Process and apparatus for analyzing specimens for the presence of microorganisms therein
First Claim
1. A device for detecting the presence of at least one specific microorganism in a specimen, said device comprising:
- receptacle means for containing a diluted specimen, a flow channel leading from the receptacle means, at least one selective culture medium in the flow channel whereby the diluted specimen will mix with the culture medium to form a diluent mixture, the culture medium being capable of sustaining a specific microorganism in the diluent mixture such that the continued existence of said living specific microorganism will change the light transmitting characteristics of the diluent mixture so as to indicate the presence of the specific microorganism in the specimen.
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Abstract
Microorganisms in a specimen are detected, identified, and enumerated by introducing the specimen into a sampling cartridge and diluting the specimen with a known volume of water within the cartridge. The cartridge has a manifold and several cassettes attached to the manifold. Each cassette contains a serpentine flow channel having a series of filters therein and a detection cell located downstream from each filter. The flow channel in each cassette also contains a culture medium which is freeze dried and is highly selective in the sense that it promotes the growth of one type of microorganism, but not others. The mixture of the specimen and water flows from the manifold into the flow channel of each cassette where it rehydrates the culture medium therein and further flows through the filters. Each filter removes a known proportion of the microorganisms from the mixture of specimen, water and medium, thereby effecting a serial dilution. After the cassettes are heated to incubate the microorganisms, the detection cells are observed for growth of the microorganisms therein which is manifested in a change in the light transmitting characteristics of the mixtures within the cells. This change is detected with great precision by projecting beams of light through the detection cells and measuring the current flowing through dedicated photocells located beyond the detection cells. The amount of current flowing through each photocell is proportional to the relative optical density of the mixture within the corresponding detection cell, and this density is plotted against time to give a unique time-related signature for each microorganism. Thus, the presence and identity of microorganisms in the detection cells is determined by mere changes in the optical density of the cells, whereas the number of microorganisms may be determined by considering the number of detection cells which change.
94 Citations
36 Claims
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1. A device for detecting the presence of at least one specific microorganism in a specimen, said device comprising:
- receptacle means for containing a diluted specimen, a flow channel leading from the receptacle means, at least one selective culture medium in the flow channel whereby the diluted specimen will mix with the culture medium to form a diluent mixture, the culture medium being capable of sustaining a specific microorganism in the diluent mixture such that the continued existence of said living specific microorganism will change the light transmitting characteristics of the diluent mixture so as to indicate the presence of the specific microorganism in the specimen.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A process for detecting and identifying microorganisms in a specimen, said process comprising diluting the specimen in a liquid;
- mixing the liquid-specimen mixture with a selective culture medium to form a diluent mixture;
heating the diluent mixture to incubate the microorgaisms therein;
filtering the diluent mixture to remove a known proportion of microorganisms of the diluent mixture; and
thereafter examining the diluent mixture for a change in the optical characteristics thereof by measuring the relative optical density of the diluent mixture. - View Dependent Claims (17, 18)
- mixing the liquid-specimen mixture with a selective culture medium to form a diluent mixture;
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19. A process for detecting and identifying microorganisms in a specimen, said process comprising diluting the specimen in a liquid;
- evacuating air from the vicinity of a selective culture medium;
thereafter mixing the liquid-specimen mixture with the selective culture medium to form a diluent mixture; and
examining the diluent mixture for a change in the optical characteristics thereof. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26)
- evacuating air from the vicinity of a selective culture medium;
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27. A process for detecting and identifying microorganisms in a specimen, said process comprising diluting the specimen in a liquid;
- causing the liquid-specimen mixture to flow into and mix with a selective culture medium without exposing the liquid-specimen mixture or the selective culture medium to the surrounding atmosphere, whereby a diluent mixture is formed; and
examining the diluent mixture for a change in the optical characteristics thereof. - View Dependent Claims (28, 29)
- causing the liquid-specimen mixture to flow into and mix with a selective culture medium without exposing the liquid-specimen mixture or the selective culture medium to the surrounding atmosphere, whereby a diluent mixture is formed; and
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30. A process for detecting and identifying a specific microorganism in a specimen, said process comprising:
- diluting the specimen in water confined within a vessel to form a water-specimen mixture;
attaching a cassette containing a flow channel to the vessel such that the flow channel communicates with the interior of the vessel, the flow channel including a detection cell which is visible from the exterior of the cassette on both sides of the cassette, the flow channel also containing a selective medium which when mixed with water will sustain the specific microorganisms and only the specific microorganism will cause a change in the light transmitting characteristics of the water-medium mixture so formed;
causing the water-specimen mixture to flow from the vessel into the flow channel within the cassette where the water-specimen mixture will mix with the selective medium in the flow channel to form a diluent mixture;
thereafter detaching the cassette from the vessel;
projecting a beam of light through the detection cell of the detached cassette and the diluent mixture therein; and
measuring the intensity of the light beyond the detection cell. - View Dependent Claims (31)
- diluting the specimen in water confined within a vessel to form a water-specimen mixture;
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32. A process for detecting and identifying a specific microorganism in a specimen;
- said process comprising;
introducing the specimen into a vessel containing the water so that the specimen and water mix to form a water-specimen mixture;
attaching a cassette containing a flow channel to the vessel such that the flow channel communicates only with the interior of the vessel, the flow channel including a detection cell which is visible from the exterior of the cassette and when unobstructed is capable of transmitting light through the cassette, the flow channel also containing a selective culture medium which when mixed with water will sustain the specific microorganism and only the specific microorganism will cause a change in the light transmitting characteristics of the water-medium mixture;
closing the vessel so that the interior of the vessel and the flow channel are substantially isolated from the surrounding atmosphere to prevent the entry of contaminants;
causing the water-specimen mixture to flow into the flow channel and mix with the selective culture medium therein to form a diluent mixture, at least some of which locates in the detection cell of the flow channel;
thereafter projecting a beam of light through the detection cell and the diluent mixture therein; and
measuring the intensity of the beam of light beyond the detection cell. - View Dependent Claims (33, 34, 35, 36)
- said process comprising;
Specification