How is Salmonella Infection Diagnosed?
Salmonella infection is diagnosed through testing of a stool sample. Salmonella can sometimes also be isolated from blood, urine or tissue samples.
Salmonella bacteria can be detected in stool. [5, 15] In cases of bacteremia or invasive illness, the bacteria can also be detected in the blood, urine, or on rare occasions in tissues.  The test consists of growing the bacteria in culture. [5, 6] A fecal, blood or other sample is placed in nutrient broth or on agar and incubated for 2-3 days. After that time, a trained microbiologist can identify the bacteria, if present, and confirm its identity by looking at biochemical reactions.
Treatment with antibiotics before collecting a specimen for testing can affect bacterial growth in culture, and lead to a negative test result even when Salmonella causes the infection.