Haemophilus parainfluenzae biliary tract infection: rationale for an ascending route of infection from the gastrointestinal tract.

Haemophilus parainfluenzae was isolated from a bile specimen of a 56-year-old patient with elevated liver enzymes and chronic cholecystitis. Several factors contributing to nonbacteremic H. parainfluenzae infection of the biliary tract include (i) the not infrequent occurrence of H. parainfluenzae in stool specimens, (ii) the presence of an outer membrane protein similar to those found in enteric bacteria which facilitates adherence to the colonic mucosa, and (iii) an adequate supply of V factor (nicotinamide adenine dinucleotide) supplied from bile and the local flora, which is necessary for H. parainfluenzae's growth. Because H. parainfluenzae rarely occurs in the biliary tract, direct cultivation of bile specimens on chocolate agar seems unwarranted. However, bile specimens showing a gram-negative coccobacillus on a Gram-stained smear that fails to grow on routine media should be subcultured on chocolate agar.