A system for determining the presence of a microorganism in a sample by concentrating the microorganism in the sample and culturing the sample with the increased microorganism concentration, the system comprising: a container adapted to receive a sample, the container having a first end and a second end; a sensor inside the container near the second end configured to detect a change in the sample indicative of at least one of the presence or absence or response of a microorganism in the sample; a retractable plunger configured to move from the first end of the container toward the second end of the container thereby reducing the volume of the sample disposed between the second end of the container and the plunger, the plunger being adapted to maintain a seal between the inside of the container and the outside of the container as the plunger moves from the first end of the container toward the second end of the container, the first and second ends of the container being in fluid communication with one another when the plunger is at the first end of the container; and a channel extending through the plunger configured to allow for a top portion of the sample to be forced through the channel as the plunger moves from the first end of the container toward the second end of the container, thereby increasing the concentration of the microorganism in the reduced volume of the sample; a reagent mixture introduced into the container, the reagent mixture including a lysing agent to selectively lyse cells in the sample other than the microorganism; a waste reservoir coupled to the channel; a nutrient reservoir coupled to the channel; and a pump operably coupled to the nutrient reservoir, the pump configured to drive fluid from the nutrient reservoir into the container thereby increasing the volume of the sample disposed between the second end of the container and the plunger by adding nutrients to the sample volume; wherein the reagent mixture is present in the container and in fluid communication with the sensor and the sample as the plunger is advanced from the first end of the container toward the second end of the container. a container adapted to receive a sample, the container having a first end and a second end; a sensor inside the container near the second end configured to detect a change in the sample indicative of at least one of the presence or absence or response of a microorganism in the sample; a retractable plunger configured to move from the first end of the container toward the second end of the container thereby reducing the volume of the sample disposed between the second end of the container and the plunger, the plunger being adapted to maintain a seal between the inside of the container and the outside of the container as the plunger moves from the first end of the container toward the second end of the container, the first and second ends of the container being in fluid communication with one another when the plunger is at the first end of the container; and a channel extending through the plunger configured to allow for a top portion of the sample to be forced through the channel as the plunger moves from the first end of the container toward the second end of the container, thereby increasing the concentration of the microorganism in the reduced volume of the sample; a reagent mixture introduced into the container, the reagent mixture including a lysing agent to selectively lyse cells in the sample other than the microorganism; a waste reservoir coupled to the channel; a nutrient reservoir coupled to the channel; and a pump operably coupled to the nutrient reservoir, the pump configured to drive fluid from the nutrient reservoir into the container thereby increasing the volume of the sample disposed between the second end of the container and the plunger by adding nutrients to the sample volume; wherein the reagent mixture is present in the container and in fluid communication with the sensor and the sample as the plunger is advanced from the first end of the container toward the second end of the container.