A simple selective and differentiating synthetic medium (X broth) that is easy to prepare was developed in liquid form for the
selective cultivation of coliform bacteria from foodstuffs. This synthetic medium contains an ammonium salt as nitrogen source,
lactose as carbon source, and buffers but is free of inhibitors. Its selectivity is based on the fact that coliform bacteria are able to
grow ifthe minimal medium consists ofsimple inorganic substances as nitrogen sources and lactose as carbon supply. The selectivity
of this medium was tested by the inoculation ofpure cultures ofdif ferent microbes belonging to the genera of Staphylococcus,
Bacillus, and Pseudomonas and the family Enterobacteriaceae and was found to be complete in this range. The applicability of the
synthetic medium was also tested by a nationwide round oftests, using quick-frozen tomato paprika.
The selectivity ofX broth proved essentially better than that ofthe standard brilliant green–bile–lactose broth. The results of
nationwide tests of coliform bacteria determination demonstrated that there was no difference in reproducibility, but the
comparability was significantly better when X broth was used.
The advantages ofthe new synthetic medium are the standard composition, the absence ofinhibitors, the reliability, the long
keeping quality and the low costs.