A microbiological testing device for testing a liquid to be analysed that is liable to contain at least one microorganism, includes a closed inner space, a microbiological filtration member and an inlet port. The device has a nutritive layer in contact with the filtration member, and in that, in a configuration for providing the device an open/close member of the inlet port is in a closed state; the absolute gas pressure inside the closed inner space is strictly less than the standard atmospheric pressure, such that the device is able to create suction through the inlet port during a first opening of the open/close member.