents episodes of bacterial translocation†

Bacterial DNA (bactDNA) is present in blood and ascitic fluid (AF) in a third of patients with cirrhosis and ascites, but whether this phenomenon represents episodes of bacterial translocation (BT), strictly considered when culture of mesenteric lymph nodes (MLNs) are positive, remains unknown. This study assessed the relationship between bactDNA detection in biological fluids and MLNs and went on to investigate the local and systemic inflammatory status according to its presence. Cirrhosis was induced in rats by ingestion of CCL4. A subgroup of five animals with cirrhosis received norfloxacin (5 mg/kg/day) for 7 days. MLNs and ascitic and pleural fluids were collected at laparotomy and cultured; samples were collected for identification of bactDNA and measurement of tumor necrosis factor‐alpha (TNF‐α), interleukin‐6 (IL‐6), and nitric oxide (NO). BactDNA was detected in MLNs in 12 of 19 animals (63.1%), corresponding in seven cases to culture‐positive MLNs, and in five to culture‐negative MLNs. BactDNA was detected in biological fluids in 11 of 19 animals (57.9%), and in all cases the same bacteria spp. detected in samples was present in MLNs. BactDNA was not detected in any biological sample from animals receiving norfloxacin. Tumor necrosis factor alpha (TNF‐α), IL‐6, and NO were similar in culture‐positive and culture‐negative/bactDNA‐positive samples, and significantly higher than those observed in animals with culture‐negative/bactDNA‐negative MLNs, animals with cirrhosis that were receiving norfloxacin, and controls. In conclusion, the presence of bactDNA in biological fluids in rats with cirrhosis constitutes a marker of BT, and it is associated with a marked inflammatory response, independent of the result of the culture. (HEPATOLOGY 2006.)

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.