Method of detecting a salmonella microorganism

1. A method of detecting Salmonella microorganisms comprising:

providing a test sample, a culture device, and a composition, the composition comprising;

a semisolid culture medium including

a gelling agent;

at least one first selective agent that inhibits the growth of Gram-positive microorganisms;

a first differential indicator system comprising at least one first differential indicator compound, wherein the at least one first differential indicator compound consists of pH indicator and a fermentable carbohydrate that can be converted by Salmonella microorganisms to a first detectable product that comprises an acidic compound or a gas; and

a second differential indicator system comprising a second differential indicator compound that is converted by urease enzyme activity to a second detectable product; and

a third differential indicator system comprising a third differential indicator compound that is converted by a β-galactosidase enzyme activity to a third detectable product;

wherein the first differential indicator compound cannot be converted to the first detectable product by a plurality of genera of non- Salmonella , Gram-negative enteric microorganisms that form detectable colonies in and/or on the semisolid culture medium;

contacting in the culture device the composition and the test sample to form an inoculated culture device;

incubating the inoculated culture device for a first period of about 14 to about 48 hours;

wherein incubating the culture device comprises incubating the culture device at a temperature between 41-44 degrees C., inclusive;

observing the culture device to detect the first detectable product, the second detectable product, and the third detectable product; and

wherein, after incubating the inoculated culture device for the first period of time, a colony that consists of Salmonella microorganisms is identified by its production of an observable quantity of the first detectable product and by its lack of production of an observable quantity of both the second and third detectable products.

2. The method of claim 1 , wherein detecting the first detectable product comprises observing a reaction of the pH indicator with an acidic compound produced by a bacterium.

3. The method of claim 1 , further comprising observing the semisolid culture medium to detect the second detectable product, wherein the second detectable product indicates a presence of a non- Salmonella microorganism.

4. The method of claim 3 , wherein detecting the second detectable product comprises observing a reaction of the pH indicator with a basic compound produced by a bacterium.

5. The method of claim 1 , wherein detecting the third detectable product comprises detecting a colored product produced by β-galactosidase enzyme activity.

6. The method of claim 1 , further comprising enumerating a number of colonies of a first type of microorganisms.

7. The method of claim 6 , further comprising enumerating a number of colonies of a second type of microorganisms.

8. The method of claim 1 , wherein observing the culture device comprises observing the culture device visually.

9. The method of claim 1 , wherein observing the culture device comprises creating an image of the culture device using an imaging device.

10. The method of claim 9 , further comprising analyzing the image using a processor.

11. The method of claim 1 , wherein a colony that consists of Salmonella microorganisms comprises Salmonella bongori and/or Salmonella typhimurium.