Process and device for detecting the activity of a substance on a micro-organism or on a mixture of micro-organisms

The presence of fermentation inhibiting activity in a sample is determined by contacting the sample with bacterial strains and detecting the inhibition of the activity of the strains. A carrier (1) carrying microtitration cups arranged in four rows of cups (8) is provided. The cups of the same row contain a lyophilisate comprising a given bacterial strain. Each sample to be tested, effected in a tube (3), is diluted in a tube (4) containing a culture medium and bromocresol purple and then poured into the cups of a given column by means of an automatic pipette and cones (5). After incubation, a drop of janus green reagent in tube (6) is introduced in each cup and, after a new incubation, the number of cups which have produced a change in color indicates the degree of contamination of the mixture. The process may be applied in the determination of bacteriophages present in cheese-making vats.