Abstract: Method for determining the sensitivity of a bacterial strain of interest to a viral strain of bacteriophages, the method comprising: a) preparing a sample, this comprising bringing bacteria, belonging to the bacterial strain of interest, into contact with bacteriophages, each bacteriophage belonging to the same viral strain, the bacteria being either in a liquid medium, or in an agar medium; b) placing the sample between a light source and an image sensor, the light source emitting a light wave in an emission spectral band comprised between 500 nm and 600 nm; c) illuminating the sample using the light source and acquiring at least one image of the sample, with the image sensor, in the emission spectral band, no image-forming optic being placed between the sample and the image sensor; d) on the basis of the acquired images, determining a sensitivity of the bacterial strain of interest to the viral strain.