Markers of bacterial translocation in end-stage liver disease

Abstract

Bacterial translocation (BT) refers to the passage of viable bacteria or bacterial products from the intestinal lumen, through the intestinal epithelium, into the systemic circulation and extraintestinal locations. The three principal mechanisms that are thought to be involved in BT include bacterial overgrowth, disruption of the gut mucosal barrier and an impaired host defence.BT is commonly observed in liver cirrhosis and has been shown to play an important role in the pathogenesis of the complications of end stage liver disease, including infections as well as hepatic encephalopathy and hepatorenal syndrome. Due to the importance of BT in the natural history of cirrhosis, there is intense interest for the discovery of biomarkers of BT. To date, several such candidates have been proposed, which include bacterial DNA, soluble CD14, lipopolysaccharides endotoxin, lipopolysaccharide-binding protein, calprotectin and procalcitonin. Studies on the association of these markers with BT have demonstrated not only promising data but, oftentimes, contradictory results. As a consequence, currently, there is no optimal marker that may be used in clinical practice as a surrogate for the presence of BT.

Circulating levels of 3‐hydroxymyristate, a direct quantification of endotoxaemia in noninfected cirrhotic patients

“…Bacterial endotoxin (lipopolysaccharide [LPS]) induces high levels of proinflammatory cytokines and the release of nitric oxide, resulting in superimposed endothelial activation, splanchnic vasodilatation, thus worsening portal hypertension (PH), even in the absence of obvious infection and perpetuating BT. Several studies have evaluated whether markers of BT could identify cirrhotic patients with detrimental events and poor prognosis, but no marker has yet emerged as an ideal surrogate of BT . LPS is the culprit component of the outer surface of Gram‐negative bacteria and has thus been considered as a marker of endotoxaemia.…”

Increased serum C‐reactive protein and decreased urinary aquaporin 2 levels are predictive of the efficacy of tolvaptan in patients with liver cirrhosis

“…Serum soluble CD14 (sCD14) is cleaved and released from membrane‐bound CD14 on peripheral blood mononuclear cells by inflammatory responses of lipopolysaccharides, with serum levels of sCD14 increasing as chronic liver disease progress . Furthermore, higher sCD14 is associated with bacterial translocation (BT) . Moreover, BT in patients with decompensated LC promotes portal hypertension and induces variceal bleeding, hepatorenal syndrome, and hepatic encephalopathy …”

The proportion of different interleukin‐17‐producing T‐cell subsets is associated with liver fibrosis in chronic hepatitis C

“…Much evidence has suggested that elevated plasmatic levels of soluble CD14 (sCD14) are indicative of bacterial translocation . Recent studies have demonstrated a relationship between sCD14 and hepatic disease outcomes in chronically HCV‐infected individuals .…”