Pigment vs cholesterol cholelithiasis - Bacteriology of gallbladder stone, bile, and tissue correlated with biliary lipid analysis

Although pigment (calcium bilirubinate) gallstones in Japanese subjects are associated with bacterial infection, the role of infection in Americans with pigment gallstones has not been assessed. Anaerobic and aerobic cultures of gallbladder bile, stone, and wall were obtained at cholecystectomy from nine patients with pigment stones and 25 with cholesterol stones. Among pigment-stone subjects, only 1 of 9 grew organisms in greater than 10⁵ colony-forming units (CFU)/ml or g in gallbladder bile or wall. Likewise, growth greater than 10⁵ CFU/ml or g was present in only 1 of 26 biles and 2 of 26 walls from cholesterol-stone patients. Propionibacterium acnes was found in less than 10⁵ CFU/g or ml in at least 1 specimen from 6 of 9 pigment- and 12 of 26 cholesterol-stone patients. This organism was considered a contaminant because propionic acid concentrations in bile, an index of active bacterial metabolism, were similar in specimens with or without low-titer growth. The concentrations of bile salts, phospholipids, cholesterol, and bilirubin in gall-bladder bile was unaffected by the type of bacteria in low-titer growth. But the lipid concentrations were markedly depressed in two biles with bacterial growth greater than 10⁵ CFU/ml. The molar ratio of bile salts and phospholipids to cholesterol was significantly higher in biles surrounding pigment stones than those surrounding cholesterol stones (P<0.01). We conclude that significant bacterial infection (>10⁵ CFU/ml) is not associated with pigment or cholesterol stones in asymptomatic American subjects at cholecystectomy. These data suggest that pigment-stone formation in the United States is not primarily related to bacterial alteration of bile composition, as the experience with Japanese patients would suggest.