Described herein are methods and apparatus for rapid detection of microorganisms in biological samples (e.g. blood) for analysis to determine the presence or absence of infectious microorganisms in the samples. The apparatus includes a cartridge with a lid and a tray, a mechanism for isolating a bulk sample into multiple smaller samples, and a sensor disposed on the tray to determine the presence or absence of microorganisms. The cartridge lid includes projections that, in a first position, allow for sample to distribute evenly in the cartridge tray and, in a second position, isolate the sample into multiple smaller volume samples. The apparatus and method shorten the time-to-detection of a microorganism in a sample and reduce the steps required from sample collection to microorganism detection.