Identification of bacterial DNA in neutrocytic and non-neutrocytic cirrhotic ascites by means of a multiplex polymerase chain reaction

Background Even though bacterial cultures of ascitic fluid are negative in up to 65% of the cases of spontaneous bacterial peritonitis (SBP); bacterial DNA (bactDNA) has been frequently detected in episodes of SBP as well as in culture-negative non-neutrocytic ascites. Aims To evaluate multiplex polymerase chain reaction (PCR) for pathogen identification in SBP and to determine the prevalence of ascitic bactDNA and its prognostic relevance in hospitalized patients with liver cirrhosis. Methods Ascitic fluid from 68 consecutive patients who underwent diagnostic paracentesis was analysed for polymorphonuclear leucocyte (PMN) count, bacterial culture and bactDNA. BactDNA was identified by gel analysis after multiplex PCR of selectively enriched prokaryotic nucleic acids. Correlations of bactDNA status with PMN count, bacterial culture result and 3-month mortality were determined for neutrocytic and for non-neutrocytic ascites. Results 11/68 patients presented with an elevated ascitic PMN count. BactDNA was detected in 5/5 culture-positive neutrocytic samples, in 1/6 culture-negative neutrocytic samples and in 8/56 culture-negative non-neutrocytic samples. Three-month mortality did not differ with respect to ascitic bactDNA status (7/14 vs. 14/47, P=0.162). 3-month mortality was increased in the presence of ascitic bactDNA for patients older than 65 years (4/5 vs. 4/14, P=0.046) and for patients with a model for end-stage liver disease score > 15 (7/10 vs. 9/30, P=0.025). Conclusions Identification of ascitic bactDNA is an appropriate alternative to bacterial ascite culture for pathogen identification in patients at risk for SBP. Its prognostic relevance as a proposed marker of bacterial translocation for certain risk groups has to be further evaluated.