Isolation and identification of Salmonella
Salmonella is gram-negative bacteria, facultatively anaerobic, and facultative intracellular parasite. There are a different kind of test for isolation and identification that are listed below
Biochemical test
In this kind of test, we can identify the salmonella on the basis of ferment so the salmonella in ferment with the maltose, dextrose, mannitol, sorbitol and clearly not fermentate with the lactose and sucrose
By the growth of salmonella
We can grow salmonella on maconky agar, heckton agar, W&B media. it’s basically a media that have a selective and differential media
On selective media
Have gram-negative enterobacter and inhibit the growth of gram-positive bacteria
On diff. media
There are two types of fermentation happen on it lactose and non-lactose fermentation the color occurs respectively bright pink and transparent color colony
By H2S
it can react with triple sugar iron it can produce the h2s gas, and cause a blackish color around the test tube
By agglutination
We can also identify salmonella by agglutination test with salmonella galinaraum take a drop of serum and mix with antigen
Blood cluster
85% of blood cluster are positive
Primary isolation media
- Blood agar incubate in the air at 35 to 37 c for 18 to 24 hour
- CLED agar incubate in the air at 35 to 37 c for 18 to 24 hour
- XLD agar incubate in the air at 35 to 37 c for 18 to 24 hour
- DCA incubate in the air at 35 to 37 c for 18 to 24 hour
Colony formation
- on blood agar the colony are moist and 1-2 mm in diameter
- on CLED it cannot fermentate with lactose but some serotype s.arizonae, s.indiana may fermentate with lactose
- on XLD red colony appear and a black center
- on DCA all colonies are black center and colorless colony
biochemical test
ureae test
salmonella can not produce urease
oxidase test
salmonella is oxidase negative if positive appear to discard and take the negative it can agglutinate with the polyvalent o and antiserum then again there are two results positive and negative in negative case urease is added at 37c for an hour then on CLED plate then again watch the negative and positive results discrete positive results now first positive of agglutination and CLDE plate again for biochemical test after that check pure culture there will be two results salmonella related and not related take related and done the agglutination tests