Gram-negative bacteria killed by complement are associated with more severe biliary infections and produce more tumor necrosis factor-α in sera

Background. We previously showed that gallstones contain bacteria and that illness severity correlates with bacterial presence. This study examined virulence differences of gram-negative biliary bacteria. Methods. Gallstones and bile were cultured, and sera obtained, from 210 patients. Infection severity was staged as: none—no clinical infection; moderate—fever, leukocytosis; or severe—bacteremia, cholangitis, hypotension, abscess, or organ failure. Gram-negative biliary bacteria were tested against patient (and control) serum for complement-mediated bacterial killing and induction of tumor necrosis factor-α (TNFα) production (using cultured monocytes) with and without sera. These results were correlated with infection severity. Results. A total of 98 (47%) patients had biliary bacteria. Infection severity distribution was none, 29%; moderate, 35%; and severe, 36%. Gram-negative organisms killed by complement were associated with more severe infections as follows: 13%, none; 60%, moderate; and 88%, severe infections (P =.024 and P