How do you diagnose Salmonella infection
Diagnosis of Salmonella infection is undertaken by
a) Isolation of Salmonella -
- Salmonella isolated using blood culture, organisms are isolated from blood stream at all stages of infection
- Salmonella species are isolated mostly from 2nd week and 3rd week from stool and urine samples respectively.
- Faeces and Urine are centrifuged and the deposits are enriched in Selenine F broth followed by inoculation in to Selective media Deoxycholate Citrate Agar (DCA)
- The colonies are tested for presence of Salmonella 'O' and 'H' antigens by slide agglutination test, followed by biochemical testing.
b) Widal test : -
- Widal test is done to detect Salmonella antibodies in the blood of infected person. Specific O and H antibodies of Salmonella are detected in blood.
- Detection of Vi antibodies in the serum is diagnostic for Salmonella chronic carriers.
- Four fold increase in antibody level is used for confirming Salmonella infection.