A new substrate for the rapid evaluation of enteric microbial overgrowth.

The possibility of a new approach to diagnosis of intestinal bacterial overgrowth has been evaluated in laboratory animals. The diagnostic test involves oral administration of an enzyme-labile substrate consisting of para-aminobenzoic acid (PABA) conjugated to a bile acid. In the presence of enteric bacteria, PABA is split from the bile acid and is rapidly absorbed and excreted in the urine. The amount of PABA recovered during the 6 hr following the administered dose of the conjugate may be used as an index of bacterial overgrowth in the upper-gastrointestinal tract. The procedure has been shown to be a reliable index of this condition in laboratory animal models.