How is Shigellosis Diagnosed?
Determining that Shigella is the cause of an illness depends on laboratory tests that identify the bacteria in the stool of an infected person. The laboratory can also do special tests to tell which species of Shigella the person has and which antibiotics would be best to treat it. Shigella is not a normal inhabitant in the colon, but the culture tests are sometimes falsely negative. This is because Shigella is somewhat difficult to isolate from a stool specimen because it has characteristics that are similar to normal colon bacteria.
Newer methods are being developed to identify foodborne pathogens, like Shigella, in food samples. These tests often work by locating segments of RNA unique to the organism.