Is the detection of microbial DNA superior to ascitic fluid bacterial culture in patients with suspected spontaneous bacterial peritonitis?

Spontaneous bacterial peritonitis (SBP) is a common and often fatal complication in patients with advanced liver cirrhosis. It is defined by an elevated absolute polymorphonuclear leukocyte (PMN) count ≥ 250/mm³ and a positive ascitic fluid bacterial culture. With current bacterial culture techniques pathogenic agents are detected in only 50% to 80% of patients with neutrocytic ascites. Hence, faster and more sensitive methods for detection for bacteria in ascitic fluid are needed. In a prospective study 96 diagnostic paracenteses were performed on 62 patients with ascites who were admitted consecutively to our department between July 2007 and July 2008. Besides determination of cell count, absolute PMN count, and ascitic fluid culture, ascites was evaluated for microbial DNA by concentration of bacterial and fungal DNA with an affinity chromatography (Looxster™) and sequence specific amplification with a multiplex PCR (Vyoo™). In 9/96 samples ascitic fluid absolute PMN count was elevated ≥ 250 cells/mm³. In two of these nine samples SBP was confirmed by a positive ascitic fluid bacterial culture; seven samples were classified as culture-negative neutrocytic ascities (CNNA). We could detect bacterial DNA in both of the SBP samples (E. coli) and in two of the CNNA samples (Stenotrophomonas, Acinetobacter). Furthermore we could detect microbial nucleic acids in 12 ascites samples with a non-elevated PMN count (1×E. coli, 1×S. agalactiae, 1×E. faecalis, 1×S. aureus, 3×Acinetobacter, 4×Staphylococcus spp. and 1×fungal DNA). Thus, molecular genetic detection of bacterial DNA is more sensitive than ascitic fluid culture or determination of PMN count for detecting bacterial seeding of ascitic fluid. Whether detection of bacterial ascitic DNA may discriminate between infection and colonization has not been resolved yet. Thus, detection of bacterial DNA in ascitic fluid may provide a rational approach to therapeutic decisions in patients with liver cirrhosis and ascites.

CNNA - SBP - ascites - bacterascites - bacterial DNA - cirrhosis - diagnostic - multiplex-PCR - neutrocytic ascites - translocation