[Glucuronidase detection and indol capillary test as reliable rapid identification procedures for the detection of E. coli in foods--toxinogenic strains included].

The fluorogenic beta-D-Glucuronidase test, together with an Indol-capillary test for rapid identification of E. coli, were proved with 60 toxinogenic, 335 nontoxinogenic wild-type strains, and 87 other gram-negative isolates from food. With a sensitivity of 96.5% and a specificity of 95.6%, the fluorogenic assay can be recommended as a reliable method for presumptive determination of E. coli. For confirmation, a time-, material- and labour-saving Indol-capillary test with simultaneous demarcation of fluorescence-positive Salmonella spp. should be carried out. This includes enterotoxigenic E. coli as well, with the exception of some fluorescence-negative Verotoxin-producing strains. As the primary cultivation medium the Plate-count-Monensin-KCl-Agar supplemented with 50 micrograms/ml 4-methyl-umbelliferyl-beta-D-glucuronide (PMK-MUG) can be recommended. Not suitable appear such media containing lactose due to acidification, while metabolizing the carbohydrate. This may significantly reduce or extinguish the fluorescence. The procedure recommended here permits also a reliable determination of lactose-negative E. coli-biotypes.