Evaluation of culture techniques for detection of spontaneous bacterial peritonitis in cirrhotic ascites

This prospective study was done in cirrhotic patients to evaluate ascitic fluid culture techniques by the conventional method and by an alternate method of bedside ascitic fluid inoculation into blood culture bottles, with an aim to improve bacteriological diagnosis of spontaneous bacterial peritonitis (SBP). Of the 300 patients who were evaluated, 43 who had a total leukocyte count greater than 500/mm3 or a polymorphonuclear cell count greater than 250/mm3 in ascitic fluid were included. There were 30 episodes of SBP in 28 patients and another 15 patients had culture-negative neutrocytic ascites (CNNA). Escherichia coli was the commonest organism cultured, being found in 60%. There was significantly greater (p < 0.001) ascitic fluid culture positivity with direct inoculation into blood culture bottles, i.e. 66.7% compared to 31.1% by conventional method at 48 hours, and this was evident even 24 hours after inoculation i.e. 33.3% positivity compared to 4.4%. Bacteremia was present in 53.3% of patients with SBP and 33.3% with CNNA. Ascitic fluid inoculation directly into blood culture bottles leads to a significantly increased percentage of culture positivity and reduces the time needed for detection of SBP from 48 to 24 hours.