Abstract: A culture monitor (10) for microbiological testing of a liquid sample includes a housing having a liquid inlet (30) and a liquid outlet (32, 34), and a liquid sample filtration means inside the housing between the liquid inlet (30) and the liquid outlet (32, 34). The liquid sample filtration means including a filter medium (16) so that a liquid sample entering the housing through the liquid inlet (30) passes through the filter medium (16), with microorganisms present in the liquid sample being retained on the filter medium (16) and spent liquid or filtrate passing through the filter medium (16). A reservoir (53) is provided in the housing downstream of the liquid sample filtration means relative to the liquid inlet (30), with a volume of a rehydration agent for a dehydrated culture medium being provided in the reservoir (53), or the reservoir (53) being adapted to retain during filtration, as a rehydration agent, a portion of the filtrate.