Method to detect and enumerate microorganisms
A method. The method includes providing a device, the device comprising: a body member comprising a self-supporting, waterproof substrate having upper and lower surfaces; and a layer of adhesive-coated on the upper surface of the substrate, the adhesive being non-inhibitory to the growth of microorganisms; and a cold-water-soluble powder adhered to the adhesive, the powder comprising: guar gum; one or more nutrients for growing microorganisms; and a cover sheet having an inner-facing surface and an outer-facing surface, the cover sheet adhered to at least a portion of the body member; incubating a sample in the device to form a gel; and counting colonies between 24 hours to 72 hours and/or determining if the gel surrounding a colony is degraded.
1 . A method, comprising
providing a device, the device comprising:
a body member comprising a self-supporting, waterproof substrate having upper and lower surfaces; and
a layer of adhesive coated on the upper surface of the substrate, the adhesive being non-inhibitory to growth of microorganisms; and a cold-water-soluble powder adhered to the adhesive, the powder comprising:
guar gum;
one or more nutrients for growing microorganisms; and
a cover sheet having an inner-facing surface and an outer-facing surface, the cover sheet adhered to at least a portion of the body member;
incubating a sample in the device to form a gel; and
counting colonies of said microorganisms said microorganism colonies between 24 hours to 72 hours and determining if the gel surrounding said colonies is degraded by an imaging system or by visual inspection and an imaging system; and
wherein determining if the gel surrounding said microorganism colony is degraded comprises pressing the coversheet to determine if there is a movement of water.
2 . The method of claim 1 , wherein the cover sheet comprises a transparent film.
3 . The method of claim 2 , wherein the transparent film is selected from the group consisting of polyester, polyethylene, polypropylene, polystyrene and silicone.
4 . The method of claim 1 , wherein the device further comprises a hydrophobic spacer element adhered to the upper surface of the substrate forming side walls to retain a predetermined amount of liquid in contact with the substrate.
5 . The method of claim 4 , wherein the spacer element comprises a hydrophobic foam sheet having a hole therein.
6 . The method of claim 5 , wherein the hydrophobic foam sheet is polystyrene.
7 . The method of claim 1 , wherein the substrate is a film selected from the group consisting of polyester, polypropylene, polyethylene and polystyrene.
8 . The method of claim 1 , wherein the substrate has a grid pattern printed thereon.
9 . The method of claim 1 , wherein the adhesive is a pressure-sensitive adhesive.
10 . The method of claim 1 , wherein the adhesive is substantially transparent when wetted with water.
11 . The method of claim 1 , wherein the adhesive is a copolymer of isooctyl acrylate and acrylamide in a mole ratio of 94:6, respectively.
12 . The method of claim 1 , wherein one of the powder and the adhesive contains a dye which is metabolizable by said microorganisms and which causes the microorganisms and/or the gel surrounding the microorganisms to be colored or fluorescent.
13 . The method of claim 12 , wherein the dye is selected from the group consisting of triphenyltetrazolium chloride, p-tolyltetrazolium red, tetrazolium violet and veratryltetrazoleum blue.