How to interpret the bile culture results of patients with biliary tract infections.

BACKGROUND/GOALS: Bile is normally sterile, but the presence of organisms in the bile does not necessarily imply an active infection. We wonder what the significance of bile culture results on antibiotics choice in cholangitis with negative blood culture. The aim of this study was to compare organisms cultured from bile with those from blood in bacteremic biliary tract infection and to evaluate factors associated with concordance between blood and bile isolates.

METHODS

Between 2000 and 2010, 266 positive blood cultures with concomitant bile culture in bacteremic biliary tract infection were identified. Follow-up bile specimens obtained after negative conversion of blood culture and clinical recovery from acute infection were collected for supplementary analysis.

RESULTS

Of the 266 events, 258 showed positive bile culture. Of the 258 bile samples, 80 yielded the same organisms with blood, 129 showed partial agreement and 49 yielded completely different organisms with blood. Only the number of organism was found to be independently associated with concordance. Of the 529 organisms isolated from bile, 227 were found in blood and gram-negative organisms showed higher rate of coincidence than gram-positive organisms. Of the 84 follow-up bile sample, 94% showed persistent positive culture and higher rate of antibiotics resistance than initial bile culture.

CONCLUSIONS

More than half of the organisms isolated from bile, especially gram-positive organisms, are not likely to be true pathogens. But single organism cultured from bile has clinical significance. Routine follow-up bile culture in patients showing clinical improvement is not necessary.