Use of Bacterial DNA Concentration in Ascites as a Marker for Spontaneous Bacterial Peritonitis

Spontaneous bacterial peritonitis (SBP) is a common and serious complication in patients with decompensated cirrhosis. Precise quantification of bacterial DNA (bactDNA) and the related inflammatory response might add further information on the course of disease. The aim of the study was to evaluate the association between bactDNA, cytokine levels and clinical outcome.

Ascites and serum samples of 98 patients with decompensated liver cirrhosis (42 with SBP and 56 without SBP) as well as serum samples of 21 healthy controls were collected. BactDNA in ascites and serum was detected and quantified by 16S rRNA PCR. Concentrations of IL-1β, TNF-α, IL-6, IL-8 and IL-10 were measured by a LEGENDplexTM multi-analyte flow assay. Clinical data were collected and analyzed retrospectively.

BactDNA was detected more frequently in ascites of patients with SBP (n = 24/42; 57.1%) than in ascites of patients without SBP (n = 5/56; 8.9%; P < 0.001). Additionally, IL-6 levels in both ascites and serum were significantly higher in patients with SBP (ascites P < 0.001, serum P = 0.036). The quantity of bactDNA in ascites was strongly correlated with polymorphonuclear neutrophil count in ascites (r = 0.755; P < 0.001) as well as ascites IL-6 levels (r = 0.399; P < 0.001). Receiver operating characteristic (ROC) curve analysis to diagnose SBP provided an AUC of 0.764 (95% CI: 0.661-0.867) for serum IL-6 levels, an AUC of 0.810 (95% CI: 0.714-0.905) for ascites IL-6 levels, and an AUC of 0.755 (95% CI: 0.651-0.858) for bactDNA levels in ascites.

The correlation between the amount of bactDNA and IL-6 confirms the pathophysiological relevance of bactDNA and IL-6 as potential biomarkers for the diagnosis of SBP.