# 2218 Bacteria Associated with Pigment May Participate in Cholesterol Gallstone Formation.
Lygia Stewart, Adair L. Oesterle, Ihsan Erden, Lawrence W. Way, San Francisco, CA

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Bacteria are thought to have a role in the pathogenesis of pigment but not cholesterol gallstones. This data suggests that bacteria are also involved in cholesterol gallstone formation. We prospectively examined Gallstones from 370 patients, of which 204 were predominantly cholesterol stones with a variable amount of visible pigment. Based on visual appearance, these stones were classified into 3 groups: 94 (46%), cholesterol stones with no visible pigment (Ch); 73 (36%), mixed cholesterol stones with a pigment center (MCh); and 37(18%), cholesterol stones with a pigment coat (Ch-PE). The presence of bacteria in the stones (obtained sterilely) was detected using scanning electron microscopy (SEM) (149 stones) and stone culture (121 stones). The stones chemical composition was determined using IR spectroscopy. Bacteria obtained from the stones were tested for slime and ß-glucuronidase production. Results: The relationship between bacteria and cholesterol content in the different kinds of stones is shown in the table. The relationship between cholesterol content and bacterial presence and was as follows: 100% cholesterol, none with bacteria; >90% cholesterol, 44% had bacteria; and <90% cholesterol, 74% had bacteria. 73% of infected stones had one or more bacterial species that produced slime, and 36% had bacterial species that produced ß-glucuronidase. Conclusions: About 30% of these Gallstones contained bacteria, and visible evidence of a pigment focus was a good predictor of bacterial presence. Nethertheless, even stones containing more than 90% cholesterol sometimes contained bacteria. Chemical composition alone did not distinguish the usually sterile Ch from MCh stones (which could contain bacteria). Bacteria found in cholesterol stones generally produced bacterial slime. These data suggest that bacteria may participate in cholesterol gallstone formation, either acting as a nidus for cholesterol precipitation or by facilitating stone growth by fostering the formation of a pigment coat.
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