A new simple test for evaluation of intestinal bacteria

We investigated a newly synthesized conjugate of ursodeoxycholic acid with para-aminobenzoic acid (PABA) to determine its suitability to evaluate enteric bacteria. This compound, PABA-UDCA, is deconjugated by cholylglycine hydrolase to release free PABA whereas it is completely resistant to deconjugation by pancreatic and intestinal mucosal enzymes. In bacteriological experiments, almost all of the microorganisms which split glycocholic acid deconjugated this compound. In animal experiments, urinary excretions of PABA were measured for 6 hours following oral administration of 10 mg PABA-UDCA. Ten control rats excreted 338.5 +/- 43.8 micrograms (mean +/- SD) of PABA; 10 rats with intestinal bacterial overgrowth due to enteric stagnant loops excreted more (673.6 +/- 222.1 micrograms; p less than 0.01), whereas 10 rats in each of 8 groups with intestinal antisepsis by oral administration of various antibiotics excreted significantly less (p less than 0.001) (ampicillin + doxycycline + fradiomycin: 18.3 +/- 16.7, polymixin B + tinidazole: 14.0 +/- 8.0, polymixin B: 224.9 +/- 74.3, tinidazole: 42.7 +/- 27.3, kanamycin: 50.3 +/- 18.2, clindamycin: 57.4 +/- 23.3, vancomycin: 70.4 +/- 27.0, and paromomycin: 160.4 +/- 51.9 micrograms). These observations indicate that this compound is likely to offer a simple and rapid method for evaluation of intestinal microorganisms without the use of radioisotopes or expensive, special apparatus.