[Determination of E. coli with MUG (Fluorocult)-lauryl sulfate broth for the testing of microbial contamination in drugs].

A test method for the determination of Escherichia coli in plant materials with the MUG (Fluorocult)-lauryl sulfate broth is described. It was found that more than 75% of the commonly used vegetable drugs exhibit fluorescence quench effects to different degrees when determining E. coli with the MUG-lauryl sulfate broth. Therefore a simple combination of two procedures was evaluated in order to avoid the matrix interferences: in a first step the drug sample was diluted eight times in a proportion of 1:10 with MUG-lauryl sulfate broth in eight separate tubes from 1 g down to 10(-7) g/tube (1st test series) and the resulting samples were incubated for 40 h at 36 degrees C. Subsequently, the tubes were tested for fluorescence. If the first tube of this series was found without fluorescence, in a second step a subsequent series of MUG-lauryl sulfate broth (2nd test series) was inoculated with 0.5 ml of the incubated culture from each of the first three tubes of series 1 and incubated again for 24 h at 36 degrees C. The results were evaluated from gas production, fluorescence as well as indole formation. Thus, the method allowed a simple and reproducible enumeration of E. coli for the test on microbial contamination in medicinal plant materials. The method was successfully applied to samples of 38 vegetable drugs for quantitative determination of E. coli (8 samples were found being contaminated with E. coli).