Comparison of two ascitic fluid culture methods in cirrhotic patients with spontaneous bacterial peritonitis

The conventional method of ascitic fluid culture detects bacteria in only 50% of cirrhotic patients with neutrocytic ascites and suspected spontaneous bacterial peritonitis (SBP). We have prospectively compared two ascites culture methods in cirrhotic patients with spontaneous bacterial peritonitis: 1) conventional (on chocolate agar, blood agar, Mac Conkay agar, and thioglycolate broth), and 2) modified [inoculation of 10 ml of ascites in a tryptic soy broth (TSB) blood culture bottle at the patient's bedside]. In a 21-month period, 70 episodes of SBP were diagnosed according to our criteria in 60 cirrhotic patients. Both culture methods were performed simultaneously. The conventional grew bacteria in 40 episodes (57%), whereas the modified grew bacteria in 54 episodes (77%), a significantly higher sensitivity (p = 0.0001). In 16 cases (23%), ascitic culture was negative by both methods. The mortality rate was higher among patients with culture-positive SBP than those with culture-negative SBP (46% vs 37%), but did not reach statistical significance. We conclude that ascitic fluid inoculated into a TSB blood culture bottle at the patient's bedside should be used routinely for ascites culture in cirrhotic patients.