Abstracts
1997 Digestive Disease Week

Enterococcus and serum-sensitive gram-negative bacteria are associated with more severe biliary infections.

L Stewart, A Oesterle, B Aagaard, J.McL Griffiss, LW Way. University of California, San Francisco.

We previously reported that patients with bacteria in their gallstones have more severe biliary illnesses. In this study, we examined the clinical significance of the bacterial species and the ability of the patients' sera to kill the bacteria obtained from their gallstones (via complement-mediated pathways). Methods: Gallstones, bile, and sera were obtained at surgery from 154 patients with gallstone disease. Stones were cultured and examined under SEM. Gram-negative bacteria from gallstones were tested against the patient's serum (and a control serum) for complement-mediated bacterial killing (serum-sensitivity). The severity of illness was staged as I) no infection; II) mild-moderate infection (fever, leukocytosis); and III) severe infection (cholangitis, bacteremia, hypotension, and/or organ failure). Results: 90 patients had sterile gallstones: 79% had stage I illness; 19% had stage II illness; and 2% had stage III illness. 64 patients' gallstones contained bacteria: 31% had stage I illness; 27% had stage II illness; and 42% had stage III illness. The most prevalent organisms cultured from the stones, bile and blood were: Enterococcus, E. coli, Klebsiella sp, Enterobacter sp and Pseudomonas sp. Bactericidal assays were performed for patients with Gram-negative organisms recovered from their gallstones. The most serious illnesses occurred in patients whose Gram-negative organisms were killed by their serum. Only 14% of patients with stage I illness had serum-sensitive bacteria, while 86% of patients with stage III illness and 55% of those with stage II illness had serum-sensitive bacteria (p < 0.001 and p < 0.05, respectively, compared with stage I patients [Fisher's exact test]). Most (78%) E. coli and Klebsiella sp were serum-sensitive, but these species were serum-resistant when obtained from patients with stage I illness. Enterococcus, E. coli, and Klebsiella were most often (75 %) associated with stage II or III illness, and these species were the ones most often cultured from blood (8 patients). In contrast, no Enterobacter and only one Pseudomonas isolate (from a patient with sepsis) were serum-sensitive, and Pseudomonas sp and Enterobacter sp were most often (68%) associated with stage I illness. Of the 9 patients with only Streptococcus in their biliary tree, 67% had stage III disease. Conclusions: Paradoxically, serum-sensitive (not serum-resistant) Gram-negative bacteria were associated with more serious biliary infections including bacteremia. Additional research will be required to determine the cause (eg, liberation of endotoxin during bacterial killing). The most severe illnesses were produced by E. coli, Klebsiella and Enterococcus species. Since they do not possess innately greater toxicity, these three species must have as yet undefined advantages for systemic invasion when in the biliary tree.