Thin-film culture device for enumerating microorganisms
A microbial detection device and methods of use are provided. The device comprises a water-proof pouch that includes a first wall portion, a second wall portion, and a porous membrane filter disposed in the pouch between the first and second wall portions. The filter membrane divides the pouch into first and second compartments. A dry, cold water-soluble gelling agent is adhered to the pouch in the first compartment and an absorbent pad is disposed in the second compartment. A sealable sample port provides access to deposit a liquid into the first compartment.
1. A microbial detection device, comprising:
a water-proof pouch comprising:
a first wall portion having an inner surface and an outer surface;
a second wall portion having an inner surface and an outer surface;
wherein the first wall portion is coupled to the second wall portion at all the periphery of the first wall portion;
a porous membrane filter disposed in the pouch between the inner surface of the first wall portion and the inner surface of the second wall portion, the membrane filter having a first major surface and a second major surface opposite the first major surface;
a first compartment defined in part by inner surface of the first wall portion and defined in part by the first major surface of the membrane filter;
a sealable sample port that provides access to deposit a liquid into the first compartment;
a second compartment defined in part by the inner surface of the second wall portion and defined in part by the second major surface of the membrane filter;
wherein the membrane filter permits passage of aqueous liquids from the first compartment to the second compartment and prevents passage of particles of a predetermined size from the first compartment to the second compartment;
a dry cold water-soluble gelling agent adhered to the pouch in the first compartment; and
an absorbent pad disposed in the second compartment.
2. The device of claim 1 , wherein the pouch comprises a deformable first wall portion disposed opposite the membrane filter in the first compartment.
3. The device of claim 1 , wherein the pouch comprises a deformable second wall portion disposed proximate the absorbent pad in the second compartment.
4. The device of claim 1 , wherein the membrane filter is coupled to a frame, wherein the frame comprises an aperture through which liquid passes from the first compartment into the membrane filter.
5. The device of claim 1 , wherein the gelling agent adhered to the pouch defines a second area, wherein the first compartment is configured to receive a predetermined volume of about 100 mL to about 150 mL, wherein the second area defines a colony enumeration area, wherein a ratio of the predetermined volume to the colony enumeration area is less than 1 cm 2 per mL.
6. The device of claim 1 , wherein the membrane filter comprises a supported membrane.
7. The device of claim 4 , wherein the absorbent pad is coupled to the second wall portion or the absorbent pad is coupled to the frame.
8. The device of claim 1 , wherein the first compartment has a first maximum capacity, wherein the device is dimensioned to receive a liquid sample having a volume between 25 mL and 150 mL, inclusive.
9. The device of claim 1 , further comprising an indicator reagent for indicating a presence of a viable microorganism, wherein the indicator reagent is disposed in the pouch.
10. The device of claim 1 , wherein the sealable sample port includes a pressure-sensitive adhesive disposed therein.
11. The device of claim 10 , further comprising a release liner removably adhered to the adhesive.
12. A method comprising:
placing a predetermined volume of aqueous sample into the first compartment through the sealable sample port of the microbial detection device of claim 1 ;
sealing the sealable sample port;
incubating the device for a period of time at a temperature that facilitates growth and detection of a target microorganism; and
detecting a presence or an absence of a colony of the target microorganism in the device.
13. The method of claim 12 , further comprising laying the outer surface of the first wall portion of the device or laying the outer surface of the second wall portion of the device onto a surface that is substantially perpendicular to gravitational force.
14. The method of claim 12 , further comprising passing at least 90% of the predetermined volume from the first compartment to the second compartment, wherein passing at least 90% of the predetermined volume comprises passing the volume by gravity force and/or capillary force.
15. The method of claim 12 , further comprising bringing the gelling agent into contact with the membrane filter.
16. The method of claim 12 , further comprising the step of combining the aqueous sample with a nutrient, nutrient medium, indicator reagent and/or selective agent prior to placing the predetermined volume into the first compartment.
17. The method of claim 12 , further comprising the step of combining the aqueous sample with a nutrient, nutrient medium, indicator reagent and/or selective agent after placing the predetermined volume into the first compartment.
18. The method of claim 12 , further comprising counting microbial colonies in the device.